Bobcat Density and Prey Selection in Central Arizona

Abstract

We trapped, ear-tagged, trailed with hounds, and collected scats from bobcats (Lynx rufus) on 28.8 km2 of the Three Bar Wildlife Area in central Arizona from May 1975 to May 1976. Their minimum estimated density on the study area was 1 per 3.6-4.1 km2. The contents of 176 scats indicated that rodents (67%) and lagomorphs (38%) were most frequently taken. The frequencies of their remains in the scats did not vary significantly among bimonthly samples. Populations of rodents and lagomorphs varied significantly during the year, but neither was correlated with bobcat prey selection. J. WILDL. MANAGE. 43(3):666-672 We studied bobcats on the Three Bar Wildlife Area in central Arizona from May 1975 to May 1976 to determine their density in the lower/upper Sonoran lifezone transition, seasonal diets in this habitat, and the relation of diet to prey availability. A statewide decline and subsequent slow recovery in mule deer (Odocoileus hemionus) populations in the early 1960's (Jantzen 1964) prompted the Arizona Game and Fish Department to initiate a series of studies to determine the causes of poor fawn survival in Arizona's mule deer herds. In 1970 the Department enclosed 246 ha of typical mule deer habitat on the Three Bar Wildlife Area with predator-resistant chain link fencing. All bobcats and coyotes (Canis latrans) were removed from the enclosure, and the interior has since been monitored for tracks to ensure that it has remained predatorfree. Between 1971 and 1975, annual deer herd composition and population counts on the Three Bar were compared with the same data from inside the enclosure. The results indicated virtually complete fawn survival inside the enclosure, while survival outside (where mule deer hunting has been closely regulated and monitored since 1964) was lower (LeCount 1975, 1977). Bobcat or coyote predation on fawns may be limiting herd size on the Three Bar. Similar findings for javelina (Dicotyles tajacu) indicate that predation may also be limiting their numbers (Day and Smith 1975). Bobcat predation on mature deer has been well documented (Young 1928, Dill 1947, Petraborg and Gunvalson 1962); thus it is logical to assume that they could prey extensively on the more vulnerable fawns. The Three Bar Wildlife Area is an ideal location for investigating such predator-prey relations because the hunting and trapping of predators has been prohibited there since 1972. We thank A. and K. LeCount, N. Woolsey, and the Three Bar research crew for their frequent assistance. We also acknowledge C. Hanson and his Desert Museum co-workers, R. Babcock, L. K. Sowls, and C. R. Hungerford, and L. and M. Jones. 1 A contribution of the Arizona Cooperative Wildlife Research Unit, University of Arizona, U.S. Fish and Wildlife Service, Arizona Game and Fish Department, and the Wildlife Management Institute cooperating. 2 Present address: Department of Zoology, Duke University, Durham, NC 27706. 666 J. Wildl. Manage. 43(3):1979 This content downloaded from 157.55.39.230 on Tue, 07 Jun 2016 05:24:03 UTC All use subject to http://about.jstor.org/terms BOBCAT DENSITY AND PREY IN ARIZONA Jones and Smith 667 Table 1. Percentages of occurrence of prey items in 176 bobcat scats collected on the Three Bar Wildlife Area, Arizona. Jun-Jul Aug-Sep Oct-Nov Dec-Jan Feb-Mar Apr-May Annual (42)a (41) (23) (19) (34) (17) (176) Food item N % N % N % N % N % N % N % Total rodentsb 29 69 32 78 16 70 11 58 19 56 10 59 117 67 Neotoma spp. 17 41 15 37 6 26 4 21 9 27 5 29 56 32 Heteromyid 10 24 7 17 2 9 3 16 4 12 2 12 28 16 Thomomys bottae 2 5 2 5 3 13 1 5 1 6 9 5 Spermophilus variegatus 2 5 3 13 1 5 1 3 1 6 8 5 Peromyscus spp. 3 7 1 2 1 6 5 3 Ammospermophilus harrisi 1 4 1 3 2 1 Unknown rodent 5 12 10 24 3 13 3 5 6 18 2 12 29 17 Lagomorph 13 31 16 39 8 35 8 42 14 41 7 41 66 38 Odocoileus spp. 4 10 1 4 5 3 Dicotyles tajacu 1 2 1 1 Mephitis spp. 1 2 1 1 Canis spp. 1 4 1 1 Eggshell 8 19 4 10 6 35 18 10 Unknown bird 1 2 4 12 2 12 7 4 Unknown snake 1 3 1 1