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For 90 years, the American Society of Mammalogists (ASM) has made science-based challenges to widespread lethal control of native mammals, particularly by the United States federal government targeting carnivores in the western states. A consensus is emerging among ecologists that extirpated, depleted, and destabilized populations of large predators are negatively affecting the biodiversity and resilience of ecosystems. This Special Feature developed from a thematic session on predator control at ASM's 2013 annual meeting, and in it we present data and arguments from the perspectives of ecology, wildlife biology and management, social science, ethics, and law and policy showing that nonlethal methods of preventing depredation of livestock by large carnivores may be more effective, more defensible on ecological, legal, and wildlife-policy grounds, and more tolerated by society than lethal methods, and that total mortality rates for a large carnivore may be driven higher than previously assumed by human causes that are often underestimated.

Predator control policies in the United States shifted in the latter half of the 20th century, largely in response to public outcry. However, few studies have assessed attitudes toward predator control at the national level. We replicated measures from a 1995 study that assessed attitudes toward predator management in the United States. We sought to determine if public support for predator management and perceptions of the humaneness of specific management practices changed over the past 2 decades. A web-based questionnaire was used to survey a representative sample of United States residents. The survey instrument contained items designed to assess attitudes toward predator management in general and the humaneness of specific predator management practices (lethal and nonlethal). We found relatively minor shifts in attitudes toward predator management, but many of the management practices assessed were rated significantly less humane than in the previous survey. Respondents were generally supportive of predator management aimed at losses of agricultural or private property; however, nonlethal methods were perceived to be far more humane than lethal methods. Our findings suggest that the public is generally supportive of predator control, but increasingly skeptical of the methods employed in control actions.

Lethal control of wildlife represents an ethical concern for managers, exacerbated by a lack of replicated or controlled data for most taxa or regions. The Gulf of Maine (GOM) has a history of intensive lethal and nonlethal predator control to protect terns (Sterna spp.) from inflated populations of predatory gulls, especially herring (Larus argentatus) and great black-backed gulls (L. marinus; large gulls). We described management strategies in the GOM, reviewed methods of nonlethal and lethal types of control, and compared the effectiveness of 3 control regimes (lethal, nonlethal-only, and no control) using weighted means of reproductive success metrics for 4 tern species. Nonlethal-only control is the least effective method of predator control; lethal control is consistently the most effective. Arctic terns (Sterna paradisaea) were the most susceptible to predation, whereas common terns (Sterna hirundo) were the most resilient. We concluded that targeted lethal control is necessary in the GOM to protect tern colonies from depredation and nesting exclusion by large gulls, and cannot be substituted with nonlethal control. Cessation of lethal control leads to abandonment of tern colonies within 6–7 years, but resumption of appropriately timed lethal control can lead to recolonization the same year. A combination of nonlethal and lethal methods can minimize the number of gulls taken. We recommend that any application of lethal control carefully considers the local needs of any target species and recognizes the need for spatial and temporal commitment.

Livestock owners traditionally use various non-lethal and lethal methods to protect their domestic animals from wild predators. However, many of these methods are implemented without first considering experimental evidence of their effectiveness in mitigating predation-related threats or avoiding ecological degradation. To inform future policy and research on predators, we systematically evaluated evidence for interventions against carnivore (canid, felid, and ursid) predation on livestock in North American and European farms. We also reviewed a selection of tests from other continents to help assess the global generality of our findings. Twelve published tests - representing five non-lethal methods and 7 lethal methods - met the accepted standard of scientific inference (random assignment or quasi-experimental case-control) without bias in sampling, treatment, measurement, or reporting. Of those twelve, prevention of livestock predation was demonstrated in six tests (four non-lethal and two lethal), whereas counterintuitive increases in predation were shown in two tests (zero non-lethal and two lethal); the remaining four (one non-lethal and three lethal) showed no effect on prédation. Only two non-lethal methods (one associated with livestockguarding dogs and the other with a visual deterrent termed \"fladry\") assigned treatments randomly, provided reliable inference, and demonstrated preventive effects. We recommend that policy makers suspend predator control efforts that lack evidence for functional effectiveness and that scientists focus on stringent standards of evidence in tests of predator control.

The introduction of mammalian predators has been detrimental to many native birds in New Zealand. One solution to this problem has been the creation of “mainland islands” in which exotic predators are systematically removed. Although mainland islands have been effective in increasing some native bird populations, few studies have measured the effect of predator-control on nest success nor what effect control measures have on sympatric populations of introduced birds. We measured the effect of predator-control on nest survival rates in both native and introduced passerines in a mainland island near Kaikoura, New Zealand. Nest survival was significantly higher in Waimangarara Bush (the site with experimental predator-control) than in Kowhai Bush (the site with no predator-control) and this pattern was found in both groups of birds. However, mammalian predator-control increased nest success of native species significantly more than nest success of introduced species. This suggests that native birds benefit disproportionately from control of introduced predators, most likely because they lack behavioural defences against mammalian predators that are present among the introduced birds.

Details surrounding any particular instance of predator control are varied. Addressing the appropriateness of predator control requires attention to those details. Here, we focus on the case of wolf (Canis lupus) hunting in Michigan. In Michigan, wolves were removed from the list of United States endangered species in December 2011. By June 2013, plans had been finalized to begin hunting wolves in fall 2013. According to these plans, a purpose of the hunt was to reduce wolf abundance in particular regions of Michigan to reduce threats to livestock and human safety. Here, we evaluate those plans using 2 basic tenets of wildlife management. The 1st tenet is the North American Model of Wildlife Conservation, which is held in high regard by many hunting organizations, wildlife professionals, and state agencies. A central component of the North American Model of Wildlife Conservation is a set of 7 principles representing ideas such as that wildlife is held in the public trust, management should be based on principles of democracy and best-available science, and wildlife should only be killed for a legitimate purpose. The 2nd tenet pertains to the ability to answer 3 fundamental questions: What is the purpose or goal of a management action? How will the management action meet the purpose or goal of the actions? Why are the purpose and goals appropriate? Plans for hunting wolves in Michigan appear not to meet the principles of either tenet. This conclusion suggests that either wolf hunting as it has been planned in Michigan is inappropriate or both sets of standards for evaluating wildlife management are inappropriate. Better understanding of issues like this will require reflecting on the fundamental nature of wildlife management and its guiding principles.

Large mammalian herbivores use a diverse array of strategies to survive predator encounters including flight, grouping, vigilance, warning signals, and fitness indicators. While anti-predator strategies appear to be driven by specific predator traits, no prior studies have rigorously evaluated whether predator hunting characteristics predict reactive anti-predator responses. We experimentally investigated behavioral decisions made by free-ranging impala, wildebeest, and zebra during encounters with model predators with different functional traits. We hypothesized that the choice of response would be driven by a predator’s hunting style (i.e., ambush vs. coursing) while the intensity at which the behavior was performed would correlate with predator traits that contribute to the prey’s relative risk (i.e., each predator’s prey preference, prey-specific capture success, and local predator density). We found that the choice and intensity of anti-predator behaviors were both shaped by hunting style and relative risk factors. All prey species directed longer periods of vigilance towards predators with higher capture success. The decision to flee was the only behavior choice driven by predator characteristics (capture success and hunting style) while intensity of vigilance, frequency of alarm-calling, and flight latency were modulated based on predator hunting strategy and relative risk level. Impala regulated only the intensity of their behaviors, while zebra and wildebeest changed both type and intensity of response based on predator traits. Zebra and impala reacted to multiple components of predation threat, while wildebeest responded solely to capture success. Overall, our findings suggest that certain behaviors potentially facilitate survival under specific contexts and that prey responses may reflect the perceived level of predation risk, suggesting that adaptive functions to reactive anti-predator behaviors may reflect potential trade-offs to their use. The strong influence of prey species identity and social and environmental context suggest that these factors may interact with predator traits to determine the optimal response to immediate predation threat.

Large carnivores' fear of the human ‘super predator’ has the potential to alter their feeding behaviour and result in human-induced trophic cascades. However, it has yet to be experimentally tested if large carnivores perceive humans as predators and react strongly enough to have cascading effects on their prey. We conducted a predator playback experiment exposing pumas to predator (human) and non-predator control (frog) sounds at puma feeding sites to measure immediate fear responses to humans and the subsequent impacts on feeding. We found that pumas fled more frequently, took longer to return, and reduced their overall feeding time by more than half in response to hearing the human ‘super predator’. Combined with our previous work showing higher kill rates of deer in more urbanized landscapes, this study reveals that fear is the mechanism driving an ecological cascade from humans to increased puma predation on deer. By demonstrating that the fear of humans can cause a strong reduction in feeding by pumas, our results support that non-consumptive forms of human disturbance may alter the ecological role of large carnivores.

The decline of terrestrial predator populations across the globe is altering top-down pressures that drive predator–prey interactions. However, a knowledge gap remains in understanding how removing terrestrial predators affects prey behavior. Using a bifactorial playback experiment, we exposed fox squirrels to predator (red-tailed hawks, coyotes, dogs) and non-predator control (Carolina wren) calls inside terrestrial predator exclosures, accessible to avian predators, and in control areas subject to ambient predation risk. Fox squirrels increased their use of terrestrial predator exclosures, a pattern that corresponded with 3 years of camera trapping. Our findings suggest fox squirrels recognized that exclosures had predictably lower predation risk. However, exclosures had no effect on their immediate behavioral response towards any call, and fox squirrels responded most severely to hawk predator calls. This study shows that anthropogenically driven predator loss creates predictably safer areas (refugia) that prey respond to proactively with increased use. However, the persistence of a lethal avian predator is sufficient to retain a reactive antipredator response towards an immediate predation threat. Some prey may benefit from shifting predator–prey interactions by gaining refugia without sacrificing a sufficient response towards potential predators.

Apex predators have experienced catastrophic declines throughout the world as a result of human persecution and habitat loss. These collapses in top predator populations are commonly associated with dramatic increases in the abundance of smaller predators. Known as “mesopredator release,” this trophic interaction has been recorded across a range of communities and ecosystems. Mesopredator outbreaks often lead to declining prey populations, sometimes destabilizing communities and driving local extinctions. We present an overview of mesopredator release and illustrate how its underlying concepts can be used to improve predator management in an increasingly fragmented world. We also examine shifts in North American carnivore ranges during the past 200 years and show that 60% of mesopredator ranges have expanded, whereas all apex predator ranges have contracted. The need to understand how best to predict and manage mesopredator release is urgent—mesopredator outbreaks are causing high ecological, economic, and social costs around the world.