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Regulated hunting re-shapes the life history of brown bears

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Management of large carnivores is among the most controversial topics in natural resource administration. Regulated hunting is a centrepiece of many carnivore management programmes and, although a number of hunting effects on population dynamics, body-size distributions and life history in other wildlife have been observed, its effects on life history and demography of large carnivores remain poorly documented. We report results from a 30-year study of brown bears (Ursus arctos) analysed using an integrated hierarchical approach. Our study revealed that regulated hunting has severely disrupted the interplay between age-specific survival and environmental factors, altered the consequences of reproductive strategies, and changed reproductive values and life expectancy in a population of the world’s largest terrestrial carnivore. Protection and sustainable management have led to numerical recovery of several populations of large carnivores, but managers and policymakers should be aware of the extent to which regulated hunting may be influencing vital rates, thereby reshaping the life history of apex predators.
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© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
1Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway. 2Université de Lyon, F-69000,
CNRS, UMR, 5558, Laboratoire de Biométrie et Biologie Évolutive, Villeurbanne, France. 3Centre for Ecological and Evolutionary Synthesis, Department of
Biosciences, University of Oslo, Oslo, Norway. 4Department of Natural Sciences and Environmental Health, University College of Southeast Norway, Bø,
Norway. 5Institute of Wildlife Biology and Game Management, University of Natural Resources and Life Sciences, Vienna, Austria. 6Department of Zoology,
University of Oxford, Oxford OX1 3PS, UK. 7Norwegian Institute for Nature Research, Trondheim, Norway. *e-mail:
Few organisms and natural processes remain untouched by
human intervention1. Large carnivores and predation are no
exception. Attempts to control and manage wildlife that com-
pete with humans for the apex of shared food webs are responsible
for the demise of some large carnivore species2 and the present-day
patterns in the abundance and distribution of those species that
remain extant3,4. Well-known examples include declines in the dis-
tribution and abundance of lions (Panthera leo) in Africa5, tigers
(Panthera tigris) in Asia6 and brown bears in North America7 and
Europe8. The latter is a particularly good example of enormous
changes attributable to manipulation by humans. State-financed
bounties introduced in the 1600s and 1700s aimed for, and nearly
accomplished, complete eradication of bears from central and
northern Europe by the early twentieth century9. Subsequent pro-
tective measures have allowed range expansion10 and numerical
recovery to levels approximating those at the end of the industrial
revolution in some regions9. Today, regulated, but intensive, hunt-
ing pressure has again resulted in a population decline in parts of
northern Europe11.
Less conspicuous than effects on abundance and distribution, yet
important, are the effects that management has on the interaction
between vital rates and their intrinsic and extrinsic determinants.
Individual variation in recruitment and survival in the context of
various drivers governs the dynamics of wild animal populations;
their demographic makeup12, their interaction with current and
future environments13, the realization of their ecological role14 and
ultimately their trajectories and fates15. Although several individual-
based longitudinal studies of carnivore demography have been car-
ried out16 and examples of population dynamic effects of hunting
have been reported17, we still lack comprehensive documentation
of how hunting, in concert with individual and environmental fac-
tors, influences vital rates in hunted carnivore populations. These
effects are better documented and understood in ungulate
populations, where hunting, particularly highly selective trophy
hunting, has been the subject of intensive study for decades18,19.
Selective hunting affects vital rates in some age and sex classes to a
greater extent than in others20. The resulting changes in survivorship
and fertility schedules lead to modifications in population dynamics,
life history and the distribution of body and trophy trait sizes21,22. It
is not surprising that corresponding examples and insights for car-
nivore populations are mostly lacking, considering the difficulty of
monitoring rare and elusive species and analysing sparse ecological
data. Taking advantage of a unique individual-based dataset from
a hunted brown bear population that has been monitored continu-
ously and intensively in Sweden since 1985 (Fig.1), we estimated
cause-specific mortality and recruitment parameters jointly, as well
as the effects of key intrinsic and extrinsic factors on these parame-
ters. We did so using a Bayesian multistate capture–recapture model
that combined information from physical captures, telemetry, re-
sightings and dead recoveries (Supplementary Fig.1). Transitions
between states were modelled across multiple years and between
three annual biological seasons (mating, hyperphagia and den-
ning) consistent with the timing of major life history events during
a year. The integrated approach for estimating vital rates revealed
pronounced influences of individual attributes and environmental
characteristics on both survival and reproduction. Most striking is
the central role of hunting in the interplay between vital rates and
their drivers (Figs.2 and 3), with direct consequences for fitness.
Results and discussion
Once they have reached adulthood, the risk of predation that apex
predators experience from non-human sources is typically low2325.
Legal hunting, one of the primary tools for defraying (or at least
mitigating) the socioeconomic and political costs of the coexistence
of humans with wildlife26,27, maintains a source of mortality that is
unique in how it selects its targets. Bears are exposed to the highest
Regulated hunting re-shapes the life history of
brown bears
Richard Bischof 1*, Christophe Bonenfant 2, Inger Maren Rivrud3, Andreas Zedrosser4,5,
Andrea Friebe1, Tim Coulson 6, Atle Mysterud 3 and Jon E. Swenson1,7
Management of large carnivores is among the most controversial topics in natural resource administration. Regulated hunting is
a centrepiece of many carnivore management programmes and, although a number of hunting effects on population dynamics,
body-size distributions and life history in other wildlife have been observed, its effects on life history and demography of large
carnivores remain poorly documented. We report results from a 30-year study of brown bears (Ursus arctos) analysed using an
integrated hierarchical approach. Our study revealed that regulated hunting has severely disrupted the interplay between age-
specific survival and environmental factors, altered the consequences of reproductive strategies, and changed reproductive
values and life expectancy in a population of the world’s largest terrestrial carnivore. Protection and sustainable management
have led to numerical recovery of several populations of large carnivores, but managers and policymakers should be aware of
the extent to which regulated hunting may be influencing vital rates, thereby reshaping the life history of apex predators.
Content courtesy of Springer Nature, terms of use apply. Rights reserved
... There is no limit to the number of bears an individual can shoot, as long as the county-level quota has not been reached. Because there is little incentive for hunters to pass on an opportunity to kill a bear, bear hunting in Sweden is mostly considered as nonselective with regard to age, sex, and size (Bischof et al., 2009), although recent estimates show that hunting may now be slightly biased toward older males and larger individuals (Bischof et al., 2018;Leclerc et al., 2016). However, since 1986, all members of a family group of bears, that is, a female accompanied by dependent offspring of any age, have been afforded legal protection from hunting . ...
... Like all modeling approaches, our predictions are based on a set of assumptions to reduce complexity, or because of the difficulty to estimate certain processes (Caswell, 2001). First, we did not account for potential age differences in vital rates within our adult female stages and used instead parameter estimates averaged for females aged between 6 and 10 years old (Bischof et al., 2018). Young adult females may still divert energy to growth and consequently show reduced reproductive output and survival probabilities due to lifehistory trade-offs (Stearns, 1992). ...
... Lastly, we assumed density independence as a previous study on the same population did not find relationships between bear density and demographic rates (Bischof et al., 2018). This may mean that the population has not reached stationarity, a phase regulated by density dependence where large populations decrease and small populations increase as resources (food, minerals, space, etc.) availability fluctuates (Coulson, 2020;Coulson et al., 2008). ...
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Harvest, through its intensity and regulation, often results in selection on female reproductive traits. Changes in female traits can have demographic consequences, as they are fundamental in shaping population dynamics. It is thus imperative to understand and quantify the demographic consequences of changes in female reproductive traits to better understand and anticipate population trajectories under different harvest intensities and regulations. Here, using a dynamic, frequency‐dependent, population model of the intensively hunted brown bear (Ursus arctos) population in Sweden, we quantify and compare population responses to changes in four reproductive traits susceptible to harvest‐induced selection: litter size, weaning age, age at first reproduction, and annual probability to reproduce. We did so for different hunting quotas and under four possible hunting regulations: (i) no individuals are protected, (ii) mothers but not dependent offspring are protected, (iii) mothers and dependent offspring of the year (cubs) are protected, and (iv) entire family groups are protected (i.e., mothers and dependent offspring of any age). We found that population growth rate declines sharply with increasing hunting quotas. Increases in litter size and the probability to reproduce have the greatest potential to affect population growth rate. Population growth rate increases the most when mothers are protected. Adding protection on offspring (of any age), however, reduces the availability of bears for hunting, which feeds back to increase hunting pressure on the non‐protected categories of individuals, leading to reduced population growth. Finally, we found that changes in reproductive traits can dampen population declines at very high hunting quotas, but only when protecting mothers. Our results illustrate that changes in female reproductive traits may have context‐dependent consequences for demography. Thus, to predict population consequences of harvest‐induced selection in wild populations, it is critical to integrate both hunting intensity and regulation, especially if hunting selectivity targets female reproductive strategies.
... Hunting is frequently permitted for wildlife management, and it is usually subject to regulations designed to guarantee sustainability. However, legal hunting can also alter wildlife communities and movements, shape life histories by artificial selection, and decimate populations to a socially acceptable but ecologically fragile minimum [6,22,23]. Herein, we aim to conduct a holistic assessment that extends beyond the simplistic binary view of "legal and sustainable" versus "illegal and unsustainable" to understand the diverse manifestations of hunting and its varying impacts on wildlife. Therefore, we define hunting as the entirety of activities involved in the management and pursuit of wildlife [9]. ...
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Hunting and its impacts on wildlife are typically studied regionally, with a particular focus on the Global South. Hunting can, however, also undermine rewilding efforts or threaten wildlife in the Global North. Little is known about how hunting manifests under varying socioeconomic and ecological contexts across the Global South and North. Herein, we examined differences and commonalities in hunting characteristics across an exemplary Global South-North gradient approximated by the Human Development Index (HDI) using face-to-face interviews with 114 protected area (PA) managers in 25 African and European countries. Generally, we observed that hunting ranges from the illegal, economically motivated, and unsustainable hunting of herbivores in the South to the legal, socially and ecologically motivated hunting of ungulates within parks and the illegal hunting of mainly predators outside parks in the North. Commonalities across this Africa-Europe South-North gradient included increased conflict-related killings in human-dominated landscapes and decreased illegal hunting with beneficial community conditions, such as mutual trust resulting from community involvement in PA management. Nevertheless, local conditions cannot outweigh the strong effect of the HDI on unsustainable hunting. Our findings highlight regional challenges that require collaborative, integrative efforts in wildlife conservation across actors, while identified commonalities may outline universal mechanisms for achieving this goal.
... This suggests that important heterogeneity cues for settlement decisions occurs within the social landscape. Changes in the social makeup of this population are largely driven by hunting (Gosselin et al. 2015;Bischof et al. 2018). As adult females are removed from the population via harvest, surviving females will shift their home ranges to "fill in" vacancies left by the deceased female (Frank et al. 2017). ...
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How and where a female selects an area to settle and breed is of central importance in dispersal and population ecology as it governs range expansion and gene flow. Social structure and organization have been shown to influence settlement decisions, but its importance in the settlement of large, solitary mammals is largely unknown. We investigate how the identity of overlapping conspecifics on the landscape, acquired during the maternal care period, influences the selection of settlement home ranges in a non-territorial, solitary mammal using location data of 56 female brown bears (Ursus arctos). We used a resource selection function to determine whether females’ settlement behavior was influenced by the presence of their mother, related females, familiar females, and female population density. Hunting may remove mothers and result in socio-spatial changes before settlement. We compared overlap between settling females and their mother’s concurrent or most recent home ranges to examine the settling female’s response to the absence or presence of her mother on the landscape. We found that females selected settlement home ranges that overlapped their mother’s home range, familiar females, that is, those they had previously overlapped with, and areas with higher density than their natal ranges. However, they did not select areas overlapping related females. We also found that when mothers were removed from the landscape, female offspring selected settlement home ranges with greater overlap of their mother’s range, compared with mothers who were alive. Our results suggest that females are acquiring and using information about their social environment when making settlement decisions.
... Age at death was on average 5.9 years (range 1-19 years) for the specimens for whom these data were available (17 specimens, 30%), consistent with life expectancy estimates for the Swedish brown bear population (5-8 years for yearlings), which is low due to hunting. 42 It is therefore probable that it was not until the mid-2000s that bears in our study population lived their entire lives under post-1995 Swedish antibiotic regulations. ...
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Following the advent of industrial-scale antibiotic production in the 1940s,¹ antimicrobial resistance (AMR) has been on the rise and now poses a major global health threat in terms of mortality, morbidity, and economic burden.²,³ Because AMR can be exchanged between humans, livestock, and wildlife, wild animals can be used as indicators of human-associated AMR contamination of the environment.⁴ However, AMR is a normal function of natural environments and is present in host-associated microbiomes, which makes it challenging to distinguish between anthropogenic and natural sources.⁴,⁵ One way to overcome this difficulty is to use historical samples that span the period from before the mass production of antibiotics to today. We used shotgun metagenomic sequencing of dental calculus, the calcified form of the oral microbial biofilm, to determine the abundance and repertoire of AMR genes in the oral microbiome of Swedish brown bears collected over the last 180 years. Our temporal metagenomics approach allowed us to establish a baseline of natural AMR in the pre-antibiotics era and to quantify a significant increase in total AMR load and diversity of AMR genes that is consistent with patterns of national human antibiotic use. We also demonstrated a significant decrease in total AMR load in bears in the last two decades, which coincides with Swedish strategies to mitigate AMR. Our study suggests that public health policies can be effective in limiting human-associated AMR contamination of the environment and wildlife.
... Both CMR and SCR models used in the present study tested and accounted for sex differences in detection and baseline encounter probability (Appendix S1: Table 2b and Fig. 2), which suggests that there should not be methodbased biases in the population, survival, or density estimates. For some hunted brown bear populations, there appears to be female bias, likely because males are often targeted for multiple reasons (McLellan 1994, Miller et al. 2003 and females with cubs are legally protected (Bischof et al. 2018, Van de Walle et al. 2018. However, in unhunted populations, it is also a reasonable possibility that sex ratio is truly skewed toward males, especially when population size is very small (Mills 2012). ...
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Information about population demography is crucial for developing and implementing conservation measures. The brown bear in the Gobi desert of southwestern Mongolia (referred to as the Gobi bear) is one of the smallest and most isolated brown bear populations in the world. We conducted genetic sampling (n = 2660 samples collected) using hair corrals around feeding sites at 13 water sources during 2009, 2013, and 2017 to evaluate population size, survival, and population trend. Bears were identified using 13 microsatellite loci and one sex marker. We detected 51 unique individuals (15F and 36M) from our targeted surveys in 2009, 2013, and 2017. Based on capture-mark-recapture robust design, population estimates were 23 (95% CI: 21-32) in 2009, 28 (95% CI: 25-35) in 2013, and 31 (95% CI: 29-38) individuals in 2017. Spatial capture-recapture analysis suggested abundance was very low (N = 27; 95% CI: 22-35), and there was no significant change from 2009 to 2017. The population density was 0.93 bears/1000 km 2 (95% CI: 0.74-1.17). Our population estimates suggested a stable population trend. However, the population is still very small, and the sex ratio is skewed toward males, raising concerns for future persistence. Annual survival based on Robust design CMR was 0.85. Low abundance and apparent survival for both sexes in this unhunted population coupled with a skewed sex ratio highlight the need for on-the-ground conservation action to conserve this isolated population of bears.
... The full legal protection of all family groups could be ethically more convenient. However, in hunted populations, the ban can affect population demographics by prolonging mother-offspring bonds (Bischof et al. 2018, Van de Walle et al. 2018). ...
Family groups with cubs-of-the-year (cubs) in Finland's brown bear Ursus arctos population are protected from hunting, but sport hunters inadvertently shoot some cubs almost every year. In our data, 39 of 1463 bears from hunting bags (and 39 of all 1503 shot bears) during 1996–2018 were cubs. Mortality of cubs owing to inadvertent shooting by hunters was estimated to be relatively low (ca 8%) and was therefore above all an ethical problem. Male bias from the 1:1 sex ratio was significant (67%, χ² = 4.333, p = 0.037) and possibly attributed to a greater resemblance with yearlings (legal game) given their larger body size. The year trend in the proportion of cubs in hunting bag was not significant (t = -1.832, p = 0.076) We examined whether the risk of cub to being killed by hunters was related to the distance from the Russian border because bear hunting has been practised for more years in eastern Finland compared with mid- and western Finland. The risk of cub being killed was not related to the distance but the risk of female cubs being killed was highest within a narrow zone at the Russian border. If the family group escapes to the Russian side, the risk of losing the hunting dog is presumably high. Given hunters' high motivation to keep their valuable bear-hunting dogs, the proportion of female cubs might be highest near the border. Systematic educational programs for hunters would likely reduce the risk of inadvertent killing of cubs. The full legal protection of all family groups is potentially the most efficient method to reduce the risk and thereby formally provide improved ethics in bear hunting. However, this practice might also prolong the mother–offspring bond.
... Activities related to wildlife tourism and ecotourism have grown continuously over the past decades, being one of the tourist sectors with greatest growth and it is not free of impacts (Balmford et al. 2009;Balmford et al. 2015;Blumstein et al. 2017). More people during longer periods in forest and mountain areas and growing large carnivore populations, as in Europe (Chapron et al. 2014), imply an increased risk of negative interactions between humans and these species (Fortin et al. 2016;Penteriani et al. 2016aPenteriani et al. , 2016bBischof et al. 2017;Bombieri et al. 2019). ...
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The current climate change scenario may produce different impacts on species, ranging from on their genes to their physiology and behaviour, and for all possible interactions between all these. As a result of global warming, the scientific literature suggests that the brown bear will be more active during the winter (spending less time hibernating) and that it will forage in more humanised areas. To what point these changes may influence its reproductive success, despite its phenotypic plasticity, is a question which needs to be addressed. Similarly, areas protected for the species may see a decline in their effectiveness, as the extent and quality of habitats adequate for the species reduce. Climate change is only considered as a threat in 11 of the 49 management or conservation documents covering the brown bear in the world. Of these, only two suggest management measures and neither of these provide indicators for these measures. Alterations in the bear’s feeding pattern in the Cantabrian Mountains, related to climate change, have been observed over the past decades. Recent projections predict a drastic population reduction, caused by the loss of large areas of the distribution of various plant species key for their feeding and cover. However, the limitations of such models, the capacity of adaptation of the species, non-linear effects of climate change and the great uncertainty about these predicted effects should all be taken into account. Additionally, the brown bear was widely distributed across the Iberian Peninsula until a few centuries ago, even as far south as Huelva and Murcia. Beyond the important necessity of favouring the conservation and restoration of habitats, the ecological connectivity between them and their bear populations, management of the human factor as the principal threat to the conservation of the Cantabrian bear in a climate change context, is essential.
... Conflict can result in retaliation and, as a matter of fact, humans and their activities cause most large carnivore mortality around the world (Woodroffe and Ginsberg, 1998), with bears being no exception (e.g. Krofel et al., 2012;Bischof et al., 2018). ...
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Reliable data and methods for assessing changes in wildlife population size over time are necessary for management and conservation. For most species, assessing abundance is an expensive and labor-intensive task that is not affordable on a frequent basis. We present a novel approach to reconstructing brown bear population dynamics in Slovenia in the period 1998-2019, based on the combination of two CMR non-invasive genetic estimates (in 2007 and 2015) and long-term mortality records, to show how the latter can help the study of population dynamics in combination with point-in-time estimates. The spring (i.e. including newborn cubs) population size estimate was 383 (CI: 336-432) bears in 1998 and 971 (CI: 825-1161) bears in 2019. In this period, the average annual population growth rate was 4.5 %. The predicted population size differed by just 7 % from the non-invasive genetic size estimate after eight years, suggesting that the method is reliable. It can predict the evolution of the population size under different management scenarios and provide information on key parameters, e.g. background mortality and the sex- and age-structure of the population. Our approach can be used for several other wildlife species, but it requires reliable mortality data over time.
... Lethal control. Regulated carnivore hunting is a common management option used to reduce conflict and that can generate revenue for conservation, but it can have indirect effects, e.g., it may not necessarily reduce poaching [190], can drive carnivore population declines if the harvest is too high [10] and, in the long term, hunting can reshape the life history of apex predators [191]. From a behavioral perspective, hunting is one of the human activities that triggers the clearest responses in large carnivores [89,102] and challenges their function as apex predators [5,123], although it could have desired effects by keeping carnivores away from humans and human property. ...
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The effects of human disturbance spread over virtually all ecosystems and ecological communities on Earth. In this review, we focus on the effects of human disturbance on terrestrial apex predators. We summarize their ecological role in nature and how they respond to different sources of human disturbance. Apex predators control their prey and smaller predators numerically and via behavioral changes to avoid predation risk, which in turn can affect lower trophic levels. Crucially, reducing population numbers and triggering behavioral responses are also the effects that human disturbance causes to apex predators, which may in turn influence their ecological role. Some populations continue to be at the brink of extinction, but others are partially recovering former ranges, via natural recolonization and through reintroductions. Carnivore recovery is both good news for conservation and a challenge for management, particularly when recovery occurs in human-dominated landscapes. Therefore, we conclude by discussing several management considerations that, adapted to local contexts, may favor the recovery of apex predator populations and their ecological functions in nature.
We investigated effects of regulated hunting on a puma (Puma concolor) population on the Uncompahgre Plateau (UPSA) in southwestern Colorado, USA. We examined the hypothesis that an annual harvest rate averaging 15% of the estimated number of independent individuals using the study area would result in a stable or increasing abundance of independent pumas. We predicted hunting mortality would be compensated by 1) a reduction in other causes of mortality, thus overall survival would stay the same or increase; 2) increased reproduction rates; or 3) increased recruitment of young animals. The study occurred over 10 years (2004–2014) and was designed with a reference period (years 1–5; i.e., RY1–RY5) without puma hunting and a treatment period (years 6–10; i.e., TY1–TY5) with hunting. We captured and marked pumas on the UPSA and monitored them year‐round to examine their demographics, reproduction, and movements. We estimated abundance of independent animals using the UPSA each winter during the Colorado hunting season from reference year 2 (RY2) to treatment year 5 (TY5) using the Lincoln‐Petersen method. In addition, we surveyed hunters to investigate how their behavior influenced harvest and the population. We captured and marked 110 and 116 unique pumas in the reference and treatment periods, respectively, during 440 total capture events. Those animals produced known‐fate data for 75 adults, 75 subadults, and 118 cubs, which we used to estimate sex‐ and life stage‐specific survival rates. In the reference period, independent pumas more than doubled in abundance and exhibited high survival. Natural mortality was the major cause of death to independent individuals, followed by other human causes (e.g., vehicle strikes, depredation control). In the treatment period, hunters killed 35 independent pumas and captured and released 30 others on the UPSA. Abundance of independent pumas using the UPSA declined 35% after 4 years of hunting with harvest rates averaging 15% annually. Harvest rates at the population scale, including marked independent pumas with home ranges exclusively on the UPSA, overlapping the UPSA, and on adjacent management units were higher, averaging 22% annually in the same 4 years leading to the population decline. Adult females comprised 21% of the total harvest. The top‐ranked model explaining variation in adult survival () indicated a period effect interacting with sex. Annual adult male survival was higher in the reference period ( = 0.96, 95% CI = 0.75–0.99) than in the treatment period ( = 0.40, 95% CI = 0.22–0.57). Annual adult female survival was 0.86 (95% CI = 0.72–0.94) in the reference period and 0.74 (95% CI = 0.63–0.82) in the treatment period. The top subadult model showed that female subadult survival was constant across the reference and treatment periods ( = 0.68, 95% CI = 0.43–0.84), whereas survival of subadult males exhibited the same trend as that of adult males: higher in the reference period ( = 0.92, 95% CI = 0.57–0.99) and lower in the treatment period ( = 0.43, 95% CI = 0.25–0.60). Cub survival was best explained by fates of mothers when cubs were dependent (mother alive = 0.51, 95% CI = 0.35–0.66; mother died = 0.14, 95% CI = 0.03–0.34). The age distribution for independent pumas skewed younger in the treatment period. Adult males were most affected by harvest; their abundance declined by 59% after 3 hunting seasons and we did not detect any males >6 years old after 2 hunting seasons. Pumas born on the UPSA that survived to subadult stage exhibited both philopatry and dispersal. Local recruitment and immigration contributed to positive growth in the reference period, but recruitment did not compensate for the losses of adult males and partially compensated for losses of adult females in the treatment period. Average birth intervals were similar in the reference and treatment periods (reference period = 18.3 months, 95% CI = 15.5–21.1; treatment period = 19.4 months, 95% CI = 16.2–22.6), but litter sizes (reference period = 2.8, 95% CI = 2.4–3.1; treatment period = 2.4, 95% CI = 2.0–2.8) and parturition rates (reference period = 0.63, 95% CI = 0.49–0.75; treatment period = 0.48, 95% CI = 0.37–0.59) declined slightly in the treatment period. Successful hunters used dogs, selected primarily males, and harvested pumas in 1–2 days (median). We found that an annual harvest rate at the population scale averaging 22% of the independent pumas over 4 years and with >20% adult females in the total harvest greatly reduced abundance. At this scale, annual mortality rates of independent animals from hunting averaged 6.3 times greater than from all other human causes and 4.6 times greater than from all natural causes during the population decline. Hunting deaths were largely additive and reproduction and recruitment did not compensate for this mortality source. Hunters generally selected male pumas, resulting in a decline in their survival and abundance, and the age structure of the population. We recommend that regulated hunting in a source‐sink structure be used to conserve puma populations, provide sustainable hunting opportunities, and address puma‐human conflicts. © 2021 The Wildlife Society. Investigamos los efectos de la cacería regulada en la población de pumas (Puma concolor) de la Uncompahgre Plateau (UPSA) en el suroeste de Colorado, USA. Exploramos la hipótesis de que una cosecha anual con una tasa promedio del 15% del número estimado de pumas independientes que están usando el área de estudio resultaría en una abundancia estable o un incremento de pumas independientes. Nuestra predicción de que la mortalidad por cacería seria compensada por: 1) una reducción en otras causas de mortalidad, por lo tanto, la supervivencia se mantendría igual o incrementaría; 2) un incremento en la tasa reproductiva; o 3) un incremento en el reclutamiento de pumas jóvenes. Este estudio se llevó a cabo a lo largo de 10 años (2004–2014) y fue diseñado con un periodo de referencia (años 1 al 5; RY1–RY5) sin cacería de pumas y un periodo de tratamiento (años 6–10; i.e., TY1–TY5) con cacería de pumas. Capturamos y marcamos pumas en la UPSA y se llevó a cabo el monitoreo a lo largo de todo el año para examinar la demografía, reproducción y movimientos de los pumas. Estimamos la abundancia de pumas independientes que usaban la UPSA cada invierno durante la estación de cacería de pumas en Colorado usando el año 2 (RY2) como referencia al año de tratamiento 5 (TY5) usando el método de Lincoln‐Petersen. Adicionalmente, llevamos a cabo prospecciones con cazadores para investigar como el comportamiento de los cazadores influía la cosecha y la población de pumas. Capturamos y marcamos un total de 110 y 116 pumas únicos dentro del periodos de referencia y de tratamiento, respectivamente, a lo largo de un total de 440 eventos de captura. Esos pumas produjeron datos de mortalidad con información conocida para 75 adultos, 75 sub‐adultos y 118 cachorros, con los cuales se estimaron tasas de supervivencia específicas por sexo y etapas de vida. En el periodo de referencia la abundancia de pumas independientes se incrementó a más del doble y exhibieron una supervivencia alta. La mortalidad natural fue la mayor causa de muerte en pumas independientes, seguida de causas producidas por seres humanos (e.g. atropellamientos, control de depredadores). En el periodo de tratamiento, los cazadores mataron 35 pumas independientes, adicionalmente capturaron y dejaron en libertad a 30 pumas en la UPSA. La abundancia de pumas independientes se redujo en un 35% después de 4 años de cacería con tasas de aprovechamiento con un promedio anual de 15% en la UPSA. Las tasas de aprovechamiento a la escala de población incluyendo pumas independientes marcados con ámbitos hogareños exclusivos dentro de la UPSA, con sobreposición en la UPSA y en unidades adyacentes de manejo fueron mayores, en promedio 22% anualmente durante los mismos 4 años que llevaron a la población al declive. Las hembras adultas comprendieron 21% de la cosecha total. El mejor modelo que explicaba la variación en la supervivencia () de los adultos indicaba un efecto del periodo interactuando con el sexo. La supervivencia anual de los machos fue más alta durante el periodo de referencia ( = 0.96, 95% CI = 0.75–0.99) que durante el periodo de tratamiento ( = 0.40, 95% CI = 0.22–0.57). La supervivencia anual de las hembras fue 0.86 (95% CI = 0.72–0.94) en el periodo de referencia y 0.74 (95% CI = 0.63–0.82) durante el tratamiento. El mejor modelo de supervivencia en hembras sub‐adultas, mostro que la supervivencia fue constante a través de los periodos de referencia y tratamiento ( = 0.68, 95% CI = 0.43–0.84), donde la supervivencia de los machos sub‐adultos exhibió el mismo patrón de supervivencia de los machos adultos: más alta en el periodo de referencia ( = 0.92, 95% CI = 0.57–0.99) y menor en el periodo de tratamiento ( = 0.43, 95% CI = 0.25–0.60). La supervivencia de los cachorros se explica mejor por el destino de sus madres, cuando estos son dependientes (madres vivas = 0.51, 95% CI = 0.35–0.66; madres muertas = 0.14, 95% CI = 0.03–0.34). La distribución por edades de los pumas independientes estuvo sesgada a animales jóvenes durante el periodo de tratamiento. Los machos adultos fueron los más afectados por el aprovechamiento, su abundancia se redujo en un 59% después de 3 temporadas de cacería, y una ausencia de machos >6 años de edad después de 2 temporadas de cacería. Los pumas nacidos en la UPSA que sobrevivieron a la etapa sub‐adulta exhibieron características filopátricas y de dispersión. El reclutamiento local y la inmigración contribuyeron al crecimiento positivo en el periodo de referencia. Sin embargo, el reclutamiento no compenso por la pérdida de machos adultos y parcialmente compenso por la pérdida de hembras durante el periodo de tratamiento. El intervalo promedio entre nacimientos fue similar entre los periodos de referencia y tratamiento (periodo de referencia = 18.3 meses, 95% CI = 15.5–21.1; periodo de tratamiento = 19.4 meses, 95% CI = 16.2–22.6), mientras que el tamaño de camada (periodos de referencia = 2.8, 95% CI = 2.4–3.1; periodo de tratamiento = 2.4, 95% CI = 2.0–2.8) y las tasas de parición (periodo de referencia = 0.63, 95% CI = 0.49–0.75; periodo de tratamiento = 0.48, 95% CI = 0.37–0.59) declinaron ligeramente durante el periodo de tratamiento. Cazadores exitosos de pumas usaron perros, seleccionaron fundamentalmente machos y cosecharon pumas en 1−2 días (mediana). Encontramos a la escala de población una tasa de aprovechamiento anual de 22% del número de pumas independientes en un periodo de 4 años y donde >20% de hembras adultas en la cosecha total redujeron en cantidad la abundancia de pumas. A esta escala, las tasas anuales de mortalidad de los pumas independientes por caceria fueron en promedio 6.3 veces mayores que todas las otras causas producidas por seres humanos, y 4.6 veces mayores que todas las causas de mortalidad natural durante la reducción en la población. La mortalidad por cacería era aditiva y la reproducción y el reclutamiento no compensaron a la mortalidad por cacería. Encontramos que los cazadores de pumas seleccionaron pumas machos, resultando en una reducción de la supervivencia, abundancia de machos y la estructura de edades dentro de la población. Recomendamos que la cacería regulada con base en una estructura poblacional de fuente‐sumidero puede ser utilizada para conservar a las poblaciones de pumas, proporcionando oportunidades para la cacería sustentable de pumas y redirigir el conflicto entre pumas y seres humanos. Nous avons examiné les effets d’une chasse régulée sur une population de puma (Puma concolor) dans le plateau de l’Uncompahgre (UPSA) dans le sud‐ouest du Colorado. Nous avons examiné l’hypothèse qu’un taux annuel de récolte de 15% du nombre estimé de pumas indépendants utilisant l’aire d’étude maintiendrait l’abondance ou accroîtrait l’abondance de pumas. Nous avons prédit que la mortalité par la chasse serait compensée par: 1) une réduction des autres causes de mortalité, entrainant une augmentation ou stabilisation de la survie; 2) une augmentation du taux de reproduction; ou 3) une augmentation du recrutement de jeunes individus. L’étude a été conduit durant, et a été construite autour d’une période de référence (années 1 à 5) sans chasse aux pumas et une période de traitement (années 6 à 10) avec une chasse aux pumas. Nous avons capturé et marqué des pumas dans l’aire d’étude (UPSA) et les avons suivis toute l’année pour récolter des données concernant leur démographie, reproduction et mouvement. L’abondance de pumas indépendants a été estimée dans l’USPA à chaque hiver durant la saison de chasse aux pumas au Colorado de l’année de référence 2 (RY2) à l’année de traitement 5 (TY5) en utilisant la méthode de Lincoln‐Petersen. De plus, nous avons sondé les chasseurs afin d’apprendre comment leur comportement influençait la récolte et la population de puma. Durant les périodes de référence et traitement, 110 et 116 pumas ont respectivement été capturés et marqués, durant 440 évènements de capture. Ces pumas ont produit des données dont le sort est connu pour 75 adultes, 75 subadultes, et 118 juvéniles qui ont été utilisés afin de modéliser le taux de survie de chaque sexe et groupe d’âge. Durant la période de référence, l’abondance des pumas indépendants a plus que doublé en abondance et montré un haut taux de survie. La mortalité naturelle était la cause principale de décès, suivie par les mortalités reliées à l’humain. Durant la période de traitement, les chasseurs ont tué 35 pumas indépendants et capturé puis relâché 30 pumas. L’abondance de pumas indépendants a décliné de 35% après 4 années de chasse avec des taux de récolte moyennant 15% dans l’UPSA. Les taux de récoltes à l’échelle de la population incluant des individus dont le domaine vital était à l’intérieur de l’USPA, chevauchant l’USPA, ou en périphérie de l’USPA étaient plus élevés et approchaient 22% durant les quatre années précédant le déclin de la population. Les femelles adultes représentaient 21% de la récolte total. Le meilleur modèle expliquant la variation dans la survie () des adultes incluait un effet de la période en interaction avec le sexe. Le taux de survie des mâles adultes était plus élevé durant la période de référence ( = 0.96, 95% CI = 0.75–0.99) que durant la période de traitement ( = 0.40, 95% CI = 0.22–0.57). Le taux de survie des femelles adultes était de 0.86 (95% CI = 0.72–0.94) durant la période de référence et de 0.74 (95% CI = 0.63–0.82) durant la période de traitement. Le meilleur modèle du taux de survie des femelles subadultes a démontré que la survie était constante entre les deux périodes de traitement ( = 0.68, 95% CI = 0.43–0.84) alors que le taux de survie des mâles subadultes a montré la même tendance que les mâles adultes: plus élevé durant la période de référence ( = 0.92, 95% CI = 0.57–0.99) que durant la période de traitement ( = 0.43, 95% CI = 0.25–0.60). Le taux de survie des petits était le mieux expliqué par le sort de la mère alors que les petits étaient dépendants (mère en vie = 0.51, 95% CI = 0.35–0.66; mère en vie = 0.14, 95% CI = 0.03–0.34). La structure des âges des pumas indépendants a décliné durant la période de traitement. Les mâles adultes étaient les plus affectés par la récolte, leur abondance a décliné de 59% après trois saisons de chasse et aucun individu de plus de 6 ans n’était présent après deux saisons de chasse. Les pumas nés dans l’UPSA qui ont survécu au stage subadulte ont exhibé de la philopatrie et de la dispersion. Le recrutement local et l’immigration ont contribué au taux de croissance durant la période de référence. Le recrutement n’a pas compensé pour la perte de mâles adultes et a compensé partiellement pour la perte de femelles adultes durant la période de traitement. L’intervalle moyen des naissances est demeuré similaire (période de référence = 18.3 mo., 95% CI = 15.5–21.1; période de traitement = 19.4 mo., 95% CI = 16.2–22.6), alors que la taille des portées (période de référence = 2.8, 95% CI = 2.4–3.1; période de traitement = 2.4, 95% CI = 2.0–2.8) et le taux de parturition (période de référence = 0.63, 95% CI = 0.49–0.75; période de traitement = 0.48, 95% CI = 0.37–0.59) ont diminué légèrement durant la période de traitement. Les chasseurs de pumas qui ont eu du succès ont utilisé des chiens, ils sélectionnaient primairement les mâles et ont récolté des pumas à l’intérieur de 1–2 jours (médiane). Nous avons trouvé qu’un taux de récolte moyen avoisinant 22% du nombre estimé de pumas indépendants sur quatre ans et avec >20% de femelles adultes dans la récolte réduisait grandement l’abondance de puma. À cette échelle, le taux de mortalité annuel provenant de la chasse était en moyenne 6.3 fois plus grand que le taux provenant de tous les autres causes de mortalité humaine et 4.6 fois plus grand que le taux de mortalité de source naturelle durant la période de déclin de la population. La mortalité par la chasse était largement additive et la reproduction et le recrutement n’ont pas compensé pour cette source de mortalité. Nous avons trouvé que les chasseurs montraient une sélection pour les pumas mâles, entrainant alors une réduction de la survie et de l’abondance des mâles et impactant la structure des âges de la population. Nous recommandons qu’une chasse régulée dans une structure source‐puit peut être utilisée afin d’aider la conservation des pumas, procurer des opportunités de chasse durable, et adresser les conflits pumas‐humains.
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Most carnivorans (members of the mammalian order Carnivora) are elusive and long lived, so long-term studies are required to understand their basic biology and, ultimately, to conserve them. Here, we review examples of the wealth of information about the social systems, ecophysiology, and ecology of gregarious, terrestrial, carnivorous carnivorans (hereafter, carnivores) generated by long-term field studies of free-living, individually recognizable carnivores. Our synthesis yields key insights about the evolutionary forces favoring cooperation and ecological forces shaping social dynamics. The genetic assignment of parentage permits elucidation of the extent of reproductive skew in natural populations spanning multiple generations. Tracking of individuals across their life spans reveals underlying physiological, behavioral, and ecological mechanisms mediating reproductive suppression and dispersal. Long-term studies permit a comprehensive understanding of the ways in which intrinsic and extrinsic factors, including conflict with humans, regulate carnivore populations. Long-term studies also provide crucial baseline information required for the conservation of carnivores in the face of burgeoning human populations and global climate change. Notably, many conservation problems unfold on timescales only addressable with long-term data. Although we have yet to exploit the full wealth of information from long-term field studies, these valuable repositories have already yielded myriad insights about mammalian carnivores that would be unobtainable from studies conducted over shorter timescales.
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Trophy hunting, the selective removal of animals for human recreation, can contribute to conservation when appropriately managed. Yet, little is known about how harvest rates or different definitions of trophy affect age structure and trophy size in harvested animals and in survivors because no controlled studies exist. To investigate the impacts of different management regimes, we developed an individual-based model for bighorn sheep (Ovis canadensis), based on empirical data on survival from a protected population and data on horn growth from 2 populations that differed in their growth rates. One population showed slow horn growth and the other population fast horn growth. We subjected these model populations to varying harvest rates and 2 different hunting regulations: 4/5 curl and full-curl definitions of a trophy male. We found that the effect of hunting regulations depends on horn growth rate. In populations with fast horn growth, the effects of trophy hunting on male age structure and horn size were greater and the effect of a change in the definition of legal male smaller than in populations with slow growth rates. High harvest rates led to a younger age structure and smaller horn size. Both effects were weakened by a more restrictive definition of trophy male. As harvest rates increased past 40% of legal males, the number of males harvested increased only marginally because an increasing proportion of the harvested males included those that had just become legal. Although our simulation focused on bighorn sheep, the link between horn growth rate and harvest effects may be applicable for any size-selective harvest regime.
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'Adaptive management', which has been defined as the repeated iteration between management action, scientific assessment and revised management action, leading to a strengthened foundation for management, is required by Swedish law to be incorporated into the management of large carnivores. We have evaluated whether the size and/or trend of the brown bear Ursus arctos population in Sweden corresponded to management-decided national objectives during five management regimes during the past 70 years (1943-2013). We found that the objective had been met in only one period, when it had been worded very vaguely. During the last period studied (2008-2013), when management was carried out on the county level and adaptive management was required by the Swedish Government, four of six counties met their trend objectives, but only one of six met the population objectives, although one was close to meeting them. Sociological studies have documented major problems in communication among the members of the county delegations responsible for the management of large carnivores. As adaptive management apparently never has been implemented successfully in brown bear management in Sweden, we recommend that the Delegations for Game Management be mandated to integrate up-to-date, scientifically documented biological information into their decisions. This is not done consistently today. Researchers should be involved in the process to inform about relevant, available information, design testable scientific 'experiments' based on the predicted results of management decisions, and evaluate the results in relation to the predictions, perhaps as members of a 'boundary organization' consisting of researchers, managers and stakeholders. This would require a new management paradigm, because many in Sweden seem to be skeptical to the idea of involving researchers in management.
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For socially monogamous species, breeder bond dissolution has important consequences for population dynamics, but the extent to which extrinsic or intrinsic population factors causes pair dissolution remain poorly understood, especially among carnivores. Using an extensive life‐history data set, a survival analysis and competing risks framework, we examined the fate of 153 different wolf (Canis lupus) pairs in the recolonizing Scandinavian wolf population, during 14 winters of snow tracking and DNA monitoring. Wolf pair dissolution was generally linked to a mortality event and was strongly affected by extrinsic (i.e. anthropogenic) causes. No divorce was observed, and among the pair dissolution where causes have been identified, death of one or both wolves was always involved. Median time from pair formation to pair dissolution was three consecutive winters (i.e. approximately 2 years). Pair dissolution was mostly human‐related, primarily caused by legal control actions (36·7%), verified poaching (9·2%) and traffic‐related causes (2·1%). Intrinsic factors, such as disease and age, accounted for only 7·7% of pair dissolutions. The remaining 44·3% of dissolution events were from unknown causes, but we argue that a large portion could be explained by an additional source of human‐caused mortality, cryptic poaching. Extrinsic population factors, such as variables describing the geographical location of the pair, had a stronger effect on risk of pair dissolution compared to anthropogenic landscape characteristics. Population intrinsic factors, such as the inbreeding coefficient of the male pair member, had a negative effect on pair bond duration. The mechanism behind this result remains unknown, but might be explained by lower survival of inbred males or more complex inbreeding effects mediated by behaviour. Our study provides quantitative estimates of breeder bond duration in a social carnivore and highlights the effect of extrinsic (i.e. anthropogenic) and intrinsic factors (i.e. inbreeding) involved in wolf pair bond duration. Unlike the effects of intrinsic and extrinsic factors that are commonly reported on individual survival or population growth, here we provide quantitative estimates of their potential effect on the social unit of the population, the wolf pair.
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Quantifying environmental crime and the effectiveness of policy interventions is difficult because perpetrators typically conceal evidence. To prevent illegal uses of natural resources, such as poaching endangered species, governments have advocated granting policy flexibility to local authorities by liberalizing culling or hunting of large carnivores. We present the first quantitative evaluation of the hypothesis that liberalizing culling will reduce poaching and improve population status of an endangered carnivore. We show that allowing wolf (Canis lupus) culling was substantially more likely to increase poaching than reduce it. Replicated, quasi-experimental changes in wolf policies in Wisconsin and Michigan, USA, revealed that a repeated policy signal to allow state culling triggered repeated slowdowns in wolf population growth, irrespective of the policy implementation measured as the number of wolves killed. The most likely explanation for these slowdowns was poaching and alternative explanations found no support. When the government kills a protected species, the perceived value of each individual of that species may decline; so liberalizing wolf culling may have sent a negative message about the value of wolves or acceptability of poaching. Our results suggest that granting management flexibility for endangered species to address illegal behaviour may instead promote such behaviour.
Bayesian statistics has exploded into biology and its sub-disciplines, such as ecology, over the past decade. The free software program WinBUGS and its open-source sister OpenBugs is currently the only flexible and general-purpose program available with which the average ecologist can conduct standard and non-standard Bayesian statistics. Bayesian Population Analysis Using WinBUGS goes right to the heart of the matter by providing ecologists with a comprehensive, yet concise, guide to applying WinBUGS to the types of models that they use most often: linear (LM), generalized linear (GLM), linear mixed (LMM) and generalized linear mixed models (GLMM). Comprehensive and richly-commented examples illustrate a wide range of models that are most relevant to the research of a modern population ecologist. All WinBUGS/OpenBUGS analyses are completely integrated in software R. Includes complete documentation of all R and WinBUGS code required to conduct analyses and shows all the necessary steps from having the data in a text file out of Excel to interpreting and processing the output from WinBUGS in R.
This latest Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) will again form the standard reference for all those concerned with climate change and its consequences, including students, researchers and policy makers in environmental science, meteorology, climatology, biology, ecology, atmospheric chemistry and environmental policy.