Risky times and risky places interact to affect prey behaviour

Harnessing the gut microbiome: a potential biomarker for wild animal welfare

The welfare of wild animal populations is critically important to conservation, with profound implications for ecosystem health, biodiversity, and zoonotic disease transmission. Animal welfare is typically defined as the accumulated affective mental state of an animal over a particular time period. However, the assessment of animal welfare in the wild poses unique challenges, primarily due to the lack of universally applicable biomarkers. This perspective explores the potential role of the gut microbiome, a dynamic and non-invasive biomarker, as a novel avenue for evaluating animal welfare in wild animals. The gut microbiome, through interactions with the host's physiology, behavior, and cognition, offers a promising opportunity to gain insights into the well-being of animals. In this synthesis, we discuss the distinction between fitness and welfare, the complexities of assessing welfare in wild populations, and the linkages between the gut microbiome and aspects of animal welfare such as behavior and cognition. We lastly elucidate how the gut microbiome could serve as a valuable tool for wildlife managers, with the potential to serve as a non-invasive yet informative window into the welfare of wild animals. As this nascent field evolves, it presents unique opportunities to enhance our understanding of the well-being of wild animals and to contribute to the preservation of ecosystems, biodiversity, and human health.

Spatial Risk Effects From Lions Compound Impacts of Prey Depletion on African Wild Dogs

Prey depletion threatens many carnivore species across the world and can especially threaten low-density subordinate competitors, particularly if subordinates are limited to low densities by their dominant competitors. Understanding the mechanisms that drive responses of carnivore density to prey depletion is not only crucial for conservation but also elucidates the balance between top-down and bottom-up limitations within the large carnivore guild. To avoid predation, competitively subordinate African wild dogs typically avoid their dominant competitors (lions) and the prey rich areas they are associated with, but no prior research has tested whether this pattern persists in ecosystems with anthropogenically-reduced prey density, and reduced lion density as a result. We used spatial data from wild dogs and lions in the prey-depleted Greater Kafue Ecosystem to test if wild dogs continue to avoid lions (despite their low density), and consequently avoid habitats with higher densities of their dominant prey species. We found that although lion density is 3X lower than comparable ecosystems, wild dogs continue to strongly avoid lions, and consequently avoid habitats associated with their two most important prey species. Although the density of lions in the GKE is low due to prey depletion, their competitive effects on wild dogs remain strong. These effects are likely compounded by prey-base homogenization, as lions in the GKE now rely heavily on the same prey preferred by wild dogs. These results suggest that a reduction in lion density does not necessarily reduce competition, and helps explain why wild dogs decline in parallel with their dominant competitors in ecosystems suffering from anthropogenic prey depletion. Protecting prey populations within the few remaining strongholds for wild dogs is vitally important to avoid substantial population declines. Globally, understanding the impacts of prey depletion on carnivore guild dynamics should be an increasingly important area of focus for conservation.

Large mammal behavioral defenses induced by the cues of human predation

Large mammals respond to human hunting via proactive and reactive responses, which can induce subsequent nonconsumptive effects (NCEs). Thus, there is evidence that large mammals exhibit considerable behavioral plasticity in response to human hunting risk. Currently, however, it is unclear which cues of human hunting large mammals may be responding to. We conducted a literature review to quantify the large mammal behavioral responses induced by the cues of human hunting. We detected 106 studies published between 1978 and 2022 of which 34 (32%) included at least one measure of cue, typically visual (n = 26 of 106, 25%) or auditory (n = 11 of 106, 10%). Space use (n = 37 of 106, 35%) and flight (n = 31 of 106, 29%) were the most common behavioral responses studied. Among the 34 studies that assessed at least one cue, six (18%) measured large mammal behavioral responses in relation to proxies of human hunting (e.g. hunting site or season). Only 14% (n = 15 of 106) of the studies quantified an NCE associated with an animal's response to human hunting. Moreover, the association between cues measured and antipredator behaviors is unclear due to a consistent lack of controls. Thus, while human hunting can shape animal populations via consumptive effects, the cues triggering these responses are poorly understood. There hence remains a need to link cues, responses, NCEs, and the dynamics of large mammal populations. Human activities can then be adjusted accordingly to prevent both overexploitation and unintended NCEs in animal populations.

Proactive cursorial and ambush predation risk avoidance in four African herbivore species

Most herbivores must balance demands to meet nutritional requirements, maintain stable thermoregulation and avoid predation. Species-specific predator and prey characteristics determine the ability of prey to avoid predation and the ability of predators to maximize hunting success. Using GPS collar data from African wild dogs, lions, impala, tsessebes, wildebeest and zebra in the Okavango Delta, Botswana, we studied proactive predation risk avoidance by herbivores. We considered predator activity level in relation to prey movement, predator and prey habitat selection, and preferential use of areas by prey. We compared herbivore behaviour to lion and wild dog activity patterns and determined the effect of seasonal resource availability and prey body mass on anti-predator behaviour. Herbivore movement patterns were more strongly correlated with lion than wild dog activity. Habitat selection by predators was not activity level dependent and, while prey and predators differed to some extent in their habitat selection, there were also overlaps, probably caused by predators seeking habitats with high prey abundance. Areas favoured by lions were used by herbivores more when lions were less active, whereas wild dog activity level was not correlated with prey use. Prey body mass was not a strong predictor of the strength of proactive predation avoidance behaviour. Herbivores showed stronger anti-predator behaviours during the rainy season when resources were abundant. Reducing movement when top predators are most active and avoiding areas with a high likelihood of predator use during the same periods appear to be common strategies to minimize predation risk. Such valuable insights into predator-prey dynamics are only possible when using similar data from multiple sympatric species of predator and prey, an approach that should become more prevalent given the ongoing integration of technological methods into ecological studies.

Predator-prey interactions across hunting mode, spatial domain size, and habitat complexities

Predator-prey interactions are a fundamental part of community ecology, yet the relative importance of consumptive and nonconsumptive effects (NCEs) (defined as a risk-induced response that alters prey fitness) has not been resolved. Theory suggests that the emergence and subsequent predominance of consumptive or NCEs depend on the given habitat's complexity as well as predator hunting mode and spatial domain sizes of both predator and prey, but their relative influence on the outcome of predator-prey interactions is unknown. We built agent-based models in NetLogo to simulate predator-prey interactions for three hunting modes-sit-and-wait, sit-and-pursue, and active-while concurrently simulating large versus small spatial domain sizes for both predators and prey. We studied (1) how hunting mode and spatial domain size interact to influence the emergence of consumptive or NCEs and (2) how, when NCEs do dominate, hunting mode and spatial domain separately or additively determine prey shifts in time, space, and habitat use. Our results indicate consumptive effects only dominate for active predators when prey habitat domains overlap completely with the predator's spatial domain and when sit-and-wait and sit-and-pursue predators and their prey both have large spatial domains. Prey are most likely to survive when they shift their time but most frequently shift their habitat. Our paper helps to better understand the underlying mechanisms that drive consumptive or NCEs to be most dominant.

The Impact of Predation Risks on the Development and Fecundity of Bactrocera dorsalis Hendel

Predators are dependent on the capture of prey to meet their energetic and nutritive requirements, which brings the risk of predation to prey. The predation risk is divided into consumptive and non-consumptive effects. Non-consumptive effects may manifest through altered growth and ontogenetic trajectories in prey species, a dynamic modulated by olfactory or other sensory cues from predators. Bactrocera dorsalis Hendel represents a major invasive threat to global horticulture. While earlier research was primarily centered on the consumptive interactions between B. dorsalis and its natural enemies, the potential consequences of non-consumptive interactions on the development of B. dorsalis have been overlooked. In this study, we investigated the impact of predation risk effects, induced by both visual exposure to the predatory mantis Hierodula patellifera Serville and its associated odor, on the life history traits of B. dorsalis. Female B. dorsalis demonstrated a reduced developmental time in the presence of a caged predator (H. patellifera) or predator odors, but showed significantly increased fecundity. Conversely, males displayed no significant change in developmental time. Additionally, neither the female nor male body weight at death was significantly influenced by the predation risk from the caged predator or predator odors. This study investigated the effects of predation risk on the development and reproduction of B. dorsalis, emphasizing the potential importance of odor risk in biological and pest control.

Human access constrains optimal foraging and habitat availability in an avian generalist

Animals balance costs of antipredator behaviors with resource acquisition to minimize hunting and other mortality risks and maximize their physiological condition. This inherent trade-off between forage abundance, its quality, and mortality risk is intensified in human-dominated landscapes because fragmentation, habitat loss, and degradation of natural vegetation communities is often coupled with artificially enhanced vegetation (i.e., food plots), creating high-risk, high-reward resource selection decisions. Our goal was to evaluate autumn-winter resource selection trade-offs for an intensively hunted avian generalist. We hypothesized human access was a reliable cue for hunting predation risk. Therefore, we predicted resource selection patterns would be spatiotemporally dependent upon levels of access and associated perceived risk. Specifically, we evaluated resource selection of local-scale flights between diel periods for 426 mallards (Anas platyrhynchos) relative to wetland type, forage quality, and differing levels of human access across hunting and nonhunting seasons. Mallards selected areas that prohibited human access and generally avoided areas that allowed access diurnally, especially during the hunting season. Mallards compensated by selecting for high-energy and greater quality foraging patches on allowable human access areas nocturnally when they were devoid of hunters. Postseason selection across human access gradients did not return to prehunting levels immediately, perhaps suggesting a delayed response to reacclimate to nonhunted activities and thus agreeing with the assessment mismatch hypothesis. Last, wetland availability and human access constrained selection for optimal natural forage quality (i.e., seed biomass and forage productivity) diurnally during preseason and hunting season, respectively; however, mallards were freed from these constraints nocturnally during hunting season and postseason periods. Our results suggest risk-avoidance of human accessible (i.e., hunted) areas is a primary driver of resource selection behaviors by mallards and could be a local to landscape-level process influencing distributions, instead of forage abundance and quality, which has long-been assumed by waterfowl conservation planners in North America. Broadly, even an avian generalist, well adapted to anthropogenic landscapes, avoids areas where hunting and human access are allowed. Future conservation planning and implementation must consider management for recreational access (i.e., people) equally important as foraging habitat management for wintering waterfowl.

Spatial memory predicts home range size and predation risk in pheasants

Most animals confine their activities to a discrete home range, long assumed to reflect the fitness benefits of obtaining spatial knowledge about the landscape. However, few empirical studies have linked spatial memory to home range development or determined how selection operates on spatial memory via the latter's role in mediating space use. We assayed the cognitive ability of juvenile pheasants (Phasianus colchicus) reared under identical conditions before releasing them into the wild. Then, we used high-throughput tracking to record their movements as they developed their home ranges, and determined the location, timing and cause of mortality events. Individuals with greater spatial reference memory developed larger home ranges. Mortality risk from predators was highest at the periphery of an individual's home range in areas where they had less experience and opportunity to obtain spatial information. Predation risk was lower in individuals with greater spatial memory and larger core home ranges, suggesting selection may operate on spatial memory by increasing the ability to learn about predation risk across the landscape. Our results reveal that spatial memory, determined from abstract cognitive assays, shapes home range development and variation, and suggests predation risk selects for spatial memory via experience-dependent spatial variation in mortality.

Predator-mediated diversity of stream fish assemblages in a boreal river basin, China

Predator-prey interactions are critical for understanding species composition and community assembly; however, there is still limited research on whether and how the prey species composition or community assembly in natural communities are mediated by predators. To address this question, we performed a field investigation to examine the influence of the presence of Lutra lutra on the diversity of fish communities of the Hunchun River Basin, Jilin Province, China. Our results indicate that L. lutra, as a potential umbrella species and generalist predator in the stream ecosystem, promotes the coexistence of a vast variety of fish taxa, which emphasizes the importance of top-down control in the ecological community. We suggest that L. lutra regulates the fish community assembly likely through the stochastic process. Although this was a pilot study regarding predator-prey interactions, the results highlight the effects of predators on the prey community assembly, and emphasize the role of predators on the maintenance of biodiversity and ecosystem function. Future conservation decisions involving ecosystem biodiversity should require the inclusion of predation intensity. The inclusion of scientific research and protection of umbrella species would thus constitute an additional and important step in biodiversity conservation.

Behavioral responses to anthropogenic noise at highways vary across temporal scales

Anthropogenic noise is pervasive across the landscape and can be present at two temporal scales: acute (occurring sporadically and stochastically over the shortest time scales, e.g., milliseconds), and chronic (more persistent than instantaneous and occurring over longer timescales, e.g., minutes, days). Acute and chronic anthropogenic noise may induce a behavioral fear-mediated response in wildlife that is analogous to a prey response to predators. Understanding wildlife responses to anthropogenic noise is especially important in the case of wildlife crossing structures that provide wildlife with access to resources across busy roadways. Focusing on two species common at wildlife crossing structures, mule deer (Odocoileus hemionus) and coyotes (Canis latrans), we addressed the hypotheses that (1) acute traffic noise causes flight behavior; and (2) chronic traffic noise causes changes in a range of behaviors associated with the vigilance–foraging trade-off (vigilance, running, and foraging). We placed camera traps at entrances to ten crossing structures for a period of ∼ 2 months each throughout California, USA. Mule deer and coyotes demonstrated a flight response to acute traffic noise at entrances to crossing structures. Both species demonstrated shifts in behavioral response to chronic traffic noise within and among structures. Coyote behavior was indicative of fear, demonstrating increased vigilance at louder times within crossing structures, and switching from vigilance to running activity at louder crossings. Mule deer responded positively, increasing foraging at both spatial scales, and demonstrating decreased vigilance at louder structures, potentially using crossing structures as a Human Shield. Our results are the first to demonstrate that anthropogenic noise at crossing structures could alter wildlife passage, and that variations in fear response to anthropogenic noise exist across temporal, spatial, and amplitude scales. This dynamic response could alter natural predator-prey interactions and scale up to ecosystem-level consequences such as trophic cascades in areas with roads.

Intensive hunting changes human-wildlife relationships

Wildlife alter their behaviors in a trade-off between consuming food and fear of becoming food themselves. The risk allocation hypothesis posits that variation in the scale, intensity and longevity of predation threats can influence the magnitude of antipredator behavioral responses. Hunting by humans represents a threat thought to be perceived by wildlife similar to how they perceive a top predator, although hunting intensity and duration varys widely around the world. Here we evaluate the effects of hunting pressure on wildlife by comparing how two communities of mammals under different management schemes differ in their relative abundance and response to humans. Using camera traps to survey wildlife across disturbance levels (yards, farms, forests) in similar landscapes in southern Germany and southeastern USA, we tested the prediction of the risk allocation hypothesis: that the higher intensity and longevity of hunting in Germany (year round vs 3 months, 4x higher harvest/km²/year) would reduce relative abundance of hunted species and result in a larger fear-based response to humans (i.e., more spatial and temporal avoidance). We further evaluated how changes in animal abundance and behavior would result in potential changes to ecological impacts (i.e., herbivory and predation). We found that hunted species were relatively less abundant in Germany and less associated with humans on the landscape (i.e., yards and urban areas), but did not avoid humans temporally in hunted areas while hunted species in the USA showed the opposite pattern. These results are consistent with the risk allocation hypothesis where we would expect more spatial avoidance in response to threats of longer duration (i.e., year-round hunting in Germany vs. 3-month duration in USA) and less spatial avoidance but more temporal avoidance for threats of shorter duration. The expected ecological impacts of mammals in all three habitats were quite different between countries, most strikingly due to the decreases in the relative abundance of hunted species in Germany, particularly deer, with no proportional increase in unhunted species, resulting in American yards facing the potential for 25x more herbivory than German yards. Our results suggest that the duration and intensity of managed hunting can have strong and predictable effects on animal abundance and behavior, with the potential for corresponding changes in the ecological impacts of wildlife. Hunting can be an effective tool for reducing wildlife conflict due to overabundance but may require more intensive harvest than is seen in much of North America.

Predation strongly limits demography of a keystone migratory herbivore in a recovering transfrontier ecosystem

Large herbivore migrations are imperiled globally; however the factors limiting a population across its migratory range are typically poorly understood. Zambia's Greater Liuwa Ecosystem (GLE) contains one of the largest remaining blue wildebeest (Connochaetes taurinus taurinus) migrations, yet the population structure, vital rates, and limiting factors are virtually unknown. We conducted a long-term demographic study of GLE wildebeest from 2012 to 2019 of 107 collared adult females and their calves, 7352 herd observations, 12 aerial population surveys, and concurrent carnivore studies. We applied methods of vital rate estimation and survival analysis within a Bayesian estimation framework. From herd composition observations, we estimated rates of fecundity, first-year survival, and recruitment as 68%, 56%, and 38% respectively, with pronounced interannual variation. Similar rates were estimated from calf-detections with collared cows. Adult survival rates declined steadily from 91% at age 2 years to 61% at age 10 years thereafter dropping more sharply to 2% at age 16 years. Predation, particularly by spotted hyena, was the predominant cause of death for all wildebeest ages and focused on older animals. Starvation only accounted for 0.8% of all unbiased known natural causes of death. Mortality risk differed substantially between wet and dry season ranges, reflecting strong spatio-temporal differences in habitat and predator densities. There was substantial evidence that mortality risk to adults was 27% higher in the wet season, and strong evidence that it was 45% higher in the migratory range where predator density was highest. The estimated vital rates were internally consistent, predicting a stable population trajectory consistent with aerial estimates. From essentially zero knowledge of GLE wildebeest dynamics, this work provides vital rates, age structure, limiting factors, and a plausible mechanism for the migratory tendency, and a robust model-based foundation to evaluate the effects of potential restrictions in migratory range, climate change, predator-prey dynamics, and poaching.

Wolf risk fails to inspire fear in two mesocarnivores suggesting facilitation prevails

Large carnivores not only supress mesocarnivores via killing and instilling fear, but also facilitate them through carrion provisioning. Hence, mesocarnivores frequently face a trade-off between risk avoidance and food acquisition. Here we used the raccoon dog and red fox in Białowieża Forest, Poland as models for investigating how large carnivores shape mesocarnivore foraging behaviour in an area with widespread large carnivore carrion provisioning. Using a giving up density experiment we quantified mesocarnivore foraging responses to wolf body odour across a landscape-scale gradient in wolf encounter rates. At locations with higher wolf encounter rates, raccoon dogs depleted feeding trays more than at plots with lower wolf encounter rates. Simulating wolf presence by adding wolf body odour caused raccoon dogs to deplete feeding trays more at locations with low wolf encounter rates, but less at locations with high wolf encounter rates. Fox foraging costs did not vary with the application of wolf body odour or wolf encounter rates. The frequency that the mesocarnivores visited experimental foraging patches was unaffected by wolf body odour or landscape level encounter rates. These results provide further evidence that large carnivore suppression can play a subordinate role to facilitation in determining mesocarnivore behaviour. The varying raccoon dog response to wolf odour across the landscape-scale gradient in wolf encounter rates shows how mesocarnivore-large carnivore interactions can be context-dependent. We suggest that rather than testing the effects of single risk cues on prey behaviour, future studies should focus on understanding how context modifies the ecological impacts of large carnivores.

LiDAR Reveals the Process of Vision-Mediated Predator–Prey Relationships

Exploring the processes of interspecific relationships is crucial to understanding the mechanisms of biodiversity maintenance. Visually detecting interspecies relationships of large mammals is limited by the reconstruction accuracy of the environmental structure and the timely detection of animal behavior. Hence, we used backpack laser scanning (BLS) to reconstruct the high-resolution three-dimensional environmental structure to simulate the process of a predator approaching its prey, indicating that predator tigers would reduce their visibility by changing their behavior. Wild boars will nibble off about 5m of branches around the nest in order to create better visibility around the nest, adopting an anti-predation strategy to detect possible predators in advance. Our study not only points out how predator–prey relationships are affected by visibility as the environment mediates it, but also provides an operable framework for exploring interspecific relationships from a more complex dimension. Finally, this study provides a new perspective for exploring the mechanisms of biodiversity maintenance.

Dynamic landscapes of fear: understanding spatiotemporal risk

The landscape of fear (LOF) concept posits that prey navigate spatial heterogeneity in perceived predation risk, balancing risk mitigation against other activities necessary for survival and reproduction. These proactive behavioral responses to risk can affect individual fitness, population dynamics, species interactions, and coexistence. Yet, antipredator responses in free-ranging prey often contradict expectations, raising questions about the generality and scalability of the LOF framework and suggesting that a purely spatial, static LOF conceptualization may be inadequate. Here, we outline a 'dynamic' LOF framework that explicitly incorporates time to account for predictable spatiotemporal variation in risk-resource trade-offs. This integrated approach suggests novel predictions about predator effects on prey behaviors to refine understanding of the role predators play in ecological communities.

Behavioral "bycatch" from camera trap surveys yields insights on prey responses to human-mediated predation risk

Human disturbance directly affects animal populations and communities, but indirect effects of disturbance on species behaviors are less well understood. For instance, disturbance may alter predator activity and cause knock-on effects to predator-sensitive foraging in prey. Camera traps provide an emerging opportunity to investigate such disturbance-mediated impacts to animal behaviors across multiple scales. We used camera trap data to test predictions about predator-sensitive behavior in three ungulate species (caribou Rangifer tarandus; white-tailed deer, Odocoileus virginianus; moose, Alces alces) across two western boreal forest landscapes varying in disturbance. We quantified behavior as the number of camera trap photos per detection event and tested its relationship to inferred human-mediated predation risk between a landscape with greater industrial disturbance and predator activity and a "control" landscape with lower human and predator activity. We also assessed the finer-scale influence on behavior of variation in predation risk (relative to habitat variation) across camera sites within the more disturbed landscape. We predicted that animals in areas with greater predation risk (e.g., more wolf activity, less cover) would travel faster past cameras and generate fewer photos per detection event, while animals in areas with less predation risk would linger (rest, forage, investigate), generating more photos per event. Our predictions were supported at the landscape-level, as caribou and moose had more photos per event in the control landscape where disturbance-mediated predation risk was lower. At a finer-scale within the disturbed landscape, no prey species showed a significant behavioral response to wolf activity, but the number of photos per event decreased for white-tailed deer with increasing line of sight (m) along seismic lines (i.e., decreasing visual cover), consistent with a predator-sensitive response. The presence of juveniles was associated with shorter behavioral events for caribou and moose, suggesting greater predator sensitivity for females with calves. Only moose demonstrated a positive behavioral association (i.e., longer events) with vegetation productivity (16-day NDVI), suggesting that for other species bottom-up influences of forage availability were generally weaker than top-down influences from predation risk. Behavioral insights can be gleaned from camera trap surveys and provide complementary information about animal responses to predation risk, and thus about the indirect impacts of human disturbances on predator-prey interactions.

White-tailed deer exploit temporal refuge from multi-predator and human risks on roads

Although most prey have multiple predator species, few studies have quantified how prey respond to the temporal niches of multiple predators which pose different levels of danger. For example, intraspecific variation in diel activity allows white-tailed deer (Odocoileus virginianus) to reduce fawn activity overlap with coyotes (Canis latrans) but finding safe times of day may be more difficult for fawns in a multi-predator context. We hypothesized that within a multi-predator system, deer would allocate antipredation behavior optimally based on combined mortality risk from multiple sources, which would vary depending on fawn presence. We measured cause-specific mortality of 777 adult (>1-year-old) and juvenile (1-4-month-old) deer and used 300 remote cameras to estimate the activity of deer, humans, and predators including American black bears (Ursus americanus), bobcats (Lynx rufus), coyotes, and wolves (Canis lupus). Predation and vehicle collisions accounted for 5.3 times greater mortality in juveniles (16% mortality from bears, coyotes, bobcats, wolves, and vehicles) compared with adults (3% mortality from coyotes, wolves, and vehicles). Deer nursery groups (i.e., ≥1 fawn present) were more diurnal than adult deer without fawns, causing fawns to have 24-38% less overlap with carnivores and 39% greater overlap with humans. Supporting our hypothesis, deer nursery groups appeared to optimize diel activity to minimize combined mortality risk. Temporal refuge for fawns was likely the result of carnivores avoiding humans, simplifying diel risk of five species into a trade-off between diurnal humans and nocturnal carnivores. Functional redundancy among multiple predators with shared behaviors may partially explain why white-tailed deer fawn predation rates are often similar among single- and multi-predator systems.

Spatio-Temporal Patterns and Source-Dispersion Modeling Towards Sloth Bear–Human Conflict Management in Central India

The impact of humans on biodiversity, in the form of the spatially extensive occurrence of humans and subsequent habitat degradation, leads to negative interactions between humans and native wildlife. However, knowledge of the spatial and temporal interface between humans and wildlife is necessary to understand the root cause of such negative interactions, yet considerably understudied in the context of human-dominated landscapes in south and south-eastern Asia. We took this opportunity, gaining insights on seasonal spatial interaction and spatio-temporal overlap between sloth bears (Melursus ursinus) and humans, and subsequently predicted the conflict source sites and dispersion (i.e., hotspots) based on the robust geographic profiling (GP) method in the Sanjay Tiger Reserve (STR), a human-dominated landscape of central India. Detection data of sloth bear and human were obtained from camera trap survey conducted for two years (2017–2018) and records of conflict incidents (2009–2019) were collected from forest department. We found that sloth bears can co-occur with humans independently of seasons, based on occupancy models. However, during summer, higher temporal overlap (Δ4 = 0.46) and lower spatial overlap (0.31) were observed between sloth bears and humans. Contrastingly, lower temporal overlap (Δ4 = 0.29) and higher spatial overlap (0.44) were observed between the same two during winter. The activity patterns of sloth bears and humans differed significantly across seasons and within the same species in different seasons. Our findings indicated that significant changes in human activity, especially during summer, increased the likelihood of sloth bear-human interaction and subsequent conflict incidents. The mapping of conflict source and dispersion (with high accuracy) also predicted a greater probability of conflict during summer, compared to winter, and thus showed the successful application of GP models in this field. Also, camera trap data alone were able to predict the occurrence of hotspots, demonstrating the use of camera trap records in the successful prediction of source-dispersion of conflict. This study would be useful for decision-makers to alleviate sloth bear–human conflict based on insights on seasonal variation of spatio-temporal overlap between the two and direct conservation efforts accordingly.

“Ecology of fear” in ungulates: Opportunities for improving conservation

Because ungulates are important contributors to ecosystem function, understanding the “ecology of fear” could be important to the conservation of ecosystems. Although studying ungulate ecology of fear is common, knowledge from ungulate systems is highly contested among ecologists. Here, we review the available literature on the ecology of fear in ungulates to generalize our current knowledge and how we can leverage it for conservation. Four general focus areas emerged from the 275 papers included in our literature search (and some papers were included in multiple categories): behavioral responses to predation risk (79%), physiological responses to predation risk (15%), trophic cascades resulting from ungulate responses to predation risk (20%), and manipulation of predation risk (1%). Of papers focused on behavior, 75% were about movement and habitat selection. Studies were biased toward North America (53%), tended to be focused on elk (Cervus canadensis; 29%), and were dominated by gray wolves (40%) or humans (39%) as predators of interest. Emerging literature suggests that we can utilize predation risk for conservation with top‐down (i.e., increasing predation risk) and bottom‐up (i.e., manipulating landscape characteristics to increase risk or risk perception) approaches. It is less clear whether fear‐related changes in physiology have population‐level fitness consequences or cascading effects, which could be fruitful avenues for future research. Conflicting evidence of trait‐mediated trophic cascades might be improved with better replication across systems and accounting for confounding effects of ungulate density. Improving our understanding of mechanisms modulating the nature of trophic cascades likely is most important to ensure desirable conservation outcomes. We recommend future work embrace the complexity of natural systems by attempting to link together the focal areas of study identified herein.

Cumulative effects of human footprint, natural features and predation risk best predict seasonal resource selection by white-tailed deer

Land modified for human use alters matrix shape and composition and is a leading contributor to global biodiversity loss. It can also play a key role in facilitating range expansion and ecosystem invasion by anthrophilic species, as it can alter food abundance and distribution while also influencing predation risk; the relative roles of these processes are key to habitat selection theory. We researched these relative influences by examining human footprint, natural habitat, and predator occurrence on seasonal habitat selection by range-expanding boreal white-tailed deer (Odocoileus virginianus) in the oil sands of western Canada. We hypothesized that polygonal industrial features (e.g. cutblocks, well sites) drive deer distributions as sources of early seral forage, while linear features (e.g. roads, trails, and seismic lines) and habitat associated with predators are avoided by deer. We developed seasonal 2nd -order resource selection models from three years of deer GPS-telemetry data, a camera-trap-based model of predator occurrence, and landscape spatial data to weigh evidence for six competing hypotheses. Deer habitat selection was best explained by the combination of polygonal and linear features, intact deciduous forest, and wolf (Canis lupus) occurrence. Deer strongly selected for linear features such as roads and trails, despite a potential increased risk of wolf encounters. Linear features may attract deer by providing high density forage opportunity in heavily exploited landscapes, facilitating expansion into the boreal north.

Variation in resting strategies across trophic levels and habitats in mammals

Mammals must carefully balance rest with other behaviors that influence fitness (e.g., foraging, finding a mate) while minimizing predation risk. However, factors influencing resting strategies and the degree to which resting strategies are driven by the activities of predators and/or prey remain largely unknown. Our goal was to examine how mammalian resting strategies varied with trophic level, body mass, and habitat. We reviewed findings from 127 publications and classified the resting strategies of terrestrial and aquatic mammalian species into three categories: social (e.g., resting in groups), temporal (e.g., resting during the day), or spatial (e.g., resting in burrows). Temporal strategies were most common (54% of cases), but the prevalence of strategies varied with body mass and among trophic levels. Specifically, lower trophic levels and smaller species such as rodents and lagomorphs used more spatial and social resting strategies, whereas top predators and larger species used mostly temporal resting strategies. Resting strategies also varied among habitat types (e.g., rainforest vs. grassland), but this was primarily because closely related species shared both habitats and resting strategies. Human presence also affected resting strategies at all trophic levels but most strongly influenced top predators through shifts in rest timing. Human-induced behavioral changes in rest patterns cascade to modify behaviors across multiple trophic levels. These findings advance our fundamental understanding of natural history and ecology in wild animals and provide a roadmap for future comparative studies.

Reactive anti-predator behavioral strategy shaped by predator characteristics

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.

Food availability and long-term predation risk interactively affect antipredator response

Food availability and temporal variation in predation risk are both important determinants of the magnitude of antipredator responses, but their effects have rarely been examined simultaneously, particularly in wild prey. Here, we determine how food availability and long-term predation risk affect antipredator responses to acute predation risk by monitoring the foraging response of free-ranging snowshoe hares (Lepus americanus) to an encounter with a Canada lynx (Lynx canadensis) in Yukon, Canada, over four winters (2015-2016 to 2018-2019). We examined how this response was influenced by natural variation in long-term predation risk (2-month mortality rate of hares) while providing some individuals with supplemental food. On average, snowshoe hares reduced foraging time up to 10 h after coming into close proximity (≤75 m) with lynx, and reduced foraging time an average of 15.28 ± 7.08 min per lynx encounter. Hares tended to respond more strongly when the distance to lynx was shorter. More importantly, the magnitude of hares' antipredator response to a lynx encounter was affected by the interaction between food-supplementation and long-term predation risk. Food-supplemented hares reduced foraging time more than control hares after a lynx encounter under low long-term risk, but decreased the magnitude of the response as long-term risk increased. In contrast, control hares increased the magnitude of their response as long-term risk increased. Our findings show that food availability and long-term predation risk interactively drive the magnitude of reactive antipredator response to acute predation risk. Determining the factors driving the magnitude of antipredator responses would contribute to a better understanding of the indirect effects of predators on prey populations.

Fear of large carnivores is tied to ungulate habitat use: evidence from a bifactorial experiment

The fear large carnivores inspire in large ungulates has been argued to have cascading effects down food webs. However, a direct link between ungulate habitat use and their fear of large carnivores has not been experimentally tested. To fill this critical gap, we conducted a bi-factorial experiment in an African savanna. We removed shrub cover and broadcast large carnivore vocalizations (leopard, hyena, dog) or non-threatening control vocalizations in both experimentally cleared and shrubby control sites. We recorded the proactive (frequency of visitation) and reactive (fleeing or vigilance) responses of multiple prey (impala, warthog, nyala and bushbuck). Critically, we found a significant proactive-reactive interaction. Ungulates were 47% more likely to run after hearing a predator vocalization in shrubby control sites than experimental clearings, demonstrating that ungulates perceived less fear from large carnivores in open habitat (clearings). Consistent with this finding, ungulates visited clearings 2.4 times more often than shrubby control sites and visited shrubby control sites less often at night, when large carnivores are most active. Combined with results from previous experiments demonstrating that the disproportionate use of available habitats by large ungulates can alter ecosystem properties, our experiment provides critical evidence that the fear large carnivores inspire in large ungulates can cause trophic cascades.

Spatial heterogeneity facilitates carnivore coexistence

Competitively dominant carnivore species can limit the population sizes and alter the behavior of inferior competitors. Established mechanisms that enable carnivore coexistence include spatial and temporal avoidance of dominant predator species by subordinates, and dietary niche separation. However, spatial heterogeneity across landscapes could provide inferior competitors with refuges in the form of areas with lower competitor density and/or locations that provide concealment from competitors. Here, we combine temporally overlapping telemetry data from dominant lions (Panthera leo) and subordinate African wild dogs (Lycaon pictus) with high-resolution remote sensing in an integrated step selection analysis to investigate how fine-scaled landscape heterogeneity might facilitate carnivore coexistence in South Africa's Hluhluwe-iMfolozi Park, where both predators occur at exceptionally high densities. We ask whether the primary lion-avoidance strategy of wild dogs is spatial avoidance of lions or areas frequented by lions, or if wild dogs selectively use landscape features to avoid detection by lions. Within this framework, we also test whether wild dogs rely on proactive or reactive responses to lion risk. In contrast to previous studies finding strong spatial avoidance of lions by wild dogs, we found that the primary wild dog lion-avoidance strategy was to select landscape features that aid in avoidance of lion detection. This habitat selection was routinely used by wild dogs, and especially when in areas and during times of high lion-encounter risk, suggesting a proactive response to lion risk. Our findings suggest that spatial landscape heterogeneity could represent an alternative mechanism for carnivore coexistence, especially as ever-shrinking carnivore ranges force inferior competitors into increased contact with dominant species.

Broadening the ecology of fear: non-lethal effects arise from diverse responses to predation and parasitism

Research on the 'ecology of fear' posits that defensive prey responses to avoid predation can cause non-lethal effects across ecological scales. Parasites also elicit defensive responses in hosts with associated non-lethal effects, which raises the longstanding, yet unresolved question of how non-lethal effects of parasites compare with those of predators. We developed a framework for systematically answering this question for all types of predator-prey and host-parasite systems. Our framework reveals likely differences in non-lethal effects not only between predators and parasites, but also between different types of predators and parasites. Trait responses should be strongest towards predators, parasitoids and parasitic castrators, but more numerous and perhaps more frequent for parasites than for predators. In a case study of larval amphibians, whose trait responses to both predators and parasites have been relatively well studied, existing data indicate that individuals generally respond more strongly and proactively to short-term predation risks than to parasitism. Apart from studies using amphibians, there have been few direct comparisons of responses to predation and parasitism, and none have incorporated responses to micropredators, parasitoids or parasitic castrators, or examined their long-term consequences. Addressing these and other data gaps highlighted by our framework can advance the field towards understanding how non-lethal effects impact prey/host population dynamics and shape food webs that contain multiple predator and parasite species.

Spatiotemporal patterns of wolf, mesocarnivores and prey in a Mediterranean area

Abstract

Spatial and temporal occurrence can mediate behavioural interactions between apex predators, mesocarnivores and herbivores. Predators should adapt their activity to that of prey, whereas predator avoidance would be expected to influence activity patterns and space use of prey and smaller competitors. We evaluated interspecific spatiotemporal relationships in a prey-rich community including an apex predator (the wolf), three wild ungulates and several smaller herbivores/mesocarnivores, through camera trapping. All considered species (i.e. wolves and potential prey/smaller competitors: wild boar, fallow deer, roe deer, crested porcupine, red fox and European badger) were active especially at night and/or twilight. Among wild ungulates, the wolf showed the greatest temporal overlap with the wild boar and the lowest one with the least abundant and used of them, i.e. the roe deer. The main prey (i.e. the fallow deer) showed more diurnal activity and a lower temporal overlap with the predator in sites with high wolf activity than in low-activity ones. Among mesocarnivores, the red fox showed extensive temporal overlap with the wolf: the overlap between the two canids was greater in sites intensively used by this apex predator than in sites with low wolf activity, supporting a concurrent study which suggested a potential for facilitative—rather than competitive—interactions. Spatiotemporal relationships suggest complex interactions between the apex predator, prey and smaller carnivores, for which a substantial temporal or spatial association was often supported.

Significance statement

There is a growing interest in the influence of apex predators on ecosystems through their effects on the behaviour of prey and smaller carnivores, especially in the light of the ongoing recovery of large carnivores in temperate areas. Predators should synchronise their activity to that of prey; conversely, prey and smaller carnivores would be expected to avoid predators. In a rich community including the wolf, three wild ungulates and several mesomammals, we detected (i) a substantial temporal overlap between wolves and wild boar, porcupines and mesocarnivores; (ii) a negative temporal association between the predator and its main prey (i.e. the fallow deer) and (iii) a great temporal overlap between the wolf and the red fox. We provide a baseline to evaluate temporal changes of predator-prey-mesocarnivore behavioural interactions along with variations of carnivore-prey densities.

Red deer allocate vigilance differently in response to spatio-temporal patterns of risk from human hunters and wolves

Abstract ContextUngulate prey can use increased vigilance to reduce their risk of predation, but little is known of the combined and interactive risk effects from humans and wolves in determining ungulate behaviour across time and space. Understanding the interplay between these risk effects is increasingly important, considering the recolonisation of several large carnivores to more human-dominated landscapes in Europe. AimThe aim of the present study was to assess the vigilance behaviour expressed by red deer (Cervus elaphus) in response to both humans and wolves in the Polish Białowieża Forest. MethodsUsing a camera-trap transect, the effect of distance to human settlements, hunting season, patterns of space use by wolves (Canis lupus), canopy openness, canopy height, time of day, as well as sex/age of individuals, on the vigilance behaviour observed in red deer was studied using a model-selection approach. Key resultsWe did not find a clear effect of patterns of space use by wolves or distance to human settlements on red deer vigilance behaviour at the landscape scale. However, red deer showed increased vigilance during the hunting season and during the day outside of protected areas and reserves, because disturbance from human hunters is highest. Conversely, we also found that red deer were more vigilant at night within more protected areas, which is likely to be explained by the increased activity of wolves because human activity is strictly limited. ConclusionsOur study showed that vigilance behaviour of red deer in Białowieża Primeval Forest is more driven by human hunting than by the frequency of wolf presence at a landscape scale. This could be explained by the higher temporal and spatial predictability of human hunting activities than wolf risk. We found that patterns of wolf space use, as opposed to the omnipresent fear effects from humans, had only localised effects by increasing vigilance levels during night hours in non-hunting areas of the forest. The reverse was observed outside of protected reserves. Understanding how prey species respond to this new combination of risk from natural predators and humans, is increasingly important in a landscape where human risk is becoming ever more potent and carnivores recolonise.

Do Female Songbirds Avoid a Mammalian Nest Predator When Selecting Their Nest Site?

Perceived predation risk can elicit strong behavioral responses in potential prey. During nest building, songbirds exhibit anti-predator behaviors under experimental conditions. Here, we hypothesized that females of two ground-nesting songbird species, the Ovenbird (Seiurus aurocapilla) and the Hermit Thrush (Catharus guttatus), would use naturally available cues of predation risk when selecting their nest site, thereby avoiding activity hotspots of Eastern Chipmunks (Tamias striatus), a predator on songbird nests and fledglings. Chipmunks are highly vocal, thus providing cues of their presence. We mapped chipmunk detections and songbird nests over four successive years in study plots located in mature deciduous forest of New Brunswick, Canada. Chipmunk activity varied by an order of magnitude among study plots and years. Nests were built further away from chipmunk detections than expected by chance in some, but not all, plot-year combinations. When comparing study plots, the proportion of nests built within hotspots of chipmunk activity was four times lower in the two plots where chipmunk activity was highest. Yet, we did not find clear evidence that chipmunk avoidance provided fitness benefits, possibly because this behavior procured little protection at high chipmunk densities. The persistence of this avoidance behavior in our focal species of ground-nesting songbirds might be linked to the benefits it procures at intermediate chipmunk densities.

The context dependence of non-consumptive predator effects

Non-consumptive predator effects (NCEs) are now widely recognised for their capacity to shape ecosystem structure and function. Yet, forecasting the propagation of these predator-induced trait changes through particular communities remains a challenge. Accordingly, focusing on plasticity in prey anti-predator behaviours, we conceptualise the multi-stage process by which predators trigger direct and indirect NCEs, review and distil potential drivers of contingencies into three key categories (properties of the prey, predator and setting), and then provide a general framework for predicting both the nature and strength of direct NCEs. Our review underscores the myriad factors that can generate NCE contingencies while guiding how research might better anticipate and account for them. Moreover, our synthesis highlights the value of mapping both habitat domains and prey-specific patterns of evasion success ('evasion landscapes') as the basis for predicting how direct NCEs are likely to manifest in any particular community. Looking ahead, we highlight two key knowledge gaps that continue to impede a comprehensive understanding of non-consumptive predator-prey interactions and their ecosystem consequences; namely, insufficient empirical exploration of (1) context-dependent indirect NCEs and (2) the ways in which direct and indirect NCEs are shaped interactively by multiple drivers of context dependence.

Fire's impact on threat detection and risk perception among vervet monkeys: Implications for hominin evolution

The spatial behavior of primates is shaped by many factors including predation risk, the distribution of food sources, and access to water. In fire-prone settings, burning is a catalyst of change, altering the distribution of both plants and animals. Recent research has shown that primates alter their behavior in response to this change. Here, we study primates' perceived threat of predation in fire-modified landscapes. We focus on the predator-related behaviors of vervet monkeys (Chlorocebus pygerythrus) after controlled burning events. We compare the occurrence of vigilance and predator-deterrent behaviors, including alarm calls, scanning, and flight across different habitats and burn conditions to test the hypothesis that subjects exhibit fewer predator-specific vigilance and predator-deterrent behaviors in burned areas. The results demonstrate that predator-related behaviors occur less often in burned habitats, suggesting that predators are less common in these areas. These results provide foundations for examining hypotheses about the use of fire-altered landscapes among extinct hominins. We set these data in the context of increasing aridity, changes in burning regimes, and the emergence of pyrophilia in the human lineage.

Inexperienced preys know when to flee or to freeze in front of a threat

Using appropriate antipredatory responses is crucial for survival. While slowing down reduces the chances of being detected from distant predators, fleeing away is advantageous in front of an approaching predator. Whether appropriate responses depend on experience with moving objects is still an open question. To clarify whether adopting appropriate fleeing or freezing responses requires previous experience, we investigated responses of chicks naive to movement. When exposed to the moving cues mimicking an approaching predator (a rapidly expanding, looming stimulus), chicks displayed a fast escape response. In contrast, when presented with a distal threat (a small stimulus sweeping overhead) they decreased their speed, a maneuver useful to avoid detection. The fast expansion of the stimulus toward the subject, rather than its size per se or change in luminance, triggered the escape response. These results show that young animals, in the absence of previous experience, can use motion cues to select the appropriate responses to different threats. The adaptive needs of young preys are thus matched by spontaneous defensive mechanisms that do not require learning.

Weak spatiotemporal response of prey to predation risk in a freely interacting system

The extent to which prey space use actively minimizes predation risk continues to ignite controversy. Methodological reasons that have hindered consensus include inconsistent measurements of predation risk, biased spatiotemporal scales at which responses are measured and lack of robust null expectations.

We addressed all three challenges in a comprehensive analysis of the spatiotemporal responses of adult female elk (Cervus elaphus) to the risk of predation by wolves (Canis lupus) during winter in northern Yellowstone, USA.

We quantified spatial overlap between the winter home ranges of GPS‐collared elk and three measures of predation risk: the intensity of wolf space use, the distribution of wolf‐killed elk and vegetation openness. We also assessed whether elk varied their use of areas characterized by more or less predation risk across hours of the day, and estimated encounter rates between simultaneous elk and wolf pack trajectories. We determined whether observed values were significantly lower than expected if elk movements were random with reference to predation risk using a null model approach.

Although a small proportion of elk did show a tendency to minimize use of open vegetation at specific times of the day, overall we highlight a notable absence of spatiotemporal response by female elk to the risk of predation posed by wolves in northern Yellowstone.

Our results suggest that predator–prey interactions may not always result in strong spatiotemporal patterns of avoidance.

Integrating temporal refugia into landscapes of fear: prey exploit predator downtimes to forage in risky places

The landscape of fear is an important driver of prey space use. However, prey can navigate the landscape of fear by exploiting temporal refuges from predation risk. We hypothesized that diel patterns of predator and prey movement and space use would be inversely correlated due to temporal constraints on predator habitat domain. Specifically, we evaluated habitat selection and activity of the vicuña and its only predator, the puma, during three diel periods: day, dawn/dusk, and night. Pumas selected the same habitats regardless of diel period-vegetated and rugged areas that feature stalking cover for pumas-but increased their activity levels during dawn/dusk and night when they benefit from reduced detection by prey. Vicuñas avoided areas selected by pumas and reduced activity at night, but selected vegetated areas and increased activity by day and dawn/dusk. Vicuña habitat selection and movement strategies appeared to reduce the risk of encountering pumas; movement rates of pumas and vicuñas were negatively correlated across the diel cycle, and habitat selection was negatively correlated during dawn/dusk and night. Our study shows that an ambush predator's temporal activity and space use patterns interact to create diel refugia and shape the antipredator behaviors of its prey. Importantly, it is likely the very nature of ambush predators' static habitat specificity that makes predator activity important to temporally varying perceptions of risk. Prey which depend on risky habitats for foraging appear to mitigate risk by feeding when they can more easily detect predators and when predators are least active.

Foraging investment in a long-lived herbivore and vulnerability to coursing and stalking predators

Allocating resources to growth and reproduction requires grazers to invest time in foraging, but foraging promotes dental senescence and constrains expression of proactive antipredator behaviors such as vigilance. We explored the relationship between carnivore prey selection and prey foraging effort using incisors collected from the kills of coursing and stalking carnivores. We predicted that prey investing less effort in foraging would be killed more frequently by coursers, predators that often exploit physical deficiencies. However, such prey could expect delayed dental senescence. We predicted that individuals investing more effort in foraging would be killed more frequently by stalkers, predators that often exploit behavioral vulnerabilities. Further these prey could expect earlier dental senescence. We tested these predictions by comparing variation in age-corrected tooth wear, a proxy of cumulative foraging effort, in adult (3.4-11.9 years) wildebeest killed by coursing and stalking carnivores. Predator type was a strong predictor of age-corrected tooth wear within each gender. We found greater foraging effort and earlier expected dental senescence, equivalent to 2.6 additional years of foraging, in female wildebeest killed by stalkers than in females killed by coursers. However, male wildebeest showed the opposite pattern with the equivalent of 2.4 years of additional tooth wear in males killed by coursers as compared to those killed by stalkers. Sex-specific variation in the effects of foraging effort on vulnerability was unexpected and suggests that behavioral and physical aspects of vulnerability may not be subject to the same selective pressures across genders in multipredator landscapes.

The control of risk hypothesis: reactive vs. proactive antipredator responses and stress-mediated vs. food-mediated costs of response

Inducible defences against predators evolve because they reduce the rate of direct predation, but this benefit is offset by the cost (if any) of defence. If antipredator responses carry costs, the effect of predators on their prey is partitioned into two components, direct killing and risk effects. There is considerable uncertainty about the strength of risk effects, the factors that affect their strength, and the mechanisms that underlie them. In some cases, antipredator responses are associated with a glucocorticoid stress response, and in other cases they are associated with trade-offs between food and safety, but there is no general theory to explain this variation. Here, I develop the control of risk (COR) hypothesis, predicting that proactive responses to predictable and controllable aspects of risk will generally have food-mediated costs, while reactive responses to unpredictable or uncontrollable aspects of predation risk will generally have stress-mediated costs. The hypothesis is grounded in laboratory studies of neuroendocrine stressors and field studies of food-safety trade-offs. Strong tests of the COR hypothesis will require more studies of responses to natural variation in predation risk and the physiological consequences of these responses, but its explanatory power can be illustrated with existing case studies.