Seasonal Foods of Blacktail Jackrabbits and Nuttall Cottontails in Southeastern Idaho

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The diets of blacktail jackrabbits (Lepus californicus) and nuttall cottontails (Sylvilagus nuttalli) were estimated by examination of fecal pellet botanical composition. The deficiencies of fecal analysis are noted, but dietary trends and relative importance of forage plants are accurate. Cluster analysis combined leporid pellets into 2 distinct groups based on botanical composition, representing feeding during spring-summer and fall-winter periods. Seven variables (plant species) accounted for significant differences (P<O.05) within and among the leporids studied in seasonal food selection. Generally, grasses and forbs were most abundant in blacktail jackrabbit and nuttall cottontail pellets during the spring-summer period, whereas shrubs were most abundant during the fall-winter period. Diet similarity was greatest between blacktail jackrabbits and nuttall cottontails during the same season. Diversity of forage consumed was greatest for both leporids during spring-summer periods. Habitat segregation minimizes competition for forage between the leporids studied. Livestock grazing appears to limit leporid population density rather than alter leporid food habits. During the period of research, authors were graduate research assistant and professor, respectively, Department of Range Science, Colorado State University, Fort Collins 80523. MacCracken's present address is P.O. Box 3145, Palmer, AK 99645. The authors thank O.D. Markham, W.J. Arthur, D.K. Halford, M.K. Johnson, G.C. Lucich, R.L. Potter, E.R. Johnson, and D. Simonson for their participation in this study. M.E. Voorhees did the microhistological work. This project was supported in part through grant DE-A507-761D-1526, MOD 006 from the U.S. Department of Energy, Idaho National Engineering Laboratory Ecology Program to Colorado State University. Manuscript received September 28, 1982. Leporids play a major role in the ecology of the Great Basin area of the western USA. They compete with livestock and other wildlife for forage, cause extensive crop damage, and are a major food source for coyotes (Clark 1972, MacCracken and Hansen 1982a) and other predators which in turn kill livestock and game animals. Leporids are primarily herbivorous, but have been reported to consume carrion (Hansen and Flinders 1969, DeCalesta 1971). When jackrabbits (Lepus spp.) become overly abundant, about every 10 years, their impact on the ecosystem is tremendous. In January 1982 such a situation existed, and it was estimated that local people killed about 64,000 jackrabbits during 6 different roundups at Mud Lake, Ida., bordering our study area. Information on food selection by jackrabbits during low and high population levels helps to determine if such controversial management procedures are justified. The foods of most species of leporids have been documented in the literature (Hansen and Flinders 1969, DeCalesta 1971). Feeding by blacktail jackrabbits (Lepus californicus) may have been the most thoroughly examined (Uresk 1978, Westoby 1980). Even though studies dealing with leporid food habits have been published, few have investigated seasonal food selection by sympatric leporids. The purpose of this paper is to present the results of a study which examined seasonal food habits of sympatric blacktail jackrabbits, and nuttall cottontail (Sylvilagus nuttalli) in southeastern Idaho when the jackrabbit population was at low levels. 256 JOURNAL OF RANGE MANAGEMENT 37(3), May 1984 This content downloaded from 40.77.167.54 on Wed, 06 Jul 2016 04:25:14 UTC All use subject to http://about.jstor.org/terms