Selectivity of Predator Control Techniques in South Texas

Abstract

During a comprehensive study to determine the role of predation in reducing the productivity of the wild turkey (Meleagris gallopavo intermedia), data were gathered on the selectivity and efficiency of M-44's, hunting, strychnine baits, and steel traps for taking certain predators. Selectivity is that property of taking only target species which, for the present study, were coyotes (Canis latrans), bobcats (Lynx rufus), and other small predatory furbearers. The M-44 and hunting were the most selective methods, each taking only target species. Strychnine baits and steel traps took a variety of animals including game animals, raptors, rodents, song birds, and reptiles. The M-44 was probably the most efficient tool for taking coyotes while bobcats were taken more efficiently with steel traps. Nontarget species in one area may be target species in another area so care should be exercised in generalizing about selectivity of predator control techniques. J. WILDL. MANAGE. 38(4):837-844 Recent reports by Leopold (1964) and Cain et al. (1972) have been critical of many aspects of the predator control program as conducted in the United States. Their discussions concern, in large part, the misuse and overuse of predator control methods in the western United States to control coyotes. They state that as a result of these control efforts many animals (nontarget species) besides coyotes are killed or injured because the control techniques are unselective. Of particular interest here is their discussion concerning the nonselectivity of steel traps, various poisons, and cyanide guns (including M-44's). A review of the literature reveals a striking paucity of published objective studies on selectivity of predator control techniques. Robinson presents some data provided by government trappers in Colorado, Wyoming, and New Mexico listing various animals taken by steel traps (1961), by thallium and compound 1080 (1948), and steel traps and cyanide guns (1943). Balser et al. (1968) list potential nest predators killed by strychnine eggs in Minnesota. The purpose of this paper is not to argue for or against predator control but to provide quantitative information in analyzing selectivity of several predator control techniques. This research was conducted as a part of a more comprehensive study designed to determine the role of predation in the productivity of wild turkeys and not simply as an exercise of predacide. The research was supported financially by the Caesar Kleberg Research Program in Wildlife Ecology through the Texas Agricultural Experiment Station, College Station. The King Ranch, Inc., was helpful in providing the area and many facilities. M. Caroline and the Division of Wildlife Services of the U.S. Fish and Wildlife Service are gratefully acknowledged for providing much of the equipment used in this study. W. H. Kiel, Jr., gave many helpful suggestions in the preparation of the manu-