No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Trophy hunting with uncertain role for population dynamics and extinction of ungulates
Animal Conservation
Abstract
Read the Feature Paper: Rarity, trophy hunting and ungulates , other Commentaries on this paper: Rarity, willingness to pay and conservation and the Response from the authors: Response: rarity, trophy hunting and ungulates
... Although we do not have information on females that died of natural causes in Oberammergau, confidence intervals in Figure 2 suggest that the slope for females in this area is significantly steeper than in the other populations, supporting the opportunity for trophy hunting also in female chamois. This result supports the suggestion by Mysterud (2012) that females may become a target for trophy hunters when sexual dimorphism is small, as in oryx (Oryx gazella) and eland (Taurotragus oryx). In chamois, the fact that females tend to live in larger groups than males (Krämer, 1969) likely increases the possibility for hunters to select individuals with longer horns (Mysterud, 2011). ...
... In chamois, the fact that females tend to live in larger groups than males (Krämer, 1969) likely increases the possibility for hunters to select individuals with longer horns (Mysterud, 2011). Given the positive correlation between early horn growth and age of primiparity (Rughetti & Festa-Bianchet, 2011a), and the occurrence of individual heterogeneity in reproductive performance (Morin et al., 2016) Year in males were calculated by refitting the models and setting males as the baseline sex using the "relevel" function in R. Significant predictors are shown in bold (Mysterud, 2012). The unexpected lack of a relationship between early horn growth and male age at harvest in Oberammergau may be partly explained by the small sample size. ...
Weaponry in ungulates may be costly to grow and maintain, and different selective pressures in males and females may lead to sex-biased natural survival. Sexual differences in the relationship between weapon growth and survival may increase under anthropogenic selection through culling, for example because of trophy hunting. Selection on weaponry growth under different scenarios has been largely investigated in males of highly dimorphic ungulates, for which survival costs (either natural or hunting-related) are thought to be greatest. Little is known, however, about the survival costs of weaponry in males and females of weakly dimorphic species. We collected information on horn length and age at death/shooting of 407 chamois Rupicapra rupicapra in a protected population and in two hunted populations with different hunting regimes, to explore sexual differences in the selection on early horn growth under contrasting selective pressures. We also investigated the variation of horn growth and body mass in yearling males (n=688) and females (n=539) culled in one of the hunted populations over 14 years. The relationship between horn growth and survival showed remarkable sexual differences under different evolutionary scenarios. Within the protected population, under natural selection, we found no significant trade-off in either males or females. Under anthropogenic pressure, selection on early horn growth of culled individuals showed diametrically opposed sex-biased patterns, depending on the culling regime and hunters’ preferences. Despite the selective bias between males and females in one of the hunted populations, we did not detect significant sex-specific differences in the long-term pattern of early growth. The relationship between early horn growth and natural survival in either sex might suggest stabilizing selection in horn size in chamois. Selection through culling can be strongly sex-biased also in weakly dimorphic species, depending on hunters’ preferences and hunting regulations, and long-term data are needed to reveal potential undesirable evolutionary consequences.
... are no examples of species extinction as a result of trophy hunting(Mysterud, 2012; Annexe 1A). On the contrary, there are a few documented examples of declining populations that have recovered as a result of the appropriate use of the considerable income generated by well managed trophy hunting(Frisina & Tareen 2009). ...
... De plus, chaque touriste prélève un nombre restreint d'individus qui suffit à générer un profit conséquent. Les prélèvements étant orientés sur les mâles, et à condition que les quotas soient bien établis et respectés, la CTT devrait avoir un impact limité sur la population(Mysterud 2012). Deuxièmement, la beauté du paysage, la diversité et l'abondance des espèces sauvages n'est pas indispensable pour la mise en place de la chasse aux trophées. ...
Trophy hunting, which is a form of recreational hunting with the main objective of collecting a trophy of interest, is a controversial subject. This activity could potentially generate an anthropogenic Allee effect (AAE). This demographic process states that the valuation of rarity could drive rare species exploitation and even lead to their extinction. Our project aims at testing the potential for an AEE in trophy hunting. We demonstrate that rare species have a high financial value, regardless of the trophy size, indicating that there is a high demand for those species. We also show that the number of trophies traded internationally and the number of recorded trophies by the Safari Club International (one of the largest clubs for international trophy hunters in the USA) rises as the degree of rarity (as measured by a rarity index) increases. Trophy hunting of rare species has been proposed as a tool to fund their conservation. However, our results indicate that there is a risk of an AAE for rare species. Furthermore, the combined effects of trophy hunting, illegal hunting, corruption as well as the lack of population knowledge and of management controls have potential to result in the unsustainable exploitation of rare species of high financial value. Nonetheless, trophy hunting has potential to generate strong financial incentives that are necessary for wildlife preservation. Such incentives are only likely to be effective if strict measures are required and enforced to prevent overexploitation of rare trophy species
... Trophy hunting has been shown to reduce horn size with time (Coltman et al., 2003;Crosmary et al., 2013). However, offtakes from trophy hunting supposedly represent only a small fraction of the male segment in hunted populations (Cumming, 1989;Caro et al., 1998), so that the impact on population dynamics appears rather limited in polygynous ungulates (Mysterud, 2012). In Africa, longterm monitoring is rare (Caro, 2011), particularly outside national parks (but see Stoner et al., 2007;Western, Russell & Cuthill, 2009). ...
... For instance, Caro et al. (1998) found few significant differences in mammal densities between hunting areas and national parks in Tanzania, and suggested that harvest rates below 10% per year were unlikely to impact population sizes. Examples in other ecosystems revealed no impact of trophy hunting on ungulate dynamics (Milner et al., 2007;Mysterud, 2012; but see Palazy et al., 2012). Surprisingly, for some species (i.e. ...
The persistence of large African herbivores in trophy hunting areas is still unclear because of a lack of data from long-term wildlife monitoring outside national parks. We compared population trends over the last 30 years in Hwange National Park, Zimbabwe, and the neighbouring Matetsi Safari Area where large herbivores were harvested at an average yearly rate of 2%. We investigated whether trophy hunting altered densities and the proportion of adult males in several large herbivore species. Large herbivores generally thrived as well, or even better, in the hunting areas than in the national park. The proportion of adult males did not differ between the two zones, except for species with higher harvest rates and proportionally more males harvested. Densities were not lower in the hunting areas than in the national park, except for elephant and impala. Large herbivores generally declined throughout the 30-year period in both zones, particularly selective grazers. This is probably because of their greater sensitivity to variation in rainfall compared with other herbivores. Rainfall indeed declined during the study period with droughts being particularly frequent during the 1990s. Browsers, mixed feeders and non-selective grazers generally declined less in the hunting areas than in the national park, possibly because of lower densities of natural predators and elephants outside the park. Our study highlighted that large herbivores may persist in trophy hunting areas as well as in national parks. When rigorously managed, trophy hunting areas may be relevant conservation areas for large herbivores, particularly under the current global decline of wildlife abundance across Africa.
... confer benefits for marine hunting are likely disadvantageous for long terrestrial chases due to an inability to 295 dissipate heat 47-48 . For instance, while brown bears run in a rotary gallop and are capable of pursuits up to 4-5 296 km ( Fig. 4; Methods), polar bears use transverse motion and engage in only short duration chases, likely due to 297 the locomotor costs and the potential for hyperthermia [41][42][43][44][45][46][47][48] . ...
Recent impacts to Earth’s biosphere include range expansions for ~17 terrestrial carnivorans, most of which carry unknown behavioral or ecological consequence for potential prey. Nowhere could such novelty be more dramatic than at high latitudes where, as sea ice declines, polar bears increase time on land and interact with the Arctic’s largest land mammal – muskoxen, a species previously exposed to predation primarily by brown bears and wolves. Remarkably, Alfred Russell Wallace opined on such possible relationships ~150 years ago. Herein, we expand upon such prey-predator interactions using field experiments across five years at Arctic Russian and Alaskan sites. We demonstrate altered muskoxen defense systems, distinguishing between polar and brown bears and fleeing on average three times farther from simulated polar than simulated brown bears. Our results demonstrate remarkable plasticity in learning ability, likely associated with eco-evolutionary differences in terrestrial pursuit capacity by bears. As anthropogenic landscapes change, macro-geographical processes and ecological reassembly will continue with unpredictable outcomes, especially for prey species unless sufficient commitments are made to on-site field assessments of species interactions.
... Biological effects of trophy hunting can be especially challenging to investigate because populations and ecosystems are dynamic and spatially and temporally diverse (Levin 1998, Benton et al. 2006. Although trophy hunting rarely influences population size, population structure may be altered by the disproportionate removal of animals relative to age or sex (Milner et al. 2007, Mysterud 2012, Lindsey et al. 2013. Additionally, shifts in the proportion of unique phenotypes (Wilfred 2012, Monteith et al. 2013, Rivrud et al. 2013, Coulson et al. 2018, LaSharr et al. 2019b or behavioral traits (Singer andZeigenfuss 2002, Leclerc et al. 2019) also may occur. ...
Reported effects of trophy harvest often are controversial. The subject is nuanced and many studies lack details necessary to place their results in context. Consequently, many studies are misunderstood or their conclusions misapplied. We propose that all dialogues about trophy hunting include a definition of how they use the term trophy, details of variables measured and why they were selected, and explanations of temporal and spatial scales employed. Only with these details can potential effects of trophy hunting be understood in context and used for management and policy decisions. © 2021 The Wildlife Society. Effects of trophy harvest often are controversial because many studies lack important details. Dialogues about trophy hunting must include a definition of how they use the term trophy, details of variables measured and why they were selected, and explanations of temporal and spatial scales employed so that potential effects of trophy hunting can be understood in context.
... Es bien sabido que la caza desmedida y el furtivismo han tenido un efecto perjudicial en varias especies animales. Algunas de ellas, debido a su rareza o peculiaridad, han sido diezmadas drásticamente e inclusive llevadas a la extinción (Loveridge et al., 2007;Mysterud, 2012;Palazy et al., 2012). Otras especies, a pesar de haberse encontrado bajo una presión casi absoluta a lo largo de años por estas mismas causas -furtivismo y caza desmedida, aunadas a otras tantas como pérdida de hábitat, competencia por sitios de pastoreo y enfermedades transmitidas por animales domésticos-han encontrado en la práctica de la caza deportiva un gran aliado (Goldman, 2017). ...
La cacería ha sido una actividad tan ligada al ser humano que se piensa llegó a jugar un papel importante en la evolución de nuestra propia especie, derivado del consumo de carne. A través de los años y en diferentes partes del mundo ha tenido diferentes concepciones y arraigos, desde culturales hasta religiosos. No obstante, su desarrollo ha sido paradójico. La caza desmedida ha sido una de las fuerzas que ha orillado a la extinción a muchas especies, pero al mismo tiempo, empleándola de manera sustentable, ha funcionado como una herramienta necesaria para la conservación. En el caso específico del jaguar (𝘗𝘢𝘯𝘵𝘩𝘦𝘳𝘢 𝘰𝘯𝘤𝘢) se cree que la cacería furtiva, o aquella derivada del conflicto jaguar-ganadería, ha diezmado sustancialmente a la especie. En la Reserva de la Biosfera Sierra del Abra Tanchipa (RBSAT) la historia no ha sido diferente. En los últimos años se han documentado al menos dos casos de cacería ilegal de jaguar en la zona, siendo estos hechos un parteaguas que reafirmó las bases de conciencia sobre la importancia de esta especie dentro de los ecosistemas presentes en la región. En el presente capítulo se recogen los testimonios de algunos de los actores involucrados en esta borrascosa convivencia entre depredadores y cazadores en el noreste del estado de San Luis Potosí.---------------------------------------------------Hunting has been an activity deeply linked to man, and is thought to have played an important role in the evolution of our own species driven by the consumption of meat. The practice of hunting has evolved with us, born and reborn around the world rooted in culture and religion. Hunting can be both detrimental and beneficial. It has
led to the extinction of many species, but has also been a powerful tool to conserve species. In the specific case of the jaguar (𝘗𝘢𝘯𝘵𝘩𝘦𝘳𝘢 𝘰𝘯𝘤𝘢) it is believed that poaching or hunting in retaliation for jaguar-livestock conflict has substantially decimated the species. In the Reserva de la Biosfera Sierra del Abra Tanchipa (RBSAT) this is the case, and in recent years at least two cases of illegal jaguar hunting have been documented in the area. This emphasizes the importance of raising awareness of the ecological and cultural importance of this species in the region. In this chapter the testimonies of some of the actors involved in this stormy coexistence between predators and hunters in the northeast of San Luis Potosí are collected.
... Es bien sabido que la caza desmedida y el furtivismo han tenido un efecto perjudicial en varias especies animales. Algunas de ellas, debido a su rareza o peculiaridad, han sido diezmadas drásticamente e inclusive llevadas a la extinción (Loveridge et al., 2007;Mysterud, 2012;Palazy et al., 2012). Otras especies, a pesar de haberse encontrado bajo una presión casi absoluta a lo largo de años por estas mismas causas -furtivismo y caza desmedida, aunadas a otras tantas como pérdida de hábitat, competencia por sitios de pastoreo y enfermedades transmitidas por animales domésticos-han encontrado en la práctica de la caza deportiva un gran aliado (Goldman, 2017). ...
El jaguar es una especie clave en todos los ecosistemas del continente americano donde habita, no obstante, su rango de distribución se ha visto disminuido, incluso siendo extirpado de algunos países. Su conservación adquiere una mayor relevancia cuando se pone en contexto con el panorama mundial, donde actualmente existe una pérdida de la biodiversidad a una velocidad insostenible. Es por esto que hoy más que nunca es ineludible nuestra responsabilidad para proteger y hacer uso razonable de los recursos naturales con los que aún contamos. La Reserva de la Biosfera Sierra del Abra Tanchipa es hogar de una población residente de jaguares, la cual subsiste en unos de los últimos relictos de vegetación Neotropical en el noreste de México. Esta reserva, al igual que muchas otras, enfrenta constantemente amenazas que ponen en vilo su delicado equilibrio ecológico, como fragmentación del hábitat, expansión de la frontera agropecuaria e incendios forestales. Este volumen es el resultado de la compilación de poco más de una década de esfuerzos de investigación, manejo y conservación en torno al tercer felino más grande del mundo y depredador ápice de las selvas de América.
... Secondly, in many cases the animals targeted are males, and in the polygynous systems typical of the hunted animals, females will not have difficulty acquiring mates unless a large proportion of the males are removed [5]. Consequently, recruitment into the population should be unaffected by hunting, meaning that in the absence of other threats populations of animals that are primarily harvested for trophies or specimens should not be at risk of extinction [6,7]. Instead, more subtle effects from trophy hunting are found, such as changes in the sociobiological makeup of populations arising from the removal of males, as seen in hunted lion populations [8], and evolutionary changes arising from selection against desirable traits for hunters such as large horns or large body size [9][10][11][12], although the magnitude of this latter effect is the subject of some debate [13][14][15]. ...
Humans commonly harvest animals based on their expression of secondary sexual traits such as horns or antlers. This selective harvest is thought to have little effect on harvested populations because offtake rates are low and usually only the males are targeted. These arguments do not, however, take the relationship between secondary sexual trait expression and animal condition into account: there is increasing evidence that in many cases the degree of expression of such traits is correlated with an animal’s overall well-being, which is partly determined by their genetic match to the environment. Using an individual-based model,we find that when there is directional environmental change, selective harvest of males with the largest secondary sexual traits can lead to extinction in otherwise resilient populations. When harvest is not selective, the males best suited to a new environment gain the majority of matings and beneficial alleles spread rapidly. When these bestadapted males are removed, however, their beneficial alleles are lost, leading to extinction. Given the current changes happening globally, these results suggest that trophy hunting and other cases of selective harvest (such as certain types of insect collection) should be managed with extreme care whenever populations are faced with changing conditions. © 2017 The Author(s) Published by the Royal Society. All rights reserved.
... The animal declines are mostly related to illegal hunting, land use changes, droughts, and isolation of protected areas through fencing181920. However, trophy hunting promotes off-takes of a supposedly small proportion of males from a population [21] and the associated impacts on population dynamics of most polygamous ungulates are expected to be minimal [22]. Trophy hunting refers to hunting by paying clients, who select animals with exceptional phenotypic attributes such as horns, tusks, body size, and skull length, usually in the company of a professional hunter [23]. ...
Long term monitoring of population estimates and trophy size trends is requisite to ensure that trophy hunting is sustainable. We explored the influence of trophy hunting on population size and trophy quality of impala (Aepyceros melampus), greater kudu (Tragelaphus strepsiceros) and sable (Hippotragus niger) antelopes from 1997 to 2014 in Cawston Ranch, Zimbabwe. Population estimates of the three species showed a cyclical declining trend, albeit being statistically insignificant for the three species. Hunting pressure had no significant effect on the population estimates of the three species for the period 1997-2014. Impala population declined (-30 %) between 2003 and 2008 possibly due to increased illegal hunting pressure associated with land invasions during this period. Trophy size of all species declined over time, 2004-2014, (impala (-1.3 %), kudu (-3.9 %), sable (-2.6 %) possibly due diet quality and loss of genetic variability in these populations. However, trophy size for greater kudu and sable were within the minimum score range of the Safari Club International. We recommend research on genetic variability and inbreeding levels of hunted populations in closed ecosystems to inform adaptive management as a way of ensuring sustainability of trophy hunting as a conservation tool in small isolated parks in Africa.
... For these species the key issue is whether trophy hunting can provide gains to conservation through social, economic and political mechanisms at local scale, which can outweigh ecological costs from loss of individual animals at local scale. These costs may include reduced population size or genetic diversity, or disruption to internal population dynamics (Packer et al., 2011;Mysterud, 2012;Palazy et al., 2012;Wielgus et al., 2013). Killing one mature male lion, for example, may lead to redistribution of territory, death of juveniles and infanticide of cubs. ...
Read the Feature Paper: Does trophy hunting matter to long‐term population trends in African herbivores of different dietary guilds? ; other Commentaries on this paper: Monitoring required for effective sustainable use of wildlife and the Response from the authors: The assessment of the role of trophy hunting in wildlife conservation
... There are no examples of species extinction as a result of trophy hunting (Mysterud 2012). On the contrary, there are a few documented examples of declining populations that have recovered as a result of the appropriate use of the considerable income generated by well managed trophy hunting (Frisina and Tareen 2009). ...
Context
Whether trophy hunting is beneficial or a threat to the conservation of species is an open and hotly debated question. The International Union for Conservation of Nature (IUCN) is in charge of assessing the need for species protection at the global scale and providing a useful guide for sustainable exploitation and conservation. Consideration of the IUCN status in wildlife management and its consequences on the attractiveness of trophy-hunted species remains to be quantified.
Aims
The present study investigated the link between the IUCN status of the trophy species and its exploitation in 124 taxa. We expected that the number of trophies should be inversely correlated with the IUCN vulnerability status across species.
Methods
Using the database of the Safari Club International, one of the largest hunting associations worldwide, we investigated the effect (1) of the first status attribution and (2) of an upgrade of the IUCN status on the number of trophies recorded by the Safari Club International, by comparing the average number of trophies 5 years before and after a status change.
Key results
First, we found that the status attributed by the IUCN in a given year had no effect on the number of recorded trophies during the following 5 years. Second, upgrading the IUCN status led to an important decrease in the number of recorded trophies for most species (75%), except for the most vulnerable ones (African elephant, Loxodonta africana; banteng, Bos javanicus; lelwel hartebeest, Alcelaphus buselaphus lelwel; European bison, Bison bonasus).
Conclusions
Our results suggest that although a protective IUCN status lowers the exploitation of the moderately threatened species, hunting pressure on the most threatened one increases instead. The findings support the possibility of an anthropogenic Allee effect (AAE), i.e. a disproportionate exploitation of the rarest species.
Implications
The highly profitable exploitation of rare species could have harmful consequences, unless appropriate management actions and protection rules are enforced.
... Det har blitt økt fokus på konsekvensene av høsting på ville hjortedyrbestander, men foreslåtte mulige effekter har i liten grad vaert dokumentert , Proaktor et al. 2007, Bischof et al. 2008, Saether et al. 2009, Mysterud and Bischof 2010, Mysterud 2011, 2012. Det har for eksempel vaert foreslått at få og i hovedsak unge bukker/okser i bestanden etter jakt kan føre til redusert drektighet, forsinket kalving og økt variasjon i kalvetidspunkt. ...
Svalbardreinen er en unik underart av reinsdyr (Rangifer tarandus platyrhynchus) som bare finnes på Svalbard. Dette innebærer at forvaltningen av arten skal være i overensstemmelse med Svalbardlovens høye miljøkrav. Jakt på svalbardrein er forbeholdt lokalbefolkningen på Svalbard og er lokalisert til Nordenskiöld Land. Siden jakt ble tillatt i 1983 har jaktuttaket økt fra 117 dyr til det dobbelte. I ”Plan for forvaltning av svalbardrein” utarbeidet av Sysselmannen på Svalbard i 2009 ble det påpekt at det ikke har vært gjort noen vurdering av hvor stor effekt dagens forvaltningspraksis med hensyn på jakt, har på bestanden av svalbardrein. I denne rapporten benytter vi matematiske modeller for bestandsdynamikken til svalbardrein til å vurdere dette.
De viktigste funnene
Resultatene tyder på at jaktuttaket av svalbardrein under dagens forvaltningspraksis har små effekter på bestandene av svalbardrein. Den viktigste gruppen dyr i bestandsdynamikken til svalbardrein er de voksne simlene. Vi anslår at man kan ta ut opptil 13 % av bestanden av voksne simler årlig uten at bestanden vil bli betydelig redusert. For de siste 10 år beregner vi at uttaket av voksne simler ligget på 4-10 % av bestanden. Sannsynligvis kan man ta ut 400-450 dyr årlig på hele Nordenskiöld Land, noe som innebærer mulighet for fortsatt vekst i antall fellingsløyver. I tillegg til å ha lite effekt på bestandsstørrelsene har jakten slik den praktiseres og forvaltes også lite effekt på kjønnsfordelingen i bestanden. Dagens uttak av like mange bukker som simler synes å stabilisere kjønnsfordelingen nært den fordelingen man ville hatt uten jakt. Det er mulig å øke uttaket av bukker, men dette vil kunne føre til en betydelig skjevere kjønnsfordeling i bestandene.
Miljøgevinst
Arbeidet gir en avklaring på spørsmålet om hvor stor effekt rekreasjonsjakten på svalbardrein har på bestandene. Den gir støtte til dagens forvaltningspraksis og dermed faglig støtte til at dagens rekreasjonsjakt på svalbardrein kan fortsette.
Forslag til tiltak
Rapporten foreslår ingen umiddelbare tiltak, men rapporten gir innspill til de vurderinger som bør gjøres hvis det blir aktuelt å fortsette å øke jaktuttaket.
Hva er viktig for miljøforvaltningen?
Analysene tyder på at det totalt kan felles oppimot 450 rein på Nordenskiöld Land årlig. I dag gis det 300-350 fellingstillatelser årlig hvorav 60 % blir benyttet. Hvis andelen som benytter fellingstillatelsen øker betydelig vil dette innebære en betydelig vekst i antall dyr felt innenfor jaktområdene. Det er mulig at dette vil kunne gi lokal overbeskatning i enkelte jaktområder. Dette vil være avhengig av hvor isolerte bestandene i jaktområdene er fra bestandene i omliggende områder der det ikke jaktes. De varslede klimaforandringene i Arktis kan forandre levevilkårene til svalbardreinen dramatisk. Forvaltningen må derfor være forberedt på at jaktuttaket kan måtte justeres.
Oppfølging
Det anbefales at man undersøker i hvilken grad bestandene i de forskjellige jaktområdene er isolerte fra bestandene i omliggende områder. Særlig gjelder det jaktområdene ved Grønnfjorden og Sassendalen. For å utvikle bedre bestandsmodeller for svalbardrein trengs det en innsats for å bedre estimatene på kalvers overlevelse gjennom vinteren, og en bedre forståelse for hvordan klimatisk variasjon påvirker bestandene.
... However, others (e.g. Mysterud 2012;Harris et al. 2013;Lyons & Natutsch 2013) have disputed the strength of this evidence, pointing out that: (i) rising prices in response to declines are not a sufficient condition for extinction, as costs also rise; (ii) the AAE framework is built on an assumption of openaccess harvesting, which is likely to be violated in harvests that have some form of central management, cooperative governance, or property rights; and (iii) in cases where only a specific segment of the population is targeted (e.g. trophy hunting of only large males), the population as a whole may not be as susceptible to collapse. ...
The market values of harvested species rise as they become depleted due to
falling supply, rarity value, or both. High price flexibility in response to
depletion can cause profits to be stable or increase as a harvested population
declines toward extinction. Demonstrating price flexibility with increasing
rarity, however, is not sufficient to document a threat of overharvesting.
Extinction requires the value of harvest to rise faster than the costs of
harvest, which also likely increase as a population declines. Drawing on
evidence from bluefin tunas, sturgeons, whales, abalones, and other marine
species, here I argue that increasing or stable profits as a population
declines are likely to be driven to a greater extent by catch rates that are
robust to abundance declines, termed 'hyperstable', usually as a result of
range contraction, which buffer harvest costs, than by price flexibility. The
hyperstability of catch rates is rarely estimated in terrestrial systems,
partly due to data limitations, which I present one possible approach to
addressing. Catch hyperstability merits further research and greater
conservation attention. My analysis also suggests a possible synergy between
threats of habitat destruction, which imposes range contraction, and
overharvesting.
The harvest and sale of wildlife can drive species to extinction when consumers are willing to pay high prices for the last harvested individuals of a very rare species, a phenomenon known as the anthropogenic Allee effect (AAE). Because demand for rarity is an inherent human desire, the AAE has the potential to affect a wide range of exploited species across several geographic regions. Here, we assess the current extent of empirical evidence for the AAE, how such evidence has been measured, and how this evidence interfaces with existing models of the AAE. We find substantial gaps in the empirical evidence base for the AAE and suggest that this deficit prevents assessment of the AAE in species extinctions. We provide a framework for generating empirical evidence that can identify when the AAE is likely occurring or has the potential to occur in the future, and recommend directions for both empirical and theoretical modeling research designed to strengthen our ability to forecast the ecological and market conditions that result in an AAE.
Simple Summary: Trophy hunting and mass tourism were introduced to Khunjerab National Park, northern Pakistan to generate income for the community and help conserve and sustain the ecosystem in the region. These initiatives have provided economic benefits, but only at the cost of other environmental problems, as both trophy hunting and mass tourism have resulted in various ecological issues. Trophy hunting has not been based on scientific population data and has thus not helped increase numbers of wild ungulates or wild carnivores. Although mass tourism has increased enormously in this region, it has damaged the ecosystem through pollution generation and negatively impacted wildlife. We suggest that trophy hunting should be stopped, and mass tourism should be shifted to ecotourism as a sustainable solution to help improve the ecosystem, while generating income for the local community. Further studies are required to investigate ecotourism as a potential mitigation measure for the conservation issues in this region. Abstract: Trophy hunting and mass tourism are the two major interventions designed to provide various socioeconomic and ecological benefits at the local and regional levels. However, these interventions have raised some serious concerns that need to be addressed. This study was conducted in Khunjerab National Park (KNP) with an aim to analyze comparatively the socioeconomic and ecological impacts of trophy hunting and mass tourism over the last three decades within the context of sustainability. Focus Group Discussions (FGDs) with key stakeholders and household interviews were conducted to collect data on trophy hunting and mass tourism, and on local attitudes towards these two interventions in and around KNP. The results revealed that 170 Ibex (Capra sibirica) and 12 Blue sheep (Pseudois nayaur) were hunted in the study area over the past three decades, and trophy hunting was not based on a sustainable harvest level. Trophy hunting on average generated USD 16,272 annual revenue, which was invested in community development. However, trophy hunting has greatly changed the attitudes of local residents towards wildlife: a positive attitude towards the wild ungulates and strongly negative attitude towards wild carnivores. In addition, trophy hunting has reduced the availability of ungulate prey species for Snow leopards (Panthera uncia), and consequently, Snow leopards have increased their predation on domestic livestock. This has, in turn, increased human-snow leopard conflict, as negative attitudes towards carnivores result in retaliatory killing of Snow leopards. Furthermore, according to official record data, the number of tourists to KNP has increased tremendously by 10,437.8%, from 1382 in 1999 to 145,633 in 2018. Mass tourism on average generated USD 33,904 annually and provided opportunities for locals to earn high incomes, but it caused damages to the environment and ecosystem in KNP through pollution generation and negative impacts on wildlife. Considering the limited benefits and significant problems created by trophy hunting and mass tourism, we suggest trophy hunting should be stopped and mass tourism Animals 2020, 10, 597 2 of 20 should be shifted to ecotourism in and around KNP. Ecotourism could mitigate human-Snow leopard conflicts and help conserve the fragile ecosystem, while generating enough revenue incentives for the community to protect biodiversity and compensate for livestock depredation losses to Snow leopards. Our results may have implications for management of trophy hunting and mass tourism in other similar regions that deserve further investigation.
Trophy hunting and mass tourism are the two major interventions designed to provide various socioeconomic and ecological benefits at the local and regional levels. However, these interventions have raised some serious concerns that need to be addressed. This study was conducted in Khunjerab National Park (KNP) with an aim to analyze comparatively the socioeconomic and ecological impacts of trophy hunting and mass tourism over the last three decades within the context of sustainability. Focus Group Discussions (FGDs) with key stakeholders and household interviews were conducted to collect data on trophy hunting and mass tourism, and on local attitudes towards these two interventions in and around KNP. The results revealed that 170 Ibex (Capra sibirica) and 12 Blue sheep (Pseudois nayaur) were hunted in the study area over the past three decades, and trophy hunting was not based on a sustainable harvest level. Trophy hunting on average generated USD 16,272 annual revenue, which was invested in community development. However, trophy hunting has greatly changed the attitudes of local residents towards wildlife: a positive attitude towards the wild ungulates and strongly negative attitude towards wild carnivores. In addition, trophy hunting has reduced the availability of ungulate prey species for Snow leopards (Panthera uncia), and consequently, Snow leopards have increased their predation on domestic livestock. This has, in turn, increased human–snow leopard conflict, as negative attitudes towards carnivores result in retaliatory killing of Snow leopards. Furthermore, according to official record data, the number of tourists to KNP has increased tremendously by 10,437.8%, from 1382 in 1999 to 145,633 in 2018. Mass tourism on average generated USD 33,904 annually and provided opportunities for locals to earn high incomes, but it caused damages to the environment and ecosystem in KNP through pollution generation and negative impacts on wildlife. Considering the limited benefits and significant problems created by trophy hunting and mass tourism, we suggest trophy hunting should be stopped and mass tourism should be shifted to ecotourism in and around KNP. Ecotourism could mitigate human–Snow leopard conflicts and help conserve the fragile ecosystem, while generating enough revenue incentives for the community to protect biodiversity and compensate for livestock depredation losses to Snow leopards. Our results may have implications for management of trophy hunting and mass tourism in other similar regions that deserve further investigation.
We compared population structure and trophy hunting statistics of Himalayan ibex (Capra sibirica) in two community-controlled hunting areas (CCHAs) of northern Pakistan with varying duration of trophy hunting and isolated populations of C. sibirica. Based on fixed-point direct count method during winter 2016–2017, 939 ibexes were counted in Khyber and 346 in Hussaini, with a density of 7.5 and 3.2 animals km-2, respectively. Though the populations of C. sibirica at both the study sites have increased compared to the past estimates, we found variations in population structures and horn sizes, presumably as a result of trophy hunting. The sex ratios are skewed toward females in Khyber (87 males/100 females) and towards males in Hussaini (115 males/100 females). The trophy size males were 7% of the population in Khyber and 11% in Hussaini. Mean group (herd) size in Khyber was 28 (range = 1–117) and Hussaini was 20 (range = 1–79). Mean horn size of the trophies harvested in Khyber was 102 cm (± range = 91–114) compared to 108 cm (range = 99–121) in Hussaini. Stringent regulatory measures are suggested to determine the number of permits.
We compared population structure and trophy hunting statistics of Himalayan ibex (Capra sibirica) in two community-controlled hunting areas (CCHAs) of northern Pakistan with varying duration of trophy hunting and isolated populations of C. sibirica. Based on fixed-point direct count method during winter 2016-2017, 939 ibexes were counted in Khyber and 346 in Hussaini, with a density of 7.5 and 3.2 animals km-2 , respectively. Though the populations of C. sibirica at both the study sites have increased compared to the past estimates, we found variations in population structures and horn sizes, presumably as a result of trophy hunting. The sex ratios are skewed toward females in Khyber (87 males/100 females) and towards males in Hussaini (115 males/100 females). The trophy size males were 7% of the population in Khy-ber and 11% in Hussaini. Mean group (herd) size in Khyber was 28 (range = 1-117) and Hussaini was 20 (range = 1-79). Mean horn size of the trophies harvested in Khyber was 102 cm (± range = 91-114) compared to 108 cm (range = 99-121) in Hussaini. Stringent regulatory measures are suggested to determine the number of permits.
Fisheries science faces a challenging combination of complexity and data limitation that places opposing pressures on theoretical research - which seeks to describe the complexity - and empirical research - which is constrained to simplicity by the limitations of available data. In this volume, I present studies aiming to reconcile theoretical and empirical approaches to assessing the current status of fished populations and designing management plans in two ways: i) by using concise mechanistic theories rooted in measurable parameters to develop new predictive assessment tools; and ii) by using ecological and economic theory to develop insights whose applications are not data-dependent or system specific. My research provides several important insights for assessment and management in fisheries: 1) Combinations of biological and socioeconomic conditions that eventually lead to extinction or overfishing can often be empirically identified decades before high harvest rates and large population declines occur, allowing for preventative management. 2) Though there is concern that harvest value, which rises as a harvested species is depleted, can allow profits to be maintained it is driven extinct, this threat most often also requires catch-rates to be substantially robust to declining abundance. Because range contraction often buffers population densities against abundance declines, habitat destruction may exacerbate threats of overharvesting. 3) Assessments based on single-species population models in multispecies fisheries can often provide reliable estimates of sustainable yields and harvest rates in populations with high vulnerability to overfishing, but often significantly overestimate sustainable yields and harvest rates in populations with lower vulnerability. However, single-species assessment frameworks can nonetheless be used to identify conditions leading to such bias, and estimate bounds on its magnitude. 4) Diversifying technologies and efficiencies within fishing fleets often leads to fewer population collapses in both managed and unmanaged fisheries; and increases the positive impact management can make on fishery yields and profits. The studies in this volume provide new perspectives on theoretical-empirical synergies in fisheries research, and maximizing the information value of fisheries data through theoretical concision and ecological abstraction.
The size and shape of a trophy constitute major determinants of its value. We postulate that the rarity of a species, whatever its causes, also plays a major role in determining its value among hunters. We investigated a role for an Anthropogenic Allee effect in trophy hunting, where human attraction to rarity could lead to an over-exploitative chain reaction that could eventually drive the targeted species to extinction. We performed an inter-specific analysis of trophy prices of 202 ungulate taxa and quantified to what extent morphological characteristics and their rarity accounted for the observed variation in their price. We found that once location and body mass were accounted for, trophies of rare species attain higher prices than those of more common species. By driving trophy price increase, this rarity effect may encourage the exploitation of rare species regardless of their availability, with potentially profound consequences for populations.
Studies of sexual size dimorphism among mammals have in the main focused on whether body weight, level of polygyny or ecological variables account for dimorphism patterns. Unfortunately, the use of different methods and indices of dimorphism has led to confusion and a failure to assess the relative role of the variables. We studied the effect of body weight, level of polygyny, feeding type and habitat type on sexual size dimorphism in ruminants. Three patterns emerged: first, dimorphism increases with body weight; second, this positive relationship is accounted for by the positive association between level of polygyny and weight; and third, the effect of feeding type is weak, and habitat type has no detectable effect. These results demonstrate that allometry is unimportant for shaping sexual size dimorphism in ungulates, and that degree of polygyny alone can almost entirely account for the phenomenon that sexual size dimorphism increases with increasing body size in ungulates. Level of polygyny increases with weight and this correlation leads to the observed positive correlation between weight and dimorphism when polygyny is not accounted for. The possibility that the relationship between weight anfl level of polygyny can be explained by density and spacing systems is discussed, and some other hypotheses concerning mechanisms of selection are presented.
In this review, we focus on how males can affect the population dynamics of ungulates (i) by being a component of population density (and thereby affecting interpretation of log‐linear models), and (ii) by considering the mechanisms by which males can actively affect the demographic rates of females.
We argue that the choice of measure of density is important, and that the inclusion or exclusion of males into models can influence results. For example, we demonstrate that if the dynamics of a population can be described with a first‐order auto‐regressive process in a log‐linear framework, the asymmetry between the effects of females on the male dynamics and vice versa can introduce a second order process, much in the same way that the interaction between disease and host or predator and prey can. It would be useful for researchers with sufficient data to explore the affects of using different density measures.
In general, even in harvested populations with highly skewed sex ratios, males are usually able to fertilize all females, though detailed studies document a lower proportion of younger females breeding when sex ratios are heavily female biased. It is well documented that the presence of males can induce oestrus in females, and that male age may also be a factor. In populations with both a skewed sex ratio and a young male age structure, calving is delayed and less synchronous. We identify several mechanisms that may be responsible for this.
Delayed calving may lower summer survival and autumn masses, which may lead to higher winter mortality. If females are born light, they may require another year of growth before they start reproducing. Delayed calving can reduce future fertility of the mother. As the proportion of calves predated during the first few weeks of life is often very high, calving synchrony may also be an important strategy to lower predation rates.
We argue that the effects of males on population dynamics of ungulates are likely to be non‐trivial, and that their potential effects should not be ignored. The mechanisms we discuss may be important – though much more research is required before we can demonstrate they are.
Tanzania holds most of the remaining large populations of African lions (Panthera leo) and has extensive areas of leopard habitat (Panthera pardus), and both species are subjected to sizable harvests by sport hunters. As a first step toward establishing sustainable management strategies, we analyzed harvest trends for lions and leopards across Tanzania's 300,000 km(2) of hunting blocks. We summarize lion population trends in protected areas where lion abundance has been directly measured and data on the frequency of lion attacks on humans in high-conflict agricultural areas. We place these findings in context of the rapidly growing human population in rural Tanzania and the concomitant effects of habitat loss, human-wildlife conflict, and cultural practices. Lion harvests declined by 50% across Tanzania between 1996 and 2008, and hunting areas with the highest initial harvests suffered the steepest declines. Although each part of the country is subject to some form of anthropogenic impact from local people, the intensity of trophy hunting was the only significant factor in a statistical analysis of lion harvest trends. Although leopard harvests were more stable, regions outside the Selous Game Reserve with the highest initial leopard harvests again showed the steepest declines. Our quantitative analyses suggest that annual hunting quotas be limited to 0.5 lions and 1.0 leopard/1000 km(2) of hunting area, except hunting blocks in the Selous Game Reserve, where harvests should be limited to 1.0 lion and 3.0 leopards/1000 km(2) .
Human exploitation may skew adult sex ratios in vertebrate populations to the extent that males become limiting for normal reproduction. In polygynous ungulates, females delay breeding in heavily harvested populations, but effects are often fairly small. We would expect a stronger effect of male harvesting in species with a monogamous mating system, but no such study has been performed. We analysed the effect of harvesting males on the timing of reproduction in the obligate monogamous beaver (Castor fiber). We found a negative impact of harvesting of adult males on the timing of parturition in female beavers. The proportion of normal breeders sank from over 80%, when no males had been shot in the territories of pregnant females, to under 20%, when three males had been shot. Harvesting of males in monogamous mammals can apparently affect their normal reproductive cycle.
In Tanzania, where tourist hunting is employed as a conservation tool for habitat protection, information on population sizes and hunting offtake was used to assess the impact of tourist hunting on mammal densities. In general, tourist hunting pressure was unrelated to local population sizes, but for most species, animals were removed at a level of less than 10% of the local population size, suggesting that over-exploitation was unlikely. Eland, however, and perhaps small antelope, bushbuck, kudu and reedbuck were hunted at levels which may be unsustainable in the long term. Analyses also identified areas of Tanzania with high levels of tourist hunting pressure, showed that, in certain areas, species with small population sizes such as eland could be declining as a result of tourist hunting, and suggested that current levels of lion and leopard offtake are too high. These findings, although preliminary, allow recommendations to be put forward for changing hunting quotas for certain species in particular areas of Tanzania.
1. Harvesting of large mammals is usually not random, and directional selection has been identified as the main cause of rapid evolution. However, selective harvesting in meat and recreational hunting cultures does not automatically imply directional selection for trait size.
2. Harvesting selectivity is more than a matter of hunter preference. Selection is influenced by management regulations, hunting methods, animal trait variance, behaviour and abundance. Most studies of hunter selection only report age- or sex-specific selection, or differences in trait size selection among hunting methods or groups of hunters, rather than trait size relative to the age-specific means required for directional selection.
3. Synthesis and applications. Managers aiming to avoid rapid evolution should not only consider directional selection and trophy hunting but also mitigate other important evolutionary forces such as harvesting intensity per se, and sexual selection processes that are affected by skewed sex ratios and age structures.
The size and shape of a trophy constitute major determinants of its value. We postulate that the rarity of a species, whatever its causes, also plays a major role in determining its value among hunters. We investigated a role for an Anthropogenic Allee effect in trophy hunting, where human attraction to rarity could lead to an over-exploitative chain reaction that could eventually drive the targeted species to extinction. We performed an inter-specific analysis of trophy prices of 202 ungulate taxa and quantified to what extent morphological characteristics and their rarity accounted for the observed variation in their price. We found that once location and body mass were accounted for, trophies of rare species attain higher prices than those of more common species. By driving trophy price increase, this rarity effect may encourage the exploitation of rare species regardless of their availability, with potentially profound consequences for populations.
The population dynamic and evolutionary effects of harvesting are receiving growing attention among biologists. Cause‐specific estimates of mortality are necessary to determine and compare the magnitude and selectivity of hunting and other types of mortalities. In addition to the logistic and financial constraints on longitudinal studies, they are complicated by the fact that nonhunting mortality in managed populations usually consists of a mix of natural and human‐caused factors.
We used multistate capture–recapture (MCR) models to estimate cause‐specific survival of brown bears ( Ursus arctos ) in two subpopulations in Sweden over a 23‐year period. In our analysis, we distinguished between legal hunting and other sources of mortality, such as intraspecific predation, accidents, poaching, and damage control removals. We also tested whether a strong increase in harvest quotas after 1997 in one of the subpopulations affected vulnerability to legal hunting.
Although only a fraction of mortalities other than legal hunting could be considered natural, this group of causes showed a general pattern of demographic selectivity expected from natural mortality regimes in populations of long‐lived species, namely greater vulnerability of young animals. On the other hand, demographic effects on hunting vulnerability were weak and inconsistent. Our findings support the assumption that hunting and other mortalities were additive.
As expected, an increase in hunting pressure coincided with a correspondingly large increase in vulnerability to hunting in the affected subpopulation. Because even unbiased harvest can lead to selective pressures on life‐history traits, such as size at primiparity, increasing harvest quotas may not only affect population growth directly, but could also alter optimal life‐history strategies in brown bears and other carnivores.
Legal hunting is the most conveniently assessed and the most easily managed cause of mortality in many wild populations of large mammals. Although legal hunting is the single‐most important cause of mortality for brown bears in Sweden, the combined mortality from other causes is of considerable magnitude and additionally shows greater selectivity in terms of sex and age than legal hunting. Therefore, its role in population dynamics and evolution should not be underestimated.
1. Trade-offs in resource allocation underline the evolution of life-history traits but their expression is frequently challenged by empirical findings. In large herbivores, males with large antlers or horns typically have high mating success. The fitness costs of large horns or antlers have rarely been quantified although they are controversial. 2. Here, using detailed longitudinal data on n = 172 bighorn (Ovis canadensis, Shaw) and the capture-mark-recapture methodology, we tested whether early horn growth leads to a survival cost in rams ('trade-off' hypothesis) or if males that can afford rapid horn growth survive better than males of lower phenotypic quality ('phenotypic quality' hypothesis). We also quantified how hunting increased survival costs of bearing large horns. 3. We found an age-specific relationship between horn growth and survival. In all age classes, natural survival was either weakly related to (lambs, adult rams) or positively associated (yearling rams) with early horn growth. Hunting mortality was markedly different from natural mortality of bighorn rams, leading to an artificial negative association between early horn growth and survival. Beginning at age 4, the yearly harvest rate ranged from 12% for males with the smallest horns up to more than 40% for males with the largest horns. 4. Growing large horns early in life is not related to any consistent survival costs, hence supporting the phenotypic quality hypothesis in males of a dimorphic and polygynous large herbivores. Rapid horn growth early in life is, however, strongly counter selected by trophy hunting. We suggest that horn size is a very poor index of reproductive effort and that males modulate their mating activities and energy allocation to horn growth to limit its impact on survival.
A common assumption is that breeding in polygnous systems is not limited by the number of males because one male can inseminate many females. But here we show that reproductive collapse in the critically endangered saiga antelope (Saiga tatarica tatarica) is likely to have been caused by a catastrophic drop in the number of adult males in this harem-breeding ungulate, probably due to selective poaching for their horns. Fecundity and calf survival are known to be affected by markedly skewed sex ratios, but in the saiga antelope the sex ratio has become so distorted as to lead to a drastic decline in the number of pregnancies - a finding that has implications both for the conservation of the species and for understanding the reproductive ecology of polygynous ungulates.
The recent proliferation of hypervariable molecular markers has ushered in a surge of techniques for the analysis of parentage in natural and experimental populations. Consequently, the potential for meaningful studies of paternity and maternity is at an all-time high. However, the details and implementation of the multifarious techniques often differ in subtle ways that can influence the results of parentage analyses. Now is a good time to reflect on the available techniques and to consider their strengths and weaknesses. Here, we review the leading techniques in parentage analysis, with a particular emphasis on those that have been implemented in readily useable software packages. Our survey leads to some important insights with respect to the utility of the different approaches. This review should serve as a useful guide to anyone who wishes to embark on the study of parentage.
The science of overabundance Deer ecology and population management Reproductive collapse in saiga antelope harems
- W J Mcshea
- H B Underwood
- E J Milner-Gulland
- O M Bukreeva
- T Coulson
- A A Lushchekina
- M V Kholodova
- A B Bekenov
- I A Grachev
McShea, W.J. & Underwood, H.B. (1997). The science of overabundance. Deer ecology and population management. Washington, DC: Smithsonian Institution Press. Milner-Gulland, E.J., Bukreeva, O.M., Coulson, T., Lushchekina, A.A., Kholodova, M.V., Bekenov, A.B. & Grachev, I.A. (2003). Reproductive collapse in saiga antelope harems. Nature 422, 135.