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A central debate in ecology has been the long-running discussion on the role of apex predators in affecting the abundance and dynamics of their prey. In terrestrial systems, research has primarily relied on correlational approaches, due to the challenge of implementing robust experiments with replication and appropriate controls. A consequence of this is that we largely suffer from a lack of mechanistic understanding of the population dynamics of interacting species, which can be surprisingly complex. Mechanistic models offer an opportunity to examine the causes and consequences of some of this complexity. We present a bioenergetic mechanistic model of a tritrophic system where the primary vegetation resource follows a seasonal growth function, and the herbivore and carnivore species are modeled using two integral projection models (IPMs) with body mass as the phenotypic trait. Within each IPM, the demographic functions are structured according to bioenergetic principles, describing how animals acquire and transform resources into body mass, energy reserves, and breeding potential. We parameterize this model to reproduce the population dynamics of grass, elk, and wolves in northern Yellowstone National Park (USA) and investigate the impact of wolf reintroduction on the system. Our model generated predictions that closely matched the observed population sizes of elk and wolf in Yellowstone prior to and following wolf reintroduction. The introduction of wolves into our basal grass-elk bioenergetic model resulted in a population of 99 wolves and a reduction in elk numbers by 61% (from 14,948 to 5823) at equilibrium. In turn, vegetation biomass increased by approximately 25% in the growing season and more than threefold in the nongrowing season. The addition of wolves to the model caused the elk population to switch from being food-limited to being predator-limited and had a stabilizing effect on elk numbers across different years. Wolf predation also led to a shift in the phenotypic composition of the elk population via a small increase in elk average body mass. Our model represents a novel approach to the study of predator-prey interactions, and demonstrates that explicitly considering and linking bioenergetics, population demography and body mass phenotypes can provide novel insights into the mechanisms behind complex ecosystem processes., (© 2023 The Authors. Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.)

Aspen sapling recruitment increased as browsing by elk decreased, following the 1995-96 reintroduction of wolves in Yellowstone National Park. We address claims by Brice et al. (2021) that previous studies exaggerated recent aspen recovery. We conclude that their results actually supported previous work showing a trophic cascade benefiting aspen., (© 2023 The Authors. Ecology Letters published by John Wiley & Sons Ltd.)

Migration is an adaptive life-history strategy across taxa that helps individuals maximise fitness by obtaining forage and avoiding predation risk. The mechanisms driving migratory changes are poorly understood, and links between migratory behaviour, space use, and demographic consequences are rare. Here, we use a nearly 20-year record of individual-based monitoring of a large herbivore, elk (Cervus canadensis) to test hypotheses for changing patterns of migration in and adjacent to a large protected area in Banff National Park (BNP), Canada. We test whether bottom-up (forage quality) or top-down (predation risk) factors explained trends in (i) the proportion of individuals using 5 different migratory tactics, (ii) differences in survival rates of migratory tactics during migration and whilst on summer ranges, (iii) cause-specific mortality by wolves and grizzly bears, and (iv) population abundance. We found dramatic shifts in migration consistent with behavioural plasticity in individual choice of annual migratory routes. Shifts were inconsistent with exposure to the bottom-up benefits of migration. Instead, exposure to landscape gradients in predation risk caused by exploitation outside the protected area drove migratory shifts. Carnivore exploitation outside the protected area led to higher survival rates for female elk remaining resident or migrating outside the protected area. Cause-specific mortality aligned with exposure to predation risk along migratory routes and summer ranges. Wolf predation risk was higher on migratory routes than summer ranges of montane-migrant tactics, but wolf predation risk traded-off with heightened risk from grizzly bears on summer ranges. A novel eastern migrant tactic emerged following a large forest fire that enhanced forage in an area with lower predation risk outside of the protected area. The changes in migratory behaviour translated to population abundance, where abundance of the montane-migratory tactics declined over time. The presence of diverse migratory life histories maintained a higher total population abundance than would have been the case with only one migratory tactic in the population. Our study demonstrates the complex ways in which migratory populations change over time through behavioural plasticity and associated demographic consequences because of individuals balancing predation risk and forage trade-offs., (© 2023 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.)

Although sampling the five tallest young aspen in a stand is useful for detecting the occurrence of any aspen recruitment, this technique overestimates the population response of aspen to wolf reintroduction. Our original conclusion that random sampling described a trophic cascade that was weaker than the one described by non-random sampling is unchanged., (© 2023 John Wiley & Sons Ltd.)

This is a Forum article in response to: Barber-Meyer, S. (2015) Trophic cascades from wolves to grizzly bears or changing abundance of bears and alternate foods? Journal of Animal Ecology, 83, doi: 10.1111/1365-2656.12338. We used multiple data sets and study areas as well as several lines of evidence to investigate potential trophic linkages in Yellowstone National Park. Our results suggest that a trophic cascade from wolves to elk to berry production to berry consumption by grizzly bears may now be underway in the Park., (© 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.)

Ecological theory predicts that the diffuse risk cues generated by wide-ranging, active predators should induce prey behavioural responses but not major, population- or community-level consequences. We evaluated the non-consumptive effects (NCEs) of an active predator, the grey wolf (Canis lupus), by simultaneously tracking wolves and the behaviour, body fat, and pregnancy of elk (Cervus elaphus), their primary prey in the Greater Yellowstone Ecosystem. When wolves approached within 1 km, elk increased their rates of movement, displacement and vigilance. Even in high-risk areas, however, these encounters occurred only once every 9 days. Ultimately, despite 20-fold variation in the frequency of encounters between wolves and individual elk, the risk of predation was not associated with elk body fat or pregnancy. Our findings suggest that the ecological consequences of actively hunting large carnivores, such as the wolf, are more likely transmitted by consumptive effects on prey survival than NCEs on prey behaviour., (© 2013 John Wiley & Sons Ltd/CNRS.)

The removal or addition of a predator in an ecosystem can trigger a trophic cascade, whereby the predator indirectly influences plants and/or abiotic processes via direct effects on its herbivore prey. A trophic cascade can operate through a density‐mediated indirect effect (DMIE), where the predator reduces herbivore density via predation, and/or through a trait‐mediated indirect effect (TMIE), where the predator induces an herbivore trait response that modifies the herbivore's effect on plants. Manipulative experiments suggest that TMIEs are an equivalent or more important driver of trophic cascades than are DMIEs. Whether this applies generally in nature is uncertain because few studies have directly compared the magnitudes of TMIEs and DMIEs on natural unmanipulated field patterns. A TMIE is often invoked to explain the textbook trophic cascade involving wolves (Canis lupus), elk (Cervus canadensis), and aspen (Populus tremuloides) in northern Yellowstone National Park. This hypothesis posits that wolves indirectly increase recruitment of young aspen into the overstory primarily through reduced elk browsing in response to spatial variation in wolf predation risk rather than through reduced elk population density. To test this hypothesis, we compared the effects of spatiotemporal variation in wolf predation risk and temporal variation in elk population density on unmanipulated patterns of browsing and recruitment of young aspen across 113 aspen stands over a 21‐year period (1999–2019) in northern Yellowstone National Park. Only 2 of 10 indices of wolf predation risk had statistically meaningful effects on browsing and recruitment of young aspen, and these effects were 8–28 times weaker than the effect of elk density. To the extent that temporal variation in elk density was attributable to wolf predation, our results suggest that the wolf–elk–aspen trophic cascade was primarily density‐mediated rather than trait‐mediated. This aligns with the alternative hypothesis that wolves and other actively hunting predators with broad habitat domains cause DMIEs to dominate whenever prey, such as elk, also have a broad habitat domain. For at least this type of predator–prey community, our study suggests that risk‐induced trait responses can be abstracted or ignored while still achieving an accurate understanding of trophic cascades. [ABSTRACT FROM AUTHOR]

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'. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Modification of food webs is a frequent cause of shifts in ecosystem states that resist reversal when the food web is restored to its original condition. We used the restoration of the large carnivore guild including gray wolves (Canis lupis), cougars (Felis concolor), and grizzly bears (Ursus arctos horribilis) to the northern range of Yellowstone National Park as a model system to understand how ecosystems might resist reconfiguration after the restoration of apex predators to the food web. The absence of wolves, cougars, and grizzly bears for nearly a century from the northern range was the primary cause of dramatic changes in riparian plant communities. Willows (Salix spp.) were suppressed in height by intense browsing by the dominant herbivore, elk (Cervus canadensis). The loss of activity by beavers (Castor canadensis) coincided with the loss of tall willows. We hypothesized that intense elk browsing interrupted the mutualism between willow and beavers: ecosystem engineering by beavers was a critical component of willow habitat and tall willows were a critical component of habitat for beavers. This interruption made riparian communities resilient to the disturbance caused by the restoration of apex predators. We hypothesized further that reductions in elk browsing attributable to reductions in elk population size were not sufficient to prevent the suppression of willow growth. To test these hypotheses, we conducted a 20‐year, factorial experiment that crossed simulated beaver dams with the exclusion of browsing. We found that willows grew to heights expected for restored communities only in the presence of dams and reduced browsing. Willows experiencing ambient conditions remained well below this expectation. We found no difference in heights or growth rates of willows in experimental controls and willows in 21 randomly chosen sites, confirming that the results of the experiment were representative of range‐wide conditions. A reorganized community of large herbivores was implicated in the suppression of willow growth. We conclude that the restoration of large carnivores to the food web failed to restore riparian plant communities on Yellowstone's northern range, supporting the hypothesis that this ecosystem is in an alternative stable state caused primarily by the extirpation of apex predators during the early 20th century. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This article discusses a study conducted in northeastern Washington, USA, which examined the survival and movement of elk, cougars, and wolves. The study found that during the day, elk avoided humans, who were responsible for 80% of adult female elk mortality. At night, elk used areas near humans, reducing their proximity to wolves but not cougars. The research highlights the impact of humans on predator-prey interactions in managed landscapes. [Extracted from the article]

Mexican gray wolf (Canis lupus baileyi) reintroduction began in 1998 in Arizona, USA, with 11 individuals initially; wolves from this population dispersed into New Mexico, USA, the following year. Numbers of wolves have steadily increased (≥241 individuals in Dec 2022) and the size of the recovery area has expanded in both states. Understanding kill rates is fundamental to the recovery and management of Mexican wolves to properly maintain a healthy and sustainable population of wolves and their prey species. We used global positioning system (GPS) cluster analysis to locate kill sites and estimate kill rates on native ungulate prey taken in the recovery area by 10 Mexican wolf groups during winter (15 Feb–15 Mar) and 8 wolf groups during summer (15 Jun–15 Jul) in 2015–2017. Elk (Cervus canadensis) composed 94% of the native ungulates documented at Mexican wolf kill sites (n = 139); the remaining 6% were mule deer (Odocoileus hemionus; n = 9). Two‐thirds of all wolf‐killed native ungulates were elk calves. We estimated kill rates as ungulate biomass killed/wolf/day. From combined results for all years, we estimated that each Mexican wolf killed on average 9.0 ± 5.4 kg (±95% CI) of ungulate biomass per day during winter and 7.8 ± 6.2 kg during the summer. Our estimates of kill rates could be overestimated if Mexican wolves obtained a substantial amount of their biomass from scavenging, particularly during 4 months of hunting seasons (Sep–Dec) not captured in winter and summer. Using data from the first 2 years of the study (2015, 2016), we developed a logistic regression model to predict probability of an elk kill occurring at a GPS cluster as a function of hours spent by a collared wolf at that GPS cluster and size of the wolf group. Applying this model to the final year of the study (2017) resulted in similar numbers of predicted (n = 16.1 and 27.2 in winter and summer, respectively) and observed numbers (n = 15 and 26) of elk kills. Additionally, the demographic composition of the 2017 elk kills closely matched that of the previous 2 years. The results of this study indicate similar predation patterns of Mexican wolves to those of wolves in northern locations and can help wildlife managers plan for potential effects from a larger population of wolves across a broad area in Arizona and New Mexico. [ABSTRACT FROM AUTHOR]

Increasing resource extraction and human activity are reshaping species' spatial distributions in human‐altered landscape and consequently shaping the dynamics of interspecific interactions, such as between predators and prey. To evaluate the effects of industrial features and human activity on the occurrence of wolves (Canis lupus), we used wildlife detection data collected in 2014 from an array of 122 remote wildlife camera traps in Alberta's Rocky Mountains and foothills near Hinton, Canada. Using generalized linear models, we compared the occurrence frequency of wolves at camera sites to natural land cover, industrial disturbance (forestry and oil/gas exploration), human activity (motorized and non‐motorized), and prey availability (moose, Alces alces; elk, Cervus elaphus; mule deer, Odocoileus hemionus; and white‐tailed deer, Odocoileus virginianus). Industrial block features (well sites and cutblocks) and prey (elk or mule deer) availability interacted to influence wolf occurrence, but models including motorized and non‐motorized human activity were not strongly supported. Wolves occurred infrequently at sites with high densities of well sites and cutblocks, except when elk or mule deer were frequently detected. Our results suggest that wolves risk using industrial block features when prey occur frequently to increase predation opportunities, but otherwise avoid them due to risk of human encounters. Effective management of wolves in anthropogenically altered landscapes thus requires the simultaneous consideration of industrial block features and populations of elk and mule deer. [ABSTRACT FROM AUTHOR]

Conversion of land for settlements and agriculture is increasing globally and can influence wildlife space use. However, there is limited research to identify the thresholds of land‐use change that incur wildlife avoidance and how these thresholds might vary across levels of selection.We evaluated multi‐level avoidance thresholds of elk Cervus canadensis impacted by residential development and irrigated agriculture across the Greater Yellowstone Ecosystem in Idaho, Montana and Wyoming. Using GPS data from 765 elk in 21 herds, we estimated habitat selection in relation to development and agriculture at three levels (home range selection, within home range selection and movement path selection). Next, using individual selection covariates and associated measures of land‐use availability, we used functional‐response models to evaluate how selection varied based on availability, and in turn, to estimate avoidance thresholds.We found individual and level‐specific variation in elk responses to environmental factors. Elk exhibited stronger responses (either selection or avoidance) when selecting home range locations (i.e. second‐order selection) than when selecting areas within home ranges (i.e. third‐order selection) or selecting movement paths (i.e. fourth‐order selection). Importantly, elk avoidance of development and agriculture changed as the amount of land in these categories changed. Across all levels of selection elk exhibited neutral selection for human development at low levels of availability (<1.1%–2.2% developed) but avoided areas that were >1.1%–2.2% developed. Conversely, elk selected positively for irrigated agriculture at low to moderate levels of availability (<52.0%–66.2% agriculture) but exhibited neutral selection in areas that were >52.0%–66.2% agriculture.Synthesis and applications. Elk avoidance of low levels of human development suggests conservation efforts such as restrictions on future development or conservation easements could focus on areas that are still below 2% developed. Additionally, because elk selection was strongest at the landscape scale, conservation actions that are based on information about the overall landscape structure may be most impactful. Our results highlight the importance of understanding variability in wildlife habitat selection at multiple levels, particularly in relation to land‐use change, and highlight how functional response modelling can help inform landscape conservation. [ABSTRACT FROM AUTHOR]

Migration is a behavioral strategy used by many ungulates to access resources and avoid predation in heterogenous landscapes. If migratory individuals access higher quality forage and avoid predation, then they should attain greater fitness. Migration can also expose individuals following distinct migratory tactics to differential mortality and harvest. We investigated how transboundary migration affected male elk (Cervus canadensis) survival and antler size when subjected to harvest with different antler point restrictions (APRs) and year‐round harvest by treaty First Nations in a multi‐carnivore system in Alberta, Canada. We measured antler size and age for 35 unmarked, harvested male elk and 90 global positioning system (GPS)‐collared adult male elk. We also estimated radio‐collared elk survival and cause‐specific mortality (105 elk‐years) from 2018 to 2020. Antler size increased as a non‐linear function of age and exposure to high quality forage for migrants. The biological effect size of exposure to higher quality forage (i.e., lower biomass) obtained by migrants was variable but biologically equivalent to the antler size difference (i.e., 33–54 cm) predicted between 5‐ and 6‐year‐old male elk. Annual mortality rate was 0.304 and the primary cause of death was hunting (cumulative incidence functions [CIF] mortality rate = 0.203, n = 33 mortalities) of which a third was by First Nations treaty harvest (CIF = 0.101, n = 12). Non‐human‐caused mortality was rare (CIF = 0.015); only 2 males died because of predation by wolves (Canis lupus). Six‐point APRs resulted in lower annual survival rates (S = 0.42) for male elk with ≥6 antler points, which were usually >4 years of age. Harvest risk increased by 20% for every 1‐km closer to an access road. Elk harvested by licensed recreational or First Nations hunters were similar with respect to male elk age, antler size, date, and location. There was very little evidence that multiple species of large carnivores influenced male elk survival. These results indicate forage quality and vulnerability to harvest by humans influence male elk age structure, and hence antler size, of transboundary and partially migratory populations, even in carnivore‐rich complex systems. [ABSTRACT FROM AUTHOR]

A study challenges the idea that wolves in Yellowstone National Park created a "landscape of fear" that allowed vegetation to recover by scaring elk away from their favorite dining spots. Instead, the impact on elk behavior was found to be weak, with a guild of predators, including human hunters, playing a significant role in reducing elk numbers and allowing vegetation to partly recover. The study suggests that the park's ecosystem has only patchily recovered, with aspen trees still struggling to grow into mature forests. The findings provide evidence that wolf effects on Yellowstone's aspen are likely weaker than previously thought, but the complex interactions in the ecosystem make it difficult to draw definitive conclusions. [Extracted from the article]

Gray Wolves (Canis lupus) are territorial, group living carnivores that live in packs typically consisting of a dominant breeding pair and their offspring. Breeding tenures are relatively short and competitive, with vacancies usually occurring following a breeder's death, and are often filled by unrelated immigrants or by relatives of the previous breeder. The frequency and conditions of active breeder displacements are poorly understood. Position changes in the dominance hierarchy are common yet rarely documented in detail. We describe a male breeding position turnover in a wolf pack by males from a neighboring pack in mid-summer 2016 in Yellowstone National Park. Over the course of two months, three males from the Mollie's pack displaced the breeding male of the neighboring Wapiti Lake pack, joined the pack's two adult females, and subsequently raised the previous male's four approximately three-month old pups. In the five years following the displacement (2017 to 2021), at least one of the intruding males has successfully bred with the dominant female and most years with a subordinate female (who was one of the pups at the time of displacement). The pack reared pups to adulthood each year. Male breeding displacements are likely influenced by male-male competition and female mate choice. These changes are the result of individuals competing to improve breeding position and may lead to increased pack stability and greater reproductive success. We report in detail on the behavior of a closely observed breeding displacement and we discuss the adaptive benefits of the change. [ABSTRACT FROM AUTHOR]

Large predators often are believed to cause declines in hunter harvests of ungulates due to direct competition for prey with hunters. In Alberta, predators of elk (Cervus elaphus), including grizzly bear (Ursus arctos), cougar (Puma concolor), and wolf (Canis lupus), have increased in recent years. We used trend analysis replicated by Wildlife Management Unit (WMU) to examine regional trends in elk harvest and hunter success. Over a 26-yr period, average harvest of elk increased by 5.46% per year for unrestricted bull and by 6.64% per year for limited-quota seasons. Also, over the same time frame, average hunter success increased by 0.2% per year for unrestricted bull and by 0.3% per year for limited-quota seasons, but no trend was detected in hunter effort (P>0.05). Our results show that increasing large-predator populations do not necessarily reduce hunter harvest of elk, and we only found evidence for this in Alberta's mountain WMUs where predation on elk calves has reduced recruitment. Furthermore, data indicate that Alberta's elk harvest management has been sustainable, i.e., hunting has continued while populations of elk have increased throughout most of the province. Wildlife agencies can justify commitments to long-term population monitoring because data allow adaptive management and can inform stakeholders on the status of populations. [ABSTRACT FROM AUTHOR]

Predators use different spatial tactics to track the prey on the landscape. Three hypotheses describe spatial tactics: prey abundance for prey that are aggregated in space; prey habitat for uniformly distributed prey; and prey catchability for prey that are difficult to catch and kill. The gray wolf (Canis lupus) is a generalist predator that likely employs more than one spatial hunting tactic to match their diverse prey with distinct distributions and behavior that are available. We conducted a study on 17 GPS collared wolves in 6 packs in Riding Mountain National Park, Manitoba, Canada where wolves prey on moose (Alces alces) and elk (Cervus canadensis). We evaluated wolf selection for prey density, habitat selection and catchability on the landscape through within-territory habitat selection analysis. We reveal support for both the prey habitat and prey catchability hypotheses. For moose, their primary prey, wolves employed a mixed habitat and catchability tactic. Wolves used spaces described by the intersection of moose habitat and moose catchability. Wolves selected for the catchability of elk, their secondary prey, but not elk habitat. Counter to our predictions, wolves avoided areas of moose and elk density, likely highlighting the ongoing space race between predator and prey. We illustrate that of the three hypotheses the primary driver was prey catchability, where the interplay of both prey habitat with catchability culminate in predator spatial behaviour in a multiprey system. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hunters support scavengers with seasonal pulses of carrion. If those hunters also deploy remote cameras at kill sites, they could simultaneously contribute data to wildlife research while gaining first‐hand knowledge of scavenger ecology. In 2018–2020, we recruited hunters to monitor carcasses and offal with remote cameras across western Montana, USA. We increased our sampling effort by also setting up cameras following successful elk (Cervus canadensis) hunts at a private ranch. Cameras recorded 19 scavenger species. Golden eagles (Aquila chrysaetos) appeared at 55% of sites, and 3 individuals wore auxiliary markers, demonstrating how hunters can augment efforts to detect tagged wildlife. Cameras also documented elusive predators (e.g., wolves [Canis lupus]) and a seasonality of scavenging among American black bears (Ursus americanus). At 42% of the sites, ≥1 cervid investigated the carrion within 1 m, a behavior that may transmit the prions associated with chronic wasting disease. Hunters are willing and competent citizen scientists that can help generate wildlife observations at a broad spatial scale. [ABSTRACT FROM AUTHOR]

Personality in wildlife has been linked to several ecological processes including mortality risk, facultative migration, and behavioral plasticity. In this paper I examined the relationship between personality and antipredator tactics exhibited by 20 wild female elk (Cervus canadensis) in Jasper National Park, Alberta. Two observers conducted 106 separate chases designed explicitly to resemble predator pursuits by wolves, the main predator of elk. We quantified and classified elk tactical responses during each chase. Elk with "shy" type personalities responded to 84% of predatorresembling pursuits by employing speed-based tactics to outrun pursuers or rejoin conspecifics. Elk with "bold" type personalities adopted this tactic just 11% of the time, and instead employed tactics where they stopped and evaluated pursuers in 45% of chases, attempted to hide from pursuers in 19% of chases, and turned aggressively toward pursuers in 17% of chases. Bold animals employed a greater variety of tactics overall and were more likely to try multiple tactics within the same 10-min chase. Shyness was also positively correlated with flight initiation distance at the start of chases. These results are important for wildlife managers who may be artificially and unwittingly selecting against certain personalities and thereby influencing management and conservation outcomes. [ABSTRACT FROM AUTHOR]

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

There is growing evidence that prey perceive the risk of predation and alter their behavior in response, resulting in changes in spatial distribution and potential fitness consequences. Previous approaches to mapping predation risk across a landscape quantify predator space use to estimate potential predator‐prey encounters, yet this approach does not account for successful predator attack resulting in prey mortality. An exception is a prey kill site that reflects an encounter resulting in mortality, but obtaining information on kill sites is expensive and requires time to accumulate adequate sample sizes.We illustrate an alternative approach using predator scat locations and their contents to quantify spatial predation risk for elk (Cervus canadensis) from multiple predators in the Rocky Mountains of Alberta, Canada. We surveyed over 1300 km to detect scats of bears (Ursus arctos/U. americanus), cougars (Puma concolor), coyotes (Canis latrans), and wolves (C. lupus). To derive spatial predation risk, we combined predictions of scat‐based resource selection functions (RSFs) weighted by predator abundance with predictions that a predator‐specific scat in a location contained elk. We evaluated the scat‐based predictions of predation risk by correlating them to predictions based on elk kill sites. We also compared scat‐based predation risk on summer ranges of elk following three migratory tactics for consistency with telemetry‐based metrics of predation risk and cause‐specific mortality of elk.We found a strong correlation between the scat‐based approach presented here and predation risk predicted by kill sites and (r =.98, p <.001). Elk migrating east of the Ya Ha Tinda winter range were exposed to the highest predation risk from cougars, resident elk summering on the Ya Ha Tinda winter range were exposed to the highest predation risk from wolves and coyotes, and elk migrating west to summer in Banff National Park were exposed to highest risk of encountering bears, but it was less likely to find elk in bear scats than in other areas. These patterns were consistent with previous estimates of spatial risk based on telemetry of collared predators and recent cause‐specific mortality patterns in elk.A scat‐based approach can provide a cost‐efficient alternative to kill sites of quantifying broad‐scale, spatial patterns in risk of predation for prey particularly in multiple predator species systems. [ABSTRACT FROM AUTHOR]

Predator–prey interactions are among the most fundamental of ecological relationships. Recolonizing gray wolf (Canis lupus Linnaeus, 1758) populations present new challenges for wildlife management in multi-prey, multi-carnivore systems. We documented diet composition and kill rates for wolves in a recently recolonized area over winter and summer seasons (2014–2015). Elk (Cervus canadensis Erxleben, 1777) were the primary ungulate prey (63%) located at wolf kill sites. Deer (mule deer (Odocoileus hemionus (Rafinesque, 1817)) and white-tailed deer (Odocoileus virginianus (Zimmermann, 1780))) were less prevalent than elk in wolf diets, but the amount of deer in diets (40%–50%) varied by pack and season. Juvenile elk were the most prevalent class of prey in wolf diets during summer (63.3%) and winter (36.3%), with adult elk (32.5%) observed nearly as often as juveniles in winter. Kill rates varied by season, with rates 2.3 times higher in summer (mean = 3.5 ungulates/week per pack) than winter (mean = 1.5 ungulates/week per pack), consistent with increased availability and use of neonate prey. Prey biomass acquisition did not vary by pack or season (summer = 243 kg/week per pack; winter = 182 kg/week per pack). Our study quantified predation patterns for a recolonizing wolf population, and patterns that we documented were similar to other multi-prey systems in North America. [ABSTRACT FROM AUTHOR]

Loss of migratory behavior or shifts in migratory ranges are growing concerns to wildlife managers. How ungulates prioritize safety from predators at the expense of high‐quality foraging opportunities during calving may be key to understanding these shifts and long‐term reproductive success. We compared trade‐offs in selection for forage and predation risk by elk (Cervus canadensis) following 3 migratory tactics (western and eastern migration and resident) during 2 time periods in a declining (by almost 70% from 2002–2016), partially migratory elk population adjacent to Banff National Park in Alberta, Canada. We hypothesized that regardless of migratory tactic, maternal elk would show stronger trade‐offs between high‐quality foraging associated with higher predation risk and forage resources of lower‐quality yet lower risk on calving ranges than on ranges used during summer because of vulnerability of their offspring. Additionally, we hypothesized these trade‐offs would occur at high (2002–2006) and low (2013–2016) elk population sizes. We used a machine‐learning algorithm to predict dates of parturition based on global positioning system (GPS) movements of elk equipped with vaginal implants (n = 60) and predictions were within 1.43 ± 0.85 (SE) days of the known date. We applied the model to an additional 58 GPS‐collared elk without vaginal implants. Based on changes in localized movements, we defined calving areas as the 26 days post‐parturition and compared habitat characteristics of calving areas to 10 similar‐sized areas centered on random locations during summer for the same individual in a latent selection framework. Across the 2 time periods, parturition occurred from 8 May–11 July with median parturition dates differing among migratory tactics and residents shifting towards an earlier parturition date in the later period. All elk, regardless of migratory tactic and time period, selected calving areas with greater forage resources than were available on areas used during summer, with no evidence for greater selection of areas that reduced predation risk at the expense of higher‐quality foraging. Calving season selection for areas with abundant forage exposed western migrants to high risk of bear (Ursus spp.) predation, residents to high risk of wolf (Canis lupus) predation, and eastern migrants to low risk of bear and wolf predation. Patterns in exposure to predation risk during calving between migratory tactics were consistent with the recent decline in western migrants and increase in eastern migrants, implying that conditions on calving areas contributed to observed changes in the number of elk following these tactics. © 2021 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Scavenging carrion is an important source of nutrition for Wolverines (Gulo gulo), which are facultative scavengers. Other large carnivores, particularly Gray Wolves (Canis lupus), may compete with and exclude Wolverines from carrion or pose a risk of death or injury to Wolverines attempting to consume these resources. We used a video-camera trap to document a Wolverine scavenging an Elk (Cervus elaphus) being actively consumed by a Gray Wolf in Idaho. The Wolverine investigated the kill, ate, scent marked, and removed pieces of the carcass to cache at other sites. Between the 2nd and 3rd visit by the Wolverine, a wolf returns to feed at the kill. These observations establish that Wolverines do not necessarily avoid kills when Gray Wolves are present and that species interactions are more complex than generally thought. [ABSTRACT FROM AUTHOR]

In the Northern Rockies of the United States, predators like wolves (Canis lupus) and mountain lions (Puma concolor) have been implicated in fluctuations or declines in populations of game species like elk (Cervus canadensis) and mule deer (Odocoileus hemionus). In particular, local distributions of these predators may affect ungulate behavior, use of space, and dynamics. Our goal was to develop generalizable predictions of habitat selection by wolves and mountain lions across western Montana. We hypothesized both predator species would select habitat that maximized their chances of encountering and killing ungulates and that minimized their chances of encountering humans. We assessed habitat selection by these predators during summer using within-home range (3rd order) resource selection functions (RSFs) in multiple study areas throughout western Montana, and tested how generalizable RSF predictions were by applying them to out-of-sample telemetry data from separate study areas. Selection for vegetation cover-types varied substantially among wolves in different study areas. Nonetheless, our predictions of 3rd order selection by wolves were highly generalizable across different study areas. Wolves consistently selected simple topography where ungulate prey may be more susceptible to their cursorial hunting mode. Topographic features may serve as better proxies of predation risk by wolves than vegetation cover-types. Predictions of mountain lion distribution were less generalizable. Use of rugged terrain by mountain lions varied across ecosystem-types, likely because mountain lions targeted the habitats of different prey species in each study area. Our findings suggest that features that facilitate the hunting mode of a predator (i.e. simple topography for cursorial predators and hiding cover for stalking predators) may be more generalizable predictors of their habitat selection than features associated with local prey densities. [ABSTRACT FROM AUTHOR]

Established in 1907, Jasper National Park (JNP) comprises 10,880 km2 of mountainous terrain in western Alberta, Canada. Its large mammals have been protected from hunting and trapping, but are subject to accidental collisions with vehicles and trains on the Yellowhead Highway and the Canadian National Railway (CNR) that transect JNP. This paper reviews the park's historical inventory of Elk (Cervus elaphus), Bighorn Sheep (Ovis Canadensis), and Gray Wolves (Canis lupus), and reports on their number killed by vehicles and trains from 1980 to 2018. Elk population estimates declined from 1000 in 1975 to 318 in 2018. An aerial survey of Bighorn Sheep flown in 2018 over all of JNPs sheep range recorded a decline of 58–62% compared to 1987. In the lower main valley, discrete bands of rams and ewes declined on 2 traditional winter ranges. The road and rail fatalities of Elk and sheep were superimposed on predation. In the late 1970s, wolves were estimated at 160, but reached an undetermined low in 2018 following year-round trapping on JNPs boundaries and accidental fatalities on the park's roads and railways. [ABSTRACT FROM AUTHOR]

While the functional response of predators is commonly measured, recent work has revealed that the age and sex composition of prey killed is often a better predictor of prey population dynamics because the reproductive value of adult females is usually higher than that of males or juveniles.Climate is often an important mediating factor in determining the composition of predator kills, but we currently lack a mechanistic understanding of how the multiple facets of climate interact with prey abundance and demography to influence the composition of predator kills.Over 20 winters, we monitored 17 wolf packs in Yellowstone National Park and recorded the sex, age and nutritional condition of kills of their dominant prey—elk—in both early and late winter periods when elk are in relatively good and relatively poor condition, respectively.Nutritional condition (as indicated by per cent marrow fat) of wolf‐killed elk varied markedly with summer plant productivity, snow water equivalent (SWE) and winter period. Moreover, marrow was poorer for wolf‐killed bulls and especially for calves than it was for cows.Wolf prey composition was influenced by a complex set of climatic and endogenous variables. In early winter, poor plant growth in either year t or t − 1, or relatively low elk abundance, increased the odds of wolves killing bulls relative to cows. Calves were most likely to get killed when elk abundance was high and when the forage productivity they experienced in utero was poor. In late winter, low SWE and a relatively large elk population increased the odds of wolves killing calves relative to cows, whereas low SWE and poor vegetation productivity 1 year prior together increased the likelihood of wolves killing a bull instead of a cow.Since climate has a strong influence on whether wolves prey on cows (who, depending on their age, are the key reproductive components of the population) or lower reproductive value of calves and bulls, our results suggest that climate can drive wolf predation to be more or less additive from year to year. [ABSTRACT FROM AUTHOR]

Understanding the behavioral responses of large carnivores to human activity in protected areas is important for conserving top predators. Roads and associated vehicle traffic have a range of impacts on wildlife, including mortality from vehicle collisions and behavioral changes from increasing traffic levels. Roads concentrate human activities and may be particularly impactful when located adjacent to high-quality habitat for wildlife. However, people often overlook road impacts in protected areas because of relatively low road densities. From 1979 to 2017, annual visits to Yellowstone National Park increased from 1.9 to 4.1 million, with many visitors in the last 25 yr focusing on the opportunity to view wild wolves (Canis lupus) in their natural habitat from the roadway. To better understand how human activity interacts with landscape attributes and prey availability to shape wolf habitat use, we developed seasonal and diel-specific step selection functions (SSF) for wolves. Wolves responded to increased human activity by using areas farther from roadways during the day and during peak visitation in summer. Prey availability, as estimated by an elk SSF, did not significantly alter habitat selection patterns by wolves. The strength of habitat selection in relation to roads varied among wolf packs. The most heavily viewed wolf packs exhibited less road avoidance, suggesting increased tolerance, which could lead to increased vulnerability to human harvest if they leave the park. Federal and state managers have implemented several measures to mitigate disturbance effects to wolves and curtail habituation. These results may inform adaptive management strategies that seek to continue to conserve natural wolf behavior. [ABSTRACT FROM AUTHOR]

The extent to which prey space use actively minimizes predation risk continues to ignite controversy. Methodological reasons that have hindered consensus include inconsistent measurements of predation risk, biased spatiotemporal scales at which responses are measured and lack of robust null expectations.We addressed all three challenges in a comprehensive analysis of the spatiotemporal responses of adult female elk (Cervus elaphus) to the risk of predation by wolves (Canis lupus) during winter in northern Yellowstone, USA.We quantified spatial overlap between the winter home ranges of GPS‐collared elk and three measures of predation risk: the intensity of wolf space use, the distribution of wolf‐killed elk and vegetation openness. We also assessed whether elk varied their use of areas characterized by more or less predation risk across hours of the day, and estimated encounter rates between simultaneous elk and wolf pack trajectories. We determined whether observed values were significantly lower than expected if elk movements were random with reference to predation risk using a null model approach.Although a small proportion of elk did show a tendency to minimize use of open vegetation at specific times of the day, overall we highlight a notable absence of spatiotemporal response by female elk to the risk of predation posed by wolves in northern Yellowstone.Our results suggest that predator–prey interactions may not always result in strong spatiotemporal patterns of avoidance. [ABSTRACT FROM AUTHOR]

Wolf (Canis lupus) diets and potential effects on prey have been a prominent subject of interest to wildlife researchers and managers since reintroduction into Yellowstone National Park, Wyoming, USA, in 1995 and 1996. Post‐reintroduction, wolves expanded south and recolonized areas in the southern Yellowstone ecosystem. Elk (Cervus elaphus) in this area are supplementally fed during winter (Dec–Mar) at state‐managed feedgrounds, resulting in high‐density congregations of elk. From December to March 2000–2007, we determined the winter predation patterns of wolves by examining the remains of 289 wolf kills on 3 state‐managed feedgrounds and adjacent winter range near Jackson, Wyoming. During winters 2002–2005, we also monitored the movements of radio‐collared elk on feedgrounds to describe the response of elk to the presence of wolf kills. Thirty‐seven percent (n = 106) of kills were located on elk feedgrounds where elk composition included 49% calves, 42% adult females, 5% adult males, and 5% unknown. Sixty‐three percent (n = 183) of kills were located on winter range adjacent to feedgrounds and prey species consisted of 90% elk (38% calves, 35% adult females, 24% adult males, 2% unknown), 9% moose (Alces alces; 13% calves, 69% adult females, 6% adult males, 1% unknown), 1% mule deer (Odocoileus hemionus; 1 fawn, 1 adult female), and 0.5% adult female bison (Bison bison). Mean age of elk killed on feedgrounds was 4.2 years (range = 0–20) and 4.6 years (range = 0–23) on winter range. Calves were selected more than available in most years with female elk killed less than expected. Adult males were killed more than expected in 2005–2007. Eighty‐eight percent (n = 198) of the time elk remained on the feedground even when wolves made a kill. Less commonly, elk left the feedground, gathered in larger herds on adjacent feedgrounds absent of wolves, and returned within a few days (6%, n = 13) or left the feedground for another feedground and did not return for the rest of the winter (6%; n = 14). Elk were less likely to leave feedgrounds in the presence of a wolf kill when there were more elk on that feedground. Elk left feedgrounds with greater topography and tree cover (Alkali and Fish Creek) and gathered on the flat, open feedgrounds (Patrol Cabin) more frequently than they left flat, open feedgrounds for feedgrounds with greater topography and tree cover. Our results indicate wolves in our study area primarily preyed on elk and exhibited a strong preference for elk calves. High‐density concentrations of elk on feedgrounds will continue to be an attractant for wolves. Although elk leave feedgrounds for reasons other than wolf presence, any displacement of elk from feedgrounds due to wolves will be temporary. State managers have the ability to alter management strategies (e.g., increasing wolf harvest, phasing out elk feeding, increasing the intensity of elk feeding) in an effort to affect predator‐prey relationships. © 2019 The Wildlife Society. We determined the winter diets of wolves near Jackson, Wyoming on 3 elk feedgrounds and adjacent winter range. We also monitored the movements of elk on feedgrounds in response of elk to the presence of wolf kills. Results indicated a preference for elk calves and when there were more elk on the feedground, elk were less likely leave the feedground when wolves made a kill. [ABSTRACT FROM AUTHOR]

Elk (Cervus canadensis) are high‐profile game animals for many states in the western United States, yet over the past several decades some populations have experienced a persistent and broad‐scale decline in recruitment. Over this same period, gray wolves (Canis lupus) have become an integral component of many western landscapes and agencies are increasingly challenged to maximize hunting opportunities of ungulates via predator management while simultaneously ensuring wolf conservation. To better understand the implications of predator management on elk populations, we monitored survival of 1,244 adult female elk and 806 6‐month‐old calves from 29 populations distributed throughout Idaho, USA, from 2004 to 2016. We developed predictive models of mortality that related mortality risk to wolf pack size, winter conditions, and individual‐level characteristics. Annual mortality rates (excluding harvest) for adult females and calves were 0.09 and 0.40, respectively. Calf mortality was predicted best with a model that included additive effects of chest girth at time of capture, mean size of surrounding wolf packs, and snow depth. Adult female mortality was predicted best with a model that included female age, mean size of surrounding wolf packs, and snow depth. Based on a sensitivity analysis, chest girth had the largest effect on risk of mortality for calves followed by pack size and snow depth. Other than the effect of senescence in the oldest (>15 yr) individuals, pack size and snow depth had the largest effect on risk of mortality for adult females. We estimated cause‐specific mortality and predation was the dominant cause of known‐fate mortalities for adult females (35% mountain lion [Puma concolor] and 32% wolf) and calves (45% mountain lion and 28% wolf), whereas malnutrition accounted for 9% and 10% of adult female and calf mortalities, respectively. Wolves preferentially selected smaller calves and older adult females, whereas mountain lions showed little preference for calf size or age class of adult females. Our study indicates managers can increase elk survival by reducing wolf pack sizes on surrounding winter ranges, especially in areas where, or during years when, snow is deep. Additionally, managers interested in improving over‐winter calf survival can implement actions to increase the size of calves entering winter by increasing the nutritional quality of summer and early fall forage resources. Although our study was prompted by management questions related to wolves, mountain lions killed more elk than wolves and differences in selection of individual elk indicate mountain lions may have comparably more of an effect on elk population dynamics. Although we were unable to relate changes in mountain lion populations to elk survival in our study, future research should seek a better understanding of multi‐predator systems, including how management of one predator affect others and ultimately how these interactions affect elk survival. © 2019 The Wildlife Society Elk survival (females and 6‐month‐old calves) in Idaho, USA, was negatively related to size of wolf packs and winter snow depth and size of calves was positively related to over‐winter survival. Because of the complexity of predator‐prey systems, the most effective strategy for improving elk populations will likely be one that recognizes multiple factors that influence elk survival including wolf and mountain lion predation and the nutritional quality of summer and early fall forage resources. [ABSTRACT FROM AUTHOR]

The reintroduction of gray wolves (Canis lupus) to Yellowstone National Park is the most celebrated ecological experiment in history. As predicted by population models, the rapid recovery of a wolf population caused both temporal and spatial variability in wolf–ungulate interactions that likewise generated temporal and spatial variation in the expression of trophic cascades. This has amplified spatial variation in vegetation in Yellowstone, particularly with willow (Salix spp.) and cottonwood (Populus spp.) in riparian areas, with associated changes in food webs. Increasing influences of grizzly bears (Ursus arctos), cougars (Puma concolor), and bison (Bison bison) are making what initially was predominantly an elk–wolf interaction into an increasingly complex system. Outside Yellowstone, however, humans have a dominant influence in western North America that overwhelms trophic cascades resulting in what appear to be bottom-up influences on community structure and function. Complex and unexpected ecosystem responses to wolf recovery in Yellowstone reinforce the value of national parks and other protected areas as ecological baseline reserves. [ABSTRACT FROM AUTHOR]

Despite encounter rates being a key component of kill rate, few studies of large carnivore predation have quantified encounter rates with prey, the factors that influence them, and the relationship between encounter rate and kill rate. The study’s primary motivation was to determine the relationship between prey density and encounter rate in understanding the mechanism behind the functional response. Elk (Cervus elaphus Linnaeus, 1758) population decline and variable weather in northern Yellowstone National Park provided an opportunity to examine how these factors influenced wolf (Canis lupus Linnaeus, 1758) encounter rates with elk. We explored how factors associated with wolf kill rate and encounter rate in other systems (season, elk density, elk group density, average elk group size, snow depth, wolf pack size, and territory size) influenced wolf–elk encounter rate in Yellowstone National Park. Elk density was the only factor significantly correlated with wolf–elk encounter rate, and we found a nonlinear density-dependent relationship that may be a mechanism for a functional response in this system. Encounter rate was correlated with number of elk killed during early winter but not late winter. Weak effects of snow depth and elk group size on encounter rate suggest that these factors influence kill rate via hunting success because kill rate is the product of hunting success and encounter rate. [ABSTRACT FROM AUTHOR]

Migration is expected to benefit individuals through exposure to higher quality forage and reducing predation rates more than non-migratory conspecifics. Previous studies of partially migratory ungulates (with migrant and resident individuals) have focused on bottom–up factors regulating resident and migrant segments, yet differential predation between strategies could also be a density-dependent regulatory mechanism. Our study tested for density-dependence in mortality, as well as mechanisms of bottom–up or top–down regulation in the resident and migrant portions of the partially migratory Ya Ha Tinda elk population. We tested for density dependence in adult female and juvenile survival rates, and then discriminated between predatorand food-regulation hypotheses by testing for density-dependence amongst mortality causes for adult female elk. Notably, the population declined almost 70% from near previously published estimates of carrying capacity over 10 years, providing ideal conditions to test for density dependence. In contrast to predictions, we found only weak support for density dependence in adult survival and juvenile survival. We also found few differences between migrant and resident elk in adult or juvenile survival, though juvenile survival differences were biologically significant. Predation by humans and grizzly bears was density dependent, but similar between migratory strategies. Predation by wolves was the leading known cause of mortality, yet remained constant with declining elk density equally for both migrant and resident elk, indicating wolf predation was density-independent. Instead of being strongly regulated by food or predation, we found adult female survival was driven by density-independent predation and climatic factors. The few differences between migratory strategies suggest equivalent fitness payoffs for migrants and residents. This population is being limited by density-independent predation leading to declines of both migratory strategies. Our results challenge classical predator–prey theory, and call for better integration between predator–prey and migration theory. [ABSTRACT FROM AUTHOR]

Throughout much of the 20th century, the heights of young quaking aspen ( Populus tremuloides ) in Yellowstone National Park’s northern ungulate winter range were suppressed due to intensive herbivory by Rocky Mountain elk ( Cervus elaphus ). However, following the 1995–96 reintroduction of gray wolves ( Canis lupus ), completing the park’s large predator guild, young aspen in various portions of the northern range began to increase in height. From 1999 to 2015, a 17-yr period of declining elk densities in the northern range, browsing rates declined and young aspen heights increased once elk densities dropped below ∼4 elk/km 2 . The inverse relationship between browsing rate and young aspen height, a relationship linking elk and plants, was consistent with a re-established trophic cascade. Within the Glen Creek study area (8.3 km 2 ), decreased browsing and increased heights of young aspen were associated, at least in part, with two hypothesized small-scale predation risk factors (i.e., escape impediment , view impediment ). However, the young aspen height increases did not occur in the Mammoth study area (6.0 km 2 ) and heights there remained short. With high levels of human activity at the Mammoth townsite, wolf activity near the townsite remained low, an example of “human shielding,” thereby allowing elk browsing to continue the suppression of young aspen. Overall, results indicated that Yellowstone’s contemporary large predator guild, by altering elk behavior and density at several spatial scales, has not only contributed to a relatively widespread pattern of increased young aspen heights across much of the park’s northern range, but also greater spatial variation in those heights. [ABSTRACT FROM AUTHOR]

Alveolar and cystic echinococcosis are emerging and reemerging in Europe, Africa, and Asia. The expansion of Echinococcus spp. tapeworms in wildlife host reservoirs appears to be driving this emergence in some areas. Recent studies suggest a similar phenomenon may be occurring in North America. We describe the context of Echinococcus spp. research in North America, with a specific focus on the contiguous United States. Although studies were conducted in the United States throughout the 1900s on various sylvatic and domestic Echinococcus spp. tapeworm cycles, data are lacking for the past ≈30 years. We review previous research, provide analysis of more recent focal studies, and suggest that Echinococcus spp. tapeworms, in particular E. canadensis, may be underrecognized. As a result, we suggest that additional research and surveillance be conducted for these tapeworms in wildlife host reservoirs across the United States. [ABSTRACT FROM AUTHOR]

Describing historic wildlife communities is important for evaluating changes in ecosystems through time and developing contemporary objectives for conservation and restoration. The early historical record in the Greater Yellowstone Ecosystem has been analyzed many times using a small number of written accounts, with interpretations vigorously disputed among historians, scientists, and other stakeholders. We compiled a comprehensive narrative of thousands of first-hand accounts of wildlife in the ecosystem during 1796-1881, summarized them in a georeferenced relational database, and categorized and mapped output from queries to clarify conflicting past perceptions and gain insights for contemporary management issues. The historical record indicates large mammals such as bison ( Bison bison), elk ( Cervus elaphus), pronghorn ( Antilocapra americana), and wolves ( Canis lupus) were present and widespread in present-day Yellowstone National Park and the larger ecosystem prior to Euro-American colonization. However, casual observations could not be used to estimate population sizes, relative abundances, seasonal movements and migration routes, or periods of occupancy with certainty. Despite these shortcomings, the approach was useful for informing contemporary management issues regarding wolf restoration, seasonal distributions of ungulates, and whether mountain goats ( Oreamnos americanus) were native to the Yellowstone area. Similar evaluations could be conducted elsewhere to clarify historic wildlife conditions and provide reference information for modern conservation decisions. [ABSTRACT FROM AUTHOR]