Do prey select for vacant hunting domains to minimize a multi-predator threat?

Friends because of foes: synchronous movement within predator-prey domains

For prey, movement synchrony represents a potent antipredator strategy. Prey, however, must balance the costs and benefits of using conspecifics to mediate risk. Thus, the emergent patterns of risk-driven sociality depend on variation in space and in the predators and prey themselves. We applied the concept of predator-prey habitat domain, the space in which animals acquire food resources, to test the conditions under which individuals synchronize their movements relative to predator and prey habitat domains. We tested the response of movement synchrony of prey to predator-prey domains in two populations of ungulates that vary in their gregariousness and predator community: (i) elk, which are preyed on by wolves; and (ii) caribou, which are preyed on by coyotes and black bears. Prey in both communities responded to cursorial predators by increasing synchrony during seasons of greater predation pressure. Elk moved more synchronously in the wolf habitat domain during winter and caribou moved more synchronously in the coyote habitat domains during spring. In the winter, caribou increased movement synchrony when coyote and caribou domains overlapped. By integrating habitat domains with movement ecology, we provide a compelling argument for social behaviours and collective movement as an antipredator response. This article is part of the theme issue 'The spatial-social interface: A theoretical and empirical integration'.

Asymmetrical predation intensity produces divergent antipredator behaviours in primary and secondary prey

It is widely recognized that predators can influence prey through both direct consumption and by inducing costly antipredator behaviours, the latter of which can produce nonconsumptive effects that cascade through trophic systems. Yet, determining how particular prey manage risk in natural settings remains challenging as empirical studies disproportionately focus on single predator-prey dyads. Here, we contrast foraging strategies within the context of a primary and secondary prey to explore how antipredator behaviours emerge as a product of predation intensity as well as the setting in which an encounter takes place. We studied the effects of spotted owls (Strix occidentalis) on two species experiencing asymmetrical risk: dusky-footed woodrats (Neotoma fuscipes; primary prey) and deer mice (Peromyscus spp.; alternative prey). Woodrats are most abundant within young forests, but predominantly captured by owls foraging within mature forests; in contrast, deer mice occur in high densities across forest types and seral stages and are consumed at lower per-capita rates overall. We deployed experimental foraging patches within areas of high and low spotted owl activity, created artificial risky and safe refuge treatments, and monitored behaviour throughout the entirety of prey foraging bouts. Woodrats were more vigilant and foraged less within mature forests and at riskier patches, although the effect of refuge treatment was contingent upon forest type. In contrast, deer mice only demonstrated consistent behavioural responses to riskier refuge treatments; forest type had little effect on perceived risk or the relative importance of refuge treatment. Thus, habitat can interact with predator activity to structure antipredator responses differently for primary versus secondary prey. Our findings show that asymmetrical predation can modulate both the magnitude of perceived risk and the strategies used to manage it, thus highlighting an important and understudied contingency in risk effects research. Evaluating the direct and indirect effects of predation through the paradigm of primary and secondary prey may improve our understanding of how nonconsumptive effects can extend to population- and community-level responses.

Keystone individuals - linking predator traits to community ecology

Individual behavioral plasticity enables animals to adjust to different scenarios. Yet, personality traits limit this flexibility, leading to consistent interindividual differences in behavior. These individual behavioral traits have the potential to govern community interactions, although testing this is difficult in complex natural systems. For large predators who often exert strong effects on ecosystem functioning, this behavioral diversity may be especially important and lead to individualized ecosystem roles. We present a framework for quantifying individual behavioral plasticity and personality traits of large wild predators, revealing the extent to which certain natural behaviors are governed by these latent traits. The outcomes will reveal how the innate characteristics of wildlife can scale up to affect community interactions.

Behavioral trade-offs and multitasking by elk in relation to predation risk from Mexican gray wolves

Predator non-consumptive effects (NCE) can alter prey foraging time and habitat use, potentially reducing fitness. Prey can mitigate NCEs by increasing vigilance, chewing-vigilance synchronization, and spatiotemporal avoidance of predators. We quantified the relationship between Mexican wolf (Canis lupus baileyi) predation risk and elk (Cervus canadensis) behavior. We conducted behavioral observations on adult female elk and developed predation risk indices using GPS collar data from Mexican wolves, locations of elk killed by wolves, and landscape covariates. We compared a priori models to determine the best predictors of adult female behavior and multitasking. Metrics that quantified both spatial and temporal predation risk were the most predictive. Vigilance was positively associated with increased predation risk. The effect of predation risk on foraging and resting differed across diurnal periods. During midday when wolf activity was lower, the probability of foraging increased while resting decreased in high-risk areas. During crepuscular periods when elk and wolves were most active, increased predation risk was associated with increased vigilance and slight decreases in foraging. Our results suggest elk are temporally avoiding predation risk from Mexican wolves by trading resting for foraging, a trade-off often not evaluated in behavioral studies. Probability of multitasking depended on canopy openness and an interaction between maternal period and predation risk; multitasking decreased prior to parturition and increased post parturition in high-risk areas. Openness was inversely related to multitasking. These results suggest adult female elk are altering the type of vigilance used depending on resource availability/quality, current energetic needs, and predation risk. Our results highlight potentially important, but often-excluded behaviors and trade-offs prey species may use to reduce the indirect effects of predation and contribute additional context to our understanding of predator-prey dynamics.

Cougars, wolves, and humans drive a dynamic landscape of fear for elk

To manage predation risk, prey navigate a dynamic landscape of fear, or spatiotemporal variation in risk perception, reflecting predator distributions, traits, and activity cycles. Prey may seek to reduce risk across this landscape using habitat at times and in places when predators are less active. In multipredator landscapes, avoiding one predator could increase vulnerability to another, making the landscape of fear difficult to predict and navigate. Additionally, humans may shape interactions between predators and prey, and induce new sources of risk. Humans can function as a shield, providing a refuge for prey from human-averse carnivores, and as a predator, causing mortality through hunting and vehicle collisions and eliciting a fear response that can exceed that of carnivores. We used telemetry data collected between 2017 and 2021 from 63 Global Positioning System-collared elk (Cervus canadensis), 42 cougars (Puma concolor), and 16 wolves (Canis lupus) to examine how elk habitat selection changed in relation to carnivores and humans in northeastern Washington, USA. Using step selection functions, we evaluated elk habitat use in relation to cougars, wolves, and humans, diel period (daytime vs. nighttime), season (summer calving season vs. fall hunting season), and habitat structure (open vs. closed habitat). The diel cycle was critical to understanding elk movement, allowing elk to reduce encounters with predators where and when they would be the largest threat. Elk strongly avoided cougars at night but had a near-neutral response to cougars during the day, whereas elk avoided wolves at all times of day. Elk generally used more open habitats where cougars and wolves were most active, rather than altering the use of habitat structure depending on the predator species. Elk avoided humans during the day and ~80% of adult female mortality was human caused, suggesting that humans functioned as a "super predator" in this system. Simultaneously, elk leveraged the human shield against wolves but not cougars at night, and no elk were confirmed to have been killed by wolves. Our results add to the mounting evidence that humans profoundly affect predator-prey interactions, highlighting the importance of studying these dynamics in anthropogenic areas.

Wolves alter the trajectory of forests by shaping the central place foraging behaviour of an ecosystem engineer

Predators can directly and indirectly alter the foraging behaviour of prey through direct predation and the risk of predation, and in doing so, initiate indirect effects that influence myriad species and ecological processes. We describe how wolves indirectly alter the trajectory of forests by constraining the distance that beavers, a central place forager and prolific ecosystem engineer, forage from water. Specifically, we demonstrate that wolves wait in ambush and kill beavers on longer feeding trails than would be expected based on the spatio-temporal availability of beavers. This pattern is driven by temporal dynamics of beaver foraging: beavers make more foraging trips and spend more time on land per trip on longer feeding trails that extend farther from water. As a result, beavers are more vulnerable on longer feeding trails than shorter ones. Wolf predation appears to be a selective evolutionary pressure propelled by consumptive and non-consumptive mechanisms that constrain the distance from water beavers forage, which in turn limits the area of forest around wetlands, lakes and rivers beavers alter through foraging. Thus, wolves appear intricately linked to boreal forest dynamics by shaping beaver foraging behaviour, a form of natural disturbance that alters the successional and ecological states of forests.

Tradeoffs between resources and risks shape the responses of a large carnivore to human disturbance

Wide-ranging carnivores experience tradeoffs between dynamic resource availabilities and heterogeneous risks from humans, with consequences for their ecological function and conservation outcomes. Yet, research investigating these tradeoffs across large carnivore distributions is rare. We assessed how resource availability and anthropogenic risks influence the strength of lion (Panthera leo) responses to disturbance using data from 31 sites across lions' contemporary range. Lions avoided human disturbance at over two-thirds of sites, though their responses varied depending on site-level characteristics. Lions were more likely to exploit human-dominated landscapes where resources were limited, indicating that resource limitation can outweigh anthropogenic risks and might exacerbate human-carnivore conflict. Lions also avoided human impacts by increasing their nocturnal activity more often at sites with higher production of cattle. The combined effects of expanding human impacts and environmental change threaten to simultaneously downgrade the ecological function of carnivores and intensify human-carnivore conflicts, escalating extinction risks for many species.

Dynamic balancing of risks and rewards in a large herbivore: Further extending predator-prey concepts to road ecology

Animal behaviour is shaped by the ability to identify risks and profitably balance the levels of risks encountered with the payoffs experienced. Anthropogenic disturbances like roads generate novel risks and opportunities that wildlife must accurately perceive and respond to. Basic concepts in predator-prey ecology are often used to understand responses of animals to roads (e.g. increased vigilance, selection for cover in their vicinity). However, prey often display complex behaviours such as modulating space use given varying risks and rewards, and it is unclear if such dynamic balancing is used by animals in the context of road crossings. We tested whether animals dynamically balance risks and rewards relative to roads using extensive field-based and GPS collar data from elk in Yoho National Park (British Columbia, Canada), where a major highway completely bisects their range during most of the year. We analysed elk behaviour by combining hidden Markov movement models with a step-selection function framework. Rewards were indexed by a dynamic map of available forage biomass, and risks were indexed by road crossings and traffic volumes. We found that elk generally selected intermediate and high forage biomass, and avoided crossing the road. Most of the time, elk modulated their behaviour given varying risks and rewards. When crossing the highway compared with not crossing, elk selected for greater forage biomass and this selection was stronger as the number of highway crossings increased. However, with traffic volume, elk only balanced foraging rewards when they crossed a single time during a travel sequence. Using a road ecology system, we empirically tested an important component of predator-prey ecology-the ability to dynamically modulate behaviour in response to varying levels of risks and rewards. Such a test articulates how decision-making processes that consider the spatiotemporal variation in risks and rewards allow animals to successfully and profitably navigate busy roads. Applying well-developed concepts in predator-prey theory helps understand how animals respond to anthropogenic disturbances and anticipate the adaptive capacity for individuals and populations to adjust to rapidly changing environments.

Density-dependent changes in elk resource selection over successional time scales following forest disturbance

There is an increasing need to understand how animals respond to modifications of their habitat following landscape-scale disturbances such as wildfire or timber harvest. Such disturbances can promote increased use by herbivores due to changes in plant community structure that improve forage conditions, but can also cause avoidance if other habitat functions provided by cover are substantially reduced or eliminated. Quantifying the total effects of these disturbances, however, is challenging because they may not fully be apparent unless observed at successional timescales. Further, the effects of disturbances that improve habitat quality may be density dependent, such that the benefits are (1) less valuable to high-density populations because the per-capita benefits are reduced when shared among more users or, alternatively, (2) more valuable to animals living in high densities because resources may be more depleted from the greater intraspecific competition. We used 30 years of telemetry data on elk occurring at two distinct population densities to quantify changes in space use at diel, monthly, and successional timescales following timber harvest. Elk selected logged areas at night only, with selection strongest during midsummer, and peak selection occurring 14 years post harvest, but persisting for 26-33 years. This pattern of increased selection at night following a reduction in overhead canopy cover is consistent with elk exploiting improved nutritional conditions for foraging. The magnitude of selection for logged areas was 73% higher for elk at low population density, consistent with predictions from the ideal free distribution. Yet elk avoided these same areas during daytime for up to 28 years post logging and instead selected untreated forest, suggesting a role for cover to meet other life history requirements. Our results demonstrate that while landscape-scale disturbances can lead to increased selection by large herbivores and suggest that the improvement in foraging conditions can persist over short-term successional timescales, the magnitude of the benefits may not be equal across population densities. Further, the enduring avoidance of logging treatments during the daytime indicates a need for structurally intact forests and suggests that a mosaic of forest patches of varying successional stages and structural completeness is likely to be the most beneficial to large herbivores.

Bison alter the northern Yellowstone ecosystem by breaking aspen saplings

The American bison (Bison bison) is a species that strongly interacts with its environment, yet the effects of this large herbivore on quaking aspen (Populus tremuloides) have received little study. We documented bison breaking the stems of aspen saplings (young aspen >2 m tall and ≤5 cm in diameter at breast height) and examined the extent of this effect in northern Yellowstone National Park (YNP). Low densities of Rocky Mountain elk (Cervus canadensis) after about 2004 created conditions conducive for new aspen recruitment in YNP's northern ungulate winter range (northern range). We sampled aspen saplings at local and landscape scales, using random sampling plots in 87 randomly selected aspen stands. Across the YNP northern range, we found that 18% of sapling stems had been broken. The causal attribution to bison was supported by multiple lines of evidence: (1) most broken saplings were in areas of high bison and low elk density; (2) saplings were broken in summer when elk were not foraging on them; (3) we directly observed bison breaking aspen saplings; and (4) mixed-effects modeling showed a positive association between scat density of bison and the proportion of saplings broken. In a stand heavily used by bison, most aspen saplings had been broken, and portions of the stand were cleared of saplings that were present in previous sampling in 2012. Bison numbers increased more than fourfold between 2004 and 2015, and their ecosystem effects have similarly increased, limiting and in some places reversing the nascent aspen recovery. This situation is further complicated by political constraints that prevent bison from dispersing to areas outside the park. Thus, one important conservation goal, the preservation of bison, is affecting another long-term conservation goal, the recovery of aspen and other deciduous woody species in northern Yellowstone.

Non-exploitative human disturbance provides shelter for prey from predator

Human activities can influence behaviors of predators and prey, as well as predator-prey interactions. Using camera trap data, we investigated whether or to what extent human activities influenced behaviors of predators (tigers and leopards) and prey (sambar deer, spotted deer, wild boar, and barking deer), and predator-prey interactions in the Barandabhar Corridor Forest (BCF), Chitwan District, Nepal. A multispecies occupancy model revealed that the presence of humans altered the conditional occupancy of both prey and predator species. Specifically, the conditional occupancy probability of prey was substantially higher (ψ = 0.91, CI = 0.89-0.92) when humans were present than when humans were absent (ψ = 0.68, CI = 0.54-0.79). The diel activity pattern of most prey species overlapped strongly with humans, whereas predators were generally more active when humans were absent. Finally, the spatiotemporal overlap analysis revealed that human-prey interactions (i.e., the probability that both humans and prey species being present on the same grid at the same hourly period) was ~3 times higher (10.5%, CI = 10.4%-10.6%) compared to spatiotemporal overlap between humans and predators (3.1%, CI = 3.0%-3.2%). Our findings are consistent with the human shield hypothesis and suggest that ungulate prey species may reduce predation risk by using areas with high human activities.

Density-dependent habitat selection alters drivers of population distribution in northern Yellowstone elk

Although it is well established that density dependence drives changes in organismal abundance over time, relatively little is known about how density dependence affects variation in abundance over space. We tested the hypothesis that spatial trade-offs between food and safety can change the drivers of population distribution, caused by opposing patterns of density-dependent habitat selection (DDHS) that are predicted by the multidimensional ideal free distribution. We addressed this using winter aerial survey data of northern Yellowstone elk (Cervus canadensis) spanning four decades. Supporting our hypothesis, we found positive DDHS for food (herbaceous biomass) and negative DDHS for safety (openness and roughness), such that the primary driver of habitat selection switched from food to safety as elk density decreased from 9.3 to 2.0 elk/km² . Our results demonstrate how population density can drive landscape-level shifts in population distribution, confounding habitat selection inference and prediction and potentially affecting community-level interactions.

Ungulate spatiotemporal responses to contrasting predation risk from wolves and snow leopards

Spatial responses to risk from multiple predators can precipitate emergent consequences for prey (i.e. multiple-predator effects, MPEs) and mediate indirect interactions between predators. How prey navigate risk from multiple predators may therefore have important ramifications for understanding the propagation of predation-risk effects (PREs) through ecosystems. The interaction of predator and prey traits has emerged as a potentially key driver of antipredator behaviour but remains underexplored in large vertebrate systems, particularly where sympatric prey share multiple predators. We sought to better generalize our understanding of how predators influence their ecosystems by considering how multiple sources of contingency drive prey distribution in a multi-predator-multi-prey system. Specifically, we explored how two sympatric ungulates with different escape tactics-vertically agile, scrambling ibex Capra sibirica and sprinting argali Ovis ammon-responded to predation risk from shared predators with contrasting hunting modes-cursorial wolves Canis lupus and vertical-ambushing, stalking snow leopards Panthera uncia. Contrasting risk posed by the two predators presented prey with clear trade-offs. Ibex selected for greater exposure to chronic long-term risk from snow leopards, and argali for wolves, in a nearly symmetrical manner that was predictable based on the compatibility of their respective traits. Yet, acute short-term risk from the same predator upended these long-term strategies, increasing each ungulates' exposure to risk from the alternate predator in a manner consistent with a scenario in which conflicting antipredator behaviours precipitate risk-enhancing MPEs and mediate predator facilitation. By contrast, reactive responses to wolves led ibex to reduce their exposure to risk from both predators-a risk-reducing MPE. Evidence of a similar reactive risk-reducing effect for argali vis-à-vis snow leopards was lacking. Our results suggest that prey spatial responses and any resulting MPEs and prey-mediated interactions between predators are contingent on the interplay of hunting mode and escape tactics. Further investigation of interactions among various drivers of contingency in PREs will contribute to a more comprehensive understanding and improved forecasting of the ecological effects of predators.

Risky business: How an herbivore navigates spatiotemporal aspects of risk from competitors and predators

Understanding factors that influence animal behavior is central to ecology. Basic principles of animal ecology imply that individuals should seek to maximize survival and reproduction, which means carefully weighing risk against reward. Decisions become increasingly complex and constrained, however, when risk is spatiotemporally variable. We advance a growing body of work in predator-prey behavior by evaluating novel questions where a prey species is confronted with multiple predators and a potential competitor. We tested how fine-scale behavior of female mule deer (Odocoileus hemionus) during the reproductive season shifted depending upon spatial and temporal variation in risk from predators and a potential competitor. We expected female deer to avoid areas of high risk when movement activity of predators and a competitor were high. We used GPS data collected from 76 adult female mule deer, 35 adult female elk, 33 adult coyotes, and six adult mountain lions. Counter to our expectations, female deer exhibited selection for multiple risk factors, however, selection for risk was dampened by the exposure to risk within home ranges of female deer, producing a functional response in habitat selection. Furthermore, temporal variation in movement activity of predators and elk across the diel cycle did not result in a shift in movement activity by female deer. Instead, the average level of risk within their home range was the predominant factor modulating the response to risk by female deer. Our results counter prevailing hypotheses of how large herbivores navigate risky landscapes and emphasize the importance of accounting for the local environment when identifying effects of risk on animal behavior. Moreover, our findings highlight additional behavioral mechanisms used by large herbivores to mitigate multiple sources of predation and potential competitive interactions.

Interactive effects of wildfires, season, and predator activity shape mule deer movements

Wildfires are increasing in size, frequency, and severity due to climate change and fire suppression, but the direct and indirect effects on wildlife remain largely unresolved. Fire removes forest canopy, which can improve forage for ungulates but also reduce snow interception, leading to a deeper snowpack and potentially increased vulnerability to predation in winter. If ungulates exhibit predator-mediated foraging, burns should generally be selected for in summer to access high-quality forage and avoided in winter to reduce predation risk in deep snow. Fires also typically increase the amount of deadfall and initiate growth of dense understory vegetation, creating obstacles that may confer a hunting advantage to stalking predators and a disadvantage to coursing predators. To minimize risk, ungulates may therefore avoid burns when and where stalking predators are most active, and use burns when and where coursing predators are most active. We used telemetry data from GPS-collared mule deer (Odocoileus hemionus), cougars (Puma concolor), and wolves (Canis lupus) to develop step selection functions to examine how mule deer navigated species-specific predation risk across a landscape in northern Washington, USA that has experienced substantial wildfire activity during the past several decades. We considered a diverse array of wildfire impacts, accounting for both the severity of the fire and time since the burn (1 to 35 years) in our analyses. We observed support for the predator mediating foraging hypothesis: mule deer generally selected for burned areas in summer and avoided burns in winter. In addition, deer increased use of burned areas when and where wolf activity was high and avoided burns when and where cougar use was high in winter, suggesting the hunting mode of resident predators mediated the seasonal response of deer to burns. Deer were not more likely to die by predation in burned than in unburned areas, indicating that they adequately manage fire-induced changes to predation risk. As fire activity increases with climate change, our findings indicate the impact on ungulates will depend on tradeoffs between enhanced summer forage and functionally reduced winter range, mediated by characteristics of the predator community.

Evaluating the summer landscapes of predation risk and forage quality for elk (Cervus canadensis)

The recovery of carnivore populations in North American has consequences for trophic interactions and population dynamics of prey. In addition to direct effects on prey populations through killing, predators can influence prey behavior by imposing the risk of predation. The mechanisms through which patterns of space use by predators are linked to behavioral response by prey and nonconsumptive effects on prey population dynamics are poorly understood. Our goal was to characterize population- and individual-level patterns of resource selection by elk (Cervus canadensis) in response to risk of wolves (Canis lupus) and mountain lions (Puma concolor) and evaluate potential nonconsumptive effects of these behavioral patterns. We tested the hypothesis that individual elk risk-avoidance behavior during summer would result in exposure to lower-quality forage and reduced body fat and pregnancy rates. First, we evaluated individuals' second-order and third-order resource selection with a used-available sampling design. At the population level, we found evidence for a positive relationship between second- and third-order selection and forage, and an interaction between forage quality and mountain lion risk such that the relative probability of use at low mountain lion risk increased with forage quality but decreased at high risk at both orders of selection. We found no evidence of a population-level trade-off between forage quality and wolf risk. However, we found substantial among-individual heterogeneity in resource selection patterns such that population-level patterns were potentially misleading. We found no evidence that the diversity of individual resource selection patterns varied predictably with available resources, or that patterns of individual risk-related resource selection translated into biologically meaningful changes in body fat or pregnancy rates. Our work highlights the importance of evaluating individual responses to predation risk and predator hunting technique when assessing responses to predators and suggests nonconsumptive effects are not operating at a population scale in this system.

Prey defense phenotype mediates multiple-predator effects in tri-trophic food-webs

1. The emphasis on mechanisms governing the interaction among predators (e.g., cooperation, competition, or intraguild predation) has driven the understanding of multiple-predator effects on prey survival and dynamics. However, overwhelming evidence shows that prey can adaptively respond to predators, exhibiting multiple defensive phenotypes to cope with predation. Nevertheless, there is still a relatively scarce theory connecting the emergence of prey defenses in complex multi-predator scenarios and their ecological consequences. 2. Using a mathematical approach, we evaluated the prevalence of defended prey phenotypes as a function of predator-induced mortality in a two-predator system, and how prey and phenotype dynamics affect trophic cascades. We also evaluated such responses when prey manifests a general defense against both predators (i.e., risk-reducing) or a specialized defense against one predator at the expense of defense against the other predator (i.e., risk trade-off), and when such phenotypes induce fitness and foraging costs. 3. We showed that the emergence of defended phenotypes under multiple predators depends on predator-induced mortality rates, the magnitude of phenotype costs, and the effect of the defensive phenotype on the performance of all predators. 4. Risk-reducing phenotypes enhance prioritized responses to predators with high killing rates, but prioritized responses are diminished when prey manifest risk trade-off phenotypes. Finally, we showed that resource abundance across the predation gradient directly depends on the prevalence of certain prey phenotypes and their effect on foraging costs. 5. Ultimately, our results depict the implications of prey defenses on prey and basal resources abundance in a multiple predators' environment, highlighting the role of the identity of defensive strategies in mediating the strength and nature of trophic cascades, via consumptive or non-consumptive effects.

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.

Scavenging vs hunting affects behavioral traits of an opportunistic carnivore

Background

Human-induced changes to ecosystems transform the availability of resources to predators, including altering prey populations and increasing access to anthropogenic foods. Opportunistic predators are likely to respond to altered food resources by changing the proportion of food they hunt versus scavenge. These shifts in foraging behavior will affect species interactions through multiple pathways, including by changing other aspects of predator behavior such as boldness, innovation, and social structure.

Methods

To understand how foraging behavior impacts predator behavior, we conducted a controlled experiment to simulate hunting by introducing a prey model to captive coyotes (Canis latrans) and compared their behavior to coyotes that continued to scavenge over one year. We used focal observations to construct behavioral budgets, and conducted novel object, puzzle box, and conspecific tests to evaluate boldness, innovation, and response to conspecifics.

Results

We documented increased time spent resting by hunting coyotes paired with decreased time spent active. Hunting coyotes increased boldness and persistence but there were no changes in innovation. Our results illustrate how foraging behavior can impact other aspects of behavior, with potential ecological consequences to predator ecology, predator-prey dynamics, and human-wildlife conflict; however, the captive nature of our study limits specific conclusions related to wild predators. We conclude that human-induced behavioral changes could have cascading ecological implications that are not fully understood.

Sampling bias exaggerates a textbook example of a trophic cascade

Understanding trophic cascades in terrestrial wildlife communities is a major challenge because these systems are difficult to sample properly. We show how a tradition of non-random sampling has confounded this understanding in a textbook system (Yellowstone National Park) where carnivore [Canis lupus (wolf)] recovery is associated with a trophic cascade involving changes in herbivore [Cervus canadensis (elk)] behaviour and density that promote plant regeneration. Long-term data indicate a practice of sampling only the tallest young plants overestimated regeneration of overstory aspen (Populus tremuloides) by a factor of 4-7 compared to random sampling because it favoured plants taller than the preferred browsing height of elk and overlooked non-regenerating aspen stands. Random sampling described a trophic cascade, but it was weaker than the one that non-random sampling described. Our findings highlight the critical importance of basic sampling principles (e.g. randomisation) for achieving an accurate understanding of trophic cascades in terrestrial wildlife systems.

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.

Light exposure mediates circadian rhythms of rhizosphere microbial communities

Microbial community circadian rhythms have a broad influence on host health and even though light-induced environmental fluctuations could regulate microbial communities, the contribution of light to the circadian rhythms of rhizosphere microbial communities has received little attention. To address this gap, we monitored diel changes in the microbial communities in rice (Oryza sativa L.) rhizosphere soil under light-dark and constant dark regimes, identifying microbes with circadian rhythms caused by light exposure and microbial circadian clocks, respectively. While rhizosphere microbial communities displayed circadian rhythms under light-dark and constant dark regimes, taxa possessing circadian rhythms under the two conditions were dissimilar. Light exposure concealed microbial circadian clocks as a regulatory driver, leading to fewer ecological niches in light versus dark communities. These findings disentangle regulation mechanisms for circadian rhythms in the rice rhizosphere microbial communities and highlight the role of light-induced regulation of rhizosphere microbial communities.

Behavioral effects of wolf presence on moose habitat selection: testing the landscape of fear hypothesis in an anthropogenic landscape

Landscape of fear refers to the spatial variation in prey perception of predation risk, that under certain conditions, may lead to changes in their behavior. Behavioral responses of prey in relation to large carnivore predation risk have mainly been conducted in areas with low anthropogenic impact. We used long-term data on the distribution of moose in different habitat types in a system characterized by intensive management of all three trophic levels (silviculture, harvest of wolves and moose) to study effects on moose habitat selection resulting from the return of an apex predator, the wolf. We assumed that coursing predators such as wolves will cause an increased risk for moose in some habitat types and tested the hypotheses that moose will avoid open or young forest habitats following wolf establishment. After wolf recolonization, moose reduced their use of one type of open habitat (bog) but there was neither change in the use of the other open habitat type (clear-cut), nor in their use of young forest. Wolf establishment did not influence the use of habitat close to dense habitat when being in open habitats. Thus, the effect of wolves varied among habitat types and there was no unidirectional support for a behavioral effect of wolves' establishment on moose habitat use. Human-driven habitat heterogeneity, concentration of moose forage to certain habitat types, and the effects of a multiple predator guild on moose may all contribute to the results found. We conclude that the landscape of fear is likely to have weak ecological effects on moose in this system.

Wolves choose ambushing locations to counter and capitalize on the sensory abilities of their prey

Comprehensive knowledge of ambush behavior requires an understanding of where a predator expects prey to be, which is generally unknowable because ambush predators often hunt mobile prey that exhibit complex, irregular, or inconspicuous movements. Wolves (Canis lupus) are primarily cursorial predators, but they use ambush strategies to hunt beavers (Castor canadensis). Terrestrial beaver activity is predictable because beavers use well-defined, conspicuous habitat features repeatedly. Thus, studying where wolves wait-in-ambush for beavers provides a unique opportunity to understand how predators choose ambush locations in relation to prey activity. We searched 11 817 clusters of GPS locations from wolves in the Greater Voyageurs Ecosystem, International Falls, MN, and documented 748 ambushing sites and 214 instances where wolves killed beavers. Wolves chose ambush locations: 1) with olfactory concealment to avoid detection from the highly developed olfactory senses of beavers and 2) close (generally <5 m) to beaver habitat features to take advantage of beavers’ inability to visually detect motionless predators. Our work describes in detail the ambush strategies wolves use to hunt beavers and continues to overturn the traditional notion that wolves rely solely on cursorial hunting strategies. We also demonstrate that ambush predators can anticipate the movements and behavior of their prey due to a fundamental understanding of their prey’s sensory abilities. Wolves, therefore, and likely ambush predators in general, appear capable of simultaneously accounting for abiotic and biotic factors when choosing ambush locations, ultimately allowing them to counter and capitalize on the sensory abilities of their prey.

Dynamic interactions between apex predators reveal contrasting seasonal attraction patterns

Apex predators play important roles in ecosystem functioning and, where they coexist, intraguild interactions can have profound effects on trophic relationships. Interactions between predators range from intraguild predation and competition to facilitation through scavenging opportunities. Despite the increased availability of fine-scale GPS data, the determinants and outcomes of encounters between apex predators remain understudied. We used simultaneous GPS data from collared spotted hyaenas (Crocuta crocuta) and African lions (Panthera leo) in Hwange National Park, Zimbabwe, to determine the environmental conditions of the encounters between the two species, which species provoked the encounter, and which species dominated the encounter. Our results show that encounters between hyaenas and lions are mostly resource-related (over a carcass or around waterholes). In the wet season, encounters mainly occur at a carcass, with lions being dominant over its access. In the dry season, encounters mainly occur in the absence of a carcass and near waterholes. Movements of hyaenas and lions before, during, and after these dry-season encounters suggest two interference scenarios: a passive interference scenario whereby both predators would be attracted to waterholes but lions would leave a waterhole used by hyaenas because of prey disturbance, and an active interference scenario whereby hyaenas would actively chase lions from waterhole areas, which are prime hunting grounds. This study highlights the seasonal dynamics of predator interactions and illustrates how the relative importance of negative interactions (interference competition during the dry season) and positive interactions (scavenging opportunities during the wet season) shifts over the course of the year.

Group density, disease, and season shape territory size and overlap of social carnivores

The spatial organization of a population can influence the spread of information, behaviour and pathogens. Group territory size and territory overlap and components of spatial organization, provide key information as these metrics may be indicators of habitat quality, resource dispersion, contact rates and environmental risk (e.g. indirectly transmitted pathogens). Furthermore, sociality and behaviour can also shape space use, and subsequently, how space use and habitat quality together impact demography. Our study aims to identify factors shaping the spatial organization of wildlife populations and assess the impact of epizootics on space use. We further aim to explore the mechanisms by which disease perturbations could cause changes in spatial organization. Here we assessed the seasonal spatial organization of Serengeti lions and Yellowstone wolves at the group level. We use network analysis to describe spatial organization and connectivity of social groups. We then examine the factors predicting mean territory size and mean territory overlap for each population using generalized additive models. We demonstrate that lions and wolves were similar in that group-level factors, such as number of groups and shaped spatial organization more than population-level factors, such as population density. Factors shaping territory size were slightly different than factors shaping territory overlap; for example, wolf pack size was an important predictor of territory overlap, but not territory size. Lion spatial networks were more highly connected, while wolf spatial networks varied seasonally. We found that resource dispersion may be more important for driving territory size and overlap for wolves than for lions. Additionally, canine distemper epizootics may have altered lion spatial organization, highlighting the importance of including infectious disease epizootics in studies of behavioural and movement ecology. We provide insight about when we might expect to observe the impacts of resource dispersion, disease perturbations, and other ecological factors on spatial organization. Our work highlights the importance of monitoring and managing social carnivore populations at the group level. Future research should elucidate the complex relationships between demographics, social and spatial structure, abiotic and biotic conditions and pathogen infections.

Humans disrupt access to prey for large African carnivores

Wildlife respond to human presence by adjusting their temporal niche, possibly modifying encounter rates among species and trophic dynamics that structure communities. We assessed wildlife diel activity responses to human presence and consequential changes in predator-prey overlap using 11,111 detections of 3 large carnivores and 11 ungulates across 21,430 camera trap-nights in West Africa. Over two-thirds of species exhibited diel responses to mainly diurnal human presence, with ungulate nocturnal activity increasing by 7.1%. Rather than traditional pairwise predator-prey diel comparisons, we considered spatiotemporally explicit predator access to several prey resources to evaluate community-level trophic responses to human presence. Although leopard prey access was not affected by humans, lion and spotted hyena access to three prey species significantly increased when prey increased their nocturnal activity to avoid humans. Human presence considerably influenced the composition of available prey, with implications for prey selection, demonstrating how humans perturb ecological processes via behavioral modifications.

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.

Where and when to hunt? Decomposing predation success of an ambush carnivore

Predator-prey games emerge when predators and prey dynamically respond to the behavior of one another, driving the outcomes of predator-prey interactions. Predation success is a function of the combined probabilities of encountering and capturing prey, which are influenced by both prey behavior and environmental features. While the relative importance of encounter and capture probabilities have been evaluated in a spatial framework, temporal variation in prey behavior and intrinsic catchability are likely to also affect the distribution of predation events. Using a single-predator-single-prey (puma-vicuña) system, we evaluated which factors predict predation events across both temporal and spatial dimensions of the components of predation by testing the prey-abundance hypothesis (predators select for high encounter probability) and the prey-catchability hypothesis (predators select for high relative capture probability) in time and space. We found that for both temporal and spatial analyses, neither the prey-abundance hypothesis nor the prey-catchability hypothesis alone predicted kill frequency or distribution; puma kill frequency was static throughout the diel cycle and pumas consistently selected a single habitat type when hunting, despite temporal and spatial variation in encounter rates and intrinsic catchability. Our integrated spatiotemporal analysis revealed that an interaction between time of day and habitat influences kill probability, suggesting that trade-offs in the temporal and spatial components of predation drive the probability of predation events. These findings reinforce the importance of examining both the temporal and spatial patterns of the components of predation, rather than unidimensional measures of predator or prey behavior, to comprehensively describe the feedbacks between predator and prey in the predator-prey game.

Evolution of ungulate mating systems: Integrating social and environmental factors

Ungulates exhibit diverse mating systems that range from monogamous pair territories to highly polygynous leks. We review mating systems and behaviors across ungulates and offer a new approach synthesizing how interacting factors may shape those mating systems. Variability exists in mating systems among and within species of ungulates and likely is affected by predation risk, availability of resources (food and mates), habitat structure, and sociality. Ungulate mating systems may be labile as a consequence of the varying strength of those interacting factors. In addition, degree of polygyny and sexual dimorphism in size are associated with the evolution of mating systems. Neither male-male combat nor paternal care, however, can completely explain differences in sexual size dimorphism for ungulates, a necessary component in understanding the development of some mating systems. Whatever the evolutionary pathway, sexual segregation limits paternal care allowing more intense male-male competition. Selection of habitat structure, because it modifies risk of predation, is a major determinant of sociality for ungulates. Likewise, ruggedness and steepness of terrain limit the types of mating systems that can occur because of limitations in group size and cohesiveness, as well as the ability of males to herd even small groups of females effectively. The quality and defensibility of resources affect mating systems, as does the defensibility of females. Population density of females also may be a critical determinant of the types of mating systems that develop. Size of groups likewise constrains the types of mating tactics that males can employ. Our aim was to use those relationships to create a broad conceptual model that predicts how various environmental and social factors interact to structure mating systems in ungulates. This model provides a useful framework for future tests of the roles of both ecological and social conditions in influencing the social systems of ungulates.