Cougar Food Habits in Southern Utah

Abstract

Diets of cougars (Felis concolor) were studied from December 1978 to August 1981, on a 4,500km2 study area near Escalante, Utah. Prey eaten by cougars was estimated from analysis of 112 animals consumed as prey and from 239 cougar scats. Composition of diet was corrected based on feeding trials using captive cougars. Mule deer (Odocoileus hemionus) were found to be the major prey item, 81% of biomass consumed. Lagomorphs, large rodents, and smaller predators were also important components of the diet. Cattle comprised less than 1% of the diet, although they were abundant on the cougars' summer range. Age structure of deer killed by cougars indicated that older (>7 years) deer were killed more often than expected (P < 0.005). J. WILDL. MANAGE. 48(1):147-155 Cougar dietary habits have been studied in Utah (Connolly 1949, Robinette et al. 1959), Idaho (Hornocker 1970), Arizona (Shaw 1977, 1982), Oregon (Toweill and Meslow 1977), British Columbia (Spalding and Lesowski 1971), and the West in general (Young and Goldman 1946). Food habits were generally similar, the diet consisting predominantly of wild and domestic ruminants, with lesser amounts of rodents, rabbits, and other predators. Results of the more intensive studies in Utah, Idaho, and Arizona differed, however, in the relative proportions of mule deer, elk (Cervus elaphus), and cattle in the diet. During years of peak snowshoe hare (Lepus americanus) abundance in British Columbia, 27% of the cougars' diet was composed of hares, indicating that cougars take advantage of numerically abundant prey. Because inferences are frequently drawn from food-habits studies of predators to predict their influence on the dynamics of prey populations, it is important tha results from such studies accurately describe the diet. Floyd et al. (1978) determined that the number of field-collectible scats produced by gray wolves (Canis lupus) was inversely related to prey size. Selective feeding on flesh alone resulted in loose, liquid scats that would seldom be found in the field. Consumption of smaller prey, on the other hand, would generally include more indigestible material and would result in more persistent scats. In addition, Johnson and Aldred (1982) and Weaver and Hoffman (1979) have documented differential digestibility of smaller mammals and the problems of enumerating small mammals in scats. The method employed to collect foodhabits data may further reduce general applicability. Dietary samples from cougars killed by sport hunters or damagecontrol personnel may be biased toward specific groups of cougars or may be restricted to specific seasons of the year (Young and Goldman 1946, Robinette et al. 1959, Spalding and Lesowski 1971, Toweill and Meslow 1977). Only Robinette et al. (1959) and Shaw (1982) reported summer food habits. Several authors have indicated that vulnerability of mule deer to cougar predation is influSFunding was provided by Utah Div. of Wildl. Resour. (UDWR), and the study was conducted under auspices of the Utah Coop. Wildl. Res. Unit, UDWR, Utah State Univ., U.S. Fish and Wildl. Serv., and Wildl. Manage. Inst. cooperating. 2 Present address: Idaho Department of Fish and Game, P.O. Box 21, Soda Springs, ID 83276. J. Wildl. Manage. 48(1):1984 147 This content downloaded from 157.55.39.175 on Thu, 11 Aug 2016 06:18:10 UTC All use subject to http://about.jstor.org/terms 148 COUGAR FOOD HABITS * Ackerman et al. enced by sex of the deer and season of the year (Robinette et al. 1959, Hornocker 1970, Shaw 1977) and by age of the deer (Hornocker 1970, Spalding and Lesowski 1971). This paper reports on an intensive effort to determine the year-round diet of cougars and relative vulnerability of the various age-classes of mule deer to cougar predation between December 1978 and August 1981. We are grateful to A. J. Button for his indispensable help as our houndsman and chief technician. T. Rettberg, our pilot, flew many long days for us. W. Button helped in capture operations and provided a site for our winter camp. The Button and Coleman families, M. Reid, F. Van Dyke, K. A. Johnson, D. Shepardson, K. Parr, M. H. Hemker, B. A. Blakesley, R. E. Gruenig, L. Cox, and R. D. Peters assisted with the field work. F. H. Coles, J. G. Guyman, N. V. Hancock, F. C. Jensen, and T. Gardiner of the UDWR provided important support and advice. F. Coles, J. A. Gessaman, and F. F. Knowlton gave valuable criticism of the manuscript. Cooperation was provided by the U.S. For. Serv. and Bur. of Land Manage. The Ecol. Cent. at Utah State Univ. provided assistance during the analysis stage.