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We investigated the influence of white-tailed deer (Odocoileus virginianus) and snowshoe hare (Lepus americanus) availability on the feeding habits of coyotes ( Canis latrans) in Nova Scotia from 1992 to 1997. We hypothesized that coyotes would switch from deer to hare as hare abundance increased. Based on the analysis of 2443 scats, deer and hare...
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... study was conducted in two areas representing the extremes in Nova Scotian winter weather (Fig. 1). The Queens County (QC) study area was located in central southwestern Nova Scotia (44°20 ′ N, 65°15 ′ W). The study area included the eastern half of Kejimkujik National Park (approximately 200 km 2 ) and approximately 300 km 2 of mostly forested land directly to the east of the park. This area was characterized by flat undulating terrain with poor drainage, resulting in many lakes and ponds. Elevation ranged from 100 to 175 m. The vegetation was characterized by spruce ( Picea spp.), balsam fir ( Abies balsamea ), eastern hemlock ( Tsuga canadensis ), and heath cover types growing on the flat land between drumlins and eskers, with hardwood and pine ( Pinus spp.) stands occupying the well-drained knolls and ridges. Agricultural fields were concentrated near the few main roads atop drumlins. The climate of this region was characterized by warm summers typified by 1700 annual degree-days >5°C and cool winters averaging –5°C in January, with moderate snowfall (Dzikowski et al. 1984). This area does not generally receive accumulations of snow in winter >20 cm, therefore local deer do not show typical yarding behaviour (MacDonald 1996; Lock 1997). The Cape Breton (CB) study area was located on Cape Breton Island (45°45 ′ N, 61°15 ′ W) and straddled two natural history theme regions (Simmons et al. 1984). The Creignish Mountains represented the Avalon Upland (Cape Breton Highlands, CBH) section of the study area, whereas the River Denys Basin represented the Carboniferous Lowlands section (Cape Breton Lowlands, CBL). This study area was centered around the 24-km 2 Eden deer wintering area, which typically contained approximately 200 deer from January through to March (B.R. Patterson, unpublished data). The northern section of the study area reaches a height of >300 m and slopes sharply at its southern fringe. The mid and upper slopes were mainly undisturbed tolerant hardwood forest of yellow birch ( Betula alleghaniensis ), sugar maple ( Acer saccharum ), and Amer- ican beech ( Fagus grandifolia ), whereas the upland surface was covered with naturally occurring and second-growth coniferous stands. Repeated disturbance of the lowland forest has resulted in softwood and intolerant cover types predominating, interspersed with agricultural fields and recent clearcuts. The lowland area slopes gently to the south, with an average elevation of <100 m. The climate in this region is generally more moist, with approximately the same annual degree-days >5°C (1600) as the QC study area (Dzikowski et al. 1984). The higher elevations, lower slopes, and abutting lowland fringe in the northern section of the study area receive 250–300 cm of snow annually, whereas the lowland areas receive 200–250 cm of snow annually (Gates 1975). Similarly, median duration of snow cover varies from 140 days on higher elevations to 130 days on lower elevations (Gates 1975). This contrasts with a median duration of snow cover of only 59 days in the QC area. The relative abundance of white-tailed deer was determined within each study area using pellet group counts conducted along approximately thirty 1000 × 2 m systematic line transects during April and May of each year of study (Neff 1968). Although the use of pellet group counts as an index of deer numbers has been criti- cized (Fuller 1991, 1992), pellet group counts in Nova Scotia were closely related to the autumn harvest in 1983–1992 ( r 2 = 0.87, P = 0.001) (B.R. Patterson, unpublished data). Regional trends in hare density were estimated using subjective fur harvester abundance rankings (Sabean 1990) obtained from licensed fur harvesters ...
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Many animals assess their risk of predation by listening to and evaluating predators' vocalizations. We reviewed the literature to draw generalizations about predator discrimination abilities, the retention of these abilities over evolutionary time, and the potential underlying proximate mechanisms responsible for discrimination. Broadly, we found...
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... If resources are high enough, this may also reduce predation pressure on fawns through prey switching by coyotes (Rodewald et al., 2011) or better fawn hiding strategies (Piccolo et al., 2010). However, fawn predation rates by coyotes even in productive habitats are generally high (Chitwood et al., 2015;Kilgo et al., 2012;Shuman et al., 2017) and prey switching may be less likely to favor relatively immobile and easy-to-catch neonates (Patterson et al., 1998), suggesting lower predation rates are less likely to explain lower coyote impacts in more productive habitats. ...
Predator–prey interactions are important for regulating populations and structuring communities but are affected by many dynamic, complex factors across large scales, making them difficult to study. Integrated population models (IPMs) offer a potential solution to understanding predator–prey relationships by providing a framework for leveraging many different datasets and testing hypotheses about interactive factors. Here, we evaluate the coyote–deer (Canis latrans–Odocoileus virginianus) predator–prey relationship across the state of North Carolina (NC). Because both species have similar habitat requirements and may respond to human disturbance, we considered net primary productivity (NPP) and urbanization as key mediating factors. We estimated deer survival and fecundity by integrating camera trap, harvest, and biological and hunter observation datasets into a two‐stage, two‐sex Lefkovich population projection matrix. We allowed survival and fecundity to vary as functions of urbanization, NPP, and coyote density, and projected abundance forward to test eight hypothetical scenarios. We estimated initial average deer and coyote densities to be 11.83 (95% CI: 5.64, 20.80) and 0.46 (95% CI: 0.02, 1.45) individuals/km², respectively. We found a negative, though highly uncertain, relationship between the current levels of coyote density and deer fecundity in most areas that became more negative under hypothetical conditions of lower NPP or higher urbanization, leading to lower projected deer abundances. Though not conclusive, our results indicate the possibility that coyotes could have stronger effects on deer populations in NC if their densities rise, but primarily in less productive and/or more suburban habitats. Our case study provides an example of how IPMs can be used to better understand the complex relationships between predator and prey under changing environmental conditions.
... We processed scats following a standard operating procedure, which combined methods from several scat analysis studies (Chenaux-Ibrahim 2015). Briefly, we transferred scats to nylon stockings and boiled them for >30 minutes under a fume hood to kill parasites (Patterson et al. 1998, Chavez and Gese 2005, Klare et al. 2011. We washed scats in the nylon stockings in a dishwasher until only bone and hair remained. ...
The moose (Alces alces; mooz in Anishinaabemowin, Ojibwe language) population has recently declined in Minnesota, USA, and gray wolf (Canis lupus; ma'iingan) predation is likely a contributing factor. We analyzed diet composition of gray wolves in northeastern Minnesota during 2011-2013 to evaluate the importance of moose as prey and seasonal and regional variations in wolf diet. We identified frequency of occurrence of prey items and biomass consumed in 1,000 wolf scats collected on and adjacent to the Grand Portage Indian Reservation and Voyageurs National Park and within the 1854 Ceded Territory (greater northeastern Minnesota). White-tailed deer (Odocoileus virginianus; waawaashkeshiwag [plural]), moose, and beaver (Castor canadensis; amikwag [plural]) composed the majority of wolf diet, with moose as the primary prey in Grand Portage (35-54% of diet by biomass across seasons) and deer the primary prey in the 1854 Ceded Territory (46-62%) and Voyageurs (63-79%). Relative importance of prey species differed by study area and season. Moose calves were an important prey item in spring in the 1854 Ceded Territory (12% of diet by biomass) but not in Grand Portage or Voyageurs. Although calves were not a majority of wolf diet by biomass, many calves were preyed upon by wolves (30% of calves born each year in Grand Portage), thus affecting recruitment in a declining moose population. Deer fawns composed 12% of wolf diet in spring and 10% in summer in Grand Portage and 19% in summer in Voyageurs. Beaver composed 16% of wolf diet by biomass in
... The energetic profitability offered by pulses in availability of neonatal ungulates during peak parturition likely exceeds that of high densities of primary prey (Petroelje et al., 2013). Indeed, in many systems, neonatal deer were the leading diet item of coyotes despite high densities of primary prey during summer months (Patterson et al., 1998). Our observations of selection and fine-scale movement behavior of coyotes indicate that abundance of primary prey played a negligible role in the shifts in selection and fine-scale movement behavior during Parturition and that coyotes actively ...
The density and distribution of resources shape animal movement and behavior and have direct implications for population dynamics. Resource availability often is "pulsed" in space and time, and individuals should cue in on resource pulses when the energetic gain of doing so exceeds that of stable resources. Birth pulses of prey represent a profitable but ephemeral resource and should thereby result in shifting functional responses by predators. We evaluated movements and resource selection of coyotes (Canis latrans) across a gradient of reproductive stages ranging from late gestation to peak lactation of female mule deer (Odocoileus hemionus) in southwest Wyoming, USA, to test whether coyotes exhibited shifts in selection and movement behavior relative to the availability and vulnerability of neonatal mule deer. We expected coyotes to track pulses in availability of neonatal mule deer, and such behavior would be represented by shifts in resource selection and search behavior of coyotes that would be strongest during peak parturition of mule deer. Coyotes selected areas of high relative probability of use by female mule deer and did so most strongly during peak parturition. Furthermore, searching behavior of coyotes intensified during pulses of availability of deer neonates. Our findings support the notion that coyotes exploit pulses of neonatal deer, presumably as an attempt to capitalize on a vulnerable, energy-rich resource. Our work quantifies the behavioral mechanisms by which coyotes consume ungulate neonates and provides one of the first examples of a mammalian predator-prey system centered on a pulsed resource.
... 2 and elk Cervus canadensis, smaller generalists such as coyotes Canis latrans now hunt mid-sized ungulates like deer (Odocoileus spp.) and pronghorn Antilocapra americana, small mammals and birds, and predate or scavenge livestock (Patterson et al. 1998, Lingle 2000, Neale and Sacks 2001, Arjo et al. 2002, Morey et al. 2007, Ward et al. 2018. The coyote's success as a mesopredator is renowned (Fener et al. 2005, Prugh et al. 2009). ...
... We obtained average weights for each species of mammalian prey detected in the coyote's diet from the literature and from rancher records for cattle, adjusting the seasonal weight of ungulates (deer, pronghorn, cattle) to reflect age classes likely to be predated or scavenged during each season as indicated in the literature with supplementary records from ranchers for cattle (Supporting information). Assessing biomass brings its own challenges and sources of error especially when a predator's diet varies widely in size and taxonomy (Klare et al. 2011), as is typically the case for coyotes (Patterson et al. 1998, Hernández et al. 2002, Prugh 2005, Azevedo et al. 2006. Nonetheless, estimated biomass is better than frequency of occurrence data in assessing the relative contribution of different prey items to a predator's diet (Klare et al. 2011). ...
... Coyotes living in the greater GNP ecosystem between January 2007 and April 2010 had a broad diet that included cattle, wild ungulates, small mammals, birds, invertebrates, and berries and seeds, consistent with reports for this generalist predator elsewhere (Patterson et al. 1998, Hernández et al. 2002, Prugh 2005, Azevedo et al. 2006). Our three main findings were: 1) a shift in consumption of sciurids from spring to fall to deer during winter; 2) relatively high consumption of cattle carrion throughout the year, even for coyotes inhabiting the portion of the park from which cattle were excluded; and 3) the proximity of scats to a prairie dog colony increased the likelihood that they contained prairie dog, and reduced the likelihood that they contained cattle. ...
As the dominant predator on North America's grasslands, coyotes Canis latrans have a large influence on biodiversity, both on working ranches and in protected parks. Ground squirrel (sciurid) species and livestock carrion are often abundant on grasslands worldwide and have the potential to influence a predator's consumption of alternative prey. We collected 1321 scats in four seasons over two years in and adjacent to Grasslands National Park, Saskatchewan, to test the hypothesis that seasonal and spatial variation in consumption of sciurid prey and cattle Bos taurus carrion influenced coyote consumption of alternative prey. Sciurid (black‐tailed prairie dog Cynomys ludovicianus and Richardson's ground squirrel Urocitellus richardsonii) remains were common from spring to fall and had a strong inverse relationship with deer (mule deer Odocoileus hemionus and white‐tailed deer O. virginianus), which were most common in winter scats. Cattle remains were most common during spring, fall and winter, and occurred in 10.6% of scats annually. Biomass estimates suggest that cattle was the highest ranked food on cattle grazing land year‐round, and the 2nd ranked food, after deer, during winter on the portion of the park from which cattle were excluded. Closer proximity of scats to a prairie dog colony increased the likelihood of prairie dog remains throughout the year and reduced the likelihood of cattle remains in scats from spring to fall, but not during winter. Individual differences in foraging and ranging behavior may explain the spatial distribution of prairie dog versus cattle in scats. Further work is needed to determine whether sciurid prey, deer, or livestock carrion support large predator populations on grassland habitats to a level that may negatively affect coexisting prey species, including species at risk.
... Coyotes (Canis latrans) are a highly adaptable canid whose behavioral plasticity has allowed them to persist in a wide array of habitats and climates, ranging from relatively undisturbed natural areas to highly developed urban environments (DeCandia et al., 2019;Gerht et al., 2009;Gompper, 2002). As opportunistic generalists, coyotes are able to switch among various food resources (Patterson et al., 1998;Randa et al., 2009), adjust their movement patterns to minimize conflicts with conspecifics, other predators, and humans (Berger & Gese, 2007;Fedriani et al., 2001), and change individual social strategies to maximize survival and reproduction (Macdonald, 1983). These characteristics have facilitated an extensive range expansion and growth of coyote populations over the past century, while other canid populations have declined (Hinton et al., 2019). ...
Coyotes (Canis latrans) are a highly adaptable canid species whose behavioral plasticity has allowed them to persist in a wide array of habitats throughout North America. As generalists, coyotes can alter movement patterns and change territorial strategies between residency (high site fidelity) and transiency (low site fidelity) to maximize fitness. Uncertainty remains about resident and transient coyote movement patterns and habitat use because research has reached conflicting conclusions regarding patterns of habitat use by both groups. We quantified effects of habitat on resident and transient coyote movement behavior using first passage time (FPT) analysis, which assesses recursive movement along an individual's movement path to delineate where they exhibit area‐restricted search (ARS) behaviors relative to habitat attributes. We quantified monthly movement rates for 171 coyotes (76 residents and 53 transients) and then used estimated FPT values in generalized linear mixed models to quantify monthly habitat use for resident and transient coyotes. Transients had greater movement rates than residents across all months except January. Resident FPT values were positively correlated with agricultural land cover during fall and winter, but negatively correlated with agriculture during spring. Resident FPT values were also negatively correlated with developed habitats during May–August, deciduous land cover during June–August, and wetlands during September–January except November. FPT values of transient coyotes were positively correlated with developed areas throughout much of the year and near wetlands during July–September. Transient FPT values were negatively correlated with agriculture during all months except June and July. High FPT values (ARS behavior) of residents and transients were generally correlated with greater densities of edge habitat. Although we observed high individual variation in space use, our study found substantive differences in habitat use between residents and transients, providing further evidence that complexity and plasticity of coyote habitat use is influenced by territorial strategy. We utilized first passage time analysis to assess differences in movement patterns of resident and transient coyotes in the southeastern United States. Although we observed high individual variation in space use and habitat selection, our study found substantive differences in habitat selection between resident and transient coyotes, providing further evidence that complexity and plasticity of coyote habitat selection is influenced by social status.
... In the study area we found that fruits were the most frequently consumed food item yearround in coyote's diet, as has been reported for this species in coniferous forests habitats in Oregon and Maine [58,59] and in some desert, coastal, tropical deciduous forest, and urban environments [23,[60][61][62][63][64]. But, this results contrast with previous works in the MBR [24,34], although former work represents a partial approximation of the diet throughout the year during the summer and spring, and with works in other parts of coyote's distribution which report wild mammals as the most consumed trophic category year-round in temperate forest of Mexico [65][66][67], the United States of America [13,[68][69][70][71][72][73][74], and Canada [75][76][77]. However, despite the above, changes in the frequency of occurrence of the different trophic categories through the seasons coincide with data reported for this species for which the highest consumption of wild mammals occurred during the first half of the year, in winter and spring, and the main consumption of fruits occurred in the second part of the year, in summer and autumn [34,64,68,74,[78][79][80][81][82]. ...
... This species has also been reported to consume larger species, such as whitetailed deer (O. virginianus), which in the case of the present study had high FO values, below rodents and lagomorphs, but which may present higher importance values in other distribution areas [66,68,74,76,[84][85][86][87][88]. These high values of mammal consumption during the first half of the year can be explained by the high demand for high-quality foods, since these periods coincide with the breeding season (1 January-15 March) and gestation (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)), such that foraging activity increases markedly in the study area to increase reproductive success [26,90]. ...
Resource partitioning, and especially dietary partitioning, is a mechanism that has been studied for several canid species as a means to understand competitive relationships and the ability of these species to coexist. Coyotes ( Canis latrans ) and gray foxes ( Urocyon cinereoargenteus ) are two canid species that are widely distributed, in Mexico, and they are sympatric throughout most of their distribution range. However, trophic dynamic and overlap between them have not been thoroughly studied. In order to better understand their ecological relationship and potential competitive interactions, we studied the trophic niche overlap between both canids in a temperate forest of Durango, Mexico. The results are based on the analysis of 540 coyote and 307 gray fox feces collected in 2018. Both species consumed a similar range of food items, but the coyote consumed large species while the gray fox did not. For both species, the most frequently consumed food categories throughout the year and seasonally were fruit and wild mammals (mainly rodents and lagomorphs). Coyotes had higher trophic diversity in their annual diet ( H’ = 2.33) than gray foxes ( H’ = 1.80). When analyzing diets by season, trophic diversity of both species was higher in winter and spring and tended to decrease in summer and autumn. When comparing between species, this parameter differed significantly during all seasons except for summer. Trophic overlap throughout the year was high ( R 0 = 0.934), with seasonal variation between R 0 = 0.821 (autumn) and R 0 = 0.945 (spring). Both species based their diet on the most available food items throughout each season of the year, having high dietary overlap which likely can lead to intense exploitative competition processes. However, differences in trophic diversity caused by differential prey use can mitigate competitive interactions, allowing these different sized canid species to coexist in the study area.
... In Poland and England, red fox rely on scavenging and anthropogenic food sources to a greater extent in winter, when rodent prey are scarcer (Jedrzejewski and Jedrzejewska 1992;Saunders et al. 1993). During periods of high snow-depth, coyotes prey more frequently on white-tailed deer and, when hunting cooperatively, are able to take down adult elk (Cervus canadensis) (Gese and Grothe 1995; Patterson et al. 1998). Annual variation in snowdepth resulting from El Niño / Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) cycles and global climate change therefore have the potential to greatly influence coyote-prey dynamics (Bowler et al. 2014). ...
Coyotes (Canis latrans) and red fox (Vulpes vulpes) are both generalist predators presently found in the Northeastern United States. This study aimed to identify major prey items of both species in suburban New York, investigate consumption of anthropogenic resources, and examine seasonal changes in diet. Scat samples were collected from 2017 to 2018 for coyotes, and from 2011 to 2012 for red fox. Hairs, feathers, bone fragments and other scat components were classified by comparison with reference collections. Logistic regression was used to determine whether season or location predicted the presence of various food items. The most common food items for coyotes were white-tailed deer (Odocoileus virginianus), found in 54.2% of samples, and cricetid rodents, found in 16.9% of samples. For red fox the most common food items were birds, found in 39% of samples, and cricetid rodents, found in 37.8% of samples. Anthropogenic waste appeared in 11.9% of coyote scat samples and made up 1.3% of the total weight of items recovered from samples. No anthropogenic items were found in red fox scat, nor were remains from threatened piping plovers (Charadrius melodus), known to breed in the study area. Seasonal changes in diet were not detected for either species. Overall our results show that coyotes and red fox in suburban areas of Southern New York are persisting primarily on natural prey items, and not being subsidized by anthropogenic food sources.
... Consideration for activity and spatial segregation between these species at finer spatial and temporal scales than the home range may provide a mechanism for coexistence. In addition, diet may be important to consider as across much of eastern North America, white-tailed deer (Odocoileus virginianus) are an important prey of wolves and coyotes (Arjo et al., 2002;Ballard et al., 1999), though deer age classes selected may differ between species (Arjo et al., 2002;Kautz et al., 2019;Mech & Boitani, 2003;Patterson et al., 1998). The onset of white-tailed deer parturition provides a large influx of vulnerable prey that exhibits immobility and hiding behavior for about 5 weeks postparturition, followed by increased mobility and social behavior (Ozoga et al., 1982). ...
Interference competition occurs when two species have similar resource requirements and one species is dominant and can suppress or exclude the subordinate species. Wolves (Canis lupus) and coyotes (C. latrans) are sympatric across much of their range in North America where white‐tailed deer (Odocoileus virginianus) can be an important prey species. We assessed the extent of niche overlap between wolves and coyotes using activity, diet, and space use as evidence for interference competition during three periods related to the availability of white‐tailed deer fawns in the Upper Great Lakes region of the USA. We assessed activity overlap (Δ) with data from accelerometers onboard global positioning system (GPS) collars worn by wolves (n = 11) and coyotes (n = 13). We analyzed wolf and coyote scat to estimate dietary breadth (B) and food niche overlap (α). We used resource utilization functions (RUFs) with canid GPS location data, white‐tailed deer RUFs, ruffed grouse (Bonasa umbellus) and snowshoe hare (Lepus americanus) densities, and landscape covariates to compare population‐level space use. Wolves and coyotes exhibited considerable overlap in activity (Δ = 0.86–0.92), diet (B = 3.1–4.9; α = 0.76–1.0), and space use of active and inactive RUFs across time periods. Coyotes relied less on deer as prey compared to wolves and consumed greater amounts of smaller prey items. Coyotes exhibited greater population‐level variation in space use compared to wolves. Additionally, while active and inactive, coyotes exhibited greater selection of some land covers as compared to wolves. Our findings lend support for interference competition between wolves and coyotes with significant overlap across resource attributes examined. The mechanisms through which wolves and coyotes coexist appear to be driven largely by how coyotes, a generalist species, exploit narrow differences in resource availability and display greater population‐level plasticity in resource use.
... Coyotes became established on Cape Breton Island, Nova Scotia, Canada, in the 1980s (Parker 1995). Previous research found the most dominant food items for coyotes in Cape Breton were white-tailed deer (Odocoileus virginianus) and snowshoe hare (Lepus americanus), while small mammals such as red-backed vole (Myodes gapperi), masked shrew (Sorex cinereus), and deer mouse (Peromyscus maniculatus) and fruit were also common (Patterson et al. 1998). Coyotes have been documented to prey on moose (Benson and Patterson 2013), but it is unclear to what extent this occurs in CBHNP. ...
... Yet, canids might have an advantage in deep snow. For example, wolves have higher ungulate kill rates in deep snow (Huggard 1993) and white-tailed deer are an important prey item for coyotes in Cape Breton (Patterson et al. 1998;Power et al. 2020). Furthermore, Patterson and Messier (2001) found that in the winter, coyotes in Cape Breton (south of the CBHNP) selected for areas with few to no deer and concluded that despite the decreased deer abundance in these areas (with deeper snow and few trails), deer vulnerability was higher. ...
... Finally, Patterson et al. (1998) found that snowshoe hare were the most common prey item of coyotes in Cape Breton during the winter and snowshoe hare are more common at higher elevations in CBHNP. ...
The dynamic environmental conditions in highly seasonal systems likely have a strong influence on how species use the landscape. Animals must balance seasonal and daily changes to landscape risk with the underlying resources provided by that landscape. One way to balance the seasonal and daily changes in the costs and benefits of a landscape is through behaviorally-explicit resource selection and temporal partitioning. Here, we test whether resource selection of coyotes (Canis latrans) in Cape Breton Highlands National Park, Nova Scotia, Canada is behaviorally-explicit and responsive to the daily and seasonal variation to presumed costs and benefits of moving on the landscape. We used GPS data and local convex hulls to estimate space use and Hidden Markov Models to estimate three types of movement behavior: encamped, foraging, and traveling. We then used integrated step-selection analysis to investigate behaviorally explicit resource selection across times of day (diurnal, crepuscular, and nocturnal) and season (snow-free and snow). We found that throughout the day and seasonally coyotes shifted foraging behavior and altered behavior and resource choices to avoid moving across what we could be a challenging landscape. These changes in behavior suggest that coyotes have a complex response to land cover, terrain, and linear corridors that are not only scale dependent but also vary by behavior, diel period, and season. By examining the resource selection across three axes (behavior, time of day, and season), we have a more nuanced understanding of how a predator balances the cost and benefits of a stochastic environment.
... Here, prey overlapped with mountain lions across prey densities, but spatial overlap increased with coyotes only at higher deer densities as subordinate deer expanded into lower quality habitats (corresponding with Figure 2a and predictions in Northfield et al. 2017). Generalist coyotes then switched from their main prey, lagomorphs, to juvenile deer (Patterson, Benjamin, & Messier, 1998). There is a dearth of specific predatorprey theory for two predator-single prey systems, but recent modeling efforts by Northfield et al. (2012Northfield et al. ( , 2017see Figure a,b therein) and conceptual reviews ) support our prediction that differential spatial overlap with 2 predators with increasing density will generate very different expected survival rates and abundances of shared prey. ...
... In our system, spatial separation of the generalist, coyote, and specialist, mountain lion occurred across an elevational gradient that also corresponded to a forage quality gradient where mule deer forage quality was highest at higher elevations ( Figure 2, Stoner et al., 2018). Coyotes were a generalist predator whose densities and habitats were strongly tied to their lower elevation dwelling, primary lagomorph prey (Hurley et al., 2011;Patterson et al., 1998). Therefore, coyote predation on mule deer juveniles occurred more at lower elevations in lower quality mule deer summer habitats and then only at higher deer density ( Figure 2, Mahoney et al. 2018;Stoner et al., 2018). ...
... Reference Treatment coyotes because of the higher abundance of lagomorph primary prey (e.g., Atwood et al., 2009;Patterson et al., 1998;Stoner et al., 2018). ...
Density‐dependent competition for food reduces vital rates, with juvenile survival often the first to decline. A clear prediction of food‐based, density‐dependent competition for large herbivores is decreasing juvenile survival with increasing density. However, competition for enemy‐free space could also be a significant mechanism for density dependence in territorial species. How juvenile survival is predicted to change across density depends critically on the nature of predator–prey dynamics and spatial overlap among predator and prey, especially in multiple‐predator systems. Here, we used a management experiment that reduced densities of a generalist predator, coyotes, and specialist predator, mountain lions, over a 5‐year period to test for spatial density dependence mediated by predation on juvenile mule deer in Idaho, USA. We tested the spatial density‐dependence hypothesis by tracking the fate of 251 juvenile mule deer, estimating cause‐specific mortality, and testing responses to changes in deer density and predator abundance. Overall juvenile mortality did not increase with deer density, but generalist coyote‐caused mortality did, but not when coyote density was reduced experimentally. Mountain lion‐caused mortality did not change with deer density in the reference area in contradiction of the food‐based competition hypothesis, but declined in the treatment area, opposite to the pattern of coyotes. These observations clearly reject the food‐based density‐dependence hypothesis for juvenile mule deer. Instead, our results provide support for the spatial density‐dependence hypothesis that competition for enemy‐free space increases predation by generalist predators on juvenile large herbivores.
