A Model for Exploited Bobcat Populations in Wyoming

Abstract

Rising fur prices and concurrent increases in aesthetic and sporting values suggest a need for more intensive management of bobcats (Lynx rufus). One hundred sixty-one animals collected from 1970 through 1973 were used to provide information on reproduction, mortality, and age-structure. An analysis of 81 reproductive tracts indicated that all females were sexually active during the breeding season. The peak period of breeding was in March. The average litter size was 2.79 and the majority of births were within two weeks of 1 June. Age-structure and harvest data supplied a basis from which to estimate annual mortality rates. From information on reproduction and mortality a model describing annual population fluctuation was constructed. Applications of this concept of the mechanics of bobcat populations are discussed with regard to sustained optimum yields and predation control. J. WILDL. MANAGE. 39(2):408-415 Bobcats, to date, have been excluded from most wildlife management plans. Harvest has been attributable to predator control efforts by U.S. Fish and Wildlife Service (USFWS) personnel and trapping by a few private individuals. Management has consisted of a laissez faire approach over much of the animal's range. Recent events suggest that more intensive management of this species may be in order if populations are to be maintained at levels offering optimum yield harvests. Prior to 1967 bobcat pelts fluctuated in price from $7 to $10 on the open market. These prices precipitated no intensive trapping efforts. During the winter of 196667, the price of bobcat furs increased to an average of $20. Prices fluctuated around this level until the winter of 1969-70 when they increased to about $36. Pelts have increased steadily in value since that time. By the spring of 1974 a large hide could bring upwards of $125. Concurrent with this increase in economic value has been an increase in sporting interest. Both predator calling and coursing with hounds have become popular as winter sport. Superimposed over these developments is an increasing awareness by the general public that all animals have a place in the ecosystem and are valuable by virtue of their presence. These considerations emphasize the economic, recreational, and aesthetic importance of the species. This paper is offered as an aid to understanding the dynamics of bobcat populations in Wyoming, and how they may be affected by exploitation. The data and findings are in large measure the results of the outstanding cooperation which I received from USFWS personnel throughout Wyoming. Without their assistance the study would have been hampered severely. This research was supported by an NDEA Title IV Graduate Fellowship and by a Theodore Roosevelt Memorial Fund Grant. Thanks are due to L. McDonald for his advice during the preparation of the manuscript. I gratefully acknowledge the assistance of T. J. Clifford, R. L. Czaplewski, and A. J. Welch for their cooperation in this work. MATERIALS AND METHODS Skulls were obtained from 161 bobcats taken throughout Wyoming by cooperating hunters and by me. Collections were made from the fall of 1970 through the 1 Present address: Wyoming Game and Fish Department, 5400 Bishop Blvd., Cheyenne 82001. 408 J. Wildl. Manage. 39(2):1975 This content downloaded from 157.55.39.54 on Thu, 30 Jun 2016 04:29:47 UTC All use subject to http://about.jstor.org/terms BOBCAT POPULATION MODEL ? Crowe 409 Table 1. Distribution by sex, month, and year of 161 bobcats captured throughout Wyoming during the years 1970 to 1973. Males are represented by the first column and females by the second in each case. Sex Age Month of capture Year of capture class Fe(years) Male male Dec. Jan. Feb. Mar. Other Total 197