Anti-Predator Strategies and Grouping Patterns in White-Tailed Deer and Mule Deer

White-tailed deer ( Odocoileus virginianus ) and mule deer ( O. hemionus ) are closely related species of similar size that differ in their anti-predator behavior. White-tails flee from coyotes ( Canis latrans ), whereas mule deer typically stand their ground and attack this predator. I used observations of coyotes hunting deer to identify: (i) changes in group structure made in response to coyotes; and (ii) the relationship between group structure and the risk of predation for each species.
In response to coyotes, groups of mule deer merged with other groups and individuals bunched together. Predation attempts were more likely to escalate when groups split and individuals failed to bunch. Coyotes typically attacked mule deer that were in outlying positions, and these deer had to move to central positions to end attacks. Due to the high frequency of attacks on small groups as well as to the level of dilution of risk, individuals in small mule deer groups were at high risk of being attacked compared with those in larger groups. In contrast to mule deer, white-tails made no consistent changes in group size or formation, and coyotes attacked individuals in central as well as in outlying positions. Variation in aspects of group cohesion was not related to the vulnerability of white-tails, and there was no obvious difference in the risk of attack facing individuals in groups of different size. These results suggest that coyote predation selects for relatively large, cohesive groups in mule deer, apparently because this type of group improves their ability to deter coyotes. Coyote predation does not have similar effects on groups formed by white-tails, which use flight rather than deterrence to avoid predation. The benefits of responding cohesively, occupying certain positions within groups, and forming groups of a certain size can vary widely depending on the anti-predator strategies used by an animal.     

Fight or flight? Antipredator behavior and the escalation of coyote encounters with deer

It is well known that prey of different size and morphology often use different antipredator strategies. The prevailing notion is that this occurs because size, morphology and weaponry determine the relative effectiveness of alternative strategies, and nowhere is this assumption more entrenched than in our view of the basic decision to stay, fight or flee. Here, we use observations of coyote (Canis latrans) packs hunting deer in winter to show that two ungulates of similar size and morphology, white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus), use different antipredator strategies when encountered or attacked. Mule deer typically responded by holding their ground and aggressively defending conspecifics, and were at high risk of being attacked and killed if they fled or were undefended. White-tails always fled when pursued or attacked by coyotes. Coyotes pursued fewer white-tails than mule deer they encountered regardless of prey response. Once pursued or attacked, white-tails faced a risk of attack and capture, respectively, that was intermediate between the high and low risk mule deer groups. The overall risk of capture per encounter for white-tails was similar to that facing mule deer that confronted coyotes, which was much lower than risk facing mule deer that fled and were undefended. Contextual variables such as the opportunity to improve one's position by joining another group, moving to rugged terrain, or the presence of companions that are willing to provide defense may explain why a mixed strategy is maintained in mule deer, despite the apparently detrimental effects of flight. These examples illustrate the value of including prey behavior in models of hunting success in so far as prey defenses may not be coupled with differences in size and morphology.     

Infectious Disease and Grouping Patterns in Mule Deer

Infectious disease dynamics are determined, to a great extent, by the social structure of the host. We evaluated sociality, or the tendency to form groups, in Rocky Mountain mule deer (Odocoileus hemionus hemionus) from a chronic wasting disease (CWD) endemic area in Saskatchewan, Canada, to better understand factors that may affect disease transmission. Using group size data collected on 365 radio-collared mule deer (2008–2013), we built a generalized linear mixed model (GLMM) to evaluate whether factors such as CWD status, season, habitat and time of day, predicted group occurrence. Then, we built another GLMM to determine factors associated with group size. Finally, we used 3 measures of group size (typical, mean and median group sizes) to quantify levels of sociality. We found that mule deer showing clinical signs of CWD were less likely to be reported in groups than clinically healthy deer after accounting for time of day, habitat, and month of observation. Mule deer groups were much more likely to occur in February and March than in July. Mixed-sex groups in early gestation were larger than any other group type in any season. Groups were largest and most likely to occur at dawn and dusk, and in open habitats, such as cropland. We discuss the implication of these results with respect to sociobiology and CWD transmission dynamics.     

Evaluating Indirect Effects of Hunting on Mule Deer Spatial Behavior

Mule deer (Odocoileus hemionus) are widely hunted throughout western North America and are experiencing population declines across much of their range. Consequently, understanding the direct and indirect effects of hunting is important for management of mule deer populations. Managers can influence deer mortality rates through changes in hunting season length or authorized tag numbers. Little is known, however, about how hunting can affect site fidelity patterns and subsequent habitat use and movement patterns of mule deer. Understanding these patterns is especially important for adult females because changes in behavior may influence their ability to acquire resources and ultimately affect their productivity. Between 2008 and 2013, we obtained global positioning system locations for 42 adult female deer at the Starkey Experimental Forest and Range in northeast Oregon, USA, during 5-day control and treatment periods in which hunters were absent (pre-hunt), present but not actively hunting (scout and post-hunt), and actively hunting male mule deer (hunt) on the landscape. We estimated summer home ranges and 5-day use areas during pre-hunt and hunt periods and calculated overlap metrics across home ranges and use areas to assess site fidelity within and across years. We used step selection functions to evaluate whether female mule deer responded to human hunters by adjusting fine-scale habitat selection and movement patterns during the hunting season compared to the pre-hunt period. Mule deer maintained site fidelity despite disturbance by hunters with 72 ± 4% (SE) within-year overlap between summer home ranges and hunt use areas and 54 ± 7% inter-annual overlap among pre-hunt use areas and 56 ± 7% among hunt use areas. Mule deer diurnal movement rates, when hunters are active on the landscape, were higher during the hunting period versus pre-hunt or scout periods. In contrast, nocturnal movement rates, when hunters are inactive on the landscape, were similar between hunting and non-hunting periods. Additionally, during the hunt, female mule deer hourly movements increased in areas with high greenness values, indicating that mule deer spent less time in areas with more vegetative productivity. Female mule deer maintained consistent habitat selection patterns before and during hunts, selecting areas that offered more forest canopy cover and high levels of vegetative productivity. Our results indicate that deer at Starkey are adopting behavioral strategies in response to hunters by increasing their movement rates and selecting habitat in well-established ranges. Therefore, considering site fidelity behavior in management planning could provide important information about the spatial behavior of animals and potential energetic costs incurred, especially by non-target animals during hunting season. © 2020 The Wildlife Society.     

Postpartum Group Cohesion of Sympatric Deer in Texas

ABSTRACT Postpartum behavior of maternal deer may be specific to species of deer and predators. We captured sympatric white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus eremicus) fawns from radiocollared adult females in 2004–2006 on rangelands of west central Texas, USA, where predators larger than bobcats (Lynx rufus) were absent. Our objective was to determine whether differences in postpartum antipredator behavior existed between deer species, and if so, examine efficacy of those strategies. We collected postpartum group cohesion data in 2004 and 2005 by using radiotelemetry and examined dead fawns for cause of mortality. During fawns' hider phase, <3 weeks postpartum, mule deer females kept fawns closer to themselves (95% CI = 39−66 m) and twins closer to each other (95% CI = 25–49 m) than did white-tailed deer females (95% CIs = 152–234 m and 163–255 m, respectively). After 30 days postpartum, familial group cohesion was similarly tight for both species. During hider phases from 2004 to 2006, predated carcasses of white-tailed deer fawns (11 of 11) were dismembered or consumed more than mule deer fawns (7 of 13, P = 0.016), which was one line of evidence for maternal defense by mule deer adults. During hider phases in 2004 and 2005, predation rate of mule deer fawns was lower than that for white-tailed deer fawns. In 2006, predation rate increased for mule deer but was similar for white-tailed deer fawns compared with previous years. The tight cohesion strategy of mule deer exhibited in 2004 and 2005 seemed successful at thwarting small predators. Without large predators, the loose cohesion strategy of white-tailed deer females was maladaptive. When meso-predators are abundant due to extermination of larger predators, predation on fawns could increase if a deer species has relatively fixed postpartum maternal antipredator behavior.     

Effects of large-scale removal of coyotes on pronghorn and mule deer productivity and abundance

We tested the hypothesis that predation by coyotes (Canis latrans) impacts pronghorn (Antilocapra americana) and mule deer (Odocoileus hemionus) populations. We did so by examining the effects of coyote removal on pronghorn and mule deer populations within 12 large areas (>10,500 km²) located in Wyoming and Utah during 2007 and 2008. Pronghorn productivity (fawn to adult female ratio) and abundance were positively correlated with the number of coyotes removed and removal effort (hours spent hunting coyotes from aircraft) although the correlation between pronghorn productivity and removal effort was not statistically significant (P = 0.08). Mule deer productivity and abundance were not correlated with either the number of coyotes removed or removal effort. Coyote removal conducted during the winter and spring provided greater benefit than removals conducted during the prior fall or summer. Our results suggest that coyote removal conducted over large areas increases fawn survival and abundance of pronghorn but not mule deer. © 2011 The Wildlife Society.     

Ecological effects of fear: How spatiotemporal heterogeneity in predation risk influences mule deer access to forage in a sky‐island system

Forage availability and predation risk interact to affect habitat use of ungulates across many biomes. Within sky‐island habitats of the Mojave Desert, increased availability of diverse forage and cover may provide ungulates with unique opportunities to extend nutrient uptake and/or to mitigate predation risk. We addressed whether habitat use and foraging patterns of female mule deer (Odocoileus hemionus) responded to normalized difference vegetation index (NDVI), NDVI rate of change (green‐up), or the occurrence of cougars (Puma concolor). Female mule deer used available green‐up primarily in spring, although growing vegetation was available during other seasons. Mule deer and cougar shared similar habitat all year, and our models indicated cougars had a consistent, negative effect on mule deer access to growing vegetation, particularly in summer when cougar occurrence became concentrated at higher elevations. A seemingly late parturition date coincided with diminishing NDVI during the lactation period. Sky‐island populations, rarely studied, provide the opportunity to determine how mule deer respond to growing foliage along steep elevation and vegetation gradients when trapped with their predators and seasonally limited by aridity. Our findings indicate that fear of predation may restrict access to the forage resources found in sky islands.     

Factors affecting the selection of and displacement within core areas by female mule deer (Odocoileus hemionus) in the Chihuahuan Desert,Mexico

Core activity areas are the most important sites within an animal’s home range as they contain the greatest density of critical resources. Because these areas are small and intensively used, they can affect the total distances covered by animals searching for resources. Our objective was to document which habitat variables affect core area selection by female mule deer (Odocoileus hemionus) in an arid environment, and to learn which variables affect their displacement within these areas. Using radiotelemetry, from 2012 to 2014 we monitored seven female mule deer. We estimated their core areas, and with this information we identified and classified the location records as inside or outside of the core area. For each record, we also recorded variables related to time (month, time of day), environmental conditions (temperature, relative humidity), and habitat characteristics (plant association, distance to the nearest water body, slope), and used them to predict the presence of the deer in the core area using Classification and Regression Trees (CART). The same variables were analyzed using a GLM to determine which factors explain variations in displacement distance. The most important variable in core area selection was the distance to the nearest body of water (<933.71 m at the population level and <1375.11 m on average for individual deer), followed by two plant associations that included the dominant species Prosopis glandulosa, Pleuraphis mutica, Larrea tridentata, Opuntia rastrera and Fouquieria splendens in areas with a gentle slope or none. Displacement distances within the core area were shorter than those outside and were affected by time of day and month. Our results are the first to elucidate the use of the core area by female mule deer in the Chihuahuan Desert, and allow us to start understanding the connection between the habitat resources essential to the survival of these deer and their movement under desert conditions.     

Cougar Prey Selection in a White-Tailed Deer and Mule Deer Community

Abstract Widespread mule deer (Odocoilus hemionous) declines coupled with white-tailed deer (O. virginianus) increases prompted us to investigate the role of cougar (Puma concolor) predation in a white-tailed deer, mule deer, and cougar community in northeast Washington, USA. We hypothesized that cougars select for and disproportionately prey on mule deer in such multiple-prey communities. We estimated relative annual and seasonal prey abundance (prey availability) and documented 60 cougar kills (prey usage) from 2002 to 2004. White-tailed deer and mule deer comprised 72% and 28% of the total large prey population and 60% and 40% of the total large prey killed, respectively. Cougars selected for mule deer on an annual basis (α_md = 0.63 vs. α_wt = 0.37; P = 0.066). We also detected strong seasonal selection for mule deer with cougars killing more mule deer in summer (α_md = 0.64) but not in winter (α_md = 0.53). Cougars showed no seasonal selection for white-tailed deer despite their higher relative abundance. The mean annual kill interval of 6.68 days between kills varied little by season (winter = 7.0 days/kill, summer = 6.6 days/kill; P = 0.78) or prey species (white-tailed deer = 7.0 days/kill, mule deer = 6.1 days/kill; P = 0.58). Kill locations for both prey species occurred at higher elevations during summer months (summer = 1,090 m, winter = 908 m; P = 0.066). We suspect that cougars are primarily subsisting on abundant white-tailed deer during winter but following these deer to higher elevations as they migrate to their summer ranges, resulting in a greater spatial overlap between cougars and mule deer and disproportionate predation on mule deer.     

Comparing Survival and Movements of Non-Urban and Urban Translocated Mule Deer

In many parts of North America, deer (Odocoileus spp.) have adapted to live in urban areas and are a source of negative human-wildlife interactions. Management strategies such as culling, immunocontraceptives, sterilization, and translocation have been implemented to manage urban deer populations. In the East Kootenay region of southern British Columbia, urban mule deer (Odocoileus hemionus) populations have been increasing, whereas non-urban mule deer populations have decreased. In 2014 a non-urban mule deer research project began in the area and in 2016 an urban deer translocation trial was approved in the same region. We fit 121 non-urban deer with global positioning system (GPS)-collars and translocated 135 urban mule deer to non-urban areas, of which 57 were fit with GPS-collars. We tested if annual survival between urban translocated (i.e., translocated) and non-urban deer differed, and if translocated deer survival increased in subsequent years after translocation. We also determined if age, body condition, release site, capture area and distance between capture and release sites affected translocated deer survival. We evaluated if translocated deer exhibited different movement behaviors than non-urban deer by comparing probability of migration, maximum net displacement, home range size, and probability of crossing a paved road. Finally, during our study we observed some translocated deer return to a municipal area after translocation and assessed if any covariates such as age, release site, or capture city could help predict this behavior. Annual survival of translocated deer was 0.48 and was significantly lower than survival of non-urban deer, which was 0.77. We observed 20 of 57 collared translocated deer return to a town after translocation. Translocated deer had larger net displacements and larger seasonal home range sizes than non-urban deer. Non-urban deer were more likely to migrate than translocated deer and crossed fewer paved roads than translocated deer. The management effectiveness of translocation to reduce urban deer densities is mixed because annual survival of translocated deer may be lower than may be acceptable to some stakeholders. Additionally, some translocated deer returned to an urban area, and the large distances traveled by deer after translocation may unintentionally spread disease. © 2020 The Wildlife Society.     

Effects of Season and Scale on Response of Elk and Mule Deer to Habitat Manipulation

Abstract: Manipulation of forest habitat via mechanical thinning or prescribed fire has become increasingly common across western North America. Nevertheless, empirical research on effects of those activities on wildlife is limited, although prescribed fire in particular often is assumed to benefit large herbivores. We evaluated effects of season and spatial scale on response of Rocky Mountain elk (Cervus elaphus) and mule deer (Odocoileus hemionus) to experimental habitat manipulation at the Starkey Experimental Forest and Range in northeastern Oregon, USA. From 2001 to 2003, 26 densely stocked stands of true fir (Abies spp.) and Douglas-fir (Pseudotsuga menziesii) were thinned and burned whereas 27 similar stands were left untreated to serve as experimental controls. We used location data for elk and mule deer collected during spring (1 Apr-14 Jun) and summer (15 Jun-31 Aug) of 1999–2006 to compare use of treated and untreated stands and to model effects of environmental covariates on use of treated stands. In spring, elk selected burned stands and avoided control stands within the study area (second-order selection; large scale). Within home ranges (third-order selection; small scale), however, elk did not exhibit selection. In addition, selection of treatment stands by elk in spring was not strongly related to environmental covariates. Conversely, in summer elk selected control stands and either avoided or used burned stands proportional to their availability at the large scale; patterns of space use within home ranges were similar to those observed in spring. Use of treatment stands by elk in summer was related to topography, proximity to roads, stand size and shape, and presence of cattle, and a model of stand use explained 50% of variation in selection ratios. Patterns of stand use by mule deer did not change following habitat manipulation, and mule deer avoided or used all stand types proportional to their availability across seasons and scales. In systems similar to Starkey, manipulating forest habitat with prescribed fire might be of greater benefit to elk than mule deer where these species are sympatric, and thus maintaining a mixture of burned and unburned (late successional) habitat might provide better long-term foraging opportunities for both species than would burning a large proportion of a landscape.     

Effectiveness of Partial Sedation to Reduce Stress in Captured Mule Deer

Information garnered from the capture and handling of free-ranging animals helps advance understanding of wildlife ecology and can aid in decisions on wildlife management. Unfortunately, animals may experience increased levels of stress, injuries, and death resulting from captures (e.g., exertional myopathy, trauma). Partial sedation is a technique proposed to alleviate stress in animals during capture, yet efficacy of partial sedation for reducing stress and promoting survival post-capture remains unclear. We evaluated the effects of partial sedation on physiological, biochemical, and behavioral indicators of acute stress and probability of survival post-capture for mule deer (Odocoileus hemionus) that were captured via helicopter net-gunning in the eastern Greater Yellowstone Ecosystem, Wyoming, USA. We administered 10–30 mg of midazolam and 15 mg of azaperone intramuscularly (IM) to 32 mule deer in 2016 and 53 mule deer in 2017, and maintained a control group (captured but not sedated) of 38 mule deer in 2016 and 54 mule deer in 2017. To evaluate indicators of acute stress, we measured heart rate, blood-oxygen saturation, body temperature, respiration rate, and levels of serum cortisol. We recorded number of kicks and vocalizations of deer during handling and evaluated behavior during release. We also measured levels of fecal glucocorticoids as an indicator of baseline stress. Midazolam and azaperone did not reduce physiological, biochemical, or behavioral indicators of acute stress or influence probability of survival post-capture. Mule deer that were administered midazolam and azaperone, however, were more likely to hesitate, stumble or fall, and walk during release compared with individuals in the control group, which were more likely to trot, stot, or run without stumbling or falling. Our findings suggest that midazolam (10–30 mg IM) and azaperone (15 mg IM) may not yield physiological or demographic benefits for captured mule deer as previously assumed and may pose adverse effects that can complicate safety for captured animals, including drug-induced lethargy. Although we failed to find efficacy of midazolam and azaperone as a method for reducing stress in captured mule deer, the efficacy of midazolam and azaperone or other combinations of partial sedatives in reducing stress may depend on the dose of tranquilizer, study animal, capture setting, and how stress is defined. © 2020 The Wildlife Society.     

Effects of risk assessment, predator behavior, and habitat on escape behavior in Columbian black-tailed deer

The relationship between preflight risk assessment by prey andthe escape behaviors they perform while fleeing from predatorsis relatively unexplored. To examine this relationship, a humanobserver approached groups of Columbian black-tailed deer (Odocoileushemionus columbianus), varying his behavior to simulate moreor less threatening behavior. We measured the focal deer's angleof escape, distance moved during flight, duration of trottingand stotting behavior, and change in elevation during flight.Analyses revealed positive relationships between the distancemoved during flight and the distance at which they fled. Whenflight was initiated when the approacher was close, deer fledrelatively shorter distances and took flight paths at more acuteangles, a property that would force a real predator to changedirection suddenly. Our results indicate that deer do not compensatefor allowing the observer to approach more closely by fleeinggreater distances. Rather, distance moved and flight initiationdistance are linked by level of reactivity and habituation:more reactive or less habituated deer both flee at a greaterdistance and move away to a greater distance during flight.More threatening behavior by the approacher led to longer durationsof rapid flight behavior (e.g., trotting and stotting), anddeer tended to flee uphill and into taller vegetation, usingthese landscape features as refuge from danger. Finally, weprovide the first evidence for Pitcher's untested "antiambush"hypothesis for the function of stotting and discuss its significance.In general, both preflight predator behavior and habitat featuresinfluence both duration and direction of escape.     

Influence of Well Pad Activity on Winter Habitat Selection Patterns of Mule Deer

ABSTRACT Conversion of native winter range into producing gas fields can affect the habitat selection and distribution patterns of mule deer (Odocoileus hemionus). Understanding how levels of human activity influence mule deer is necessary to evaluate mitigation measures and reduce indirect habitat loss to mule deer on winter ranges with natural gas development. We examined how 3 types of well pads with varying levels of vehicle traffic influenced mule deer habitat selection in western Wyoming during the winters of 2005–2006 and 2006–2007. Well pad types included producing wells without a liquids gathering system (LGS), producing wells with a LGS, and well pads with active directional drilling. We used 36,699 Global Positioning System locations collected from a sample (n = 31) of adult (>1.5-yr-old) female mule deer to model probability of use as a function of traffic level and other habitat covariates. We treated each deer as the experimental unit and developed a population-level resource selection function for each winter by averaging coefficients among models for individual deer. Model coefficients and predictive maps for both winters suggested that mule deer avoided all types of well pads and selected areas further from well pads with high levels of traffic. Accordingly, impacts to mule deer could probably be reduced through technology and planning that minimizes the number of well pads and amount of human activity associated with them. Our results suggested that indirect habitat loss may be reduced by approximately 38–63% when condensate and produced water are collected in LGS pipelines rather than stored at well pads and removed via tanker trucks. The LGS seemed to reduce long-term (i.e., production phase) indirect habitat loss to wintering mule deer, whereas drilling in crucial winter range created a short-term (i.e., drilling phase) increase in deer disturbance and indirect habitat loss. Recognizing how mule deer respond to different types of well pads and traffic regimes may improve the ability of agencies and industry to estimate cumulative effects and quantify indirect habitat losses associated with different development scenarios.     

Overabundance of Black-Tailed Deer in Urbanized Coastal California

Abundance of mule deer (Odocoileus hemionus) in western North America is often considered lower than desirable for hunting. Some coastal populations of Columbian black-tailed deer (O. h. columbianus) in California, USA, near urban development, however, are perceived as a nuisance and may be overabundant. To determine the density of a potential nuisance population in Marin County, California, we used a combination of fecal DNA surveys, camera stations, and 2 sources of ancillary data on wildlife observations. We estimated an average density of 18.3 deer/km² (90% CI = 15.8–20.7) throughout Marin County during late summer and early fall, 2015 and 2016. Within the county, areas with intermediate human density (885 people/km², 90% CI = 125–1,646) were associated with the highest deer densities (25–44/km²). Our estimate of average deer density was 1.7–6.1 times higher than published density estimates for deer from elsewhere in California and on the low end of densities reported for mule and white-tailed (O. virginianus) deer in regions where they routinely cause a nuisance to humans. High black-tailed deer densities in Marin County may be partially attributed to a paucity of large predators, but more investigation is warranted to evaluate the effects of a recent increase in coyotes (Canis latrans) on the deer population. Analyses of highway road kill rates and citizen science surveys suggest that the deer population in Marin County has been stable over the past 10 years. Our results demonstrate how robust estimation of deer density can inform human–wildlife conflict issues, not just managed hunting. © 2020 The Wildlife Society.     

Wolf predation on moose and roe deer: chase distances and outcome of encounters

We examined chase distances of gray wolves Canis lupus Linnaeus, 1758 hunting moose Alces alces and roe deer Capreolus capreolus, and recorded details of encounters between wolves and prey on the Scandinavian Peninsula, 1997–2003. In total, 252 wolf attacks on moose and 64 attacks on roe deer were registered during 4200 km of snow tracking in 28 wolf territories. Average chase distances were 76 m for moose and 237 m for roe deer, a difference likely due to variation in body size and vigilance between prey species. A model including prey species, outcome of the attack, and snow depth explained 15–19% of the variation found in chase distances, with shorter chase distances associated with greater snow depth and with successful attacks on moose but not on roe deer. Wolf hunting success did not differ between prey species (moose 43%, roe deer 47%) but in 11% of the wolf attacks on moose at least one moose was injured but not killed, whereas no injured roe deer survived. Compared with most North American wolf studies chase distances were shorter, hunting success was greater, and fewer moose made a stand when attacked by wolves in our study. Differences in wolf encounters with moose and roe deer likely result from different anti-predator behaviour and predator-prey history between prey species.     

Effects of predator behavior and proximity on risk assessment by Columbian black-tailed deer

In predator-prey encounters, many factors influence risk perceptionby prey and their decision to flee. Previous studies indicatethat prey take flight at longer distances when they detect predatorsat longer distances and when the predator's behavior indicatesthe increased likelihood of attack. We examined the flight decisionsof Columbian black-tailed deer (Odocoileus hemionus columbianus)using an approaching human whose speed, directness of approach,directness of gaze, and simulated gun carrying varied. Deerfled at greater distances when approached more quickly and directly,and there was a concave-down quadratic trend in the relationshipbetween the distances at which the predator began its approachand at which the deer became alert (alert distance [AD]), indicatingthat deer have a zone of awareness beyond which there is a delayin detecting an approaching predator. Time spent assessing theapproacher (assessment time) was shorter during faster approachesand was positively related with AD. Deer fled at longer distancesand had shorter assessment times when they were already alertto the predator at the initiation of approach. Males fled atshorter distances than females when approached during the gun-holdingcondition, and males had shorter assessment times than femaleswhen the approacher averted his gaze. Such sex differences inrisk assessment might reflect male motivation during the matingseason as well as exposure to human hunting. We suggest thatrisk assessment is affected the by the predator's behavior,the state of awareness of the prey, and the distance at whichthey detect the predator.     

Chimpanzee and felid diet composition is influenced by prey brain size

Prey use a wide variety of anti-predator defence strategies, including morphological and chemical defences as well as behavioural traits (risk-modulated habitat use, changes in activity patterns, foraging decisions and group living). The critical test of how effective anti-predator strategies are is to relate them to relative indices of mortality across predators. Here, we compare biases in predator diet composition with prey characteristics and show that chimpanzee (Pan troglodytes) and felid show the strongest and the most consistent predator bias towards small-brained prey. We propose that large-brained prey are likely to be more effective at evading predators because they can effectively alter their behavioural responses to specific predator encounters. Thus, we provide evidence for the hypothesis that brain size evolution is potentially driven by selection for more sophisticated and behaviourally flexible anti-predator strategies.     

Mule deer and energy development—Long‐term trends of habituation and abundance

As the extent and intensity of energy development in North America increases, so do disturbances to wildlife and the habitats they rely upon. Impacts to mule deer are of particular concern because some of the largest gas fields in the USA overlap critical winter ranges. Short‐term studies of 2–3 years have shown that mule deer and other ungulates avoid energy infrastructure; however, there remains a common perception that ungulates habituate to energy development, and thus, the potential for a demographic effect is low. We used telemetry data from 187 individual deer across a 17‐year period, including 2 years predevelopment and 15 years during development, to determine whether mule deer habituated to natural gas development and if their response to disturbance varied with winter severity. Concurrently, we measured abundance of mule deer to indirectly link behavior with demography. Mule deer consistently avoided energy infrastructure through the 15‐year period of development and used habitats that were an average of 913 m further from well pads compared with predevelopment patterns of habitat use. Even during the last 3 years of study, when most wells were in production and reclamation efforts underway, mule deer remained >1 km away from well pads. The magnitude of avoidance behavior, however, was mediated by winter severity, where aversion to well pads decreased as winter severity increased. Mule deer abundance declined by 36% during the development period, despite aggressive onsite mitigation efforts (e.g. directional drilling and liquid gathering systems) and a 45% reduction in deer harvest. Our results indicate behavioral effects of energy development on mule deer are long term and may affect population abundance by displacing animals and thereby functionally reducing the amount of available habitat.