Cougar Kill Rate and Prey Composition in a Multiprey System

Abstract

Assessing the impact of large carnivores on ungulate prey has been challenging in part because even basic components of predation are difficult to measure. For cougars (Puma concolor), limited field data are available concerning fundamental aspects of predation, such as kill rate, or the influence of season, cougar demography, or prey vulnerability on predation, leading to uncertainty over how best to predict or interpret cougar-ungulate dynamics. Global Positioning System (GPS) telemetry used to locate predation events in the field is an efficient way to monitor large numbers of cougars over long periods in all seasons. We applied GPS telemetry techniques combined with occasional snow-tracking to locate 1,509 predation events for 53 marked and an unknown number of unmarked cougars and amassed 9,543 days of continuous predation monitoring for a subset of 42 GPS-collared cougars in west-central Alberta, Canada. Cougars killed ungulates at rates near the upper end of the previously recorded range, and demography substantially influenced annual kill rate in terms of both number of ungulates (subad F [SAF] 5 24, subad M [SAM] 5 31, ad M 5 35, ad F 5 42, ad F with kittens ,6 months 5 47, ad F with kittens .6 months 5 67) and kg of prey (SAF 5 1,441, SAM 5 2,051, ad M 5 4,708, ad F 5 2,423, ad F with kittens ,6 months 5 2,794, ad F with kittens .6 months 5 4,280). Demography also influenced prey composition; adult females subsisted primarily on deer (Odocoileus spp.), whereas adult males killed more large ungulates (e.g., moose [Alces alces]), and subadults incorporated the highest proportion of nonungulate prey. Predation patterns varied by season and cougars killed ungulates 1.5 times more frequently in summer when juveniles dominated the diet. Higher kill rate in summer appeared to be driven primarily by greater vulnerability of juvenile prey and secondarily by reduced handling time for smaller prey. Moreover, in accordance with predictions of the reproductive vulnerability hypothesis, female ungulates made up a higher proportion of cougar diet in spring just prior to and during the birthing period, whereas the proportion of males increased dramatically in autumn during the rut, supporting the notion that prey vulnerability influences cougar predation. Our results have implications for the impact cougars have on ungulate populations and have application for using cougar harvest to manage ungulates.

Seasonal variation in the feeding ecology of pumas (Puma concolor) in northern California

“…We found that pumas killed a greater number of black-tailed deer in summer and autumn, which coincided with the birth pulse of fawns in summer. Past studies have hypothesized that increases in puma and gray wolf (Canis lupus L., 1758) kill rates during summer were due to increased availability of vulnerable young ungulates (Sand et al 2008;Knopff et al 2010;Metz et al 2012), and the number of fawns killed in summer and autumn in our study area supports this hypothesis. However, the notably lower handling times in summer and autumn may also have contributed to the increase in puma kill rates in summer and autumn and suggest that additional potential mechanisms may be influencing puma kill rates.…”

“…Ungulate migrations therefore result in significant redistributions of resources making it necessary for predators to respond to spatial and temporal variation in prey availability. Recent studies using GPS-collar technology have shown that top-level predators respond to seasonal variation in prey availability and vulnerability in numerous ways, including temporal changes in diet and species-specific kill rates (Sand et al 2008;Knopff et al 2010;Metz et al 2012;Elbroch et al 2013;Gervasi et al 2014).…”

“…Pumas (Puma concolor (L., 1771)) are solitary top-level predators that prey upon ungulates throughout their range in North America and South America (Sunquist and Sunquist 2002), and there are conflicting results and hypotheses concerning seasonal variation in puma feeding ecology (Knopff et al 2010;Ruth and Murphy 2010a). Among kill rates, for example, previous studies have shown either no variation among seasons, an increase in winter, or an increase in summer (Knopff et al 2010;Elbroch et al 2013).…”

“…Among kill rates, for example, previous studies have shown either no variation among seasons, an increase in winter, or an increase in summer (Knopff et al 2010;Elbroch et al 2013). Knopff et al (2010) found higher kill rates in summer and hypothesized that was due to the increased availability of ungulates born in early summer, which are easier to prey upon than adult ungulates. In contrast, Hornocker (1970) hypothesized ungulate kill rates would be lower in summer due to the increased availability of small nonungulate prey.…”

“…To determine whether puma feeding ecology varied among seasons, we studied (i) puma kill rates, (ii) mean daily movements of collared pumas, (iii) puma handling times of adult deer and their correlation with black bear presence, (iv) the elevation at which black-tailed deer were killed, and (v) whether the elevations used by black-tailed deer correlated with the elevations used by pumas. Based on Knopff et al (2010) and the increased availability of black-tailed deer fawns during the birth pulse in summer, we hypothesized that puma kill rates (number of ungulates/week and kg/day) would be higher in summer and autumn than in winter and spring. Based on Cooley et al (2008) and Pierce et al (1999), we hypothesized that mean daily movements of pumas would be shorter in winter when black-tailed deer populations were more concentrated than during other seasons.…”