Cougar kill rates and prey selection in a multiple-prey system in northeast Oregon

Abstract

Cougars (Puma concolor) are a primary predator of mule deer (Odocoileus hemionus) and elk (Cervus elaphus) throughout western North America. Effective management of predator‐prey systems requires a solid understanding of kill rates, prey use, and selection. We implemented a 3‐year study in northeast Oregon to investigate cougar diet, kill rates, and prey selection in a multiple‐prey system to assess the degree to which patterns in cougar predation may be generalizable across systems and to identify selective predation patterns of cougars that may affect ungulate populations. We marked 25 adult cougars with global positioning system (GPS) collars and monitored predation sequences for 7,642 days to identify kill sites. In field investigation of kill sites, we identified remains of 1,213 prey items killed by cougars, of which 1,158 (95.4%) were native ungulates. On average, cougars killed 1.03 ungulates/week (95% CI = 0.92–1.14), but kill rates varied by season, sex, and reproductive status of cougars. Cougars killed ungulate prey 1.55 (95% CI = 1.47–1.66) times more frequently during summer (May–Oct) than winter (Nov–Apr). Kill rates were higher in summer because juvenile ungulates were the most frequently killed prey item and were smaller than prey killed in winter. Female cougars with kittens >6 months old killed prey more frequently than males, solitary females, and females with kittens <6 months old likely in response to the increased energetic burden of raising kittens. Male cougars killed larger prey than females, which likely explains why males killed at similar rates as solitary females, despite the larger body size of males. We documented patterns in prey selection influenced by season and demographic classification of cougars. Diets of male cougars included roughly equal amounts of elk (52.2%) and deer (47.8%), whereas diets of females were dominated by deer (74.6%). Male and female cougars displayed strong patterns of selection for elk calves during summer. During winter, female cougars selected deer fawns and males selected elk calves. Female cougars with kittens >6 months old demonstrated little selection for any age class or species of prey, highlighting an opportunistic foraging strategy to maximize energy gains while feeding young. Across all cougars, we observed a pattern of selection for adult male deer during winter but not summer and did not observe patterns of selection for adult elk according to sex. Our results strongly supported the hypothesis proposed by [Knopff et al. (2010) Journal of Wildlife Management, 74: 1435–1447] that cougar predation is influenced by season and demographic classifications of cougars and our results provide strong evidence that this hypothesis should be generalizable to other areas. The patterns of selection for juvenile elk and deer suggested wildlife managers should consider the potential negative effects of cougars on ungulate populations in areas where juvenile recruitment has been chronically low. © 2014 The Wildlife Society.

Estimating cougar densities in northeast Oregon using conservation detection dogs

“…Four GPS‐collared cougars used our study area from 8 April to 4 July 2011, and we collected at least 1 scat sample from each of these cougars ( = 3.3, range = 1–11). We used a mean home range radius of 8.0 km for males and 4.8 km females (Clark ) to buffer our study area, resulting in an effective trapping area of 741 km 2 and 509 km 2 for males and females, respectively. The top AIC c ranked Huggins capture–recapture model from Program MARK included an additive effect of sex in capture probabilities and accounted for 84.2% of the model weights (Table ).…”

“…Emily WMU, allowing them to generalize across cougars. In addition to cougar and bobcat scat, our dogs were trained to find prey remains at potential cougar kill sites (Clark ). This resulted in the dogs giving false positive indications on prey remains, which were present in non‐target scat (bear in particular) early in our study.…”

“…We excluded 5 km 2 west of Interstate Highway 84 (I‐84) from our survey area because the interstate, which is the southern border of the Mt. Emily WMU, was a barrier to cougar movement (Beier , Clark ). Two detection dog teams (each comprised of a dog and handler) conducted 4 separate survey sessions within each of 8 25‐km 2 and 1 20‐km 2 quadrats within the 220‐km 2 study area (36 total surveys) from 8 June to 4 July 2011 (Fig.…”

“…In association with a concurrent cougar predation study in the Mt. Emily WMU (Clark ), we captured cougars, fitted them with GPS collars, and collected a tissue sample for DNA analysis (see laboratory analysis methods below). We identified individuals known to use our study area (i.e., collared cougars) and compared these to individuals identified from collected scat samples to assess the efficiency of our methods .…”

Big Game and Cattle Influence on Aspen Community Regeneration Following Prescribed Fire

“…Although mountain lions may display strong patterns of selection for elk calves (Clark et al 2014), along with black bears and coyotes occasionally preying on elk, there are no known instances of predators causing elk herd declines in Utah. Predator management occurs in some elk herd units due to declining or depressed mule deer populations on shared ranges, and also occurs when deer herds are chronically below population objectives (UDWR 2011a).…”