Variation In Predation Risk Research Articles

Finotypic plasticity: Predator-induced plasticity in fin size, darkness and display behaviour in a teleost fish.

Fish fins are remarkable devices of propulsion. Fin morphology is intimately linked to locomotor performance, and hence to behaviours that influence fitness, such as foraging and predator avoidance. This foreshadows a connection between fin morphology and variation in predation risk. Yet, whether prey can adjust fin morphology according to changes in perceived risk within their lifetime (a.k.a. predator-induced plasticity) remains elusive. Here, we quantify the structural size of five focal fins in crucian carp (Carassius carassius) following controlled manipulations to perceived predation risk (presence/absence of pike Esox lucius). We also assess if crucian carp respond to increased predation risk by shifts in dorsal fin colouration, and test for differences in how fish actively use their dorsal fins by quantifying the area of the fin displayed in behavioural trials. We find that crucian carp show phenotypic plasticity with regards to fin size as predator-exposed fish consistently have larger fins. Individuals exposed to perceived predation risk also increased dorsal fin darkness and actively displayed a larger area of the fin to potential predators. Our results thus provide compelling evidence for predator-induced fin enlargement, which should result in enhanced escape swimming performance. Moreover, fin-size plasticity may evolve synergistically with fin colouration and display behaviour, and we suggest that the adaptive value of this synergy is to enhance the silhouette of deep-bodied and hard-to-capture prey to deter gape-limited predators prior to attack. Together, our results provide new perspectives on the role of predation risk in development and evolution of fins.

Music production and its role in coalition signaling during foraging contexts in a hunter-gatherer society.

Music is a cultural activity universally present in all human societies. Several hypotheses have been formulated to understand the possible origins of music and the reasons for its emergence. Here, we test two hypotheses: (1) the coalition signaling hypothesis which posits that music could have emerged as a tool to signal cooperative intent and signal strength of alliances and (2) music as a strategy to deter potential predators. In addition, we further explore the link between tactile cues and the propensity of mothers to sing toward infants. For this, we investigated the singing behaviors of hunter-gatherer mothers during daily foraging trips among the Mbendjele BaYaka in the Republic of the Congo. Although singing is a significant component of their daily activities, such as when walking in the forest or collecting food sources, studies on human music production in hunter-gatherer societies are mostly conducted during their ritual ceremonies. In this study, we collected foraging and singing behavioral data of mothers by using focal follows of five BaYaka women during their foraging trips in the forest. In accordance with our predictions for the coalition signaling hypothesis, women were more likely to sing when present in large groups, especially when group members were less familiar. However, predictions of the predation deterrence hypothesis were not supported as the interaction between group size and distance from the village did not have a significant effect on the likelihood of singing. The latter may be due to limited variation in predation risk in the foraging areas, because of the intense bush meat trade, and hence, future studies should include foraging areas with higher densities of wild animals. Lastly, we found that mothers were more likely to sing when they were carrying infants compared to when infants were close, but carried by others, supporting the prediction that touch plays an important prerequisite role in musical interaction between the mother and child. Our study provides important insight into the role of music as a tool in displaying the intent between or within groups to strengthen potentially conflict-free alliances during joint foraging activities.

Numerical response of predator to prey: Dynamic interactions and population cycles in Eurasian lynx and roe deer

AbstractThe dynamic interactions between predators and their prey have two fundamental processes: numerical and functional responses. Numerical response is defined as predator growth rate as a function of prey density or both prey and predator densities [dP/dt = f(N, P)]. Functional response is defined as the kill rate by an individual predator being a function of prey density or prey and predator densities combined. Although there are relatively many studies on the functional response in mammalian predators, the numerical response remains poorly documented. We studied the numerical response of Eurasian lynx (Lynx lynx) to various densities of its primary prey species, roe deer (Capreolus capreolus), and to itself (lynx). We exploited an unusual natural situation, spanning three decades where lynx, after a period of absence in central and southern Sweden, during which roe deer populations had grown to high densities, subsequently recolonized region after region, from north to south. We divided the study area into seven regions, with increasing productivity from north to south. We found strong effects of both roe deer density and lynx density on lynx numerical response. Thus, both resources and intraspecific competition for these resources are important to understanding the lynx population dynamic. We built a series of deterministic lynx–roe deer models, and applied them to the seven regions. We found a very good fit between these Lotka–Volterra type models and the data. The deterministic models produced almost cyclic dynamics or dampened cycles in five of the seven regions. Thus, we documented population cycles in this large predator–large herbivore system, which is rarely done. The amplitudes in the dampened cycles decreased toward the south. Thus, the dynamics between lynx and roe deer became more stable with increasing carrying capacity for roe deer, which is related to higher productivity in the environment. This increased stability could be explained by variation in predation risk, where human presence can act as prey refugia, and by a more diverse prey guild that will weaken the direct interaction between lynx and roe deer.

Within‐lake variatiability in predation risk shapes the spatio‐temporal structure of the zooplankton community

Abstract While it is well‐accepted that predation plays a key role in shaping both size structure and species composition in natural ecosystems, fine‐scale variation in predation risk within ecosystems has been largely neglected. The objective of this study was to use normalised size spectra (NSS) to investigate whether small‐scale spatial variation in predation risk (by fish) can modulate zooplankton community structure at the within‐lake level in a small temperate lake. We tested the difference in the NSS between two hydrologically well‐connected basins of a lake exhibiting contrasting thermal regimes. The first is a well‐mixed shallow basin (max. depth 2.5 m) that is inaccessible to brook charr (Salvelinus fontinalis) during summer because the temperature is too warm. The second is a deeper basin (max. depth 18 m) offering a thermal refuge during summer because of lake stratification. As a consequence of these differences in fish accessibility, the fishless basin should contain larger and more abundant zooplankters, inducing a change in NSS slope and height. Our results showed that both the zooplankton size structure and taxonomic composition were distinct in the two basins, with a higher proportion of small individuals and a higher abundance of zooplankton in the shallow basin compared to the deep one. Furthermore, following cooling of the epilimnion in late summer, the zooplankton communities of both basins exhibited a clear shift in size structure and species composition: in autumn, there were smaller individuals and larger proportions of Bosminidae and Daphniidae compared to colonial rotifers than in summer. These results suggest a potential effect of the change in the spatial distribution of brook charr which feed preferentially on large individuals, reducing the average body size of the zooplankton community. Our results show that predation risk by fish can induce a spatial and temporal variation in zooplankton community structure within small temperate lake ecosystems exhibiting contrasted thermal regimes. Other potential predators also influenced the zooplankton community structure, creating a complex interplay that has to be taken into account to disentangle ecological processes and predict their future changes.

Back to the drawing board: re‐thinking growth–defense tradeoffs

Well‐established ecological equations such as logistic growth may carry implicit assumptions that are not immediately obvious. When such equations are adapted for a different context, missing awareness of their hidden assumptions can confound our conclusions. We demonstrate how this has happened in predator–prey models with rapid adaptation of prey defense to variable predation risk, where costs of defense typically manifest as a growth‐defense tradeoff. Assuming logistic prey growth, this tradeoff is often implemented as a reduced intrinsic growth rate, while the carrying capacity is unaffected. We show that this assumption is not only extremely ecologically unrealistic, but also results in highly problematic model behavior and destroys any potential for eco‐evolutionary or biomass‐trait feedbacks. To reconcile the problematic results of this assumption with its ubiquity in existing models with rapid adaptation, we conducted a literature survey of models on prey adaptation or predator–prey co‐adaptation. This reveals that many models, despite describing a tradeoff affecting only the intrinsic growth rate, do incorporate an additional cost affecting the carrying capacity, but in a way that is implicit and not acknowledged. It is this cost that drives the famous feedbacks between defense adaptation and predator–prey dynamics. Finally, we discuss the implications for existing theory on eco‐evolutionary dynamics, and provide guidelines for implementing growth‐defense tradeoffs in a more realistic way.

Predation risk estimated on live and artificial insect prey follows different patterns.

Models mimicking prey organisms are increasingly used in ecological studies, including testing fundamental ecological and evolutionary theories. The general consensus is that predation risk estimated on artificial models may not quantitatively correspond to predation pressure on live prey, but it still can be used in various comparisons. We tested whether the use of live and artificial prey reveals the same patterns of variation in predation risk. We exposed live prey (blowfly larvae and puparia) and plasticine models of blowfly puparia in two boreal forest sites, both openly and in ant- and bird-exclusion treatments, and we quantified attacks by both avian and invertebrate predators. Bird attack rates were always higher on live puparia than on their plasticine models, but the magnitude of this difference declined from 8.4-fold in early summer to 2-fold in mid- and late-summer. We attribute these changes to different responses to prey by experienced adult birds that dominate the bird communities in early summer versus explorative juvenile birds that are abundant later in the season. Invertebrate daily predation rates on maggots decreased from 56% in early summer to 28% in late summer, but invertebrate attacks on plasticine models showed no seasonal changes. Overall, invertebrate predation on maggots was 67-fold greater than their predation on models. Observations showed that wood ants did not attack plasticine models and did not leave on them any damage marks. Estimates based on artificial prey indicate a much greater role of bird predation than invertebrate predation, while estimates based on live prey suggest the opposite pattern. Thus, using live and artificial prey may lead to different conclusions about relative importance of different predator groups in a locality. Moreover, for both avian and invertebrate predators, predation risk based on artificial and live prey shows different seasonal changes and may potentially demonstrate different spatial patterns.

Predators affect a plant virus through density and trait-mediated indirect effects on vectors

Biological control programs frequently rely on insect predators to control pests that vector plant pathogens in agroecosystems. Predators affect vectors by eating them (consumptive effects) and by inducing antipredator behaviors (non-consumptive effects), and these interactions may affect transmission of vector-borne pathogens. However, it has proven difficult to experimentally tease apart the effects of predators on vector fitness and behavior as they are often correlated. We addressed this problem by assessing how both aphids and an aphid-borne pathogen were affected by variable predation risk. Specifically, we experimentally manipulated ladybeetle predators' mouthparts to isolate consumptive, and non-consumptive, effects of predators on aphid fitness, movement, and virus transmission. We show that although lethal predators decreased aphid vector abundance, they increased pathogen transmission by increasing aphid movement among hosts. Moreover, aphids responded to risk of predation by moving to younger plant tissue that was more susceptible to the pathogen. Aphids also responded to predator risk through compensatory reproduction, which offset direct consumptive effects. Our results support predictions of disease models showing alterations of vector movement due to predators can have greater effects on transmission of pathogens than vector consumption, which should be considered when examining natural enemies' role in pathogen dynamics. Broadly, our study shows isolating direct and indirect predation effects can reveal novel pathways by which predators affect vector-borne pathogens.

Predation and parasitism as determinants of animal personalities.

Within the same population, proactive (i.e. bolder, more exploratory, active and aggressive) and reactive (i.e. more timid, less exploratory, less active and more passive) individuals could be hypothetically maintained due a trade-off between foraging and vigilance behaviours, provided that both phenotypes differ in their state (e.g. metabolic rates, body condition or energetic needs). Yet, recent findings indicate that among-individual variation in intrinsic state can explain only a small proportion of variation in behaviour, meaning that other mechanisms, such as the presence of trophically transmitted parasites, might contribute to maintaining inter-individual behavioural differences. Empirical evidence, indeed, suggests strong relationships between certain animal personality traits and parasitic load within host populations. However, the direction of causation between these traits remains unclear: are different behaviours in infected hosts in contrast to uninfected ones the result of manipulation by parasites to increase host predation, or are some personalities inherently more susceptible to infection than others? To better understand the role of parasites in shaping behavioural differences within host populations and examine to what extent parasite manipulation and/or intrinsic differences in parasite susceptibility contribute to maintaining behavioural differences, we used a simulation approach and analysed the change in the frequencies of proactive and reactive individuals over time under different predation and starvation scenarios, when individual phenotype either affected a host's risk of infection or not. We found that in the absence of parasites, predation pressure strongly affected the expression of host personality, but the trade-off between foraging and vigilance behaviours alone could not explain the maintenance of inter-individual behavioural differences without temporal variation in predation pressure. By contrast, in the presence of parasites, the two host phenotypes could coexist within populations even when individuals experienced no temporal variations in predation risk, but only when proactive and reactive hosts were equally susceptible to parasitism. Our findings, thus, indicate that parasites can play an important role in maintaining genetic diversity in their host populations in addition to generating behavioural differences though manipulation.

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.

Risk in one is not risk in all: snails show differential decision making under high- and low-risk environments

Predation is a major force that shapes prey phenotypes, species interactions and ecological communities. Prey respond to variation in predation risk and intensity by either increasing or decreasing vigilance and balancing energy requirements under high- or low-risk scenarios. We test the possible mechanism of sensory adaptation and decision making while responding to risk in the pond snail Lymnaea stagnalis . We maintained three risk treatment groups (no risk, low risk and high risk) for 20 days before testing them under multiple cognitive and behavioural challenges involving a predatory stimulus. Under a configural learning procedure where snails learned to forgo feeding when encountering food in the presence of a predatory threat, the high-risk group snails did not show learning/memory formation. However, when high-risk group individuals were transferred to a no-risk environment for 20 days, they were able to form configural learning memory. In a social interaction trial, snails from the no-risk group reduced interactions under threat whereas the high-risk group showed no change between risk environments. All risk groups responded similarly to an operant conditioning training under predation threat that enhanced memory. The decreased antipredator response of the high-risk group in comparison to the low-risk groups shows that snails are able to respond to risk based on past experience, especially when there exists a trade-off between survival and antipredator response. The variation in response to predation threat under different circumstances provides evidence of decision making rather than sensory adaptation as the mechanism involved in prey response. Our study combines multiple phenotypic responses to elucidate animal decision making under different intensities of risk and highlights the importance of experience in shaping antipredator responses. • We tested snails' responses (sensory adaptation/decision making) to predation risk. • Two cognitive tests and one social behavioural assay were used as response. • High-risk group animals showed weaker antipredator responses. • Response variation across risk groups support a decision-making mechanism at work.

African wild dog movements show contrasting responses to long and short term risk of encountering lions: analysis using dynamic Brownian bridge movement models

BackgroundPrey depletion is a threat to the world’s large carnivores, and is likely to affect subordinate competitors within the large carnivore guild disproportionately. African lions limit African wild dog populations through interference competition and intraguild predation. When lion density is reduced as a result of prey depletion, wild dogs are not competitively released, and their population density remains low. Research examining distributions has demonstrated spatial avoidance of lions by wild dogs, but the effects of lions on patterns of movement have not been tested. Movement is one of the most energetically costly activities for many species and is particularly costly for cursorial hunters like wild dogs. Therefore, testing how top-down, bottom-up, and anthropogenic variables affect movement patterns can provide insight into mechanisms that limit wild dogs (and other subordinate competitors) in resource-depleted ecosystems.MethodsWe measured movement rates using the motion variance from dynamic Brownian Bridge Movement Models (dBBMMs) fit to data from GPS-collared wild dogs, then used a generalized linear model to test for effects on movement of predation risk from lions, predictors of prey density, and anthropogenic and seasonal variables.ResultsWild dogs proactively reduced movement in areas with high lion density, but reactively increased movement when lions were immediately nearby. Predictors of prey density had consistently weaker effects on movement than lions did, but movements were reduced in the wet season and when dependent offspring were present.ConclusionWild dogs alter their patterns of movement in response to lions in ways that are likely to have important energetic consequences. Our results support the recent suggestion that competitive limitation of wild dogs by lions remains strong in ecosystems where lion and wild dog densities are both low as a result of anthropogenic prey depletion. Our results reinforce an emerging pattern that movements often show contrasting responses to long-term and short-term variation in predation risk.

Predation risk can modify the foraging behaviour of frugivorous carnivores: Implications of rewilding apex predators for plant-animal mutualisms.

Apex predators play key roles in food webs and their recovery can trigger trophic cascades in some ecosystems. Intra‐guild competition can reduce the abundances of smaller predators and perceived predation risk can alter their foraging behaviour thereby limiting seed dispersal by frugivorous carnivores. However, little is known about how plant–frugivore mutualisms could be disturbed in the presence of larger predators.We evaluated the top‐down effect of the regional superpredator, the Iberian lynx Lynx pardinus, on the number of visits and fruits consumed by medium‐sized frugivorous carnivores, as well as the foraging behaviour of identified individuals, by examining the consumption likelihood and the foraging time.We carried out a field experiment in which we placed Iberian pear Pyrus bourgaeana fruits beneath fruiting trees and monitored pear removal by frugivorous carnivores, both inside and outside lynx ranges. Using camera traps, we recorded the presence of the red fox Vulpes vulpes, the Eurasian badger Meles meles and the stone marten Martes foina, as well as the number of fruits they consumed and their time spent foraging.Red fox was the most frequent fruit consumer carnivore. We found there were fewer visits and less fruit consumed by foxes inside lynx ranges, but lynx presence did not seem to affect badgers. We did not observe any stone marten visits inside lynx territories. The foraging behaviour of red foxes was also altered inside lynx ranges whereby foxes were less efficient, consuming less fruit per unit of time and having shorter visits. Local availability of fruit resources, forest coverage and individual personality also were important variables to understand visitation and foraging in a landscape of fear.Our results show a potential trophic cascade from apex predators to primary producers. The presence of lynx can reduce frugivorous carnivore numbers and induce shifts in their feeding behaviour that may modify the seed dispersal patterns with likely consequences for the demography of many fleshy‐fruited plant species. We conclude that knowledge of the ecological interactions making up trophic webs is an asset to design effective conservation strategies, particularly in rewilding programs.

Behavioral responses to spatial variation in perceived predation risk and resource availability in an arboreal primate

AbstractPrey species must often face a trade‐off between acquiring resources and minimizing predation risk. The spatial variation in predation risk across a landscape, as perceived by prey across their foraging or home range, creates a “landscape of fear” by which individuals modify their behavior in response to the level of perceived risk. Here, we explored the influence of perceived predation risk, habitat features associated with risk, and fruit availability, on the spatial variation in behavior of the endangered forest‐dwelling samango monkey (Cercopithecus albogularis schwarzi). We collected behavioral and location data on two habituated samango monkey groups in the Soutpansberg Mountains, South Africa, between 2012 and 2016. We further collected location data of the samango monkey's acoustically distinct alarm call, which has an unambiguous association with aerial predators, to spatially map perceived risk across the landscape. Using generalized linear mixed models, we found that perceived risk from eagles significantly influenced the spatial distribution of critical life‐functioning behaviors, with samango monkeys increasing feeding and foraging in high‐risk areas. To mitigate this risk, samangos increased cohesion between group members, which subsequently reduced vigilance levels. Group cohesion further increased in high‐risk areas with abundant fruit, relative to high‐risk, fruit‐poor areas, demonstrating the monkey's foraging/risk trade‐off. Feeding was also reduced in areas of low canopy height, while vigilance decreased with increasing understory visibility and distance from sleep site, showing the influence of landscape features on risk perception from other predator guilds. Thus, for arboreal species foraging in a 3‐D landscape, risk perception may occur at multiple scales and in response to multiple predator guilds. Only moving was influenced by fruit availability, either due to moving between localized food patches or from escaping high‐risk areas following feeding bouts. These findings highlight that risk‐taking in samango monkeys is only associated with behaviors fundamental to survival at a given location and that increased cohesion between neighbors is the main antipredator response in this species.

Canopy openness of individual tree promotes seed dispersal by scatter-hoarding rodents

Scatter-hoarding rodents are important seed predators and dispersers in various forest ecosystems and significantly influence the seed fate and seedling regeneration of many tree species. Canopy openness is believed to have an important influence on the foraging behavior of scatter-hoarding rodents, mainly because of the variation in predation risk between open and canopy microsites. Most of the current studies have mainly focused on the spatial variation in canopy openness within a forest or on comparisons among forests; however, the question of how variation in canopy openness at the individual tree scale affects seed-rodent interaction has received little attention, although tree-to-tree variation in canopy openness is ubiquitous. In this study, we measured the individual canopy openness of 45 trees belonging to three species in a subtropical forest, and compared seed dispersal and predation by rodents under the selected trees by labeling and tracking 4,500 seeds. Our results showed that canopy openness differed among individual trees both within and across species. More importantly, our results proved that individual tree variation in canopy openness significantly affected seed dispersal and predation by rodents, although not all species followed a consistent pattern. Seeds under trees with larger canopy openness were more likely to be removed rather than eaten in situ and dispersed farther. Our study highlights the pattern that individual tree characteristics (e.g., canopy openness) have profound effects on rodent-mediated seed dispersal services, which may further lead to tree-to-tree variation in seed fate and seedling regeneration. Our results also provide important implications for forest conservation and management: crown pruning can promote seed dispersal by rodents and natural seedling regeneration.

Behaviour of a large ungulate reflects temporal patterns of predation risk

Context Many prey species exhibit antipredator behaviours when threatened, yet prey response to temporal variation in predation risk is not well-understood, despite being foundational to predator–prey dynamics and an important consideration among game population managers and recreationalists. Aims To examine white-tailed deer (Odocoileus virginianus) behaviour in response to temporal variation in predation risk imposed by recreational hunters and to assess the effect of deer sex and age on antipredator response. Methods Global positioning system (GPS) collars were used to monitor behaviour of female and male deer in response to diel and weekly patterns of recreational hunting in Alabama, USA. Key results Deer behaviour on weekends (i.e. Friday–Sunday), corresponding to periods of elevated risk, was similar to behaviour on weekdays (i.e. Monday–Thursday). However, when behaviour was examined by individual day of the week, movement rate decreased by 17%, net displacement decreased by 31%, and the probability of activity decreased by 24% during daylight hours on Sundays compared with Fridays. Behavioural changes among days were not detected at night. Daytime behavioural shifts persisted until Wednesdays, despite lower weekday hunting activity. Behavioural variation by deer sex and age was also observed. Conclusions Deer perceive temporal variation in predation risk and modify their behaviour to reduce the likelihood of predation. Variation in response across sex and age classes may be driven by previous experience with hunters and/or survival- and fitness-related trade-offs that affect prey decisions at the individual level. Antipredator response was not initially detectable when examined at a broad temporal scale (i.e. weekend vs weekday); however, a behavioural response was shown with a finer-scale analysis (i.e. individual day of the week), which more closely reflected the pattern of risk fluctuation. Implications Our findings demonstrated the acute awareness of a large ungulate to temporal changes in predation risk and provided insight into ways in which these prey behaviourally respond to reduce the likelihood of predatory encounters. Future studies should consider the temporal scale of risk fluctuation when examining antipredator response to avoid false conclusions. Ungulate hunters and managers can use this information to more efficiently achieve their goals.

The predator activity landscape predicts the anti‐predator behavior and distribution of prey in a tundra community

AbstractPredation shapes communities through consumptive and non‐consumptive effects. In the latter case, prey respond to perceived predation risk through proactive or reactive risk management strategies occurring at different spatial and temporal scales. The predator–prey space race and landscape of fear concepts are useful to better understand how predation risk affects prey behavioral decisions and distribution. We assessed predation risk effects in a terrestrial Arctic community, where the arctic fox is the main predator of ground‐nesting birds. Using high‐frequency GPS data, we estimated a predator activity landscape corresponding to fox space use patterns and validated with an artificial prey experiment that this predator activity landscape correlated with the predation risk landscape. We then investigated the effects of the fox activity landscape on multiple prey species, by assessing the anti‐predator behavior of a main prey (snow goose) actively searched for by foxes, and the nest distribution of several incidental prey species. We first found that snow geese showed a stronger level of nest defense in areas highly used by foxes, possibly responding with a reactive strategy to variation in predation risk. Then, nests of incidental prey reproducing in habitats easily accessed by foxes had a lower probability of occurrence in areas highly used by foxes, suggesting these birds may use a proactive risk management strategy by shifting their distribution away from risky areas. For incidental prey species nesting in microhabitat refuges difficult to access by foxes, probability of nest occurrence was independent of predation risk in the surrounding area, as they avoid risk at a finer spatial scale. By tracking all individuals of the dominant predator species in our study area, we demonstrated the value of using predator space use patterns to infer spatial variation in predation risk. Overall, we highlight the diversity of risk management strategies in prey sharing a common predator, hence refining our understanding of the mechanisms driving species distribution and community structure.

Incorporating thermodynamics in predator-prey games predicts the diel foraging patterns of poikilothermic predators.

Models of foraging behaviour typically assume that prey do not adapt to temporal variation in predation risk, such as by avoiding foraging at certain times of the day. When this behavioural plasticity is considered-such as in predator-prey games-the role of abiotic factors is usually ignored. An abiotic factor that exerts strong influence on the physiology and behaviour of many animals is ambient temperature, although it is often ignored from game models as it is implicitly assumed that both predators and prey are homothermic. However, poikilotherms' performance may be reduced in cold conditions due to reduced muscle function, limiting the prey-capture ability of predators and the predator-avoidance and foraging abilities of prey. Here, we use a game-theoretic predator-prey model in which diel temperature changes influence foraging gains and costs to predict the evolutionarily stable diel activity of predators. Our model predicts the range of patterns observed in nature, including nocturnal, diurnal, crepuscular and a previously unexplained post-sunset crepuscular pattern observed in some sharks. In general, smaller predators are predicted to be more diurnal than larger ones. The safety of prey when not foraging is critical, explaining why predators in coral reef systems (with safe refuges) may often have different foraging patterns to pelagic predators. We make a range of testable predictions that will enable the further evaluation of this theoretical framework for understanding diel foraging patterns in poikilotherms.

Contrasting patterns of risk from human and non-human predators shape temporal activity of prey.

Spatiotemporal variation in predation risk arises from interactions between landscape heterogeneity, predator densities and predator hunting mode, generating landscapes of fear for prey species that can have important effects on prey behaviour and ecosystem dynamics. As widespread apex predators, humans present a significant source of risk for hunted animal populations. Spatiotemporal patterns of risk from hunters can overlap or contrast with patterns of risk from other predators. Human infrastructure can also reshape spatial patterns of risk by facilitating or impeding hunter or predator movement, or deterring predators that are themselves wary of humans. We examined how anthropogenic and natural landscape features interact with hunting modes of rifle hunters and mountain lions Puma concolor to generate spatiotemporal patterns of risk for their primary prey. We explored the implications of human-modified landscapes of fear for Columbian black-tailed deer Odocoileus hemionus columbianus in Mendocino County, California. We used historical harvest records, hunter GPS trackers and camera trap records of mountain lions to model patterns of risk for deer. We then used camera traps to examine deer spatial and temporal activity patterns in response to this variation in risk. Hunters and mountain lions exhibited distinct, contrasting patterns of spatiotemporal activity. Risk from rifle hunters, who rely on long lines of sight, was highest in open grasslands and near roads and was confined to the daytime. Risk from mountain lions, an ambush predator, was highest in dense shrubland habitat, farther from developed areas, and during the night and crepuscular periods. Areas of human settlement provided a refuge from both hunters and mountain lions. We found no evidence that deer avoided risk in space at the scale of our observations, but deer adjusted their temporal activity patterns to reduce the risk of encounters with humans and mountain lions in areas of higher risk. Our study demonstrates that interactions between human infrastructure, habitat cover and predator hunting mode can result in distinct spatial patterns of predation risk from hunters and other predators that may lead to trade-offs for prey species. However, distinct diel activity patterns of predators may create vacant hunting domains that reduce costly trade-offs for prey. Our study highlights the importance of temporal partitioning as a mechanism of predation risk avoidance.

The impact of variable predation risk on stress in snowshoe hares over the cycle in North America’s boreal forest: adjusting to change

The boreal forest is one of the world's ecosystems most affected by global climate warming. The snowshoe hare, its predators, and their population dynamics dominate the mammalian component of the North American boreal forest. Our past research has shown the 9-11-year hare cycle to be predator driven, both directly as virtually all hares that die are killed by their predators, and indirectly through sublethal risk effects on hare stress physiology, behavior, and reproduction. We replicated this research over the entire cycle by measuring changes in predation risk expected to drive changes in chronic stress. We examined changes in hare condition and stress axis function using a hormonal challenge protocol in the late winter of 7years-spanning all phases of the cycle from the increase through to the low (2014-2020). We simultaneously monitored changes in hare abundance as well as those of their primary predators, lynx and coyotes. Despite observing the expected changes in hare-predator numbers over the cycle, we did not see the predicted changes in chronic stress metrics in the peak and decline phases. Thus, the comprehensive physiological signature indicative of chronic predator-induced stress seen from our previous work was not present in this current cycle. We postulate that hares may now be increasingly showing behavior-mediated rather than stress-mediated responses to their predators. We present evidence that increases in primary productivity have affected boreal community structure and function. We speculate that climate change has caused this major shift in the indirect effects of predation on hares.

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 10h after coming into close proximity (≤75m) with lynx, and reduced foraging time an average of 15.28±7.08min 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.