Dynamics of a Harvested Bobcat Population in Oklahoma

Abstract

Demographic parameters of bobcats (Felis rufus) in Oklahoma were determined in order to evaluate population status. A maximum density of one adult bobcat per 11.0 km2 was estimated for the Ouachita National Forest in southeastern Oklahoma assuming complete intersexual home-range overlap and no unoccupied areas. Statewide population trends determined by scent-station surveys declined (P = 0.004) from 1977 to 1981, with a finite rate of increase (X) of 0.89/year. Sex and age structure and reproductive rates were determined from examination of 553 carcasses and/or skulls. Sex ratios did not differ (P = 0.16) from an expected 50:50 ratio. The age structure of the harvest was 26% juveniles, 32% yearlings, and 43% adults. Pregnancy rate of yearling females (46%) was lower (P < 0.001) than in adults (92%). Yearling pregnancy rate was further reduced following a major drought which probably caused the observed decline in prey abundance on the Ouachita National Forest. Mean in utero litter sizes of yearlings and adults were 2.3 and 2.7 kittens/litter, respectively. Estimates of adult survival rate ranged from 0.53 to 0.66; juvenile survival was 0.30. Harvest was the sole source of non-study-related mortality of radio-collared bobcats. Continued harvest of already low density bobcat populations may further depress the populations and result in local extirpations. Reduction of harvest during periods of negative rates of increase is recommended. J. WILDL. MANAGE. 49(2):283-292 The economic value of bobcat pelts has increased dramatically during the last decade. The 1970-71 nationwide average price of bobcat pelts was $12 (Deems and Pursley 1978). In Oklahoma, the average price paid for bobcat pelts increased from $12 in 1974-75 to $67 in 1980-81 (Day 1978; Okla. Dep. Wildl. Conserv., unpubl, rep., Fed. Aid Proj. W-82-R-20, 1982). Increased value of pelts has resulted in increased harvest in Oklahoma as well as nationally. The 1974-75 estimated harvest of bobcats in Oklahoma was 1,458 compared to 2,782 in 1980-81 (Okla. Dep. Wildl. Conserv., unpubl. reps., Fed. Aid Proj. W-82-R-19, 1980, and W-82-R-20, 1982). The reported nationwide harvest in 1970-71 was 10,822 (Deems and Pursley 1978) but increased to 86,998 in 1980-81 (U.S. Fish and Wildl. Serv. unpubl. rep., Amendment to Appendix II of the CITES, 1982). A better understanding of bobcat population dynamics is needed to evaluate the impact of increased harvest pressure. Crowe (1975a) presented a model of an exploited bobcat population in Wyoming. He assumed a non-age-related pregnancy rate of 100% and estimated the annual adult survival rate as 67%. This may have been biased because his sample was drawn from an apparently declining population (Caughley 1966). The purpose of the present study was to quantify demographic parameters of bobcats in Oklahoma, population density and trend, sex and age composition, and rates of reproduction and mortality, and to evaluate population status and assess the effects of exploitation. The effects of fluctuations in food availability on age-specific reproductive parameters were also examined. This study would not have been possible without the advice and guidance of J. H. Shaw, F. Schitoskey, P. A. Vohs, J. M. Gray, and G. A. Bukenhofer. Field assistance provided by M. E. Stewart, M. E. Wagner, and L. A. Ashford is greatly appreciated. C. D. Clubb, T. G. Clubb, and D. C. Clubb assisted with trapping. W. D. Warde assisted with statistical analyses. I am grateful for the assistance of the pilots and staff of the Poteau Flying Service. Special thanks are due to R. T. Hatcher for providing unpublished data from the Okla. Dep. of Wildl. Conserv. C. J. Brand reviewed an earlier draft of this manuscript. This study was funded by a contribution from Okla. Fed. Aid to Wildl. Restoration Proj. W-129-R through the Okla. Coop. Wildl. Res. Unit. Cooperators of the Okla. Coop. Wildl. Res. Unit include Oklahoma State Univ., Okla. Dep. of Wildl. Conserv., U.S. Fish and Wildl. Serv., and Wildl. Manage. Inst.