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Population Dynamics and Harvest Characteristics of Wolves in the Central Brooks Range, Alaska
Abstract
ABSTRACT Our understanding of wolf (Canis lupus) population dynamics in North America comes largely from studies of protected areas, at-risk populations, and wolf control programs, although most North American wolves experience moderate levels of regulated harvest. During 1986–1992, we investigated the population dynamics and harvests of wolves in the newly created Gates of the Arctic National Park and Preserve in northern Alaska, USA, where wolves were harvested by local residents. Our objectives were to determine wolf abundance, estimate important vital rates (i.e., productivity, survival, emigration), and characterize wolf harvests. We monitored 50 radiocollared wolves in 25 packs over 4 years (Apr 1987–Apr 1991) to assess patterns of dispersal, emigration, survival and mortality causes in the wolf population. We determined pack sizes, home ranges, and pups per pack in autumn (1 Oct) for instrumented wolf packs, and calculated wolf densities in autumn and spring (15 Apr) based on the number of wolves in instrumented packs and the aggregate area those packs inhabited. We also gathered information from local hunters and trappers on the timing, location, methods, and sex-age composition of wolf harvests during 6 winter harvest seasons (Aug 1987–Apr 1992).Wolf densities averaged 6.6 wolves per 1,000 km2 and 4.5 wolves per 1,000 km2 in autumn and spring, respectively, and spring densities increased by 5% per year during our study. On average, pups constituted 50% of the resident wolf population each autumn. An estimated 12% of the population was harvested annually. Natural mortality, primarily intraspecific strife, equaled 11% per year. Young wolves emigrated from the study area at high annual rates (47% and 27% for yearlings and 2-yr-olds, respectively), and we estimated the emigration rate for the population at ≥19% annually. Yearlings and 2-year-olds were lost from the population at rates of 60% per year and 45% per year, respectively, primarily as a result of emigration; mortality was the principal cause of the 26% annual loss of wolves ≥3 years old.On average, 47 wolves were harvested each winter from our study population, or twice the harvest we estimated from survival analyses of radiocollared wolves (23 wolves/yr). We suggest that the additional harvested wolves were transients, including local dispersers and migrants from outside the study area. Trapping harvest was well-distributed throughout the trapping season (Nov-Apr), whereas shooting harvest occurred mainly in February and March. Of 35 individuals who harvested wolves in the area, 6 accounted for 66% of the harvest.We analyzed information from North American wolf populations and determined that annual rates of increase have an inverse, curvilinear relationship with human-caused mortality (r2 = 0.68, P < 0.001) such that population trends were not correlated with annual human take ≤29% (P = 0.614). We provide evidence that wolf populations compensate for human exploitation ≤29% primarily via adjustments in dispersal components (i.e., local dispersal, emigration, and immigration), whereas responses in productivity or natural mortality have little or no role in offsetting harvests. Given the limited effects of moderate levels of human take on wolf population trends and biases in assessing wolf populations and harvests resulting from the existence of transient wolves, the risks of reducing wolf populations inadvertently through regulated harvest are quite low.RESEMEN Nuestra comprensión de la dinámica poblacional del lobo (Canis lupus) en Norteamérica procede sobre todo de estudios en áreas protegidas, de poblaciones amenazadas y de programas de control de lobos, aunque la mayoría de los lobos norteamericanos experimentan niveles moderados de explotación regulada. Durante 1986–1992, hemos investigado la dinámica poblacional y el aprovechamiento del lobo en el recientemente creado Parque Nacional y Reserva Gates of the Arctic, en el norte de Alaska, donde los lobos fueron explotados por los residentes locales. Nuestros objetivos han sido determinar la abundancia de lobos, estimar los parámetros vitales más importantes (productividad, supervivencia, emigración) y caracterizar la explotación de los lobos. Hemos seguido 50 lobos radiomarcados en 25 manadas durante 4 años (abril de 1987–abril de 1991) para conocer los patrones de dispersión, la emigración, la supervivencia y las causas de mortalidad de la población. Hemos determinado los tamaños de manada, las áreas de campeo y los cachorros/manada en otoño (1 de octubre) en las manadas con lobos marcados, y hemos calculado la densidad de lobos en otoño y primavera (15 de abril) considerando el número de lobos en las manadas controladas y la superficie total ocupada por dichas manadas. También hemos recogido información de cazadores y tramperos locales sobre la estacionalidad, localización, métodos y composición de sexo y edad de los lobos muertos en 6 periodos invernales de aprovechamiento (agosto de 1987–abril de 1992).La densidad media fue de 6,6 lobos/1.000 km2 y 4,5 /1,000 km2 en otoño y primavera, respectivamente, y las densidades en primavera aumentaron un 5% anual durante el estudio. De media, los cachorros constituyeron el 50% de la población residente cada otoño. Hemos estimado que cada año se extrajo el 12% de la población. La mortalidad natural, fundamentalmente por luchas intraespecíficas, alcanzó el 11% anual. Los ejemplares jóvenes del área de estudio presentaron elevadas tasas anuales de emigración (el 47% y el 27% para lobos de 1 a 2 años y de 2 a 3 años, respectivamente), y la tasa de emigración anual estimada para la población ha sido ≥19%. El 60% y el 45% de los lobos de 1 a 2 y de 2 a 3 años respectivamente desaparecieron cada año de la población, sobre todo a causa de la emigración; la mortalidad fue la principal causa de la pérdida del 26% anual de los lobos ≥3 años.De media, se extrajeron 47 lobos cada invierno en los programas de aprovechamiento en el área de estudio, es decir, el doble de la cifra que hemos estimado analizando la supervivencia de los lobos radiomarcados (23 lobos/año). Sugerimos que los restantes lobos extraídos eran transeúntes, incluyendo dispersants locales y migrantes de fuera del área de estudio. La extracción por trampeo estuvo bien distribuida a lo largo de la estación de trampeo (noviembre-abril), mientras que la extracción con armas de fuego se produjo sobre todo en febrero y marzo. De los 35 individuos que extrajeron lobos en la zona, 6 acapararon el 66% de las capturas.Tras analizar la información de las poblaciones norteamericanas de lobos, hemos determinado que las tasas anuales de aumento muestran una relación inversa y curvilinear con la mortalidad causada por el hombre (r2 = 0,68, P < 0,001), de tal forma que las tendencias de las poblaciones no estaban correlacionadas con la mortalidad humana cuando ésta fue ≤29% anual (P = 0,614). Aportamos pruebas de que, cuando las tasas anuales de explotación por el hombre son ≤29%, las poblaciones de lobos las compensan fundamentalmente ajustando los componentes de la dispersión (es decir, la dispersión local, la emigración y la inmigración), mientras que las respuestas en productividad o mortalidad natural tienen un papel escaso o nulo al compensar las extracciones. Considerando que unos niveles moderados de extracción por el hombre tienen un impacto limitado sobre la tendencia de las poblaciones de lobos y que existen sesgos en la estima de las poblaciones y en la extracción causados por la existencia de lobos transeúntes, los riesgos de reducir las poblaciones de forma inadvertida con un aprovechamiento regulado son bastante bajos.RÉSUMÉ Notre compréhension de la dynamique des populations de loups (Canis lupus) d'Amérique du Nord provient grandement d'aires protégées, de populations menacées ou de programmes de contrǒle bien que la plupart des loups du continent subissent des niveaux d'exploitation modérés. Entre 1986 et 1992, nous avons étudié la dynamique des populations et la récolte de loups dans le nouveau parc national et la réserve Gates of the Arctic, au nord de l'Alaska, où les résidents locaux récoltaient des loups. Nos objectifs étaient de déterminer l'abondance des loups, d'estimer des taux d'évènements naturels importants (c-à-d. la productivité, la survie, l'émigration), et de caractériser la récolte de loups. À l'aide de colliers émetteurs, nous avons suivi, pendant 4 ans (avril 1987 à avril 1991), 50 loups appartenant à 25 meutes afin d'évaluer leurs patrons de dispersion, l'émigration, la survie et les causes de mortalité au sein de la population. Nous avons déterminé la taille des meutes, les domaines vitaux, et le nombre de louveteaux par meute en automne (1er octobre) pour les meutes comptant des loups marqués, et nous avons calculé les densités de loups en automne et au printemps (15 avril) d'après le nombre de loups par meute suivie et l'aire que ces meutes habitaient. Nous avons également recueilli des informations auprès des chasseurs et trappeurs locaux sur la chronologie, le lieu, les méthodes et la composition (sexe/ǎge) de la récolte de loups durant 6 saisons hivernales (aoǔt 1987 à avril 1992).Les densités moyennes de loups atteignaient 6,6 loups/1 000 km et 4,5 loups/1000 km2 en automne et au printemps, respectivement, et les densités printanières augmentèrent de 5% par année durant notre étude. En moyenne, les louveteaux représentaient 50% de la population résidente, chaque automne. Nous avons estimé la récolte annuelle moyenne à 12% de la population. La mortalité naturelle, principalement des conflits intraspécifiques, atteignait 11% par année. Les jeunes loups émigrèrent de l'aire d'étude à des taux élevés (47% et 27% pour les loups d'un an et de deux ans, respectivement) et nous avons estimé le taux d'émigration annuel pour l'ensemble de la population à ≥19%. Les loups d'un an et de deux ans disparaissaient de la population à des taux annuels de 60% et 45%, respectivement, principalement à cause de l'émigration; la mort était la principale cause de disparition des loups de 3 ans et plus qui quittaient la population chaque année (26%).En moyenne, 47 loups furent récoltés chaque hiver dans la population étudiée, soit 2 fois la récolte estimée par les analyses de survie des loups marqués (23 loups par an). Nous proposons que le surplus de loups récoltés provenait d'animaux de passage, incluant les loups locaux en dispersion et d'autres provenant de l'extérieur de l'aire d'étude. La récolte par piégeage s'étendait uniformément durant toute la saison (novembre à avril) alors que la récolte par la chasse se concentrait surtout en février et mars. Six des 35 personnes récoltant des loups dans l'aire d'étude étaient responsables à elles seules de 66% des prises.Nous avons analysé des données provenant de diverses populations de loups d'Amérique du Nord et trouvé que les taux d'accroissement possédaient une relation inverse et curvilinéaire avec les causes de mortalité induites par les humains (r2 = 0,68, P < 0,001) de telle sorte que les tendances démographiques n'étaient pas corrélées aux récoltes humaines (P = 0,614). Nous fournissons des évidences à l'effet que les populations de loups compensent pour l'exploitation humaine ≤29% principalement par l'entremise d'ajustements dans les facteurs de dispersion (c.-à-d. dispersion locale, émigration, immigration), alors que la productivité et la mortalité naturelle compensent peu ou pas du tout pour les récoltes. Étant donné les effets limités d'une récolte humaine modérée sur les tendances démographiques des populations de loups et les biais d'estimation des effectifs et des récoltes à cause de l'existence de loups de passage, les risques de reduction accidentelle de populations de loups résultant d'une récolte réglementée sont très faibles.
... Wolves have been harvested, controlled, or extirpated throughout much of their historical range (Musiani and Paquet 2004), and the additivity of human-caused mortality has been a primary subject of management debate (Adams et al. 2008, Creel and Rotella 2010, Gude et al. 2012, Creel et al. 2015. Although conventional hunting and trapping can limit wolf populations (Peterson et al. 1984, Ballard et al. 1997, Person and Russell 2008, wolf populations appear to sustain conventional harvest at rates of 22-29% of the annual fall population (Fuller et al. 2003, Adams et al. 2008, Creel et al. 2015. ...
... Wolves have been harvested, controlled, or extirpated throughout much of their historical range (Musiani and Paquet 2004), and the additivity of human-caused mortality has been a primary subject of management debate (Adams et al. 2008, Creel and Rotella 2010, Gude et al. 2012, Creel et al. 2015. Although conventional hunting and trapping can limit wolf populations (Peterson et al. 1984, Ballard et al. 1997, Person and Russell 2008, wolf populations appear to sustain conventional harvest at rates of 22-29% of the annual fall population (Fuller et al. 2003, Adams et al. 2008, Creel et al. 2015. Because of difficulties in reducing populations through conventional hunting and trapping, more intensive wolf control programs have been implemented to further reduce densities in targeted areas with the goal of increasing ungulate abundance (Ballard et al. 1987;Gasaway et al. 1992;Boertje et al. 1996Boertje et al. , 2012Boertje et al. , 2017National Research Council 1997;Hayes et al. 2003). ...
... Vital rates may be altered during population reduction, allowing wolf populations to compensate numerically for increased mortality and changes in food supply. Change in dispersal rates has been suggested as the primary mechanism for short-term responses to changes in ungulate resources and low to moderate human exploitation (Fuller et al. 2003, Adams et al. 2008. Young wolves are most susceptible to conventional harvest and are also the most likely to disperse; therefore, conventional harvest may be partially compensated by reduced dispersal rates Boitani 2003, Adams et al. 2008). ...
Long-term wolf (Canis lupus) research programs have provided many insights into wolf population dynamics. Understanding the mechanisms controlling responses of wolf populations to changes in density, environmental conditions, and human-caused mortality are important as wolf management becomes increasingly intensive. Competition with humans for ungulate prey has led to large-scale wolf control programs, particularly in Alaska, and although wolf populations may sustain relatively high (e.g., 22–29%) rates of conventional harvest, control programs are specifically designed to have lasting population-level effects.
... Monitoring has also relied on deploying radio-and global positioning system (GPS)collars, which is increasingly challenging due to difficulty of capture and frequent collar loss caused by collar failures and mortalities. Furthermore, there is frequent turnover of packs, and public harvest can affect behavioral dynamics of wolves (Adams et al. 2008, Brainerd et al. 2008. ...
... There is no consensus for how harvest affects wolves (Fuller et al. 2003, Adams et al. 2008, Creel and Rotella 2010). Harvest appears to be mostly an additive source of mortality for yearlings and adults (Creel and Rotella 2010, Horne et al. 2019 and to reduce pup survival and recruitment (Ausband et al. 2015. ...
... This may be due to increased immigration into Montana or decreased dispersal (i.e., positive net immigration). Immigration and dispersal can be important processes in dynamics of wolf populations (Hayes and Harestad 2000, Fuller et al. 2003, Adams et al. 2008, Bassing 2017. It is unclear, however, whether net immigration occurs in Montana and if so, how it affects wolf population dynamics. ...
Improving estimation of wolf recruitment and abundance, and development of an adaptive harvest management program for wolves in Montana. Final Report for Federal Aid in Wildlife Restoration Grant W-161-R-1.
... illegal killing. Several studies have estimated it as rivaling or exceeding the subset of reported poaching detected and measured by authorities 9,10,15 . Therefore, in places where poaching is often cryptic, official estimates of mortality process and pattern are systematically biased to under-estimate the risk of poaching, unless analysts adequately account for uncertainty. ...
... A plausible hypothesis for how liberalized killing periods may increase the incidence of emigration of monitored wolves would be through legal killing possibly causing disruption of wolf behavioral and social dynamics [34][35][36] , leading to breeding pair dissolution or pack disbanding and perhaps increasing the number of dispersers leaving the state before the next monitoring period. However, the scientific evidence on the effects of anthropogenic mortality on wolf dispersal to date suggests the opposite effect; that low-to-moderate levels of anthropogenic mortality may instead be compensated by increased immigration from adjacent populations, and increased pup survival 15,37 . In their analysis of the effects of anthropogenic mortality on the wolf population in northern Alaska, Adams et al. 15 conclude that immigration was the main mechanism allowing otherwise unsustainable killing to continue for several years. ...
... However, the scientific evidence on the effects of anthropogenic mortality on wolf dispersal to date suggests the opposite effect; that low-to-moderate levels of anthropogenic mortality may instead be compensated by increased immigration from adjacent populations, and increased pup survival 15,37 . In their analysis of the effects of anthropogenic mortality on the wolf population in northern Alaska, Adams et al. 15 conclude that immigration was the main mechanism allowing otherwise unsustainable killing to continue for several years. Consistent with this, 7 times more radio-collared wolves entered Wisconsin from neighboring Michigan than went in the reverse direction, especially during the years with liberalized wolf-killing policies 5 . ...
Although poaching (illegal killing) is an important cause of death for large carnivores globally, the effect of lethal management policies on poaching is unknown for many populations. Two opposing hypotheses have been proposed: liberalizing killing may decrease poaching incidence (‘tolerance hunting’) or increase it (‘facilitated poaching’). For gray wolves in Wisconsin, USA, we evaluated how five causes of death and disappearances of monitored, adult wolves were influenced by policy changes. We found slight decreases in reported wolf poaching hazard and incidence during six liberalized killing periods, but that was outweighed by larger increases in hazard and incidence of disappearance. Although the observed increase in the hazard of disappearance cannot be definitively shown to have been caused by an increase in cryptic poaching, we discuss two additional independent lines of evidence making this the most likely explanation for changing incidence among n = 513 wolves’ deaths or disappearances during 12 replicated changes in policy. Support for the facilitated poaching hypothesis suggests the increase (11–34%) in disappearances reflects that poachers killed more wolves and concealed more evidence when the government relaxed protections for endangered wolves. We propose a refinement of the hypothesis of ‘facilitated poaching’ that narrows the cognitive and behavioral mechanisms underlying wolf-killing.
... Failed efforts often are attributed to the removal of too few predators over too small of an area or a lack of sustained effort (Valkenburg et al., 2004). Wolves can compensate for a high rate of mortality, showing little population change even following a 29%-40% annual reduction through human harvest (Adams et al., 2008;Hayes et al., 2003;Peterson et al., 1984;Webb et al., 2011). For example, Hervieux et al. (2014) reported no change in annual removal rates of wolves even following intensive removal (>100 wolves/year) over a 7-year period. ...
... For example, Hervieux et al. (2014) reported no change in annual removal rates of wolves even following intensive removal (>100 wolves/year) over a 7-year period. The mechanism for that demographic response is often immigration (i.e., spillover predation) or increased reproduction resulting from a lack of intraspecific competition for prey (Adams et al., 2008;Frenette et al., 2020). Similarly, where prey is abundant, coyotes can support annual mortality rates as high as 40% without noticeable changes in population density (Knowlton, 1972). ...
... For one thing, caribou are Endangered or Threatened and disappearing across much of their range. In comparison, wolves are not a species of conservation concern across most caribou ranges and they are resilient to high levels of harvest (Adams et al., 2008;National Research Council, 1997). That removes much of the concern of focused predator management resulting in the extirpation or loss of wolves, as was the history for the species across much of the United States (Musiani & Paquet, 2004). ...
Lethal population control has a history of application to wildlife management and conservation. There is debate about the efficacy of the practice, but more controversial is the ethical justification and methods of killing one species in favor of another. This is the situation facing the conservation of woodland caribou (Rangifer tarandus caribou) in Canada. Across multiple jurisdictions, large numbers of wolves (Canis lupus), and to a lesser extent bears (Ursus americanus) and coyotes (C. latrans), are killed through trapping, poisoning or aerial shooting to halt or reverse continued declines of woodland caribou. While there is evidence to support the effectiveness of predator management as a stop‐gap solution, questions remain about the extent to which this activity can make a meaningful contribution to long‐term recovery. Also, there are myriad ethical objections to the lethal removal of predators, even if that activity is in the name of conservation. Debates about predator management, just one of numerous invasive actions for maintaining caribou, are made even more complex by the conflation of ethics and efficacy. Ultimately, long‐term solutions for the recovery of caribou require governments to stop delaying difficult decisions that address the real causes of population decline, habitat change.
... lupus) until study of the mortality and poaching of Scandinavian wolves (Liberg et al. 2012). When Adams et al. (2008) documented that 74% of human-caused deaths went unreported in an Alaskan gray wolf population, even that high rate of loss of data on wolves did not raise concerns, perhaps because unreported killing seemed inconsequential to a large, resilient wolf population. Later, parallel analyses of Northern Rocky Mountain (NRM) gray wolves appeared to accept the assumption of uninformative censoring (Murray et al. 2010). ...
... It also raised questions about the assumption that unknown fates resembled known fates in mortality risk and rate (i.e., censoring was informative in the Scandinavian study). Further evidence of a problem with the latter assumption followed reanalysis of data from Adams et al. (2008), working in the Brooks Range of Central Alaska. Schmidt et al. (2015) reported at least 15% higher mortality among unmarked gray wolves compared to their marked pack-mates. ...
... If marked and unmarked animals experience differential per capita hazard rates, then marked animals will become less representative of the population as the relative risk of human-caused mortality increases. Such a relationship could account for the empirical observations of accelerating declines in wolf population growth as human-caused mortality increases (Adams et al. 2008;Creel and Rotella 2010;Vucetich 2012). ...
Measuring rates and causes of mortalities is important in animal ecology and management. Observing the fates of known individuals is a common method of estimating life history variables, including mortality patterns. It has long been assumed that data lost when known animals disappear were unbiased. We test and reject this assumption under conditions common to most, if not all, studies using marked animals. We illustrate the bias for 4 endangered Wolf populations in the United States by reanalyzing data and assumptions about the known and unknown fates of marked wolves to calculate the degree to which risks of different causes of death were mismeasured. We find that, when using traditional methods, the relative risk of mortality from legal killing measured as a proportion of all known fates was overestimated by 0.05-0.16 and the relative risk of poaching was underestimated by 0.17-0.44. We show that published government estimates are affected by these biases and, importantly, are underestimating the risk of poaching. The underestimates have obscured the magnitude of poaching as the major threat to endangered Wolf populations. We offer methods to correct estimates of mortality risk for marked animals of any taxon and describe the conditions under which traditional methods produce more or less bias. We also show how correcting past and future estimates of mortality parameters can address uncertainty about wildlife populations and increase the predictability and sustainability of wildlife management interventions. © The Author 2017. Published by Oxford University Press on behalf of American Society of Mammalogists.
... Although most wolf populations in the contiguous United States have been delisted, controversy persists partly due to public wolf harvests that commenced soon after delisting (Ausband, 2016;Creel and Rotella, 2010;Epstein, 2017;Hogberg et al., 2016;Mech, 2017;Olson et al., 2015). Well-informed wolf management requires understanding of key vital rates, including survival and causespecific mortality (Adams et al., 2008;Creel and Rotella, 2010;Gude et al., 2012;Murray et al., 2010;O'Neil et al., 2017;Smith et al., 2010Smith et al., , 2020Stenglein et al., 2015Stenglein et al., , 2018. Because wolves may have "a survival-driven life history compared to the recruitment-driven strategy of most harvested species" , information on anthropogenic (human-caused) mortality sources, such as harvest, based on estimates from individual-based models (rather than only population-level studies), is especially needed Stenglein et al., 2015). ...
... Our study area in the SNF included part of the federallydesignated Boundary Waters Canoe Area Wilderness, with no roads or motorized conveyances and with limited and regulated access during high human-use periods. The importance of wilderness, refugia, and/or protected areas to wolf population dynamics has been examined (Adams et al., 2008;Benson et al., 2014;Hebblewhite and Whittington, 2020;Mech, 1989;Smith et al., 2010Smith et al., , 2020, but our 50-year study was unique in that the wolf population 1) was long extant (i.e., not reintroduced or recolonized), 2) was not subject to harvest in our study area until recently, and 3) used both wilderness and adjacent, mainly public, nonwilderness. Because federally-designated wilderness (as defined in The 1964 Wilderness Act, Public Law 88-577, 16 U.S.C. 1131-1136) represents some of the least human-affected landscapes, assessments of wolf population dynamics there and in adjacent non-wilderness areas are important for better understanding human impacts on otherwise natural variation in wolf vital rates . ...
... We suspected that most natural mortality would be intraspecific strife (wolf-killed wolf, hereafter "strife") (Adams et al., 2008;Cubaynes et al., 2014;Mech, 1977), and we predicted that starvation and disease rates would be greater for pups than adults (Mech and Goyal, 1993, 1995, 2011Mech et al., 2008;Smith et al., 2020). Based on our field observations, we also expected increased illegal mortality to coincide with fall ungulate harvest seasons when higher opportunistic poaching was likely to occur. ...
We assessed the relative importance of wilderness to gray wolf (Canis lupus) population dynamics over 50 years in a population that 1) was long extant (i.e., not reintroduced or recolonized), 2) was not subject to harvest in our study area until recently, and 3) used both wilderness and adjacent, mainly public, non-wilderness. We analyzed the survival of radiocollared wolves (n = 756 collared-wolf tenures) during 1968–2018 in the Superior National Forest, Minnesota, USA, including the Boundary Waters Canoe Area Wilderness. Over 50 years, adult annual survival was 78%. Wolves captured in wilderness tended to exhibit higher survival than those captured in non-wilderness, but the difference was more pronounced during harvest years and post-harvest years when wilderness wolf survival remained relatively high and non-wilderness wolf survival dropped (relative to pre-harvest). During Nov–Apr of pre-harvest years for adults, the natural mortality rate was similar for non-wilderness wolves and wilderness wolves (both 6%), but the anthropogenic mortality rate was higher for non-wilderness wolves than wilderness wolves (7% versus 1%), as was the illegal mortality rate (5% versus 1%). During Nov–Apr of pre-harvest years, wilderness wolves were less likely to die than non-wilderness wolves (p = 0.042; hazard ratio = 0.59), pups were more likely to die than adults (p = 0.002; hazard ratio = 1.84), and males were less likely to die than females (p = 0.053; hazard ratio = 0.73). Our long-term wolf survival, cause-specific mortality, and hazard results will inform management agencies whenever wolves are delisted, and jurisdiction for them passes to states.
... The estimates of stabilizing levels of human-induced mortality that would be sustainable ranges from 28-29% (Adams et al., 2008) to 5-10% lower estimates by (Fuller et al., 2003;Creel & Rotella, 2010;Vucetich, 2012). A higher estimate by Gude et al. (2012) has been questioned because of seeming errors in calculations (Vucetich, 2012), so their higher estimate needs replication or correction. ...
... We use the preceding meaning of sustainability, not the other meaning of sustain suggesting a wolf population can withstand 1 or 2 years of higher rates of mortality before extirpation. Our justification apart from the literature comes from the Wisconsin DNR itself, using the Adams et al. (2008) estimate in prior wolf-hunting plans (Natural Resources Board, 2012;Natural Resources Board, 2014), citation of those quota plans in 2021 (Natural Resources Board, 2021a), and explicit mention of using a 24% threshold on 15 February 2021 (Natural Resources Board, 2021b). Evaluating sustainability of natural resource uses demands long-term data, so here we only discuss the 1-year outcome in light of the objectives. ...
... The latter works improved upon earlier efforts (Olson et al., 2015;Stenglein et al., 2015), as did (Stenglein, Wydeven & Deelen, 2018), but those we use here also improved by explicitly accounting for radio-collared wolves that disappeared as a function of the length of time wolves were exposed to policy periods that reduced ESA protections (Santiago-Ávila, Chappell & Treves, 2020). Unregulated and often undocumented illegal killing (poaching) exceeded legal, reported wolf-killing in every population studied thus far Adams et al., 2008;Liberg et al., 2012;Agan, Treves & Willey, 2020). Therefore, it is essential to accurate monitoring and quota-setting that prudent managers consider these additional deaths and count all mortality, or at least all anthropogenic mortality, when planning and communicating public hunting seasons. ...
Predators and their protection are controversial worldwide. Gray wolves, Canis lupus , lost U.S. federal protection (delisting) and the State of Wisconsin began lethal management first among all states and tribes that regained authority over wolves. Here we evaluated the initial success of reaching the state’s explicit objective, “…to allow for a sustainable harvest that neither increases nor decreases the state’s wolf population…” We used official state figures for hunter-killed wolves, population estimates from April 2017–2020, and the latest peer-reviewed model of individual wolf survival to estimate additional deaths resulting from federal delisting. More than half of the additional deaths were predicted to be cryptic poaching under the assumption that this period resembled past periods of liberalized wolf-killing in Wisconsin. We used a precautionary approach to construct three conservative scenarios to predict the current status of this wolf population and a minimum estimate of population decline since April 2020. From our scenarios that vary in growth rates and additional mortality estimates, we expect a maximum of 695–751 wolves to be alive in Wisconsin by 15 April 2021, a minimum 27–33% decline in the preceding 12 months. This contradicts the state expectation of no change in the population size. We draw a conclusion about the adequacy of regulatory mechanisms under state control of wolves and discuss the particular governance conditions met in Wisconsin. We recommend greater rigor and independent review of the science used by agencies to plan wolf hunting quotas and methods. We recommend clearer division of duties between state wildlife agencies, legislatures, and courts. We recommend federal governments reconsider the practice of sudden deregulation of wolf management and instead recommend they consider protecting predators as non-game or transition more slowly to subnational authority, to avoid the need for emergency relisting.
... Nevertheless, mean pack size was not a significant predictor of annual population dispersal rates (Jimenez et al., 2017). Most dispersals are documented during late autumn, winter and spring (Fritts & Mech, 1981;Peterson, Woolington & Bailey, 1984;Ballard, Whitman & Gardner, 1987;Mech, 1987;Fuller, 1989;Gese & Mech, 1991;Boyd et al., 1995;Boyd & Pletscher, 1999;Kojola et al., 2006;Adams et al., 2008;Jimenez et al., 2017). Several studies speculated that social interactions within packs occurring during these periods act as ultimate determinants: food shortage for yearlings resulting from large pups still being provisioned with food during late autumn (Mech et al., 1998; Factors that influence individual strategies at each dispersal stage and that we grouped as individual, social, and environmental (i.e. ...
... spring) (Boyd & Pletscher, 1999). One study found that changes in dispersal rate across seasons applied only to young individuals, while adults older than 2 years dispersed at a similarly low rate throughout the year (Adams et al., 2008). Finally, breeder turnover in an established population did not affect the number of helpers aged ≥2 years present in groups (Ausband, Mitchell & Waits, 2017), suggesting that subordinates do not exhibit increased dispersal after breeder turnover. ...
... A widespread belief is that wolf populations can compensate for human exploitation rates of ≤0.29 wolves per year. This arose from the observation that exponential growth rates reported from North American wolf studies were generally positive or stable below annual humancaused mortality rates of 0.29 wolves [see Adams et al., 2008 for an update of Fuller, Mech & Cochrane, 2003]. Adams et al. (2008) concluded that compensation occurred via adjustments in dispersal components (i.e. ...
Dispersal is a key demographic process involving three stages: emigration, transience and settlement; each of which is influenced by individual, social and environmental determinants. An integrated understanding of species dispersal is essential for demographic modelling and conservation planning. Here, we review the dispersal patterns and determinants documented in the scientific literature for the grey wolf (Canis lupus) across its distribution range. We showed a surprisingly high variability within and among study areas on all dispersal parameters – dispersal rate, direction, distance, duration and success. We found that such large variability is due to multiple individual, social and environmental determinants, but also due to previously overlooked methodological research issues. We revealed a potential non-linear relationship between dispersal rate and population density, with dispersal rate higher at both ends of the gradient of population density. We found that human-caused mortality reduces distance, duration and success of dispersal events. Furthermore, dispersers avoid interaction with humans, and highly exposed areas like agricultural lands hamper population connectivity in many cases. We identified numerous methodological research problems that make it difficult to obtain robust estimates of dispersal parameters and robust inferences on dispersal patterns and their determinants. In particular, analyses where confounding factors were not accounted for led to substantial knowledge gaps on all aspects of dispersal in an otherwise much-studied species. Our understanding of wolf biology and management would significantly benefit if wolf dispersal studies reported the results and possible factors affecting wolf dispersal more transparently.
... Gray wolves (Canis lupus) are a cooperatively breeding carnivore known for long-distance dispersal that also experience sustained harvest throughout most of their current distribution. Adams et al. (2008) estimated wolf populations can withstand a mean annual harvest of ≤29% and maintain stable densities, suggesting some cooperatively breeding species can compensate for harvest mortality up to a certain threshold; above this annual rate, harvest can lead to population declines in wolves (e.g. Ballard, Whitman & Gardner, 1987;Person & Russell, 2008). ...
... Ballard, Whitman & Gardner, 1987;Person & Russell, 2008). There is limited evidence that natural mortality decreases in response to low or intermediate levels of harvest mortality in wolf populations (Adams et al., 2008, but see Murray et al., 2010). Reproductive success is lower in groups when breeder mortality occurs (Brainerd et al., 2008), and groups recruit fewer offspring into the adult population when harvest occurs . ...
... Changes in natural mortality and reproduction did not appear to offset harvest mortality in central Idaho Horne et al., 2019), leaving immigration from adjacent populations as a reasonable explanation for how groups could compensate for harvest mortality in this region. Additionally, immigration is presumably an important process for persistence of heavily harvested populations of wolves, even if natural mortality also declines at higher harvest rates (Adams et al., 2008). Therefore, immigration into groups should be an important compensatory process in south-western Alberta as well. ...
The effects of harvest on cooperatively breeding species are often more complex than simply subtracting the number of animals that died from the group count. Changes in demographic rates, particularly dispersal, could offset some effects of harvest mortality in groups but this is rarely explored with cooperative breeders. We asked whether a cooperatively breeding species known for long‐distance dispersal could compensate for the effect of harvest mortality on density by adopting immigrants into the group. We used genetic samples to estimate the minimum density of gray wolves (Canis lupus) and proportion of immigrants in groups in the northern US Rocky Mountains after an annual harvest regime was initiated and in the Canadian Rocky Mountains where wolves were managed consistently under an annual harvest regime. We tested whether immigration (1) compensated, (2) partially compensated or (3) did not compensate numerically for harvest mortality in groups and hypothesized immigration would increase with increasing harvest intensity. Density of wolves in groups declined after harvest was initiated whereas immigration into groups was consistently low and did not change with harvest in the US study area. Immigration into groups was similarly low and density even lower in the Canadian study area compared to the US study area. Our results indicate immigration did not compensate for harvest mortality in groups in two separate populations of a cooperatively breeding carnivore. We hypothesize the social structure of wolf groups may limit the potentially compensatory response of immigration in some populations. The effects of hunting and trapping on cooperatively breeding species are complex but changes in demographic rates, like dispersal, may offset some effects of harvest on groups. Using noninvasive genetic data, we tested whether compensatory immigration maintained the density of group‐dwelling gray wolves (Canis lupus) when public harvest occurred in two populations of wolves in the US and Canadian Rocky Mountains. We found the density of group‐dwelling wolves decline after harvest but immigration into the groups was consistently low, suggesting that immigration did not offset harvest mortality within groups. Photo credit: Spencer Rettler.
... We derived the distribution from a beta-binomial model with parameters a and b estimated from an integrated population model fit to count and known-fate data from Idaho, USA, 2005USA, -2016 in our study, and compensation could have occurred through reductions in senescent-related mortality rates. Additionally, Adams et al. (2008) reported no relationship between natural versus harvest mortality in studies where harvest was 0.29. However, for populations with harvest >0.29, natural mortality was half the amount of populations with lower harvest rates. ...
... However, for populations with harvest >0.29, natural mortality was half the amount of populations with lower harvest rates. Thus, Adams et al. (2008) concluded that a threshold of 29% harvest mortality must be reached before reductions in natural mortality compensate for harvest. Given these observations, our harvest may have been too low to result in compensatory effects with non-harvest mortality. ...
... Alternatively, an increase in recruitment may occur when wolves are harvested from packs, particularly during times of low prey availability, because competition within the pack is reduced (Malcolm andMarten 1982, Harrington et al. 1983). Our estimate of mean mid-year recruitment (4.0 wolves/pack) is similar to several other studies (Ballard et al. 1987, Fuller 1989, McNay et al. 2006, Adams et al. 2008, Webb et al. 2011), but we found no change in mid-year recruitment post-harvest. Thus, our results do not support or refute either of the hypotheses related to the positive or negative effects of harvest on pup survival up to 1 October of their birth year. ...
... Models using empirical data from wolves, tigers (Panthera tigris), leopards (P. pardus), and mountain lions (Puma concolor) suggest total mortality rates higher than 15-31% cannot be sustained (Adams et al. 2008;Chapron et al. 2008;Vucetich 2012). The models are supported by estimates from 8 populations, whose growths were slowed or reversed by mortality rates of 19-37% or human-caused mortality rates of 14-32% (Whitman et al. 2004;Woodroffe and Frank 2005;Goodrich et al. 2008;Creel and Rotella 2010;Smith et al. 2010;Liberg et al. 2012;Vucetich 2012;Artelle et al. 2013). ...
... Although population growth and decline is becoming better understood, scientific uncertainty persists about the indirect responses of individual carnivores and social groups to human-caused mortality. Local sinks (sites with very high levels of mortality) and superadditive mortality (direct killing that results in additional, indirect deaths due to breeding failure, infanticide, social group dissolution, etc.) may diminish large carnivore populations across broader regions than the localities around each death (Swenson et al. 1997;Andren et al. 2006;Loveridge et al. 2007;Adams et al. 2008;Brainerd et al. 2008;Person and Russell 2008;Borg et al. 2015). Furthermore, the common management tactic of setting future quotas according to past rates of legal human-caused mortality (Logan and Sweanor 2001) may amplify natural oscillations in the sizes of hunted populations and thereby raise the probability of a population crash (Fryxell et al. 2010). ...
... Unreported wolf mortality is not new. Adams et al. (2008) reported 73% of "harvested" wolves were not reported to the state authorities. Both reported poaching and unreported poaching merit deeper scrutiny because we found no correlation between annual rates of the 2. Therefore, estimating poaching rates from only the reported cases seems incorrect, contra Olson et al. (2014). ...
Starting in the 1970s, many populations of large-bodied mammalian carnivores began to recover from centuries of human-caused eradication and habitat destruction. The recovery of several such populations has since slowed or reversed due to mortality caused by humans. Illegal killing (poaching) is a primary cause of death in many carnivore populations. Law enforcement agencies face difficulties in preventing poaching and scientists face challenges in measuring it. Both challenges are exacerbated when evidence is concealed or ignored. We present data on deaths of 937 Wisconsin gray wolves (Canis lupus) from October 1979 to April 2012 during a period in which wolves were recolonizing historic range mainly under federal government protection. We found and partially remedied sampling and measurement biases in the source data by reexamining necropsy reports and reconstructing the numbers and causes of some wolf deaths that were never reported. From 431 deaths and disappearances of radiocollared wolves aged > 7.5 months, we estimated human causes accounted for two-thirds of reported and reconstructed deaths, including poaching in 39-45%, vehicle collisions in 13%, legal killing by state agents in 6%, and nonhuman causes in 36-42%. Our estimate of poaching remained an underestimate because of persistent sources of uncertainty and systematic underreporting. Unreported deaths accounted for over two-thirds of all mortality annually among wolves > 7.5 months old. One-half of all poached wolves went unreported, or > 80% of poached wolves not being monitored by radiotelemetry went unreported. The annual mortality rate averaged 18% ± 10% for monitored wolves but 47% ± 19% for unmonitored wolves. That difference appeared to be due largely to radiocollaring being concentrated in the core areas of wolf range, as well as higher rates of human-caused mortality in the periphery of wolf range. We detected an average 4% decline in wolf population growth in the last 5 years of the study. Because our estimates of poaching risk and overall mortality rate exceeded official estimates after 2012, we present all data for transparency and replication. More recent additions of public hunting quotas after 2012 appear unsustainable without effective curtailment of poaching. Effective antipoaching enforcement will require more accurate estimates of poaching rate, location, and timing than currently available. Independent scientific review of methods and data will improve antipoaching policies for large carnivore conservation, especially for controversial species facing high levels of human-induced mortality.
... vehicle strike) , Gude et al. 2012, Stenglein et al. 2015a. The relative influence of human-caused mortality is debated (Creel and Rotella 2010, Gude et al. 2012, with some subpopulations apparently sustaining high mortality rates (Adams et al. 2008, Creel and Rotella 2010, Mech and Boitani 2010. Monitoring and precise estimation of adult survival in the presence of human-caused mortality is a key input for effective management. ...
... Recent estimates have ranged from 0.75 (Wydeven et al. 2009b) to 0.79 (Adams et al. 2008, Wydeven et al. 2009a, Cubaynes et al. 2014. However, the spatiotemporal landscape of survival has not been explored with the detail provided here. ...
... Survival rates for wolves have historically been lowest where human influence is high. Annual estimates have ranged from 0.55 -0.85 for wolves > 1 year old in generally unexploited populations (Fuller et al. 2003, Adams et al. 2008, Benson et al. 2014, Stenglein 2014). However, lower (0.34 -0.54) survival estimates have been recorded for wolves subject to significant annual take (Person and Russell 2008), and lower estimates often correspond with areas of lower habitat quality , Stenglein 2014, Stenglein et al. 2015a. ...
All natural processes are dynamic in space and time. Establishing the links between spatiotemporal patterns and ecological processes is critical for improving our understanding of natural systems. Empirical data representing wildlife populations is accumulating and increasingly involves spatiotemporal components. Wildlife monitoring programs for threatened, endangered, or other species of interest often involve radio-tracking of a sample of individual animals combined with census data. Such data are valuable both for conservation and management of populations and for testing ecological theories about species distribution and what influences patterns over time. We used 20 years of radio telemetry and snow tracking data to evaluate spatiotemporal patterns in gray wolf (Canis lupus) distribution, habitat selection, survival, and mortality in the Upper Peninsula (UP) of Michigan, USA. Wolves recolonized the study area during the early 1990s and exceeded a population size of 600 individuals before the end of the study. In addition, wolves were on the Endangered Species List during the majority of the study. This work therefore explores the spatial ecology of endangered wolves during a period of population recovery. We analyzed winter prey distributions of wolves, evaluated theoretical and modern empirically-driven models of density dependent habitat selection, estimated annual survival, and explored cause-specific mortality. Our methods included isodar analysis, spatiotemporal generalized linear mixed models of habitat selection, proportional hazards models with time-dependent spatial covariates, and competing risks analysis. Winter prey distributions exhibited a habitat functional response depending on winter snow conditions, resulting in a geographic prey limitation that affected wolf territory occupancy within the study area. Density-dependence in habitat selection revealed that wolf selection patterns were more consistent with an ideal-preemptive habitat distribution, as opposed to the ideal-free distribution. Density-dependent habitat selection patterns revealed decreasing selection for prey availability at greater wolf densities, while selection for anthropogenic features such as road density increased. However, selection across time exhibited occupancy-dependence as opposed to density-dependence. Wolf annual survival was ~ 75% and was influenced by sex, age, transient status, agriculture, habitat edge, wolf density, and Julian day, as well as several individual factors. Survival declined as wolf density increased, resulting in a shifting mosaic of wolf survival. Human-caused mortality increased with wolf density and was the primary mortality source of UP wolves, comprising ~ 17% annually. Much of human-caused mortality was attributed to illegal killing. Human-caused mortality was partially compensated for by natural mortality, and negative impacts on population growth rate were most evident when human-caused and natural mortality were both high. The spatial ecology of wolves in this study describes patterns associated with a growing and shifting population. Density-dependent effects population dynamics occurred with expanding wolf range, where later colonizers were forced to utilize habitats closer to human populations. Theoretical tests revealed potential for source-sink population dynamics. Evidence suggested the population had stabilized by the end of the study, and that suitable habitat was saturated. Future conservation of the population will likely depend on preservation of high quality source habitats and managing human conflicts associated with high wolf density areas occurring near population centers.
... A shorter lifespan due to high hunting pressure can cause higher breeder turnover in the population, thus reducing social and spatial stability. Disrupted population structure can lead to changes in animal behavior and dispersal patterns, reproduction rates, and genetic parameters, as well as the demographic and kinship structure of the population [18,[60][61][62], which in turn can have negative effects on species long-term fitness, conservation, and sustainability [27,56,63]. Additionally, younger animals may lack knowledge and experience to be proficient hunters and therefore resort to livestock depredation [18]. ...
... From a hunter's perspective, wolf culling in Latvia is considered to be unselective because of difficulties in distinguishing the sex (and, from autumn, also age) of a wolf in a hunting situation and a tendency to use every available opportunity to kill a wolf. Therefore, more vulnerable or less fit individuals are more likely to be culled [60]. ...
Large carnivores are essential components of natural ecosystems. In populated areas, their conservation depends on preserving a favorable status in coexistence with humans, which may require the elimination of excess carnivores to minimize public concerns. As the Baltic region currently hosts a thriving wolf population, locally sustainable management of wolves is important for preserving biodiversity at a European scale. In this paper, we provide a dynamic assessment of the Latvian wolf subpopulation from 1998 until 2020. This study is based on age composition and fecundity data from teeth, uteri, and ovaria inspections obtained from samples of legally culled or accidentally killed individuals. The abundance estimates indicated population growth that exceeded the previously predicted carrying capacity. The proportion of juveniles among the culled individuals increased in recent years, but the mean age of culled adults exhibited a stable trend. In presumably nonselective hunting, the juveniles and individuals older than 3 years had greater culling mortality estimates in comparison with other age classes, and the culling rates for adult females of particular age classes were higher than for males of the same age. While creating significant hunting pressure, wolf management in Latvia may have contributed to the population growth by affecting its demographic processes.
... mean 0.14) is comparable or higher than most reported poaching rates on wolves. In North America, reported poaching rates commonly range between 0.05 and 0.10 (Adams et al., 2008;Pletscher et al., 1997;Stenglein et al., 2018). In a large study from three adjacent areas in Northern Rocky Mountains in USA, the average annual rate of poaching was 0.06 . ...
... Based on data from 18 North American wolf populations, Fuller (1989) concluded that the breaking point was 0.29, and at lower levels humancaused mortality was compensatory to other mortality (but see Stenglein et al., 2018 for further discussion on the role of compensatory mortality in wolves). This estimate was supported in a later study (Adams et al., 2008). Creel and Rotella (2010) demonstrated considerably lower levels, i.e. 0.22 for the Northern Rocky Mountain population, and 0.25 for other North American wolf populations, but their results were questioned by Gude et al. (2012) for including years with poor monitoring in their analysis and not considering variation in recruitment rates. ...
Poaching is an important limiting factor for many large carnivore populations worldwide and the effect that legal culling has on poaching rate on wolf (Canis lupus) is debated. We used data linked to population monitoring and research to analyze rate and risk of disappearance without known cause for territorial pair-living wolves (n = 444) in Sweden 2000/01–2016/17. Known mortalities included legal kills (n = 103), natural causes (n = 23), traffic (n = 8) and verified poaching (n = 20) but most (n = 189) wolves disappeared without known cause. Careful evaluation of alternative causes supported the assumption that poaching was the most likely reason for the majority of these disappearances. Disappearance rate was0.14 for the entire study period, and increased from 0.09 in 2000/01–2009/10 to 0.21 in 2010/11–2016/17, while a Kaplan-Meier analysis on a sub-sample of radio collared wolves (n = 77) gave an average annual poaching rate of 0.12 for the entire study period and 0.10 and 0.18 for the corresponding two sub-periods. Factors affecting disappearance rate were modeled using logistic regression and Cox proportional hazards regression. Population size had a strong positive effect on disappearance rate in both models, whereas legal culling rate had a negative effect, significant only in the Cox model. The combined effect of legal culling rate and disappearance rate during the latter part of our study period has halted population growth. Our results contribute to an increased understanding of two vital drivers predicted to affect poaching rate: population size and legal culling.
... Mortality and mortality risk had variable effects on wolf group sizes ( Figure 4; size relatively unaffected at low levels of harvest through potential effects on dispersal decisions; however, populations declined at higher harvest rates (Adams et al. 2008). Similarly, wolf group sizes in southern Alaska declined at higher harvest rates (Peterson et al. 1984 individuals (Brainerd et al. 2008). ...
... Dispersal in response to greater harvest intensity would serve to replenish breeder or territory vacancies quickly, which in turn could lead to more compensation under intensive harvest than may otherwise be expected. We suspect effects on dispersal and take of transient wolves helps explain the apparent overall stability of some harvested wolf populations like ours despite years of intensive harvest (Fuller et al. 2003, Adams et al. 2008, Inman et al. 2019). ...
Group living is found in only 10–15% of carnivorans and can shape demographic processes. Sociality is associated with benefits including increased ability to acquire resources, decreased risk of mortality, and increased reproductive success. We hypothesized that carnivore group size is influenced by conditions related to competition, prey, and mortality risk, which should affect benefits and costs of sociality and resulting demographic processes. We evaluated our hypotheses with gray wolves (Canis lupus) using a 14‐year dataset from a large, heavily managed population in the northern Rocky Mountains, USA. Annual mean group size ranged 4.86–7.03 and averaged 5.92 overall. Most groups were relatively small, with 80% containing ≤8 members. Groups were larger in areas with higher densities of conspecific groups, and smaller where prey availability was low. Group sizes remained largely stable while the population was unharvested or under low‐intensity harvest but declined under high‐intensity harvest. Results support the hypothesis that as habitat becomes saturated, inclusive fitness may become increasingly important such that subordinates delay dispersal. In addition to direct implications for birth and deaths, conditions related to prey and mortality risk may also influence dispersal decisions. Our work also provided a model to predict group size of wolves in our system, directly fulfilling a management need. We hypothesized that carnivore group size is influenced by conditions related to competition, prey, mortality, and mortality risk, which should affect benefits and costs of sociality and resulting demographic processes. We evaluated our hypotheses on gray wolves (Canis lupus) and found that groups were larger in areas with higher densities of conspecific groups, and smaller where prey availability was low. Group sizes remained largely stable while the population was unharvested or under low‐intensity harvest but declined under high‐intensity harvest.
... Harvest mortality in this region was likely similar to that in adjacent westcentral Alberta, where the annual harvest rate for wolves was reported to be approximately 35% of the regional wolf population (Robichaud andBoyce 2010, Webb et al. 2011). Given that population growth appears to decline once harvest mortality exceeds approximately 29% of a wolf population (Adams et al. 2008), we considered the harvest rate in southwestern Alberta to be relatively high. ...
... Contrary to the hypothesis that harvested populations of wolves are often sustained by immigrants dispersing into the population (Ballard et al. 1987, Haight et al. 1998, Hayes and Harestad 2000, Fuller et al. 2003, most individuals adopted into the packs that we genetically sampled dispersed from neighboring packs (i.e., packs within the study area or ones on the periphery; Bassing 2017). This suggests pack stability and occupancy were generally maintained from within the population, supporting the hypotheses that reduced emigration can offset harvest mortality (Adams et al. 2008). We found a weak positive relationship between detection probability and harvest of wolves. ...
Harvesting gray wolves (Canis lupus) could affect the abundance and distribution of packs, but the frequency of change in pack occurrence (i.e., turnover) and relative effects of harvest compared to environmental factors is unclear. We used noninvasive genetic sampling, hunter surveys, and occupancy models to evaluate the effect of harvest on occurrence and turnover of packs in a population of wolves managed with intensive harvest in the Canadian Rocky Mountains, 2012–2014. We tested 2 alternative hypotheses: the abundance and distribution of wolf packs were dynamic because of harvest or the abundance and distribution of wolf packs were generally stable regardless of harvest. We found the mean annual probability for wolf pack occupancy ranged 0.72–0.74 and the estimated distribution of wolf packs was consistent over time, 2012–2014. Our top model indicated wolf pack occupancy was positively associated with forest cover and the probability of detecting a wolf pack was positively associated with the intensity of harvest for wolves in that area. We observed frequent turnover of individuals within packs that were genetically sampled consecutive years but not of entire packs. Because turnover of packs occurred infrequently during our study, we could not reject our hypothesis that occurrence of packs was generally stable in a harvested population of wolves. Our results suggest environmental factors have a stronger effect than harvest on the abundance and distribution of wolf packs in southwestern Alberta, but harvest appears to strongly influence turnover of individuals within packs. We hypothesize local dispersal from within the study area and neighboring packs on the periphery of the study area helped promote pack stability.
... Although not included in our analyses, predator avoidance may be an additional factor influencing CAH winter range selection, since predation pressure is likely different between the two general wintering areas. During snow-free months, wolves (Canis lupus), grizzly bears (Ursus arctos), and golden eagles (Aquila chrysaetos) prey on CAH caribou, but in winter, wolves are expected to be their primary predator [137,138]. Wolf surveys report higher wolf densities in the BR mountains (6 wolves per 1000 km 2 ; [137]) than further north on the tundra of the coastal plain (2-4 wolves per 1000 km 2 ; [139]). Further research is needed to understand how forage availability and predation pressure, and their interaction with snow, may affect the CAH selection of winter range location and local movement once on winter range. ...
... During snow-free months, wolves (Canis lupus), grizzly bears (Ursus arctos), and golden eagles (Aquila chrysaetos) prey on CAH caribou, but in winter, wolves are expected to be their primary predator [137,138]. Wolf surveys report higher wolf densities in the BR mountains (6 wolves per 1000 km 2 ; [137]) than further north on the tundra of the coastal plain (2-4 wolves per 1000 km 2 ; [139]). Further research is needed to understand how forage availability and predation pressure, and their interaction with snow, may affect the CAH selection of winter range location and local movement once on winter range. ...
Background
Caribou and reindeer across the Arctic spend more than two thirds of their lives moving in snow. Yet snow-specific mechanisms driving their winter ecology and potentially influencing herd health and movement patterns are not well known. Integrative research coupling snow and wildlife sciences using observations, models, and wildlife tracking technologies can help fill this knowledge void.
Methods
Here, we quantified the effects of snow depth on caribou winter range selection and movement. We used location data of Central Arctic Herd (CAH) caribou in Arctic Alaska collected from 2014 to 2020 and spatially distributed and temporally evolving snow depth data produced by SnowModel. These landscape-scale (90 m), daily snow depth data reproduced the observed spatial snow-depth variability across typical areal extents occupied by a wintering caribou during a 24-h period.
Results
We found that fall snow depths encountered by the herd north of the Brooks Range exerted a strong influence on selection of two distinct winter range locations. In winters with relatively shallow fall snow depth (2016/17, 2018/19, and 2019/20), the majority of the CAH wintered on the tundra north of the Brooks Range mountains. In contrast, during the winters with relatively deep fall snow depth (2014/15, 2015/16, and 2017/18), the majority of the CAH caribou wintered in the mountainous boreal forest south of the Brooks Range. Long-term (19 winters; 2001–2020) monitoring of CAH caribou winter distributions confirmed this relationship. Additionally, snow depth affected movement and selection differently within these two habitats: in the mountainous boreal forest, caribou avoided areas with deeper snow, but when on the tundra, snow depth did not trigger significant deep-snow avoidance. In both wintering habitats, CAH caribou selected areas with higher lichen abundance, and they moved significantly slower when encountering deeper snow.
Conclusions
In general, our findings indicate that regional-scale selection of winter range is influenced by snow depth at or prior to fall migration. During winter, daily decision-making within the winter range is driven largely by snow depth. This integrative approach of coupling snow and wildlife observations with snow-evolution and caribou-movement modeling to quantify the multi-facetted effects of snow on wildlife ecology is applicable to caribou and reindeer herds throughout the Arctic.
... In addition, the overall frequency of winter packs composed by just two wolves in our study (18%, 160 packyears) was somewhat lower than in other studies (e.g. 25% in Adams et al 2008;31% in Kittle et al. 2015; metrics estimated from the data reported in both studies). There were fewer estimates of summer wolf pack size in the literature (Table 3), despite that summer observations can provide estimates of reproductive success. ...
... Thus they do not indicate average number of pups per pack because wolf populations include substantial though variable proportion of non-breeding and unsuccessful packs: 15% in protected areas without lethal management (e.g. Denali National Park, Alaska, Mech et al. 1998), and up to 20% in protected areas with some lethal management (Adams et al. 2008). Mitchell et al. (2008) found that smaller packs living in areas with high human-caused mortality rates in the Rocky Mountains of the U.S. had lower probability of raising pups, and there were between 16 and 28% of unsuccessful packs. ...
Group living is an important behavioral feature in some species of mammals, although somewhat uncommon in the Order Carnivora. Wolves Canis lupus are highly social and cooperative carnivores that live in family groups, i.e. packs. The number of wolves in a pack affects social, reproductive and predatory behavior, thus conditioning population dynamics. Despite its relevance to management decisions, pack size has not been thoroughly studied in populations inhabiting human dominated landscapes such as the Iberian Peninsula. We estimated variation of wolf pack size from 1990 to 2018 in
northern Spain, both in winter and summer. Winter data corresponded to direct observations and snow tracking at 42 localities (n = 253 data, 160 pack-years), whereas summer data corresponded to observations at rendezvous sites at 22 localities (n = 237 data, 43 pack-years). We estimated average pack size from the largest number of wolves recorded at each locality and year. Winter pack size averaged 4.2 ± 1.7 (mean ± SD) individuals. At summer rendezvous sites adult/subadult wolves (older than one year) averaged 3.1 ± 1.3 individuals, whereas pups averaged 4.0 ± 1.9. Generalized linear mixed
models (GLMM) showed that pack size declined through the winter from 4.9 (4.2–5.6, 95% CI) wolves in November to 3.8 (2.9–4.9, 95% CI) wolves in April. We found no trend in pack size, neither in winter nor in summer. We discuss our results compared with other studies and populations worldwide, and its usefulness to comprehend the dynamics of this vulnerable population.
... A frequent albeit crude approach to the discussion focuses on the percentage of the wolf population taken each year. A 30% exploitation threshold has been often used as benchmark for numerical sustainability of wolf populations, but with a large uncertainty on that threshold (reviewed in Fuller et al. 2003; see also Adams et al. 2008). To apply that benchmark to the Iberian wolf population, we would need to know several population parameters that are just not available. ...
... Dispersing wolves travel through unfamiliar terrain, and sometimes through already held wolf territories, which increases their risk of being hunted or culled (Mech and Boitani 2003;Schmidt et al. 2017). There is evidence that exploitation reduces local dispersal, emigration, and immigration of wolves, either as direct demographic compensation for human exploitation (Adams et al. 2008) or as a consequence of reduced intraspecific competition (Rick et al. 2017). ...
In previous centuries, wolves were extirpated across much of their range worldwide, but they started to recover in Europe since the end of last century. A general pattern of this recovery is the expansion of the range occupied by local populations. The Iberian wolf population, shared by Portugal and Spain, reached its lowest extent and abundance around the middle of the twentieth century. Unlike other populations in Europe, its range recovery and pack counts seem to have stalled since the first Spanish country-wide census of 1986–1988. The population shows low effective population size and remains isolated from other European wolves. This is unexpected given the protection offered by European legislation, i.e., the Habitats Directive, and the apparent availability of habitat outside its present range. We compiled records of wolves killed legally in Spain, reviewed the legislative and management framework for the Iberian wolf population, and discussed potential implications of a policy of lethal management for the ecology, genetics and conservation status of wolves in the Iberian Peninsula. Wolves are strictly protected in Portugal. Meanwhile, they are subject to culling and hunting in Spain. No wolf was legally removed by culling or hunting during the study period in Portugal, whereas 623 wolves were legally killed in Spain between 2008 and 2013. Twenty-nine of those wolves were killed in areas under strict protection according to European legislation. Despite the transboundary nature of this wolf population, we are not aware of coordinated conservation plans. Management is further fragmented at the sub-national level in Spain, both due to the authority of Spanish autonomous regions over their wildlife, and because wolves were listed in multiple annexes of the Habitats Directive. Fragmentation of management was apparent in the uneven adherence to the obligations of the Habitats Directive among Spanish regions. A similar situation is found for other large predator populations in Europe. We suggest that lethal management as carried out in Spain is a hindrance to transit and settlement of wolves, both within and beyond the Iberian wolf population. Reducing the pressure of lethal management appears a feasible policy change to improve the conservation status of the population and foster transboundary connectivity.
... The reported harvest of 218 animals (Johnson and Schneider, 2021) equaled 20% of the state's wolf population; the number of unrecovered crippling loss or animals intentionally left unretrieved is unknown. Only later was it discovered that a computing error existed in the application of the harvest model (Adams et al., 2008) that the Wisconsin Department of Natural Resources (WDNR) used to inform the quota setting process (D. MacFarland per. ...
... On the basis of studies such as Brainerd et al. (2008) which examined the impacts of breeder loss, Wisconsin's Green Fire estimated that 24-40% of recruitment was likely lost (Wisconsin's Green Fire, 2021). While harvest models such as Fuller et al. (2003) and Adams et al. (2008) suggest the population could recover to pre-hunt levels in 2-3 years if no further harvest were to take place, the WDNR was forced to begin preparing for a fall season to comply with Wisconsin Act 169, legislation that requires an annual season whenever wolves are not on the Wisconsin or Federal endangered species list. However, the fall 2021 season was halted by a stay issued in State court (Great Lakes Wildlife Alliance et al.;v. ...
In February 2021, the Wisconsin DNR implemented a wolf season in which > 20% of the population was killed in 63 h. Wisconsin’s Ojibwe tribes had a visceral reaction to this killing. This paper provides a perspective for this reaction by reviewing the Ojibwe relationship with Ma’iingan. This relationship maintains that Ma’iingan and Ojibwe are to be considered relatives whose fates are intertwined. Ma’iingan and Ojibwe have lived parallel histories, suffering from the effects of colonization, the decimation of wolf populations and decline of tribal culture. The Ojibwe tribes ceded vast territories in treaties with the United States while retaining common use rights, including the right to hunt and fish. These rights were reaffirmed just as wolves were reestablishing themselves in Wisconsin. The tribes continue to strengthen their culture, while wolf populations continue to recover. By examining these comparative histories, it becomes apparent that “whatever happens to one happens to the other.” Unfortunately, Ma’iingan were not adjudicated during the Wisconsin treaty case, creating uncertainty over how the relationship between the Ojibwe and Ma’iingan is to be respected by the state. The tribes believe their treaty right includes protection for wolves, so that wolves can fulfill their cultural and ecological purposes. Tribes maintain that Ma’iingan should determine their own population levels, in order to provide ecological and cultural benefits. A respectful and appreciative relationship with Ma’iingan should be maintained so that the future well-being of both Ma’iingan and the Ojibwe will be assured.
... Most mortality was caused by wolf-caused mortality in this protected population (~40% of all mortality rates were intraspecific wolf caused mortality). In comparison, it is remarkable that we found zero wolf-caused mortality in BNP, yet low intraspecific mortality is a hallmark of exploited populations (Adams et al., 2008;Webb et al., 2011). In a similar transboundary protected area setting, Benson et al. (2014) studied survival of 147 wolves in Algonquin PP in Ontario, Canada, and found that wolf survival declined outside of buffered protected areas as hunting and trapping access (secondary road) increased. ...
... Another has to do with whether human-caused mortality compensates with mortality from 'natural', non-human causes such as disease, starvation or intraspecific mortality. In a review across studies Adams et al. (2008) found little evidence for compensation between human-caused mortality and natural mortality if human-caused mortality is <29%. In adjacent provincial lands of Alberta, Webb et al. (2011) reported > 1-year old survival of 84 wolves was 0.62 and that trapping mortality (0.22) was twice that of hunting mortality (0.12). ...
Large carnivores are important ecological drivers of ecosystem dynamics when they occur at ecologically effective densities. They are also challenging to conserve, especially in transboundary settings such as along borders of parks and protected areas. Here, we tested for effects of transboundary movements on survival of 72 radiocollared gray wolves from 1987 to 2018 in and adjacent to Banff National Park, Canada. We fit Bayesian counting-process survival models to known-fate radiotelemetry data and tested for the influence of intrinsic covariates such as sex and age, time, and movements outside of protected areas on survival of wolves. We also estimated cause-specific mortality. Non-parametric survival was 0.733 (95% CI 0.622–0.816), and the top Bayesian survival model indicated that wolves outside the park had much lower annual survival rates (0.44, 95% BCI = 0.24–0.65) compared to wolves inside the park (0.84, 95% BCI = 0.73–0.91). The cumulative risk of mortality was on average 6.7 times higher (odds ratio 95% BCI = 2.2–21.4) for wolves outside the park, peaking during the winter hunting and trapping seasons. We found weak evidence for declining survival over time, opposite to patterns predicted by density-dependence. Bayesian cause-specific mortality indicated that the top three sources of mortality were trapping (rate = 0.080, 36% of mortality), followed by hunting (0.053, 18%), and highway (0.046, 18%) mortality. Surprisingly, we found no intraspecific mortality, and low dispersal from Banff National Park. This demographic profile is akin to other exploited populations across North America. While we were unable to combine survival rates with reproduction to estimate population trends, the overall mortality rates within our study area are consistent with a stable wolf population. Nonetheless, the long-term stability and ecological effectiveness of wolves likely differed inside and outside of protected areas, which highlights a challenge with managing transboundary carnivores exposed to different management regimes.
... First, source-sink population dynamics are generally not considered in management of wolves and other large carnivores, but are more likely to occur under IPD/IDD than IFD (Heinrichs, Lawler, & Schumaker, 2016;Mosser et al., 2009;Pulliam & Danielson, 1991). For example, it is thought that human offtake of wolves can reach 20%-30% of the population without causing population decline (Adams, Stephenson, Dale, Ahgook, & Demma, 2008;Fuller, Mech, & Cochrane, 2003;Gude et al., 2012;Murray et al., 2010). However, these conclusions are primarily based on findings that assume closed populations (Creel & Rotella, 2010) and do not explicitly account for source-sink structured populations. ...
... If individuals respond to spatially varying mortality risk according to the IPD, the prediction would be that high-risk sites are selected only after low-risk sites have become occupied. Such an outcome could lead to high-risk sites acting as sinks where growth rate and density are suppressed by high rates of human-caused mortality, but populations are maintained by immigration from neighbouring sites (Adams et al., 2008;Stenglein, Gilbert, et al., 2015). ...
According to the ideal‐free distribution (IFD), individuals within a population are free to select habitats that maximize their chances of success. Assuming knowledge of habitat quality, the IFD predicts that average fitness will be approximately equal among individuals and between habitats, while density varies, implying that habitat selection will be density dependent. Populations are often assumed to follow an IFD, although this assumption is rarely tested with empirical data, and may be incorrect when territoriality indicates habitat selection tactics that deviate from the IFD (e.g. ideal despotic distribution or ideal preemptive distribution). When territoriality influences habitat selection, species’ density will not directly reflect components of fitness such as reproductive success or survival. In such cases, assuming an IFD can lead to false conclusions about habitat quality. We tested theoretical models of density‐dependent habitat selection on a species known to exhibit territorial behavior in order to determine whether commonly applied habitat models are appropriate under these circumstances. We combined long‐term radio telemetry and census data from gray wolves (Canis lupus) in the Upper Peninsula of Michigan, USA to relate spatiotemporal variability in wolf density to underlying classifications of habitat within a hierarchical state‐space modeling framework. We then iteratively applied isodar analysis to evaluate which distribution of habitat selection best described this recolonizing wolf population. The wolf population in our study expanded by >1000% during our study (~ 50 to > 600 individuals), and density‐dependent habitat selection was most consistent with the ideal preemptive distribution, as opposed to the ideal‐free or ideal‐despotic alternatives. Population density of terrestrial carnivores may not be positively correlated with the fitness value of their habitats, and density‐dependent habitat selection patterns may help to explain complex predator‐prey dynamics and cascading indirect effects. Source‐sink population dynamics appear likely when species exhibit rapid growth and occupy interspersed habitats of contrasting quality. These conditions are likely and have implications for large carnivores in many systems, such as areas in North America and Europe where large predator species are currently recolonizing their former ranges.
... For example, moose densities were elevated from 207 to 1103 moose/1000 km 2 , harvests from 16 to 84 moose/1000 km 2 , and wolf densities from 7 to 12 wolves/1000 km 2 when wolf removal rates were increased from 10 to 30%. The modelled wolf population was able to sustain removal rates up to 31% which was consistent with Adams et al. (2008) who analysed information from 39 North American wolf populations and determined that populations were able to compensate for removal rates up to 29%. ...
... Several studies have shown that winter kill rates by individual wolves are inversely related to pack size, and that wolf predation should be modelled by the number and size of packs (Ballard et al. 1987, McNay and Delong 1998, Hayes et al. 2000. Adams et al. (2008) discussed how wolves adjust dispersal rates as a primary mechanism to compensate for human harvest which also could be modelled. Most northern wolf-ungulate studies have identified stochastic weather events as a significant component in predator-prey systems (Gasaway et al. 1983Gasaway et al. 1992, Boertje et al.1996, 2009, Ballard and Van Ballenberghe 1998, McNay and Delong 1998. ...
One of the fundamental principles of wildlife harvesting is that it must result in a sustained yield (SY), a harvest that can be taken year after year without jeopardizing future harvests. Predator-prey models are rarely incorporated into estimates of SYs for moose, despite preda-tion of moose by wolf (Canis lupus), grizzly bear (Ursus arctos), and black bear (U. americanus) throughout much of western North America. A simple predator-prey model was parameterized from a stable moose-wolf-bear system in central British Columbia during 1987-1998. Modelled moose, wolf, and harvest parameters compared favourably with observed parameters when the annual rate of wolf removal (human-caused wolf mortality) was 31%. SY curves were modelled by incremen-tally increasing wolf removal rates from 0 to 40% while maintaining selective moose harvests of 16% bulls, 2% cows and 9% calves. SYs displayed an S-shape curve with wolf removal rates, a hook-shape curve with wolf densities, and were linearly related to moose density. Optimal harvests included a moderate harvest of bulls (16-21%), a nil-to-very low harvest of cows (0-0.2%), and moderate-to-high harvests of calves (15-43%) when wolf removal rates were ≥ 20%. Higher cow harvest rates (2%) could be accommodated without substantially lowering SYs if calf harvest rates were reduced. Optimal harvest rates did not improve yields over bull-only hunting when wolf removal rates were 0-10% and management constraints were placed on adult sex ratios. This study supports previous findings that the optimal harvest strategy for moose should primarily target bulls and calves, whereas cows should be harvested minimally. However, for low-density, predator-limited moose populations, bull-only harvests may provide equivalent yields while maintaining higher moose and wolf densities.
... We found that colonization was mainly infl uenced by the number of observed occupied neighbors at short and long-distances, showing that dispersal and competition for space with other packs is a key factor of the dynamic of occupancy. ese results corroborate those of Adams et al. (2008) who showed that dispersal was the main component explaining wolf population dynamics. Several long-distance dispersal events have been documented across the alpine area (Wolf Alpine Group 2014) and in France (Duchamp et al. unpubl.). ...
Les grands carnivores recolonisent l’Europe grâce à une augmentation des forêts et des populations d'ongulés sauvages ainsi que des mesures de conservation. Or, les carnivores entrent en interactions avec les activités humaines telles que l’élevage. Quantifier leur distribution peut aider à situer les impacts sur ces activités. Ces espèces sont très mobiles, difficiles à observer et vivent à de faibles densités. La modélisation de leur distribution présente plusieurs défis en raison 1) de leur détectabilité imparfaite, 2) de leur distribution dynamique dans le temps et 3) du suivi à grande échelle basé sur la collecte de données opportunistes sans mesure formelle de l'effort d'échantillonnage. Dans cette thèse, nous nous sommes concentrés sur deux espèces de grands carnivores, le loup et le lynx boréal, pour développer les méthodologies liées à la modélisation de la distribution d’espèces. Nous avons exploré l’application des modèles d’occupancy dans le contexte du suivi des grands carnivores en Europe. Ces modèles établissent le lien entre la présence d’une espèce et l’environnement dans le but d’établir la proportion d'une zone d'étude que l’espèce occupe, tout en prenant en compte une détectabilité imparfaite.Plus précisément, nous avons d'abord évalué la dynamique de la distribution des loups en France de 1994 à 2016, tout en prenant en compte leur détection imparfaite. Nous avons montré l'importance de prendre en compte l’effort d'échantillonnage variant dans le temps et dans l'espace à l’aide de de modèles d’occupancy dynamique.Deuxièmement, comme des faux positifs peuvent être présents lors de la surveillance d'espèces rares, nous avons développé un modèle dynamique d’occupancy qui tenait compte simultanément des faux négatifs et des faux positifs pour analyser conjointement des données qui contenaient à la fois des détections certaines et des détections incertaines. L'analyse des données sur le lynx boréal dans les pays alpins a suggéré que l'incorporation de détections incertaines produisait des estimations des paramètres écologiques plus précises.Troisièmement, nous avons développé un modèle qui prenait en compte l'hétérogénéité de la détection tout en traitant les faux positifs. En appliquant notre nouvelle approche au loup en France, nous avons démontré que l'hétérogénéité de la détection du loup était principalement due à un effort d'échantillonnage hétérogène dans l'espace.Quatrièmement, pour traiter des sources de données multiples, nous avons développé un modèle de processus ponctuel de Poisson qui permettait l'inclusion de différentes sources de données lors de la construction des SDMs. Nous avons montré comment la combinaison des données sur la distribution permettait d’optimiser un suivi en répondant à la question de savoir quelle(s) source(s) d'information apporterait l’essentiel de l’information lors du suivi du lynx en Norvège.Cinquièmement, pour comprendre les mécanismes sous-jacents de la colonisation des loups en France, nous avons développé un cadre statistique pour estimer l'occupation spatio-temporelle et la dynamique des effectifs en utilisant le cadre de diffusion écologique. Nous avons montré le potentiel de notre approche pour prédire la distribution future potentielle du loup à court terme, un élément qui pourrait contribuer à cibler des zones de gestion ou se concentrer sur des zones de conflit potentiel.Dans l'ensemble, nos travaux montrent que les données opportunistes peuvent être analysées à l'aide de modèles de distribution d’espèces qui prennent en compte les contraintes liées au type de suivi utilisé pour produire les données. Nos approches peuvent être utilisées par les gestionnaires pour optimiser la surveillance des grands carnivores, cibler des zones de présence potentielles et contribuer à proposer des mesures destinées à atténuer les conflits.
... Legal killing comprised 23%, traffic 9% and natural causes (disease, age, trauma) another 17% of total mortality. Total annual survival rates of 0.75 correspond well with the average for many wolf populations in North America (Fuller 1989, Fuller et al. 2003, Adams et al. 2008). This is somewhat lower than what is typical for nonharvested wolf populations (Ballard et al. 1987, Hayes andHarestad 2000) but well above the level typical for declining populations (Ballard et al. 1987). ...
... Therefore, interactions between human causes of death are important to our understanding of the intended and unintended effects of predator removal, as are the effects of interventions meant to curb human causes of mortality. For example, poaching (illegal killing by people) was found to be the major cause of mortality in four endangered wolf populations of the USA, and unregulated killing was the major cause in one Alaskan sub-population (Adams et al., 2008;Treves et al., 2017a). Those studies also revealed that poaching was systematically under-estimated by traditional measures of risk and hazard or that mortality of marked animals differed from that of unmarked animals under legal, lethal management regimes (Schmidt et al., 2015;Treves et al., 2017c;Santiago-Ávila, 2019;Treves, 2019a). ...
Rapid, global changes, such as extinction and climate change, put a premium on evidence-based, environmental policies and interventions, including predator control efforts. Lack of solid scientific evidence precludes strong inference about responses of predators, people, and prey of both, to various types of predator control. Here we formulate two opposing hypotheses with possible underlying mechanisms and propose experiments to test four pairs of opposed predictions about responses of predators, domestic animals, and people in a coupled, dynamic system. We outline the design of a platinum-standard experiment, namely randomized, controlled experiment with cross-over design and multiple steps to blind measurement, analysis, and peer review to avoid pervasive biases. The gold-standard has been proven feasible in field experiments with predators and livestock, so we call for replicating that across the world on different methods of predator control, in addition to striving for an even higher standard that can improve reproducibility and reliability of the science of predator control.
... Control of large carnivores (i.e., wolves and mountain lions) can be effective for reversing ungulate population declines (Orians et al. 1997, Rominger 2018. Wolf populations are resilient to moderate annual harvests ( Adams et al. 2008), so control efforts must be intensive to reduce wolf numbers and sustain them at low levels for several years to evoke a population response in their ungulate prey (Orians et al. 1997). Only 3 of the 8 aerial wolf control programs reviewed by Orians et al. (1997) could demonstrate an increase in the target ungulate population; these programs reported ≥69% reductions in wolf abundance and lasted for 6-7 years ( Gas- away et al. 1983, Farnell and McDonald 1988, Hayes et al. 2003, Farnell 2009. ...
Predation is a major limiting factor for most small sedentary caribou (Rangifer tarandus) populations, particularly those that are threatened or endangered across the southern extent of the species’ range. Thus, reducing predation impacts is often a management goal for improving the status of small caribou populations, and lethal predator removal is the primary approach that has been applied. Given that predator control programs are often contentious, other management options that can garner broader public acceptance need to be considered.
Substantial calf losses to predation in the few weeks following birth are common for these small caribou populations. Therefore, we employed a novel experimental approach of maternal penning with the goal of reducing early calf mortality in the Chisana Caribou Herd, a declining population in southwest Yukon and adjacent Alaska thought to number around 300 individuals. Maternal penning entailed temporarily holding pregnant females on their native range in a large pen secure from predators from late March through the initial weeks of calf rearing to mid-June. During 2003–2006, we conducted 4 annual penning trials with 17–50 pregnant females each year (n = 146 total), assessed survival of calves born in the pens, and evaluated survival and nutritional effects of penning for females that were held. We also investigated the herd’s population dynamics during 2003–2008 to determine effects of maternal penning on calf recruitment and population growth. In addition to information gained during maternal penning, we determined natality and survival patterns via radiotelemetry, conducted autumn age-sex composition surveys each year, and censused the population in mid-October 2003, 2005, and 2007. Based on our penning trials and demographic investigations, we used simulation models to evaluate the effects of maternal penning relative to a population’s inherent growth rate (finite rate of increase [λ] without maternal penning) and penning effort (proportion of calves born in penning) to provide perspective on utility of this approach for improving the status of small imperiled caribou populations.
Pregnant females held in maternal penning tolerated captivity well in that they exhibited positive nutritional responses to ad libitum feed we provided and higher survival than free-ranging females (0.993 and 0.951 for penned and free-ranging females, respectively). Survival of pen calves from birth to mid-June was substantially higher than that of free-ranging calves ( = 0.950 and 0.376, respectively). This initial period accounted for 76% of the annual calf mortality in the free-ranging population. Pen-born calves maintained their survival advantage over wild-born calves to the end of their first year ( = 0.575 and 0.192, respectively) during years penning occurred.
Females in the Chisana Herd were highly productive with 57% producing their first offspring at 2 years of age, and annual natality rates averaging 0.842 calves/female ≥2 years old. Age-specific natality rates exceeded 0.900 for 4–9-year-olds, exhibiting senescent decline to 0.467 by 19 years old. Annual survival of free-ranging adult females and calves averaged 0.892 and 0.184, respectively, over all study years; both were reduced during 2004 because of poor winter survival. We noted reduced nutritional condition of caribou late that winter in that females we captured were lighter than in other years and produced lighter calves. We suspect that the reduced survival during winter 2004 and the observed nutritional characteristics resulted from adverse snow conditions in combination with effects of the extreme drought experienced the previous summer. Age-specific survival of adult females was ≥0.900 through 10 years of age, then declined with age.
The Chisana Herd numbered 720 caribou in mid-October 2003, or more than twice that estimated prior to initiating maternal penning, and increased to 766 caribou by mid-October 2007. We calculated that penning added 54.2 yearling recruits, or 40% of calves released from penning. Based on the maternal penning results and the population’s vital rates, we determined that the herd would have been stable during 2003–2007 at about 713 caribou without maternal penning; thus, the increase in herd size we observed resulted from maternal penning and was equivalent to the estimate of additional yearling recruits. The improvement in the population trend invoked by maternal penning was limited by the larger than expected population size and resulting low penning effort ( = 11% of calves born in pen).
Our simulations corroborated that maternal penning increased population size by the number of additional recruits provided, even at low penning effort, for inherently stable populations. As the inherent rate of increase dropped below λ = 1.000, more of the additional recruits from penning were needed to offset the downward population inertia, thus requiring increased penning effort to reach stability. For populations declining at λ < 0.890, stability could not be achieved with 100% penning effort given the vital rates in our models.
Maternal penning in its limited application to date has proven to be broadly popular as a nonlethal management action aimed at reducing initial calf mortality from predation in small caribou populations. However, based on the Chisana program and 3 subsequent efforts elsewhere, improvement in population trends have been modest at best and come at a high financial cost. Given the necessity of maximizing penning effort, maternal penning may have a role in addressing conservation challenges for some small caribou populations that are stable or slowly declining, but its application should be primarily driven by objective assessment of the likelihood of improving population trends rather than popularity relative to other management options.
... One of the most common means to estimate wolf density is aerial telemetry of marked individuals, wherein wolves are radiocollared from every pack in the survey area, minimum counts of pack sizes are obtained visually through aerial observations, and the total number of wolves is divided by the sum of the pack territory areas (i.e., territory mapping; Peterson et al. 1984, Fuller 1989, Hayes 1995. The aerial radiotelemetry approach has been widely used since the 1970s and remains commonly applied in areas with open terrain (Ballard et al. 1997, Hayes et al. 2003, Adams et al. 2008, Lake et al. 2015, Boertje et al. 2017. This method is effective if a sufficient number of wolves are radiocollared and monitored in all adjacent packs in a region (Burch et al. 2005); yet, meeting these requirements is generally expensive, time-consuming, and difficult to apply over a large area (Boitani 2003, Schmidt et al. 2017). ...
Estimating population abundance of wolves (Canis lupus) in densely forested landscapes is challenging because reduced visibility lowers the success of methods such as aerial surveys and enumeration of group size using radiotelemetry. However, regular population estimates of wolves are necessary for population monitoring and sustainable management. We used noninvasive hair snaring and spatially explicit capture–recapture (SECR) to estimate wolf abundance on Prince of Wales Island (POW), Alaska, USA, during 2012–2015. We monitored 36–82 hair-snare stations weekly for 9–11 weeks during autumn. The noninvasive study area covered 1,683 km ² during 2012–2013 and was expanded to 3,281 km ² during 2014–2015. We identified 57 individual wolves during the study period using DNA from hair follicles genotyped at 10 microsatellite loci. We used population density estimates using SECR (2013: 24.5 wolves/1,000 km ² [95% CI = 14.4–41.9 wolves/1,000 km ² ], 2014: 9.9 wolves/1,000 km ² [95% CI = 5.5–17.7/1,000 km ² ], 2015: 11.9 wolves/1,000 km ² [95% CI = 7.7–18.5 wolves/1,000 km ² ]) to predict the autumn population for the POW management unit (2013: 221.1 wolves [95% CI = 130–378]; 2014: 89.1 wolves [95% CI = 49.8–159.4]; 2015: 107.5 wolves [95% CI = 69–167]). We detected and redetected more wolves and increased the precision of the density estimate after increasing the hair sampling intensity and sampling area in 2014–2015. Our results demonstrate that estimating wolf abundance using noninvasive sampling and SECR was feasible and reliably applied producing a statistically robust population estimate for monitoring wolf populations in densely forested areas. These methods have promise for application to widely ranging carnivores at population-level scales and may be especially useful when regular density estimates are necessary for management and conservation.
... Predators of moose, such as wolves (Canis lupus), grizzly bears (Ursus arctos), and black bears (U. americanus) occur at relatively low densities. Contemporary, quantitative density estimates of these predators are lacking for this region (but see Bertram and Vivion, 2002a;Adams et al., 2008;Lake et al., 2013). Caribou (Rangifer tarandus) can be in found in the region at low densities during the winter months (Wilson et al., 2014) and Dall's sheep (Ovis dalli) at low densities throughout the year in the mountainous regions (Schmidt and Rattenbury, 2013). ...
Predation, habitat, hunting, and environmental conditions have all been implicated as regulatory mechanisms in ungulate populations. The low-density equilibrium hypothesis predicts that in low-density populations, predators regulate their prey and that the population will not escape unless predation pressure is eased. We evaluated survival of adult and juvenile moose (Alces alces) in north-central Alaska to determine whether or not the population supported the hypothesis. We instrumented adult male and female moose with radiocollars and used aerial observations to track parturition and subsequent survival of juvenile moose. Generalized linear mixed-effects models were used to assess survival. Adult annual survival rates were high (∼89%), but may be negatively influenced by winter conditions. Migratory status did not affect moose survivorship or productivity. Approximately 60% of the calf crop died before 5 months of age. Productivity was significantly lower in the northern section of the study area where there is less high-quality habitat, suggesting that, even in this low-density population, nutrition could be a limiting factor. It appears that predation on young calves, winter weather, and nutritional constraints may be interacting to limit this population. Latent traits, such as overproduction of calves and migratory behavior, which do not currently enhance fitness, may persist within this population so that individuals with these traits can reap benefits when environmental conditions change.
... MCP is a crude estimate of the occurrence distribution that is sensitive to extreme data points and sample size, ignores the interior data points, and implies uniform use within the boundary (White and Garrot 1990;Powell 2000). Nevertheless, MCPs may provide an adequate estimate of home range in some cases such as when (i) comparing sizes across taxa where large differences in range size mask smaller differences due to the choice of home range estimator (Nilsen et al. 2008); (ii) generating abundance estimates based on territory occupation and size (Adams et al. 2008;Suwanrat et al. 2015); or (iii) defining used habitats for second-order resource selection ) or an outer boundary of availability for third-order resource selection (Zeale et al. 2012 ...
Estimating animal home ranges and understanding the processes that influence home range behavior are important components of ecological investigations. While ecologists have been interested in the concept of home range for many decades, turning this conceptinto a usable statistical model or quantifiable metric for scientific purposes has been quite challenging. Keys to overcoming this challenge are (i) letting well-defined questions, and a solid understanding of the study system point to a specific home range metric to be quantified;(ii) choosing an appropriate estimator of this target metric;(iii) collecting location data during appropriate time periods and at the right sampling frequency; and (iv) understanding the trade-off between simplicity and complexity in modeling ecological data. If researchers follow these recommendations, many of the traditional challenges to studying animal home ranges will be alleviated due to technological advances in tracking systems and a solid foundation of models for understanding space use. However, we should continue to strive for more fundamental approaches to understanding animal movements. In particular, we see great opportunity for the continued development of agent-based models (ABM) of animal movements that allow for home range behavior to be an emergent property of the model instead of an a priori structure imposed on the data.
... First, the carnivore harvest objective may not be achievable using hunter harvest (White et al. 2010, Bischof et al. 2012, Tatman et al. 2018. Second, the achieved harvest may not result in a biologically significant change in carnivore abundance (Adams et al. 2008, Robinson et al. 2014. Moreover, in many previous studies of the effects of carnivore management on ungulate populations, changes in both populations harvest and abundance were often not measured, resulting in relatively weak inferences (National Research Council 1997). ...
Understanding the effectiveness of harvest regulations to manipulate population abundances is a priority for wildlife managers, and reliable methods are needed to monitor populations. This is particularly true in controversial situations such as integrated carnivore‐ungulate management. We used an observational before‐after‐control‐treatment approach to evaluate a case study in west‐central Montana, USA, that applied conservative ungulate harvest together with liberalized carnivore harvest to achieve short‐term decreases in carnivore abundance and increases in ungulate recruitment. Our study areas included the Bitterroot treatment area and the Clark Fork control area, where mountain lion populations (Felis concolor) were managed for a 30% reduction and for stability, respectively. The goals of the mountain lion harvest were to provide a short‐term reduction of mountain lion predation on elk (Cervus canadensis) calves and an increase in elk recruitment, elk population growth rate, and ultimately elk abundance. We estimated mountain lion population abundance in the Bitterroot treatment and Clark Fork control areas before and 4 years after implementation of the 2012 harvest treatment. We developed a multi‐strata spatial capture‐recapture model that integrated recapture and telemetry data to evaluate mountain lion population responses to harvest changes. Mountain lion abundance declined with increasing harvest in the Bitterroot treatment area from 161 (90% credible interval [CrI] = 104, 233) to 115 (CrI = 69, 173). The proportion of males changed from 0.50 (CrI = 0.33, 0.67) to 0.28 (CrI = 0.17, 0.40), which translated into a decline in the abundance of males, and similar abundances of females (before: males = 80 [CrI = 52, 116], females = 81 [CrI = 52, 117]; after: males = 33 [CrI = 20, 49], females = 82 [CrI = 49, 124]). In the Clark Fork control area, an area twice as large as the Bitterroot treatment area, we found no evidence of changes in overall abundance or proportion of males in the population. The proportion of males changed from 0.42 (CrI = 0.26, 0.58) to 0.39 (CrI = 0.25, 0.54), which translated into similar abundances of males and females (before: males = 24 [CrI = 16, 36], females = 33 [CrI = 21, 39]; after: males = 28 [CrI = 18, 41], females = 44 [CrI = 29, 64]). To evaluate if elk recruitment and population growth rate increased following treatment, we developed an integrated elk population model. We compared recruitment and population growth rate during the 5 years prior to and 5 years following implementation of the mountain lion harvest treatment for 2 elk populations within the Bitterroot treatment area and 2 elk populations within the Clark Fork control area. We found strong evidence that temporal trends differed between the 2 areas. In the Bitterroot treatment area, per capita elk recruitment was stable around an estimated median value of 0.23 (CrI = 0.17, 0.36) in the pre‐treatment period (2007–2011), increased immediately after treatment (2013) to 0.42 (CrI = 0.29, 0.56), and then declined to 0.21 (CrI = 0.11, 0.32) in 2017. In contrast, per capita elk recruitment estimates in the Clark Fork control area had similar median values during the pre‐ (2007–2011: 0.30, CrI = 0.2, 0.35) and post‐treatment periods (2013–2017: 0.31, CrI = 0.26, 0.36). These changes in recruitment corresponded to similar changes in elk population growth rate, although population growth rates were also subject to variation due to changing elk harvest. In the Bitterroot treatment area, population growth rates in the pre‐treatment period were stable to slightly declining, with an estimated median value of 0.92 (CrI = 0.88, 1.07) in the pre‐treatment period (2007–2011). Population growth rate during the post‐treatment period increased immediately after treatment (2012: 1.17, CrI = 1.14, 1.20) prior to declining to 1.06 (CrI = 1.04, 1.09) in 2016. In contrast, the median population growth rates were roughly equal in the Clark Fork control area during the pre‐treatment period (1.01, CrI = 0.86, 1.09) from 2007 to 2011 and post‐treatment period (1.00, CrI = 0.83, 1.15) from 2013 to 2017. Together, these results indicate that the harvest treatment achieved a moderate (i.e., 29%) reduction in mountain lion population abundance within the treatment area that corresponded with short‐term increases in elk recruitment and population growth. Elk population demographic responses suggest that the harvest treatment effect was strongest immediately after the mountain lion harvest treatment was implemented and lessened over time as the harvest treatment was reduced. This suggests that the short‐term harvest treatment resulted in short‐term demographic responses in elk populations, and more sustained harvest treatments would be necessary to achieve longer‐term elk population demographic responses. We recommend that wildlife managers seeking to balance carnivore and ungulate population objectives design rigorous carnivore and ungulate population monitoring programs to assess the effects of harvest management programs. Assessing and understanding effects of carnivore harvest management programs will help to set realistic expectations regarding the effects of management programs on carnivore and ungulate populations and allow managers to better design programs to meet desired carnivore and ungulate population objectives. Comprendre l'efficacité des règlements de récolte à contrôler l'abondance des populations est une priorité pour les gestionnaires de la faune, et des méthodes fiables sont nécessaires pour suivre l'état des populations. Cela est particulièrement vrai face à des situations controversées telles que la gestion intégrée des carnivores et des cervidés. Nous avons utilisé une approche observationnelle avant‐après‐témoin‐traitement dans le cadre d'une étude de cas prenant place dans le centre‐ouest du Montana, aux États‐Unis. L'étude impliquait une récolte de cervidés conservatrice et une récolte de carnivores plus permissive afin de réduire l'abondance des carnivores à court terme et d'augmenter le recrutement de cervidés. Nos aires d'étude comprenaient la zone expérimentale de la Bitterroot où la gestion visait à réduire les populations de couguars (Felis concolor) de 30%, ainsi que la zone témoin de Clark Fork où l'objectif était de maintenir des populations stables. La récolte de couguars visait la réduction à court terme de la prédation sur les faons de wapitis (Cervus canadensis), tout en augmentant le recrutement de wapitis, de même que le taux de croissance et l'abondance de leur population. Nous avons estimé l'abondance des couguars dans la zone de traitement de la Bitterroot et dans la zone témoin de Clark Fork avant la mise en œuvre du traitement de récolte en 2012, puis 4 ans après. Nous avons développé un modèle spatial de capture‐marquage‐recapture pour population stratifée qui intégrait des données de recapture et de télémétrie afin d'évaluer comment la population de couguars réagit aux variations du taux de récolte. L'abondance de couguars a diminué avec l'augmentation de la récolte dans la zone de traitement de la Bitterroot, passant de 161 (intervalle de crédibilité à 90% [ICr] = 104, 233) à 115 (ICr = 69, 173). La proportion de mâles est alors passée de 0,50 (ICr = 0,33, 0,67) à 0,28 (ICr = 0,17, 0,40), ce qui reflète la diminution de l'abondance des mâles et le maintien de l'abondance des femelles (avant: mâles = 80 [ICr = 52, 116], femelles = 81 [ICr = 52, 117]; après: mâles = 33 [ICr = 20, 49], femelles = 82 [ICr = 49, 124]). Dans la zone témoin de Clark Fork, une zone deux fois plus grande que la zone de traitement de la Bitterroot, nous n'avons détecté aucun changement dans l'abondance des mâles ou dans leur proportion au sein de la population. La proportion de mâles est passée de 0,42 (ICr = 0,26, 0,58) à 0,39 (ICr = 0,25, 0,54), se traduisant par une abondance similaire entre les mâles et les femelles (avant: mâles = 24 [ICr = 16, 36], femelles = 33 [ICr = 21, 39]; après: mâles = 28 [ICr = 18, 41], femelles = 44 [ICr = 29, 64]). Pour évaluer si le recrutement de wapitis et le taux de croissance de leur population ont augmenté suite au traitement, nous avons développé un modèle intégré des populations de wapitis. Nous avons comparé le taux de recrutement et de croissance de 4 populations de wapitis au cours des 5 années qui ont précédé et des 5 qui ont suivi le début de la récolte de couguars. Deux populations de wapitis se situaient dans la zone de traitement de la Bitterroot et 2 dans la zone témoin de Clark Fork. Nos résultats suggèrent fortement que les variations temporelles des populations différaient entre les 2 aires d'étude. Dans la zone de traitement de la Bitterroot, le recrutement des wapitis par individu était stable autour d'une valeur médiane de 0,23 (ICr = 0,17, 0,36) durant la période de prétraitement (2007–2011), il a augmenté suite au traitement pour atteindre un niveau intermédiaire de 0,42 (ICr = 0,29, 0,56) en 2013, puis il a diminué à 0,21 (ICr = 0,11, 0,32) en 2017. En revanche, le recrutement des wapitis par individu avait des valeurs médianes similaires durant les périodes pré‐ (2007–2011: 0,30, ICr = 0,2, 0,35) et de post‐traitement (2013–2017: 0,31, ICr = 0,26, 0,36) dans la zone témoin de Clark Fork. Les variations du recrutement étaient liées à des changements similaires dans le taux de croissance des populations de wapitis, bien que le taux de croissance des populations ait également varié suite aux variations de récolte de wapitis. Dans la zone de traitement de la Bitterroot, les taux de croissance des populations étaient stables ou légèrement en baisse durant la période de prétraitement (2007–2011), avec une valeur médiane de 0,92 (ICr = 0,88, 1,07). Le taux de croissance de la population a augmenté immédiatement après le traitement (2012: 1,17, ICr = 1,14, 1,20), avant de diminuer à 1,06 (ICr = 1,04, 1,09) en 2016. En revanche, le taux de croissance médian des populations de la zone témoin de Clark Fork est demeuré semblable entre la période prétraitement (1,01, ICr = 0,86, 1,09) de 2007 à 2011 et celle post‐traitement (1,00, ICr = 0,83, 1,15) de 2013 à 2017. Globalement ces résultats indiquent que le traitement de récolte a permis une réduction modérée (c.‐à‐d. 29%) de l'abondance des couguars dans la zone expérimentale, de même qu'une augmentation à court terme à la fois du recrutement et de la taille de la population de wapitis. Les changements démographiques de la population de wapitis suggèrent que l'effet du traitement de récolte a été maximal immédiatement après le début du traitement de récolte de couguars, puis a graduellement diminué suivant le réduction du taux de récolte. Ce résultat suggère que le traitement de récolte a eu une influence à court terme sur la démographie des populations de wapitis et, par conséquent, qu'un traitement de récolte plus soutenu serait nécessaire pour espérer un impact à plus long terme. Nous recommandons aux gestionnaires de la faune qui visent à gérer à la fois les populations de carnivores et de cervidés, de concevoir des programmes de surveillance permettant une évaluation rigoureuse des effets de la récolte sur ces populations. L'évaluation et la compréhension de l'effet des programmes de gestion de la récolte des carnivores aideront à établir des attentes réalistes quant aux effets de ces programmes sur les populations de carnivores et de cervidés, tout en permettant aux gestionnaires de concevoir des programmes permettant de mieux rencontrer les objectifs de gestion pour toutes ces populations.
... Research into whether human-caused mortality is compensatory or additive with other causes of mortality is controversial and has been identified as an important research need in wolf conservation (Vucetich and Peterson 2004). Analysis of mortality rates from North American wolf populations resulted in conflicting conclusions of compensation, additivity and super-additivity of mortality sources (Adams et al. 2008;Creel and Rotella 2010;Fuller et al. 2003). Rate of intraspecific killing among wolves is lower in exploited wolf populations, potentially suggesting compensatory mechanisms (Cubaynes et al. 2014). ...
Populations of large terrestrial carnivores are in various stages of recovery worldwide and the question of whether there is compensation in mortality sources is relevant to conservation. Here, we show variation in Wisconsin wolf survival from 1979 to 2013 by jointly estimating the hazard of wolves’ radio-telemetry ending (endpoint) and endpoint cause. In previous analyses, wolves lost to radio-telemetry follow-up (collar loss) were censored from analysis, thereby assuming collar loss was unconfounded with mortality. Our approach allowed us to explicitly estimate hazard due to collar loss and did not require censoring these records from analysis. We found mean annual survival was 76% and mean annual causes of mortality were illegal killing (9.4%), natural and unknown causes (9.5%), and other human-caused mortality such as hunting, vehicle collisions and lethal control (5.1%). Illegal killing and natural mortality were highest during winter, causing wolf survival to decrease relative to summer. Mortality was highest during early recovery and lowest during a period of sustained population growth. Wolves again experienced higher risk of human-caused mortality relative to natural mortality as wolves expanded into areas with more human activity. We detected partial compensation in human- and natural-caused mortality since 2004 as the population saturated more available habitat. Prior to 2004, we detected additivity in mortality sources. Assessments of wolf survival and cause of mortality rates and the finding of partial compensation in mortality sources will inform wolf conservation and management efforts by identifying sources and sinks, finding areas of conservation need, and assessing management zone delineation.
... These rates were in addition to natural mortality rates (12% for adults), which would translate to a 27 to 32% total mortality rate, for a slightly increasing and slightly declining population, respectively. These findings were compatible with other studies which demonstrated wolf populations were sustainable with total mortality rates up to 25-30% (Adams et al. 2008, Creel and Rotella 2010, Sparkman et al. 2011). From 2009-2018 human-caused mortality rates (authorized and unauthorized) did not exceed 10% annually of minimum counts in Oregon, suggesting the wolf population should continue to increase so long as total human-caused mortality continues to stay below 15% and natural mortliaty rates remain the same. ...
... Estimates of sustainable harvest rates for wolves vary from < 30% ( Adams et al. 2008;Creel and Rotella 2010) up to approximately 70% ( Fuller et al., 2003;Gude et al. 2011) depending especially on the productivity of the population. Breeding adult survival is a key para- meter for the recruitment rate in a wolf population (Borg et al., 2015), and selective harvesting of breeding animals increases the risk of pack dissolution ( Borg et al., 2015;Brainerd et al., 2008;Milleret et al., 2016) and may affect the hunting success of the pack (Sand et al., 2006). ...
Poaching may threaten population viability and can occur in both non-harvested and legally harvested populations. Telemetry facilitates the determination of the fates of individual animals, and the resultant mortality scenarios can be used to evaluate the role of poaching in population changes. Finland's legally hunted wolf (Canis lupus) population fluctuated between 100 and 300 animals during 1998–2016, and this cannot be explained by the rates of legal hunting and other known mortalities alone. We examined the role of poaching in wolf population changes. We created different scenarios based on multi-source information on poaching among 130 collared wolves. Poaching has been the primary cause of death followed by legal hunting. We calculated the survival rate and cause-specific mortality risk; wolves whose fates were unknown were censored. As one of the event alternatives (unknown fate or known mortality cause), censoring was related to social status; breeding adults were more often poached, whereas dispersers were censored. We created two sets of scenarios based on the censoring procedure (random and non-random), and for both sets, we created 4 scenarios ranging from high to no poaching based on decreasing confidence in the data. Annual survival ranged from 0.11–0.24 (high poaching scenario) to 0.43–0.60 (no poaching); survival dropped in mid-winter. The poaching rate varied between years from less than 0.09–0.13 up to 0.31–0.43. We consider poaching to be a regulatory factor; it focused on breeding adults and seemed to escalate as a response to increased population size. We conclude that tolerance for carnivores cannot be promoted by legal hunting alone, so more comprehensive conservation efforts are needed.
... Many studies show wolves face high levels of anthropogenic mortality [19,28,34,49], however the persistence of some carnivore populations in areas of high human density show human-carnivore coexistence with minimal killing is possible under certain conditions [50,51]. For example, Carter et al. found that tigers and humans co-existed even at small spatial scales, likely because tigers adjusted their activity to avoid encounters with people [51]. ...
The reintroduced red wolf (Canis rufus) population in northeastern North Carolina declined to 7 known wolves by October 2020, the majority of which is due to poaching (illegal killing), the major component of verified anthropogenic mortality in this and many other carnivore populations. Poaching is still not well understood and is often underestimated, partly as a result of cryptic poaching, when poachers conceal evidence. Cryptic poaching inhibits our understanding of the causes and consequences of anthropogenic mortality, which is important to conservation as it can inform us about future population patterns within changing political and human landscapes. We estimate risk for marked adult red wolves of 5 causes of death (COD: legal, nonhuman, unknown, vehicle and poached) and disappearance, describe variation in COD in relation to hunting season, and compare time to disappearance or death. We include unknown fates in our risk estimates. We found that anthropogenic COD accounted for 0.78-0.85 of 508 marked animals, including poaching and cryptic poaching, which we estimated at 0.51-0.64. Risk of poaching and disappearance was significantly higher during hunting season. Mean time from collaring until nonhuman COD averaged 376 days longer than time until poached and 642 days longer than time until disappearance. Our estimates of risk differed from prior published estimates, as expected by accounting for unknown fates explicitly. We quantify the effects on risk for three scenarios for unknown fates, which span conservative to most likely COD. Implementing proven practices that prevent poaching or hasten successful reintroduction may reverse the decline to extinction in the wild of this critically endangered population. Our findings add to a growing literature on endangered species protections and enhancing the science used to measure poaching worldwide.
... Liberg et al., 2020) and Finland (natural: 0.03, traffic: <0.07: Suutarinen & Kojola, 2017). They also exceeded the maximum sustainable harvest rates (≤0.29) and total sustainable mortality rates (0.34) estimated for wolf populations (Adams et al., 2008;Fuller et al., 2003), suggesting that the Jutland peninsula constitutes a population sink. ...
Large carnivores are currently recolonizing Europe following legal protection, but increased mortality in landscapes highly impacted by humans may limit further population expansion. We analyzed mortality and disappearance rates of 35 wolves (of which three emigrated, nine died and 14 disappeared by 1 January 2020) by genetic monitoring in the heavily cultivated and densely populated Jutland peninsula (Denmark and Schleswig‐Holstein, Germany). Annual traffic kill rate estimates ranged from 0.37 (95% CI: 0.11–0.85) to 0.78 (0.51–0.96) in the German part, equivalent to 0.08 (0.02–0.29)–0.25 (0.13–0.46) for the entire region, in the absence of any registered Danish roadkills. In Denmark, annual mortality rate estimates ranged from 0.46 (0.29–0.67) to 0.52 (0.35–0.71), predominantly from cryptic mortality. Despite successful reproductions, we conclude the region is a wolf population sink, primarily driven by cryptic mortality, most likely illegal killing. We hypothesize that frequent encounters between wolves and wolf‐averse persecutors in cultivated landscapes may cause unsustainably high mortality rates despite the majority of hunters respecting protection laws.
... However, these benefits may apply differently across wintering areas, based on differences in wintering area conditions. Predator density [83][84][85][86], forage quantity or quality [87][88][89], snow depth and density [90,91], or exposure to human development and activity [92] may influence TCH use of specific wintering areas. Individual factors such as body size, presence of a calf, or age may compound these differences, leading to varying nutritional needs, sensitivity to disturbance, and susceptibility to predation, parasites, or disease. ...
Many animals migrate to take advantage of temporal and spatial variability in resources. These benefits are offset with costs like increased energetic expenditure and travel through unfamiliar areas. Differences in the cost-benefit ratio for individuals may lead to partial migration with one portion of a population migrating while another does not. We investigated migration dynamics and winter site fidelity for a long-distance partial migrant, barren ground caribou ( Rangifer tarandus granti ) of the Teshekpuk Caribou Herd in northern Alaska. We used GPS telemetry for 76 female caribou over 164 annual movement trajectories to identify timing and location of migration and winter use, proportion of migrants, and fidelity to different herd wintering areas. We found within-individual variation in movement behavior and wintering area use by the Teshekpuk Caribou Herd, adding caribou to the growing list of ungulates that can exhibit migratory plasticity. Using a first passage time–net squared displacement approach, we classified 78.7% of annual movement paths as migration, 11.6% as residency, and 9.8% as another strategy. Timing and distance of migration varied by season and wintering area. Duration of migration was longer for fall migration than for spring, which may relate to the latter featuring more directed movement. Caribou utilized four wintering areas, with multiple areas used each year. This variation occurred not just among different individuals, but state sequence analyses indicated low fidelity of individuals to wintering areas among years. Variability in movement behavior can have fitness consequences. As caribou face the pressures of a rapidly warming Arctic and ongoing human development and activities, further research is needed to investigate what factors influence this diversity of behaviors in Alaska and across the circumpolar Arctic.
... For example, Golden eagles (Aquila chrysaetos) migrate from Arctic Alaska to the intermountain west of the United States, whereas Arctic terns (Sterna paradisaea) migrate even farther from the Arctic to Antarctica [1]. Mammals remain within Arctic or subarctic environments (e.g., wolves (Canis lupis) [2]; caribou (Rangifer tarandus granti) [3]), but the availability of terrestrial habitat (i.e., land available for animals to occupy) is more consistent across seasons. Interestingly, caribou in the Arctic exhibit the longest terrestrial migrations on the planet, whereas wolves move the most within a year [4]. ...
Amphidromous fish such as Dolly Varden (S alvelinus malma ) and Arctic Cisco ( Coregonus autumnalis ) have distinct life histories that facilitate their success in Arctic environments. Both species spawn in freshwater and make annual migrations between marine, brackish, or freshwater environments. Dolly Varden rear for one or more years in freshwater before migrating to sea whereas Arctic Cisco migrate to sea during their first summer. By contrast, Pacific salmon ( Oncorhynchus spp.) spawn in freshwater, but once they smolt and go to sea they remain there until they mature and return to spawn. Salmon migrate at variable ages depending on species. Arctic marine environments offer productive food resources during summer, but during winter they are too cold for salmonids that lack antifreeze proteins. To avoid the cold sea during winter, Dolly Varden return to freshwater while Arctic Cisco overwinter in brackish estuaries. The lack of migration back to freshwater for overwintering helps explain why Pacific salmon success is limited in Arctic waters and suggests major increases in success will not be realized until Arctic seas provide suitable overwinter conditions. In this paper we contrast these migration strategies, discuss potential changes in a warming Arctic, and highlight information needs especially for juvenile fish.
... Here, we distinguish between these two poaching variants by their detection on the landscape, following 12,15,17,18 : while 'reported poaching' refers to the component of total poaching that is reported, evidenced and thus detected by management agencies, 'cryptic poaching' refers to poaching that remains concealed and thus undetected. The concealment of poaching (its cryptic component) contributes to its systematic underestimation 12,15,[17][18][19] , increasing concerns over the viability of large carnivore populations subject to additional sources of anthropogenic mortality [20][21][22][23] . Given both its prevalence and cryptic nature, mitigating poaching seems imperative for the persistence of many large carnivore populations, including endangered ones that are not subject to hunting seasons 10,11,[16][17][18]24 . ...
Poaching is the main cause of mortality for many large carnivores, and mitigating it is imperative for the persistence of their populations. For Wisconsin gray wolves (Canis lupus), periods of increased risk in overall mortality and poaching seem to overlap temporally with legal hunting seasons for other large mammals (hunting wolves was prohibited). We analyzed monitoring data from adult, collared wolves in Wisconsin, USA (1979–2012, n = 495) using a competing-risk approach to test explicitly if seasons during which it was legal to train hunting hounds (hounding) or hunt other large mammals (hunting) affected wolves’ hazard of cause-specific mortality and disappearance. We found increases in hazard for disappearances and documented (‘reported’) poaching during seasons with hunting, hounding or snow cover relative to a season without these factors. The ‘reported poached’ hazard increased > 650% during seasons with hunting and snow cover, which may be due to a seasonal surge in numbers of potential poachers or to some poachers augmenting their activities. Snow cover was a major environmental factor contributing to poaching, presumably through increased detection of wolves. Our study suggests poaching is by far the highest mortality hazard for wolves and reinforces the need for protections and policies targeting poaching of protected populations.
... Large carnivores in the United States are frequently subject to legal (e.g., hunting, lethal control), illegal (poaching), and incidental killing (e.g., vehicle strike) Thompson, Jenks, & Fecske, 2014;Vickers et al., 2015). The relative influence of human-caused mortality on population dynamics is debated (Creel & Rotella, 2010;Robinson et al., 2014;Stoner, Wolfe, & Choate, 2006) with some subpopulations apparently sustaining highmortality rates (Adams, Stephenson, Dale, Ahgook, & Demma, 2008;Creel & Rotella, 2010;Stoner et al., 2006). Monitoring and precise estimation of adult survival in the presence of human-caused mortality are critical for effective management of large carnivore populations. ...
Understanding landscape patterns in mortality risk is crucial for promoting recovery of threatened and endangered species. Humans affect mortality risk in large carnivores such as wolves (Canis lupus), but spatiotemporally varying density dependence can significantly influence the landscape of survival. This potentially occurs when density varies spatially and risk is unevenly distributed. We quantified spatiotemporal sources of variation in survival rates of gray wolves (C. lupus) during a 21-year period of population recovery in the Upper Peninsula of Michigan, USA. We focused on mapping risk across time using Cox Proportional Hazards (CPH) models with time-dependent covariates, thus exploring a shifting mosaic of survival. Extended CPH models and time-dependent covariates revealed influences of seasonality, density dependence and experience, as well as individual-level factors and landscape predictors of risk. We used results to predict the shifting landscape of risk at the beginning, middle, and end of the wolf recovery time series. Survival rates varied spatially and declined over time. Long-term change was density-dependent, with landscape predictors such as agricultural land cover and edge densities contributing negatively to survival. Survival also varied seasonally and depended on individual experience, sex, and resident versus transient status. The shifting landscape of survival suggested that increasing density contributed to greater potential for human conflict and wolf mortality risk. Long-term spatial variation in key population vital rates is largely unquantified in many threatened, endangered, and recovering species. Variation in risk may indicate potential for source-sink population dynamics, especially where individuals preemptively occupy suitable territories, which forces new individuals into riskier habitat types as density increases. We encourage managers to explore relationships between adult survival and localized changes in population density. Density-dependent risk maps can identify increasing conflict areas or potential habitat sinks which may persist due to high recruitment in adjacent habitats.
... Second, the science of sustainable hunting of wolves is unsettled. Although reviews of wolf population dynamics and sustainable levels of killing include many data points and seem to converge on a range of sustainable, annual human-caused mortality rates [32][33][34][35][36], the literature nonetheless concludes with three-fold differences in magnitude for estimates ranging from high teens to 48%. Although the prior literature would seem to guide decisionmakers in Wisconsin to choose a Fall 2021 wolfs-hunt quota that would not change the population, the wide variation in estimates above and the novelty of a second wolf-hunt in a single year produces new and greater uncertainties than the literature addresses. ...
When humanity confronts the risk of extinction of species, many people invoke precautions, especially in the face of uncertainty. Although precautionary approaches are value judgments, the optimal design and effect of precautions or lack thereof are scientific questions. We investigated Wisconsin gray wolves Canis lupus facing a second wolf-hunt in November 2021 and use three legal thresholds as the societal value judgments about precautions: (1) the 1999 population goal, 350 wolves, (2) the threshold for statutory listing under the state threatened and endangered species act, 250 wolves; and (3) state extirpation <2 wolves. This allows us to explore the quantitative relationship between precaution and uncertainty. Working from estimates of the size wolf population in April 2021 and reproduction to November, we constructed a simple linear model with uninformative priors for the period April 2021-April 2022 including an uncertain wolf-hunt in November 2021. Our first result is that the state government under-counted wolf deaths in the year preceding both wolf-hunts. We recommend better scientific analysis be used when setting wolf-hunt quotas. We find official recommendations for a quota for the November 2021 wolf-hunt risk undesirable outcomes. Even a quota of zero has a 13% chance of crossing threshold 1. Therefore, a zero death toll would be precautionary. Proponents for high quotas bear the burden of proof that their estimates are accurate, precise, and reproducible. We discuss why our approach is transferable to non-wolves. We show how scientists have the tools and concepts for quantifying and explaining the probabilities of crossing thresholds set by laws or other social norms. We recommend that scientists grapple with data gaps by explaining what the uncertainty means for policy and the public including the consequences of being wrong.
... We estimated home ranges using the 95% isopleth Garrott 1990, Laver andKelly 2008) of the utilization distribution (UD; Van Winkle 1975). We defined an excursion as a temporary movement !1 km from the nearest location within the 95% UD isopleth calculated with all excursions included (Adams et al. 2008, Skuldt et al. 2008. We excluded excursions from UD calculations because they can greatly influence home range estimates (Dunn andGipson 1977, Kernohan et al. 2001) and bias them to include largely unused areas (Kenward 2001). ...
Disease, predation, and genetic isolation resulted in 4 of 6 island fox (Urocyon littoralis) subspecies being listed as endangered in 2004. Potential for disease outbreaks continues to pose a major threat to the persistence of these isolated, endemic populations. We examined how roads influence the spatial ecology of San Clemente Island foxes (U. l. clementae), particularly in regard to spread of disease, to provide management recommendations for preventing or minimizing a disease outbreak on San Clemente Island, California, USA. Home range areas ( = 0.75 km²) and core areas ( = 0.19 km²) of foxes on San Clemente Island were 0.36–1.23 and 2.17 times larger, respectively, than estimates from Santa Cruz Island foxes (U. l. santacruzae). Home ranges and core areas were 78% larger and 73% larger, respectively, for foxes near roads than for foxes away from roads. Home ranges were also largest when foxes were not caring for offspring (i.e., seasons of pup‐independence and breeding). We did not detect any dispersal movements, but foxes living near roads moved 33% farther in 2‐hours periods than foxes not living near roads. Foxes near roads move faster, range more widely, and could more rapidly spread a pathogen throughout the island; therefore, roads might serve as transmission corridors. We recommend reducing this risk by increasing widths of vaccination firewalls (areas where vaccination is used to induce a disease‐resistant or immune population of foxes), ensuring these areas deliberately intersect roads, and vaccinating a higher proportion of foxes living near roads. Disease risk models incorporating these strategies could inform the lowest risk scenarios. © 2018 The Wildlife Society.
Survival is a key determinant of population growth and persistence; computation and understanding of this metric is key to successful population management, especially for recovering populations of large carnivores such as wolves. Using a Bayesian frailty analytical approach, we evaluated information from 150 radio-tagged wolves over a 16-year time period to determine temporal trends and age- and sex-specific survival rates of wolves in Minnesota, United States. Based on our analyses, overall annual survival of wolves during the study was 0.67, with no clear evidence for age- or sex-specific differences in the population. Our model demonstrated statistical support for a temporal trend in annual survival; the highest survival was predicted at the beginning of the time series (0.87), with lowest survival (0.55) during 2018. We did not observe evidence that survival was markedly reduced during years when a regulated hunting and trapping season was implemented for wolves (years 2012–2014). However, cause-specific mortality analysis indicated that most mortality was human-caused. While the estimate for increasing human-caused mortality over time was positive, the evidence was not statistically significant. Anthropogenic causes resulted in ∼66% of known mortalities, including legal and illegal killing, and vehicular collisions. Trends in wolf survival in Minnesota may reflect an expanding distribution; wolf range has spread to areas with more human development during the study, presumably leading to increased hazard and reduced survival. Our results provide foundational information for evaluating and guiding future policy decisions pertaining to the Great Lakes wolf population.
Characterizing population distribution and abundance over space and time is central to population ecology and conservation of natural populations. However, species distribution models and population dynamic models have rarely been integrated into a single modelling framework. Consequently, fine‐scale spatial heterogeneity is often ignored in resource assessments. We develop and test a novel spatiotemporal assessment framework to better address fine‐scale spatial heterogeneities based on theories of fish population dynamic and spatiotemporal statistics. The spatiotemporal model links species distribution and population dynamic models within a single statistical framework that is flexible enough to permit inference for each state variable through space and time. We illustrate the model with a simulation–estimation experiment tailored to two exploited marine species: snow crab (Chionoecetes opilio, Oregoniidae) in the Eastern Bering Sea and northern shrimp (Pandalus borealis, Pandalidae) in the Gulf of Maine. These two species have different types of life history. We compare the spatiotemporal model with a spatially aggregated model and systematically evaluate the spatiotemporal model based on simulation experiments. We show that the spatiotemporal model can recover spatial patterns in population and exploitation pressure as well as provide unbiased estimates of spatially aggregated population quantities. The spatiotemporal model also implicitly accounts for individual movement rates and can outperform spatially aggregated models by accounting for time‐and‐size varying selectivity caused by spatial heterogeneity. We conclude that spatiotemporal modelling framework is a feasible and promising approach to address the spatial structure of natural resource populations, which is a major challenge in understanding population dynamics and conducting resource assessments and management.
Human‐dominated landscapes are being recolonized by large carnivores, thereby increasing conflicts worldwide via predation of livestock and harvested wildlife such as ungulates. Recent meta‐analyses have shown that predator control (hereafter, predator removal) has mixed success in reducing livestock predation. Yet, it is unknown how effective predator removal is in decreasing predation on ungulates due to a lack of quantitative synthesis, despite the long history of implementation in North America. We quantified the demographic responses of ungulate survival and recruitment rates, abundance, and population growth to experimental predator removal and identified the ecological and experimental design factors affecting ungulate responses to predator removal. We conducted a literature review of management and natural experiments to increase ungulate demography finding 52 predator removal experiments and 10 natural experiments from 47 publications. We then conducted a meta‐analysis to determine the overall effect size and factors which increased ungulate demography during predator removal. Lastly, we tested for evidence of publication bias and experimental rigour for these experiments. We found that predator removal in both management and natural experiments increased ungulate demographic responses by 13% (95% CI = 4.1%–23%), yet prediction intervals overlapped with 0 (95% PI = −34% to 93%). Focusing just on management removals, ungulate demographic responses increased only by 7.8% (95% PI = −32% to 72%), indicating that future experiments could have negligible effects. Predator removal in both management and natural experiments was more successful in improving the demography of young (e.g. recruitment ES = 44%, 95% CI = 13%–83%) but equivocal in improving adult survival (ES = 5.4%, 95% CI = −18% to 36%) and ungulate abundance (ES = 13%, 95% CI = −17% to 31%). The low and variable effectiveness of predator removal for ungulate populations might be linked to ungulates' slow life history and the compensatory mortality of carnivores on ungulates, though effects were stronger on endangered prey. We identified the experimental design factors that led to greater uncertainty in ungulate responses to predator removal, including lack of randomization, low replication and short temporal length. Lastly, we found evidence of publication bias, where experiments with poor rigour and negative effects (i.e. reduced ungulate demography following predator removal) were under‐reported. Synthesis and Applications. We recommend future predator removal experiments be conducted with a more rigorous experimental design to overcome these weaknesses, especially for endangered species where predator removal may work more effectively. We suggest that managers attempting to evaluate experimental practices to increase ungulate populations through predator removal could employ an open standards framework akin to the ‘Open Standards for the Practice of Conservation’ framework. We recommend future predator removal experiments be conducted with a more rigorous experimental design to overcome these weaknesses, especially for endangered species where predator removal may work more effectively. We suggest that managers attempting to evaluate experimental practices to increase ungulate populations through predator removal could employ an open standards framework akin to the ‘Open Standards for the Practice of Conservation’ framework.
The reintroduced red wolf population in northeastern North Carolina declined to 7 known wolves by October 2020. Poaching (illegal killing) is the major component of verified anthropogenic mortality in this and many other carnivore populations, but it is still not well understood. Poaching is often underestimated, partly as a result of cryptic poaching, when poachers conceal evidence. Cryptic poaching inhibits our understanding of the causes and consequences of anthropogenic mortality which is important to conservation as it can inform us about future population patterns within changing political and human landscapes. We estimate risk for marked adult red wolves of 5 causes of death (COD: legal, nonhuman, unknown, vehicle and poached) and disappearance, describe variation in COD in relation to hunting season, and compare time to disappearance or death. We include unknown fates in our risk estimates. We found that anthropogenic COD accounted for 0.724 – 0.787, including cryptic and reported poaching estimated at 0.510 – 0.635 of 508 marked animals. Risk of poaching and disappearance was significantly higher during hunting season. Mean time from collaring until nonhuman COD averaged 376 days longer than time until reported poached and 642 days longer than time until disappearance. Our estimates of risk differed from prior published estimates, as expected by accounting for unknown fates explicitly. We quantify the effects on risk for three scenarios for disappearances, which span conservative to most likely COD. Implementing proven practices that prevent poaching or hasten successful reintroduction may reverse the decline to extinction in the wild of this critically endangered population. Our findings add to a growing literature on endangered species protections and enhancing the science used to measure poaching worldwide.
This study reports the disappearance of a small Arctic wolf population in north-east
Greenland founded in 1979 and provides the first long-term information on the
wolf packs of this region. Data sources comprised specialized wolf surveys in two of
three distributional core areas during three summers, 2012–14, and incidental
sightings of wolves by military ground patrols during winter and by others year-round.
The resulting time series spans 40 years (1979–2018). After gradually
increasing for 14 years, the sighting rate peaked in 1996 and then declined to zero
after May 2002, suggesting that the population went extinct. The crash occurred
despite year-round legal protection in a national park and resulted in a 51.2%
reduction in the extent of the occupied wolf range in Greenland and a 41.8%
reduction in Greenland’s wolf population size. It was outside the scope of this study
to conduct a complete analysis of all potential factors in the disappearance. In north
Greenland, a small population of up to 32 wolves during optimal years continues
to exist, and dispersers reach north-east Greenland occasionally. A number of measures
are proposed that, if implemented by the Greenland Home Rule Government,
would help secure the future of the few remaining wolves on the island.
As climate change accelerates in northern latitudes, there is an increasing need to understand the role of climate in influencing predator-prey systems. We investigated wolf population dynamics and numerical response in Denali National Park and Preserve in Alaska, United States from 1986 to 2016 under a long-term range of varying climatic conditions and in the context of prey vulnerability, abundance, and population structure using an integrated population modeling approach. We found that wolf natality, or the number of wolves added to packs, increased with higher caribou population size, calf:cow ratio, and hare numbers, responding to a 1-year lag. Apparent survival increased in years with higher calf:cow ratios and cumulative snowfall in the prior winter, indicators of a vulnerable prey base. Thus, indices of prey abundance and vulnerability led to responses in wolf demographics, but we did not find that the wolf population responded numerically. During recent caribou and moose population increases wolf natality increased yet wolf population size declined. The decline in wolf population size is attributed to fewer packs in recent years with a few very large packs as opposed to several packs of comparable size. Our results suggest that territoriality can play a vital role in our study area on regulating population growth. These results provide a baseline comparison of wolf responses to climatic and prey variability in an area with relatively low levels of human disturbance, a rare feature in wolf habitat worldwide.
Understanding the types and magnitude of human-caused mortality is essential for maintaining viable large carnivore populations. We used a database of cause-specific mortality to examine how hunting regulations and landscape configurations influenced human-caused mortality of North American gray wolves (Canis lupus). Our dataset included 21 studies that monitored the fates of 3564 wolves and reported 1442 mortalities. Human-caused mortality accounted for 61% of mortality overall, with 23% due to illegal harvest, 16% due to legal harvest, and 12% the result of management removal. The overall proportion of anthropogenic wolf mortality was lowest in areas with an open hunting season compared to areas with a closed hunting season or mixed hunting regulations, suggesting that harvest mortality was neither fully additive nor compensatory. Proportion of mortality from management removal was reduced in areas with an open hunting season, suggesting that legal harvest may reduce human-wolf conflicts or alternatively that areas with legal harvest have less potential for management removals (e.g., less livestock depredation). Proportion of natural habitat was negatively correlated with the proportion of anthropogenic and illegal harvest mortality. Additionally, the proportion of mortality due to illegal harvest increased with greater natural habitat fragmentation. The observed association between large patches of natural habitat and reductions in several sources of anthro-pogenic wolf mortality reiterate the importance of habitat preservation to maintain wolf populations. Furthermore, effective management of wolf populations via implementation of harvest may reduce conflict with humans. Effective wolf conservation will depend on holistic strategies that integrate ecological and socioeconomic factors to facilitate their long-term coexistence with humans. K E Y W O R D S Canis lupus, carnivore, cause-specific mortality, meta-analysis, telemetry
Bieszczady National Park and its buffer zone is an area of permanent living and
breeding of wolves within family groups. In the years 2006–2020, four wolf packs were
monitored in home ranges of 113–311 km2. A total area of 562–903 km2 was monitored.
Basic population indicators (e.g. numbers, reproduction, distribution of home ranges)
were obtained using: telemetry (4504 locations), long-distance snow tracking (558 km),
collection of point information (2091 records), phototraps (454 locations). The total
number of wolves in the monitored area was 15–45 individuals, at densities 2.60–4.98
individual/100 km2. The average litter size in six registered cases ranged from 6.5 to 6.8
puppies (min/max range 4–10 individuals). Tracked wolves preferred forest areas (82%
of the tracking length) and rarely used paved forest roads and paved roads in open areas
(22% and 5% of the tracking length, respectively). The average marking frequency was: a)
urine 0.49 / km tracking; b) scratching 0.20 / km tracking. The frequency of feces found
on the trail (excretion, odour function) was 0.34/km of tracking. During snow tracking,
46 resting sites were found (0.08/km of tracking), characterized by 51% of their location
under natural cover (e.g. under the canopy of spruce or in the fir thicket). Natural preys
were also found during tracking (52 locations; frequency 0.09/km tracking). An analysis
of all database records for apparently wolf preys (105 locations) showed that deer were
the most common wolf victim – 84% (bulls 64%, doe 36%; age structure of victims: 85%
adults, 15% calves); other species were: wild boar 10%, roe deer 5%, and other (hare, dog)
– 1%.
A LARGE, DARK WOLF poked his nose out of the pines in Yellowstone National Park as he thrust a broad foot deep into the snow and plowed ahead. Soon a second animal appeared, then another, and a fourth. A few minutes later, a pack of thirteen lanky wolves had filed out of the pines and onto the open hillside. Wolf packs are the main social units of a wolf population. As numbers of wolves in packs change, so too, then, does the wolf population (Rausch 1967). Trying to understand the factors and mechanisms that affect these changes is what the field of wolf population dynamics is all about. In this chapter, we will explore this topic using two main approaches: (1) meta-analysis using data from studies from many areas and periods, and (2) case histories of key long-term studies. The combination presents a good picture-a picture, however, that is still incomplete. We also caution that the data sets summarized in the analyses represent snapshots of wolf population dynamics under widely varying conditions and population trends, and that the figures used are usually composites or averages. Nevertheless, they should allow generalizations that provide important insight into wolf population dynamics.
Subsampling large sets of radio telemetry locations of Canis lupus of N-central Minnesota indicated that 30-35 individual radio locations obtained at least 2 days apart described 87-90% of a pack's territory in winter. Pack size, territory size and number of radio-marked wolves had little impact on minimum number of locations needed to describe territories. -from Authors
During September 1980-December 1986, 81 radio-collared wolves (Canis lupus) were monitored in and near the 839-km2 Bearville Study Area )BSA) in north-central Minnesota. Each year winter-territory size averaged 78-153 km2; no territories had road densities >0.72 km/km2. From zero to 30% of radiomarked pup, yearling, or adult wolves left their territories each month. Pups left natal packs during January-March and older wolves left frequently during September-April. Wolves temporarily leaving territories moved 5-105 km away and were absent 3-118 days; up to 6 exploratory moves were made prior to dispersal. Dispersing wolves traveled 5-100 km away during periods of 1-265 days. One disperser joined and established pack, but 16 others formed new packs. Annual dispersal rates were about 0.17 for adults, 0.49 for yearlings, and 0.10 for pups.
Each year mean pack size ranged from 5-9 in November/December to 4-6 in March. Annual wolf density (including 16% lone wolves) ranged from 39-59 wolves/1,000 km2 in November-December and 29-40 wolves/1,000 km2 in March. Annual immigration was 7%. The observed mean annual finite rate of increase was 1.02, and annual rates of increase were correlated with mean number of pups per pack in November. Litters averaged 6.6 pups at birth and 3.2 pups by mid-November, at which time pups made up 46% of pack members. Annual survival of radio-marked wolves >5 months old was 0.64. Despite legal protection, 80% of identified wolf mortality was human caused (30% shot, 12% snared, 11% hit by vehicles, 6% killed by government trappers, and 21% kill by humans in some undetermined manner); 10% of wolves that died were killed by other wolves.
During sample periods in 2 winters, wolves were located twice daily to estimate predation rates on white-tailed deer (Odocoileus virginianus). Estimated minimum kill rates during January-February (x = 21 days/kill/wolf) did not differ between winters with differing snow depths. Winter consumption averaged 2.0 kg deer/wolf/day (6% body wt/day). Scat analyses indicated deer were the primary prey in winter and spring, but beaver (Castor canadensis) were an important secondary prey (20-47% of items in scats) during April-May. Neonatal deer fawns occurred in 25-60% of scats during June-July whereas the occurrence of beaver declined markedly. Overall, deer provided 79-98% of biomass consumed each month. Adult wolves consumed an estimated 19/year, of which 11 were fawns.
A review of North American studies indicates that wolf numbers are directly related to ungulate biomass. Where deer are primary prey, territory size is related to deer density. Per capita biomass availability likely affects pup survival, the major factor in wolf population growth. Annual rates of increase of exploited populations vary directly with mortality rates, and harvest exceeding 28% of the winter population often result in declines. Management decisions concerning wolf and ungulate density and ungulate harvest by humans can be made using equations that incorporate estimate of wolf density, annual ungulated kill per wolf, ungulate densities, potential rate of increase for ungulates, and harvest.
We conducted a large-scale, controlled experiment to study the responses of declining woodland caribou (Rangifer tarandus), moose (Alces alces), and Dall sheep (Ovis dalli) to a 5-year reduction in wolf (Canis lupus) numbers in the Aishihik area in the southwestern Yukon. We monitored 10 contemporary controls including 3 caribou herds and 3 moose, 1 Dall sheep, and 3 wolf populations. We tested the hypothesis that wolf predation was the main factor limiting recruitment, adult survival, and population size for the 3 ungulates. Caribou productivity, winter forage quality, disease prevalence, snow depth, snowmelt phenology, harvest, and migration were also assessed. For moose, we also examined harvest, snow depth, and spring and summer growing seasons. Treated moose and caribou populations showed the greatest differences in changes in rates of increase during wolf treatment compared to controls, supporting the wolf predation hypothesis. We found evidence that wolf predation strongly limited recruitment of caribou and moose, and survival of adult moose. We found no evidence that adult survival of caribou improved when wolf numbers were reduced, nor did we find evidence that Dall sheep recruitment or adult numbers responded to lower wolf numbers. Wolf predation and human hunting were probably the main causes of caribou and moose declines before our study. The combination of reduced hunting and lowered predation by wolves was the primary factor causing the increase in the treated Aishihik caribou herd. Lowered predation by wolves, especially upon adult moose, was more important than harvest reduction to the moose increase in the Aishihik area. We hypothesize that woodland caribou herds are linked to the population dynamics of low-density moose in the Yukon. We conclude that natural predation is the main force maintaining low abundance of moose, and that maximum harvest rates should be set conservatively at 2% for caribou and 5% for moose. We recommend that managers use habitat enhancement and public wolf trapping to sustain higher ungulate densities and avoid the need for reactive broad-scale wolf control. We found that wolf fertility control was effective in reducing the rate of increase of wolves and that it was more publicly acceptable than lethal control. We evaluate large-scale wolf-prey experiments as an adaptive management approach.
Methods are presented for estimating survival and cause-specific mortality rates from radiomarked animals. Time is partitioned into intervals during which the daily rates are assumed to be constant. The rates are estimated from the number of transmitter-days, the number of mortalities due to particular causes, and the number of days in the time intervals. Potential biases arising from combining data from several individuals marked at different times within an interval or from combining rates from different intervals are identified. Variances and confidence intervals for the estimators are presented. Hypothesis testing and sample-size considerations are also illustrated. Simulation showed that the influence of errors in date of death was small, but misdiagnosis of fate had serious consequences. A microcomputer program is available for performing the analyses.
During 1980-1986, monitoring of radiomarked wolves (Canis lupus), an observation of copulation and presence of newborn pups indicated that birth occurred during the 2nd week of April in N-central Minnesota. Wolves remained at natal dens for a mean minimum of 25 days before moving to a second site. Individual dens were used up to 6 consecutive years. Dens were either excavated or in hollow logs.
Population studies of wolves (Canis lupus) were carried out during October 1975-June 1978 on 2 study areas in northern Alberta; 13 wolves in 6 packs and 2 lone wolves were captured, radio-collared, and located 939 times. Telemetry data indicated a winter wolf density of 1/158 km2 near Fort McMurray. Numbers increased from 1975 to 1977 at a rate of about 21% annually. The winter wolf density of 1/90km2 on a study area in the Swan Hills, 300 km southwest, appeared lower than in past years. The difference in wolf density between the 2 areas reflected available food resources. Trapping and early pup deaths were likely the major mortality factors. Wolves killed disproportionately more young, old, and probably debilitated moose (Alces alces), as well as more female calves and adult bulls. Most wolf kills in winter (88%) were made in lowland habitats despite an even distribution of moose in uplands and lowlands. Deeper snow and colder temperatures in 1978 resulted in decreased travel by 1 pack (straight-line distances between daily locations of 5.7 vs. 9.0 km/day). The mean kill rate of this pack was similar in both years (1 moose/4.7 days); per capita consumption decreased slightly in 1978 (0.12 vs. 0.15 kg prey/kg wolf/day) because of larger mean pack size (9.8 vs. 9.2). An equation was derived for calculating true kill rates when relocation flights were spaced more than 1 day apart. Summer food habits of wolves (1,723 scats analyzed) indicated that adult moose remained the staple food in all areas. Use of beaver (Castor canadensis) was related to availability. One wolf pack annually consumed about 15% of the yearling and older moose in their territory, close to the estimated 19% annual recruitment of new yearlings. Two lone wolves and 2 packs were partially dependent on dumps for food during winter; predation rates by these packs were much lower. Wolf densities near disturbed sites were higher than in surrounding areas.
We compared wolf (Canis lupus) reproductive data for March and April, when ungulate biomass per wolf was high, moderate, and low. The percentage of reproductively active adult females was significantly lower (66% compared with ≥96%, P < 0.001) when ungulate biomass per wolf was low versus moderate or high. Reproductively inactive adult females had significantly less subcutaneous fat (P < 0.01) than reproductively active females when ungulate biomass per wolf was relatively abundant. Average litter size, estimated by counting blastocysts or fetuses, declined significantly (P < 0.001), from 6.9 to 4.6, as ungulate biomass per wolf declined. We conclude that wolf productivity declines as prey availability per wolf declines. However, only when ungulate biomass per wolf declined below levels previously reported in the literature did we observe significant declines in reproductive potential. Ungulate biomass per wolf was low because of large, rapid declines in ungulates and lesser declines in wolves. We recognize that functional relationships, e.g., prey vulnerability and feeding dominance, can influence wolf productivity independently of ungulate biomass per wolf.
We examined the dispersal patterns of radio-collared wolves (Canis lupus) from 21 packs in the Superior National Forest, Minnesota, from 1969 to 1989. A total of 316 wolves (542 wolf-years) were captured, radio-collared, and followed during 21 years of radio-tracking; 75 were identified as dispersers. Both sexes dispersed equally. Of the adults, yearlings, and pups, 8, 75, and 16%, respectively, dispersed. Most dispersers left when they were 11–12 months old, only a few wolves dispersing as adults. Dispersal occurred mainly in February–April and October–November. Adults dispersed short distances into nearby territories, but yearlings and pups dispersed both short and long distances. Yearling and pup dispersal rates were highest when the wolf population was increasing or decreasing and low when the population was stable. Adults had the highest pairing and denning success. Yearlings had moderate pairing and low denning success, and pups had low pairing and denning success. Yearlings and pups that dispersed a short distance had a higher success of settling in a new territory, likely reflecting available vacancies in nearby territories. Thirty-five percent of the known-age wolves remained in their natal territory for >2 years; two wolves were known to have remained for >7 years. The relative weight of pups at capture apparently did not affect their age or success of dispersal or the tendency to disperse.
We studied the dynamics of a wolf (Canis lupus) population recovering from intensive reduction in the Finlayson Lake area, Yukon, Canada. Within 6 years, numbers increased from 29 wolves, then stabilized at 245. The colonization of vacant territories by young wolf pairs was the primary mechanism of early population recovery. Reproduction and a low dispersal rate increased pack size in later years, and pack splitting allowed dispersing wolves to remain near natal packs. The rate of increase in the wolf population was density-dependent and related to wolf density, but was also related to the dispersal rate. The dispersal rate was density-independent and related to mean pack size and prey biomass : wolf index. The survival rate was age-dependent and not related to wolf density. In the early years of recovery, the rate of increase was supported by high survival rates and low dispersal rates. In later years, dispersal rates increased, stabilizing mean pack size and wolf density. Wolf density stabilized at levels predicted by the prey supply, but whether the wolf population is regulated by the availability of prey resources remains unresolved. Wolf density, pack density, and mean pack size were similar in 1983 and 1996, despite a 2- to 3-fold difference in prey biomass. We suggest that the interaction of wolf density and mean pack size in stable prey systems needs to be studied to determine the roles played by food supply and wolf social behavior in regulating wolf abundance.
Within the 2700km² Beltrami Island State Forest, near the W edge of the primary range of Canis lupus in Minnesota, wolf population density was low at the start of the study in 1972 but increased substantially up to 1977 (end of study). At least 8 of 13 social units present in mid-1976 had formed since 1972. Size of litters of established packs averaged 4.6 pups, and those of newly-formed pairs averaged 4.1. Mortality decreased over the study period, and recruitment of young wolves exceeded mortality following legal protection. A high rate of dispersal of young from packs was documented. Dispersal peaked in autumn. Most wolves paired within a few days of leaving their packs. Average territory size decreased as both population and pack numbers increased. Behaviour of alpha males, alpha females and subordinate members of the packs is discussed. Deer and moose comprised 94% of animal biomass eaten by wolves, with deer along accounting for 67%. Seasonal differences in food taken and energy requirements are noted.-P.J.Jarvis
Moose Alces alces and caribou Rangifer tarandus populations increased following a wolf Canis lupus reduction program in the 1950's and reached peak abundance in the 1960's. Deep snow and heavy browsing caused an initial crash of moose in 1965-66. Moose continued to decline until 1976, primarily due to periodic deep snow, harvest by man, and wolf predation. The long-term effect of moose mortality from deep snow was to increase the impact of predation by lowering moose/wolf ratios. Hunting and wolf predation were the principal causes of moose mortality from 1971-75. Harvests removed 6-19% of the moose population annually; mean harvest rate equalled mean yearling recruitment. After 1974, harvest removed 2% of the moose. Predation by wolves removed 13-34% of moose during winters 1973-74 and 1974-75 and a high proportion of calves during summer. Mortality from predation during winter exceeded recruitment of calf moose. Hunting and wolf predation were also the primary proximate mortality causes in the decline of caribou, but calf recruitment was so low from 1971-75 that a significant decline would have occurred without hunting. After 1973 when hunting was stopped, predation limited the population. Following a 61% reduction in wolves in 1976, survival of calf and yearling moose increased 2- to 4-fold, adult mortality declined, and the moose population increased. Survival of caribou calves also increased significantly, and the population grew rapidly. -from Authors
Examined Canis lupus demography, movement patterns, predation characteristics in relation to migratory Rangifer tarandus granti. Wolf packs usually did not follow migratory caribou but maintained year-round resident territories that averaged 1 868 km2. However, during years when caribou were absent and moose Alces alces densities were low up to 17% of the radio-marked wolf packs followed migratory caribou and then returned to their original territory for denning. Radio-collared wolves dispersed primarily during April through September. Spring wolf densities increased from 2.7-4.4 wolves/1 000 km2 during 1987-1990, then declined to 1.5 wolves/1 000 km2 following a rabies epizootic. Annual wolf survival rates averaged 0.552 (range 0.464-0.656). Annual survival during 1990-91 and 1991-92 was lower than other years due to a rabies epizootic. Overall, hunting was the main cause of death (69%) for wolves (n=52). Most (63%) mortality occurred during December through March when snow cover permitted wolf hunting from snowmobiles. Caribou and moose composed 51 and 42%, respectively, of the kills observed during the study; 59% of caribou and 64% of moose kills were adult. Ungulate kills averaged 4.6/wolf/100 days and provided 5.3 kg of available food/wolf/day. When caribou densities were >200/1 000 km2, wolves switched to preying on resident moose. Wolves within the range of the Western Arctic Caribou Herd killed 6-7% of this caribou population annually. Caribou left wolf pack territories during winter, and wolves switched to preying on moose for c. 4 months of each year. Wolves killed 11-14% of the moose population annually. Wolf densities were limited by hunting and trapping, and wolf predation at levels found in 1987-91 did not strongly limit caribou population growth. However, existing wolf population may be able to regulate local, low-density moose populations that have become established during the past 40 yr.
Canis lupus recolonized the Kenai Peninsula in the 1960s following a 50-yr absence. Wolf density ranged from 11-20 wolves/1000 km². Wolves fed primarily on moose Alces alces (density 0.8/km²); predation rate in winter averaged 1 moose/pack/4.7 days. Food consumption in winter was 0.12 kg/kg wolf/day, but intake apparently declined in summer. Calves composed 20% of the moose population but 47% of wolf-killed moose examined; proportionately more calves were killed during a winter with deep snow. Wolf predation selectively removed the oldest moose in the population. All but 3 of 72 wolf-killed adult moose of which sex could be ascertained were females. Typically 1 litter of wolf pups was born annually to the dominant female in each pack. Pups born to a socially subordinate female were growth-retarded and apparently died. Extraterritorial movements were most commonly undertaken by subordinate adult wolves during the February breeding season. Survival of dispersing wolves was only half that of nondispersers; most dispersers were killed before they could reproduce successfully. Mortality was largely human-caused, averaging 33% annually. Harvest increased rapidly, reducing pack size and causing declines in pack territory size. Additional packs developed in vacated areas, and total wolf density was maintained until annual kill exceeded 30-40% of the early winter population.-from Authors
We measured nipple sizes of 29 captive wolves (Canis lupus), of known breeding histories, throughout the year and tested distinctions among various known breeding statuses of 20 wild wolves examined in northeastern Minnesota from May through September. For ca. 8 mo of the year only breeders and nonbreeders can be classified. Distinctions between current and former breeders were not reliable.