Habitat use by black bears in relation to conspecifics and competitors

Sympatric black bears (Ursus americanus) and brown bears (Ursus arctos) are common in many boreal systems; however, few predator assemblages are known to coexist on a single seasonally abundant large prey item. In lowland southwestern interior Alaska, black bears and brown bears are considered the primary cause of moose (Alces alces) calf mortality during the first 6 weeks of life. The objective of this study was to document habitat use of global-positioning system (GPS)-collared black bears during peak and non-peak seasons of black bear-induced and brown bear-induced moose calf mortality within southwestern interior Alaska, in spring 2002. We compared habitats of GPS-collared black bears to those of presumably uncollared black bears and brown bears at their moose calf mortality sites. Results from this study suggest that GPS-collared black bears use similar habitat as conspecifics more than expected during the peak period of black bear predation on moose calves, whereas they use habitat in proportion to home range availability during the peak in brown bear predation on moose calves. Sex-specific Ivlev's electivity indices describe greater than expected use of mixed-deciduous forest and needleleaf forest by male GPS-collared black bears during the peak of moose calf predation, whereas females have a tendency to use these habitats less than expected. Juvenile GPS-collared black bears largely use the same habitat as other sympatric predators during the peak of moose calf predation, whereas during the non-peak period juveniles use opposite habitats as adult GPS-collared black bears. The outcome of this study offers possible explanations (e.g., sex, age) for spatial overlap or segregation in one member of a complex predator guild in relation to a seasonal pulse of preferred prey.     

Summer kill rates and predation pattern in a wolf–moose system: can we rely on winter estimates?

So far the vast majority of studies on large carnivore predation, including kill rates and consumption, have been based on winter studies. Because large carnivores relying on ungulates as prey often show a preference for juveniles, kill rates may be both higher and more variable during the summer season than during the rest of the year leading to serious underestimates of the total annual predation rate. This study is the first to present detailed empirical data on kill rates and prey selection in a wolf–moose system during summer (June–September) as obtained by applying modern Global Positioning System-collar techniques on individual wolves (Canis lupus) in Scandinavia. Moose (Alces alces) was the dominant prey species both by number (74.4%) and biomass (95.6%); 89.9% of all moose killed were juveniles, representing 76.0% of the biomass consumed by wolves. Kill rate in terms of the kilogram biomass/kilogram wolf per day averaged 0.20 (range: 0.07–0.32) among wolf territories and was above, or well above, the daily minimum food requirements in most territories. The average number of days between moose kills across wolf territories and study periods was 1.71 days, but increased with time and size of growing moose calves during summer. Over the entire summer (June–September, 122 days), a group (from two to nine) of wolves killed a total of 66 (confidence interval 95%; 56–81) moose. Incorporation of body growth functions of moose calves and yearlings and wolf pups over the summer period showed that wolves adjusted their kill rate on moose, so the amount of biomass/kilogram wolf was relatively constant or increased. The kill rate was much higher (94–116%) than estimated from the winter period. As a consequence, projecting winter kill rates to obtain annual estimates of predation in similar predator–prey systems may result in a significant underestimation of the total number of prey killed. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Assessing the influence of prey–predator ratio,prey age structure and packs size on wolf kill rates

Traditional predation theory assumes that prey density is the primary determinant of kill rate. More recently, the ratio of prey‐to‐predator has been shown to be a better predictor of kill rate. However, the selective behavior of many predators also suggests that age structure of the prey population should be an important predictor of kill rate. We compared wolf–moose predation dynamics in two sites, south‐central Scandinavia (SCA) and Isle Royale, Lake Superior, North America (IR), where prey density was similar, but where prey age structure and prey‐to‐predator ratio differed. Per capita kill rates of wolves preying on moose in SCA are three times greater than on IR. Because SCA and IR have similar prey densities differences in kill rate cannot be explained by prey density. Instead, differences in kill rate are explained by differences in the ratio of prey‐to‐predator, pack size and age structure of the prey populations. Although ratio‐dependent functional responses was an important variable for explaining differences in kill rates between SCA and IR, kill rates tended to be higher when calves comprised a greater portion of wolves’ diet (p =0.05). Our study is the first to suggest how age structure of the prey population can affect kill rate for a mammalian predator. Differences in age structure of the SCA and IR prey populations are, in large part, the result of moose and forests being exploited in SCA, but not in IR. While predator conservation is largely motivated by restoring trophic cascades and other top–down influences, our results show how human enterprises can also alter predation through bottom–up processes.     

Evaluation of Potential Factors Predisposing Livestock to Predation by Jaguars

ABSTRACT Depredation of livestock by large carnivores is an important but poorly understood source of human-carnivore conflict. We examined patterns of livestock depredation by jaguars (Panthera onca) and pumas (Puma concolor) on a ranch-wildlife reserve in western Brazil to assess factors contributing to prey mortality. We predicted jaguars would kill a greater proportion of calves than yearling and adult cattle and that proximity to suitable habitat would increase mortality risk. We further speculated that exposure to predation risk would promote livestock grouping and increased movement distance. We recorded 169 cattle mortality incidents during 2003–2004, of which 19% were due to predation by jaguars and pumas. This level of mortality represented 0.2–0.3% of the total livestock holdings on the ranch. Jaguars caused most (69%) cattle predation events, and survival in allotments was lower for calves than for other age classes. Forest proximity was the only variable we found to explain patterns of livestock mortality, with predation risk increasing as distance to forest cover declined. Due to low predation risk, cattle movement patterns and grouping behavior did not vary relative to level of spatial overlap with radiocollared jaguars. The overall effect of predation on cattle was low and livestock likely constituted an alternative prey for large cats in our study area. However, selection of calves over other age cohorts and higher predation risk among cattle in proximity to forest cover is suggestive of selection of substandard individuals. Cattle ranchers in the Pantanal region may reduce cattle mortality rates by concentrating on losses due to nonpredation causes that could be more easily controlled.     

Predicting the potential demographic impact of predators on their prey: a comparative analysis of two carnivore-ungulate systems in Scandinavia

1. Understanding the role of predation in shaping the dynamics of animal communities is a fundamental issue in ecological research. Nevertheless, the complex nature of predator-prey interactions often prevents researchers from modelling them explicitly. 2. By using periodic Leslie-Usher matrices and a simulation approach together with parameters obtained from long-term field projects, we reconstructed the underlying mechanisms of predator-prey demographic interactions and compared the dynamics of the roe deer-red fox-Eurasian lynx-human harvest system with those of the moose-brown bear-gray wolf-human harvest system in the boreal forest ecosystem of the southern Scandinavian Peninsula. 3. The functional relationship of both roe deer and moose λ to changes in predation rates from the four predators was remarkably different. Lynx had the strongest impact among the four predators, whereas predation rates by wolves, red foxes, or brown bears generated minor variations in prey population λ. Elasticity values of lynx, wolf, fox and bear predation rates were -0·157, -0·056, -0·031 and -0·006, respectively, but varied with both predator and prey densities. 4. Differences in predation impact were only partially related to differences in kill or predation rates, but were rather a result of different distribution of predation events among prey age classes. Therefore, the age composition of killed individuals emerged as the main underlying factor determining the overall per capita impact of predation. 5. Our results confirm the complex nature of predator-prey interactions in large terrestrial mammals, by showing that different carnivores preying on the same prey species can exert a dramatically different demographic impact, even in the same ecological context, as a direct consequence of their predation patterns. Similar applications of this analytical framework in other geographical and ecological contexts are needed, but a more general evaluation of the subject is also required, aimed to assess, on a broader systematic and ecological range, what specific traits of a carnivore are most related to its potential impact on prey species.     

Landscape‐scale accessibility of livestock to tigers: implications of spatial grain for modeling predation risk to mitigate human–carnivore conflict

Innovative conservation tools are greatly needed to reduce livelihood losses and wildlife declines resulting from human–carnivore conflict. Spatial risk modeling is an emerging method for assessing the spatial patterns of predator–prey interactions, with applications for mitigating carnivore attacks on livestock. Large carnivores that ambush prey attack and kill over small areas, requiring models at fine spatial grains to predict livestock depredation hot spots. To detect the best resolution for predicting where carnivores access livestock, we examined the spatial attributes associated with livestock killed by tigers in Kanha Tiger Reserve, India, using risk models generated at 20, 100, and 200‐m spatial grains. We analyzed land‐use, human presence, and vegetation structure variables at 138 kill sites and 439 random sites to identify key landscape attributes where livestock were vulnerable to tigers. Land‐use and human presence variables contributed strongly to predation risk models, with most variables showing high relative importance (≥0.85) at all spatial grains. The risk of a tiger killing livestock increased near dense forests and near the boundary of the park core zone where human presence is restricted. Risk was nonlinearly related to human infrastructure and open vegetation, with the greatest risk occurring 1.2 km from roads, 1.1 km from villages, and 8.0 km from scrubland. Kill sites were characterized by denser, patchier, and more complex vegetation with lower visibility than random sites. Risk maps revealed high‐risk hot spots inside of the core zone boundary and in several patches in the human‐dominated buffer zone. Validation against known kills revealed predictive accuracy for only the 20 m model, the resolution best representing the kill stage of hunting for large carnivores that ambush prey, like the tiger. Results demonstrate that risk models developed at fine spatial grains can offer accurate guidance on landscape attributes livestock should avoid to minimize human–carnivore conflict.     

Effects of predator treatments,individual traits,and environment on moose survival in Alaska

We studied moose (Alces alces) survival, physical condition, and abundance in a 3-predator system in western Interior Alaska, USA, during 2001–2007. Our objective was to quantify the effects of predator treatments on moose population dynamics by investigating changes in survival while evaluating the contribution of potentially confounding covariates. In May 2003 and 2004, we reduced black bear (Ursus americanus) and brown bear (U. arctos) numbers by translocating bears ≥240 km from the study area. Aircraft-assisted take reduced wolf (Canis lupus) numbers markedly in the study area during 2004–2007. We estimated black bears were reduced by approximately 96% by June 2004 and recovered to within 27% of untreated numbers by May 2007. Brown bears were reduced approximately 50% by June 2004. Late-winter wolf numbers were reduced by 75% by 2005 and likely remained at these levels through 2007. In addition to predator treatments, moose hunting closures during 2004–2007 reduced harvests of male moose by 60% in the study area. Predator treatments resulted in increased calf survival rates during summer (primarily from reduced black bear predation) and autumn (primarily from reduced wolf predation). Predator treatments had little influence on survival of moose calves during winter; instead, calf survival was influenced by snow depth and possibly temperature. Increased survival of moose calves during summer and autumn combined with relatively constant winter survival in most years led to a corresponding increase in annual survival of calves following predator treatments. Nonpredation mortalities of calves increased following predator treatments; however, this increase provided little compensation to the decrease in predation mortalities resulting from treatments. Thus, predator-induced calf mortality was primarily additive. Summer survival of moose calves was positively related to calf mass (β > 0.07, SE = 0.073) during treated years and lower (β = −0.82, SE = 0.247) for twins than singletons during all years. Following predator treatments, survival of yearling moose increased 8.7% for females and 21.4% for males during summer and 2.2% for females and 15.6% for males during autumn. Annual survival of adult (≥2 yr old) female moose also increased in treated years and was negatively (β = −0.21, SE = 0.078) related to age. Moose density increased 45%, from 0.38 moose/km² in 2001 to 0.55 moose/km² in 2007, which resulted from annual increases in overall survival of moose, not increases in reproductive rates. Indices of nutritional status remained constant throughout our study despite increased moose density. This information can be used by wildlife managers and policymakers to better understand the outcomes of predator treatments in Alaska and similar environments. © 2011 The Wildlife Society.     

Mobility of moose—comparing the effects of wolf predation risk,reproductive status,and seasonality

In a predator–prey system, prey species may adapt to the presence of predators with behavioral changes such as increased vigilance, shifting habitats, or changes in their mobility. In North America, moose (Alces alces) have shown behavioral adaptations to presence of predators, but such antipredator behavioral responses have not yet been found in Scandinavian moose in response to the recolonization of wolves (Canis lupus). We studied travel speed and direction of movement of GPS‐collared female moose (n = 26) in relation to spatiotemporal differences in wolf predation risk, reproductive status, and time of year. Travel speed was highest during the calving (May–July) and postcalving (August–October) seasons and was lower for females with calves than females without calves. Similarly, time of year and reproductive status affected the direction of movement, as more concentrated movement was observed for females with calves at heel, during the calving season. We did not find support for that wolf predation risk was an important factor affecting moose travel speed or direction of movement. Likely causal factors for the weak effect of wolf predation risk on mobility of moose include high moose‐to‐wolf ratio and intensive hunter harvest of the moose population during the past century.     

Predation on Moose Calves by European Brown Bears

Abstract: In North America, brown bears (Ursus arctos) can be a significant predator on moose (Alces alces) calves. Our study in Sweden is the first in which brown bears are the only predator on moose calves. Bears and moose occurred at densities of about 30/1,000 km² and 920/1,000 km², respectively, and bears killed about 26% of the calves. Ninety-two percent of the predation took place when calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears. Females that lost their calves in spring produced more calves the following year (1.54 calves/F) than females that kept their calves (1.11 calves/F), which reduced the net loss of calves due to predation to about 22%.     

Seasonal patterns of predation for gray wolves in the multi-prey system of Yellowstone National Park

1.?For large predators living in seasonal environments, patterns of predation are likely to vary among seasons because of related changes in prey vulnerability. Variation in prey vulnerability underlies the influence of predators on prey populations and the response of predators to seasonal variation in rates of biomass acquisition. Despite its importance, seasonal variation in predation is poorly understood. 2.?We assessed seasonal variation in prey composition and kill rate for wolves Canis lupus living on the Northern Range (NR) of Yellowstone National Park. Our assessment was based on data collected over 14 winters (1995-2009) and five spring-summers between 2004 and 2009. 3.?The species composition of wolf-killed prey and the age and sex composition of wolf-killed elk Cervus elaphus (the primary prey for NR wolves) varied among seasons. 4.?One's understanding of predation depends critically on the metric used to quantify kill rate. For example, kill rate was greatest in summer when quantified as the number of ungulates acquired per wolf per day, and least during summer when kill rate was quantified as the biomass acquired per wolf per day. This finding contradicts previous research that suggests that rates of biomass acquisition for large terrestrial carnivores tend not to vary among seasons. 5.?Kill rates were not well correlated among seasons. For example, knowing that early-winter kill rate is higher than average (compared with other early winters) provides little basis for anticipating whether kill rates a few months later during late winter will be higher or lower than average (compared with other late winters). This observation indicates how observing, for example, higher-than-average kill rates throughout any particular season is an unreliable basis for inferring that the year-round average kill rate would be higher than average. 6.?Our work shows how a large carnivore living in a seasonal environment displays marked seasonal variation in predation because of changes in prey vulnerability. Patterns of wolf predation were influenced by the nutritional condition of adult elk and the availability of smaller prey (i.e. elk calves, deer). We discuss how these patterns affect our overall understanding of predator and prey population dynamics.     

Prey Animals of Tiger (<Emphasis Type="Italic">Panthera tigris tigris</Emphasis>) in Dudhwa Landscape,Terai Region,North India

Livestock depredation by carnivores cause substantial human carnivore conflict and subsequently decreased support for carnivore conservation. Thus, understanding carnivore diet with respect to wild prey availability has major implications to determine the reasons behind livestock depredation. A study was conducted to investigate food habits and prey use of tiger at four study sites (Dudhwa National Park, Kishanpur Wildlife Sanctuary, Pilibhit Forest Division and Katerniaghat Wildlife Sanctuary) in Dudhwa landscape, Terai Region, North India for further understanding of prey–predator relationship and partial impact of wild prey availability on livestock depredation by tiger through scat analysis. Scat analysis shows that the tigers depend mostly on medium sized prey throughout the study area (74.11, 73.58, 71.79, 47.62%). In Dudhwa National Park and Kishanpur Wildlife Sanctuary, predation was attempted subsequently on wider prey variety of eleven and nine different available prey species where livestock depredation were only 3.77 and 5.36% respectively. While, in absence of wider prey variety, large sized livestock (21.91, 16.55%) and nilgai (24.41, 5.57%) contributed much higher in tiger diet in Pilibhit Forest Division and Katerniaghat Wildlife Sanctuary respectively. Our study suggested that availability of prey variety has an important role in reduced livestock depredation. Medium sized preys were mostly contributing in tiger diet and seems to be a significant parameter for sustaining tiger population where abundance of large sized prey is rare. Conservation of medium sized preys is important but along with natural restoration of the population of large sized prey species like sambar and swamp deer is essential in order to reduce livestock depredation.     

Effect of sociality and season on gray wolf (Canis lupus) foraging behavior: implications for estimating summer kill rate

Background

Understanding how kill rates vary among seasons is required to understand predation by vertebrate species living in temperate climates. Unfortunately, kill rates are only rarely estimated during summer.

Methodology/Principal Findings

For several wolf packs in Yellowstone National Park, we used pairs of collared wolves living in the same pack and the double-count method to estimate the probability of attendance (PA) for an individual wolf at a carcass. PA quantifies an important aspect of social foraging behavior (i.e., the cohesiveness of foraging). We used PA to estimate summer kill rates for packs containing GPS-collared wolves between 2004 and 2009. Estimated rates of daily prey acquisition (edible biomass per wolf) decreased from 8.4±0.9 kg (mean ± SE) in May to 4.1±0.4 kg in July. Failure to account for PA would have resulted in underestimating kill rate by 32%. PA was 0.72±0.05 for large ungulate prey and 0.46±0.04 for small ungulate prey. To assess seasonal differences in social foraging behavior, we also evaluated PA during winter for VHF-collared wolves between 1997 and 2009. During winter, PA was 0.95±0.01. PA was not influenced by prey size but was influenced by wolf age and pack size.

Conclusions/Significance

Our results demonstrate that seasonal patterns in the foraging behavior of social carnivores have important implications for understanding their social behavior and estimating kill rates. Synthesizing our findings with previous insights suggests that there is important seasonal variation in how and why social carnivores live in groups. Our findings are also important for applications of GPS collars to estimate kill rates. Specifically, because the factors affecting the PA of social carnivores likely differ between seasons, kill rates estimated through GPS collars should account for seasonal differences in social foraging behavior.     

Encounter frequencies between GPS-collared wolves (Canis lupus) and moose (Alces alces) in a Scandinavian wolf territory

Over 6,000 GPS fixes from two wolves (Canis lupus) and 30,000 GPS fixes from five moose (Alces alces) in a wolf territory in southern Scandinavia were used to assess the static and dynamic interactions between predator and prey individuals. Our results showed that wolves were closer to some of the moose when inside their home ranges than expected if they had moved independently of each other, and we also found a higher number of close encounters (<500 m) than expected. This suggests that the wolves were actively seeking the individual moose within their territory. Furthermore, the wolves showed a preference for moving on gravel forest roads, which may be used as convenient travel routes when patrolling the territory and seeking areas where the moose are. However, due to the particularly large size of the wolf territory combined with relatively high moose densities, the wolves generally spent a very small proportion of their time inside the home range of each individual moose, and the frequency of encounters between the wolves and any particular moose was very low. We suggest that the high moose:wolf ratio in this large Scandinavian wolf territory compared to that typically occurring in North America, results in a relatively low encounter frequency and a low predation risk for individual moose, as the predation pressure is spread over a high number of prey individuals.     

A Conservation-Based Approach to Compensation for Livestock Depredation: The Florida Panther Case Study

Calf (Bos taurus) depredation by the federally endangered Florida panther (Puma concolor coryi) on ranches in southwest Florida is an important issue because ranches represent mixed landscapes that provide habitat critical to panther recovery. The objectives of this study were to (1) quantify calf depredation by panthers on two ranches in southwest Florida, and (2) develop a habitat suitability model to evaluate the quality of panther hunting habitat on ranchlands, assess whether the model could predict predation risk to calves, and discuss its potential to be incorporated into an incentive-based compensation program. We ear-tagged 409 calves with VHF transmitters on two ranches during 2011–2013 to document calf mortality. We developed a model to evaluate the quality of panther hunting habitat on private lands in southwest Florida using environmental variables obtained from the Florida Natural Areas Inventory (FNAI) Cooperative Landcover Database and nocturnal GPS locations of panthers provided by the Florida Fish and Wildlife Conservation Commission (FWC). We then tested whether the model could predict the location of calf depredation sites. Tagged calf loss to panthers varied between the two ranches (0.5%/yr to 5.3%/yr) and may have been influenced by the amount of panther hunting habitat on each ranch as the ranch that experienced higher depredation rates contained a significantly higher probability of panther presence. Depredation sites of tagged calves had a significantly greater probability of panther presence than depredation sites of untagged calves that were found by ranchers in open pastures. This suggests that there may be more calves killed in high risk environments than are being found and reported by ranchers and that panthers can hunt effectively in open environments. It also suggests that the model may provide a means for evaluating the quality of panther hunting habitat and the corresponding risk of depredation to livestock across the landscape. We suggest that our approach could be applied to prioritize and categorize private lands for participation in a Payment for Ecosystem Services program that compensates landowners for livestock loss and incentivizes conserving high quality habitat for large carnivores where livestock depredation is a concern.     

Science and Values Influencing Predator Control for Alaska Moose Management

ABSTRACT We encourage informed and transparent decision-making processes concerning the recently expanded programs in Alaska, USA, to reduce predation on moose (Alces alces). The decision whether to implement predator control ultimately concerns what society should value; therefore, policymakers, not objective biologists, play a leadership role. From a management and scientific standpoint, biological support for these predator-control programs requires convincing evidence that 1) predators kill substantial numbers of moose that would otherwise mostly live and be available for harvest, 2) low predation can facilitate reliably higher harvests of moose, 3) given less predation, habitats can sustain more moose and be protected from too many moose, and 4) sustainable populations of Alaska's brown bears (Ursus arctos), black bears (Ursus americanus), and wolves (Canis lupus) will exist in and out of control areas. We reviewed 10 moose mortality studies, 36 case histories, 10 manipulative studies, 15 moose nutrition studies, and 3 recent successful uses of nutrition-based management to harvest excess female moose. Results of these studies support application of long-term, substantial predator control for increasing yield of moose in these simple systems where moose are a primary prey of 3 effective predators. We found no substantive, contradictory results in these systems. However, to identify and administer feasible moose population objectives, recently established moose nutritional indices must be monitored, and regulatory bodies must accept nutrition-based management. In addition, the efficacy of techniques to reduce bear predation requires further study. Predicting precise results of predator control on subsequent harvest of moose will continue to be problematic because of a diversity of changing interactions among biological, environmental, and practical factors. In Alaska, the governor has the prerogative to influence regulations on predator control by appointing members to the Board of Game. At least annually, the Board of Game hears a wide spectrum of public opinions opposing and favoring predator control. We summarized these opinions as well as the societal and cultural values and expectations that are often the primary basis for debates. Advocates on both sides of the debate suggest they hold the higher conservation ethic, and both sides provide biased science. We recommend a more constructive and credible dialogue that focuses openly on values rather than on biased science and fabricated conspiracies. To be credible and to add substance in this divisive political arena, biologists must be well informed and provide complete information in an unbiased and respectful manner without exaggeration.     

Predictability of repeated carnivore attacks on livestock favours reactive use of mitigation measures

1. Predation on livestock is one of the main reasons for low tolerance against large carnivores in many parts of the world. Measures to reduce the conflicts have been developed, but resources for using them are often scarce. If wildlife managers as well as farmers learn more about when the risk of predation on livestock is higher, they will be able to make more effective use of resources for reducing predation.
2. In this study, we tested the hypothesis that the risk of predation on livestock immediately after an attack is higher on the affected farm compared with other farms in the same area. Data on sheep predation by brown bear Ursus arctos , lynx Lynx lynx and wolf Canis lupus in Sweden 1998–2006 were used in the analysis.
3. On depredated farms there was approximately a 55 times higher risk for a repeat predation event within 12 months compared to any other farm in the same area. During the first 5 weeks, 63%, 60% and 50% of the repeat attacks had occurred.
4. We suggest that the main mechanism behind repeat attacks on livestock is that carnivores return to the kill site to feed on carrion. Where livestock are still present and unprotected at the kill site when the carnivore returns, the farms will suffer a higher likelihood of a further attack compared to livestock on other farms. This study uses data from Sweden but we argue that the pattern will be the same in any part of the world where the ranges of livestock and large carnivores overlap.
4. Synthesis and applications . As the risk of an attack is higher directly after an initial attack, it will be more cost-effective to implement measures designed to reduce livestock predation by large carnivores at that time, i.e. within the following 5 weeks. Temporary proactive measures are usually simpler and cheaper than permanent deterrents and we recommend their use wherever resources are limited.     

Do pastoralist cattle fear African lions?

Fear of predators fundamentally shapes the ecology of prey species and drives both inter- and intra-specific interactions. Extensive research has examined the consequences of predation risk from large carnivores on the behavior of wild ungulate prey species. However, many large carnivores not only hunt wild prey but also depredate domestic livestock, especially in pastoralist systems where livestock share land and resources with large carnivores. Northern Tanzania is a hotspot for human–carnivore conflict driven by livestock depredation and interactions are particularly severe between African lions Panthera leo and pastoralist cattle Bos taurus. In this ecosystem, we explored the degree to which pastoralist cattle exhibited anti-predator behaviors during their daily grazing routines. Using focal animal sampling, we compared two typical anti-predator behaviors, vigilance and grouping, among cattle in village rangelands with high and low background depredation rates. We found that cattle in high risk village rangelands formed 21.2% larger groups than cattle in low risk village rangelands. Interestingly, cattle in low risk village rangelands spent 68.4% more time vigilant than cattle in high risk village rangelands. These patterns were influenced significantly by the time of day: as sunset approached, cattle in low risk village rangelands spent more time vigilant and cattle in high risk village rangelands formed larger groups. These results suggest that pastoralist cattle exhibit anti-predator strategies that vary both spatially and temporally, and that such strategies might help livestock optimally tradeoff the costs and benefits of anti-predator behavior across timescales (i.e. the risk allocation hypothesis). We discuss the implications of our results for husbandry techniques that might reduce behavioral costs associated with cattle anti-predator behaviors and help increase tolerance for lions and other large carnivores. These improvements are critical to human–carnivore coexistence given the prevalence of pastoralism globally and the rising potential for conflict with large carnivores such as lions.     

Quantifying Economic Impacts of Large-Carnivore Depredation on Bovine Calves

Abstract: We examined and quantified the economic impact of grizzly bear (Ursus arctos) and gray wolf (Canis lupus) depredation on calves in the Upper Green River Cattle Allotment in western Wyoming, USA, using records of the number of animals grazed and number lost during 1990–2004. Our analysis indicated that increased calf losses coincided with grizzly bear and gray wolf arrival and population establishment, with the first confirmed depredation by grizzly bears in 1995 and the first confirmed wolf depredation in 2000. From 1995 through 2004, 29,693 calves grazed on the allotment, and of the 1,332 calves lost to all causes, an estimated 520 calves were lost to grizzly bear depredation and 177 calves to gray wolf depredation. We examined past and current grizzly and gray wolf compensation programs with respect to reimbursement of producers for costs associated with large-carnivore depredation. Estimated 1995–2004 uncompensated financial impacts from grizzly bear and gray wolf calf losses on the allotment were US222,500. Our analysis suggested equitable compensation factors of 3.8:1 for grizzly bear depredation and 6.3:1 for gray wolf depredation. Inadequate compensation for livestock depredation results in resistance to large-carnivore recovery programs. Development of compensation programs that fairly reimburse livestock producers for losses is, therefore, a necessary component of carnivore recovery efforts. Our analysis also suggested that grizzly bear management actions were effectively targeting livestock-depredating grizzly bears on the allotment.     

Building a mechanistic understanding of predation with GPS-based movement data

Quantifying kill rates and sources of variation in kill rates remains an important challenge in linking predators to their prey. We address current approaches to using global positioning system (GPS)-based movement data for quantifying key predation components of large carnivores. We review approaches to identify kill sites from GPS movement data as a means to estimate kill rates and address advantages of using GPS-based data over past approaches. Despite considerable progress, modelling the probability that a cluster of GPS points is a kill site is no substitute for field visits, but can guide our field efforts. Once kill sites are identified, time spent at a kill site (handling time) and time between kills (killing time) can be determined. We show how statistical models can be used to investigate the influence of factors such as animal characteristics (e.g. age, sex, group size) and landscape features on either handling time or killing efficiency. If we know the prey densities along paths to a kill, we can quantify the ‘attack success’ parameter in functional response models directly. Problems remain in incorporating the behavioural complexity derived from GPS movement paths into functional response models, particularly in multi-prey systems, but we believe that exploring the details of GPS movement data has put us on the right path.     

Livestock husbandry as a tool for carnivore conservation in Africa’s community rangelands: a case–control study

Conflict between people and wildlife is a major issue in both wildlife conservation and rural development. In African rangelands, species such as African wild dogs (Lycaon pictus), cheetahs (Acinonyx jubatus), lions (Panthera leo), leopards (Panthera pardus), and spotted hyaenas (Crocuta crocuta) may kill livestock and are therefore themselves killed by local pastoralists. Such conflict has led to the extirpation of these species from many areas, and also impacts the livelihoods of local livestock farmers. To investigate the possibilities for coexistence of people, livestock, and large predators in community rangelands, we measured the effectiveness of traditional livestock husbandry in reducing depredation by wild carnivores, using a case–control approach. Different measures were effective against different predator species but, overall, the risk of predator attack by day was lowest for small herds, accompanied by herd dogs as well as human herders, grazing in open habitat. By night, the risk of attack was lowest for herds held in enclosures (‘bomas’) with dense walls, pierced by few gates, where both men and domestic dogs were present. Unexpectedly, the presence of scarecrows increased the risks of attack on bomas. Our findings suggest that improvements to livestock husbandry can contribute to the conservation and recovery of large carnivores in community rangelands, although other measures such as prey conservation and control of domestic dog diseases are also likely to be necessary for some species.