Population Characteristics of Bobcats in Washington State

Abstract

Age structures, sex ratios, and reproductive status of two bobcat (Felis rufus) populations in Washington state were determined by examination of 1,238 bobcat carcasses. Carcasses were collected between October and March from hunters and trappers from 1976 through 1980. Bobcat kittens ( 1 and 2 years old) females averaged 2.54 kittens/litter in WW and 2.79 in EW. Average age of bobcats killed by hunters in WW was 2.45 years compared to 2.79 for trapped specimens, and age decreased for both methods as the season progressed. Sex ratios were 1.31 for bobcats shot and 1.01 for those trapped. The proportion of males in the hunted sample increased from November through February. J. WILDL. MANAGE. 49(3):721-728 Management of bobcat populations should be based on knowledge of population size and trends aided by information on age structure, sex ratio, and reproductive rates. Recent interest in bobcat populations, stimulated by higher fur prices and subsequent increase in harvest pressures (Deems and Pursley 1978), has emphasized the need for these data. Hunter and trapper cooperation in providing bobcat carcasses and aging by dental cementum annuli (Crowe 1972) have resulted in recent analyses of bobcat age structures (Crowe 1975a, Fritts and Sealander 1978, Escherich and Blum 1979). We discuss estimates of age structures, sex ratios, and reproductive parameters of bobcats taken by hunting and trapping in Washington state from 1976 through 1980. Changes in these sample statistics, relative to harvest method and time of harvest season, are interpreted. Hall and Kelson (1959:970-971) described two bobcat subspecies in Washington: Lynx (Felis) rufus fasciatus occurs west of the Cascade Mountain crest and L. r. pallescens is found east. We treated our data as two separate populations based on this geographic and subspecific delineation. Bobcats are classified as game animals and furbearers in Washington, with separate management policies for western and eastern Washington. Harvest is primarily by hunting with hounds and trapping, with a small proportion taken incidentally while hunting other species. Hunting and trapping activities overlapped spatially, though not always temporally, due to different harvest seasons. Western Washington (WW) is characterized by large areas of coniferous forest habitat in varying stages of growth effected by logging or burning (Franklin and Dyrness 1973). Bobcat density on a study area in WW was approximately 1/5.5 km2; males occupied radio-telemetry-determined home ranges of 6.5-15.5 km2 and female home ranges were from 3.9 to 8.4 km2 (Brittell et al. 1979). Mountain beavers (Apolodontia rufa) and snowshoe hares (Lepus americanus) were the primary foods of bobcats in WW (Knick et al. 1984). Eastern Washington (EW) is a more diverse region ranging from dry steppe to forest (Daubenmire 1956). Primary productivity is generally lower than in WW due mainly to drier climate on the east side of the Cascade Moun721 'Present address: Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT 59812. 2 Present address: 4145 55th SW, Seattle, WA 98116. This content downloaded from 157.55.39.148 on Tue, 12 Jul 2016 05:20:35 UTC All use subject to http://about.jstor.org/terms 722 BOBCAT POPULATIONS IN WASHINGTON * Knick et al. J. Wildl. Manage. 49(3):1985