Bands of domestic sheep lambing on the open range in south central Wyoming were monitored for predator losses before and following coyote (Canis latrans) removals. Experimental treatments, including (1) no removal (control), (2) removal of 2 adults and their pups, and (3) removal of pups only, were replicated 15 times each. Predation incidents (events) declined 98.2% and the number of sheep killed was reduced by 98.8% when adults and pups were removed. Removing only litters of pups resulted in a decrease of 87.7% in predation incidents and total kills decreased 91.6%. Overall, 23 of 30 predation sequences terminated immediately, whereas in all instances predation ceased within 3 days after removing adult coyotes, their pups, or both. In terms of individuals, denning can be a selective means of coyote depredation control. Removing only litters of offending adults can be nearly as effective in stopping losses as removing the adults. Litter size did not appear to influence kill frequencies. A cost-effectiveness analysis is presented. J. WILDL. MANAGE. 47(4): 1018-1025 Depredations by coyotes on domestic sheep result in greater losses of domestic livestock than any other predator-domestic prey interaction in the western United States (Balser 1974). Although several techniques used to alleviate such losses have been subjectively ranked with regard to efficiency, selectivity, and other factors (U.S. Dep. Inter. 1978a), there are few quantitative data concerning the efficacy of any method. A critical response (West. Reg. Coordinating Comm., WRCC 26, 1980) to a recent policy change for predator control (memorandum from C. D. Andrus to Assistant Secretary for Fish, Wildlife, and Parks, 8 November 1980) accentuates the need for objective evaluation of coyote control methods. Our study attempted to determine the efficacy of denning, the practice of seeking out the dens of depredating coyotes and destroying the young, adults, or both in stopping depredations upon sheep. Denning has been criticized for being unselective in terms of individual animals (Defenders Wildl. 1978, Sierra Club 1978, Humane Soc. 1978) and removal of individuals that obviously are not responsible for depredations. One author maintains that denning is solely a means of coyote population reduction (Gier 1968). Experienced predator control field personnel claim that denning can be a selective method for resolving specific depredation situations. Conceivably, predation on domestic sheep by adult coyotes can be influenced indirectly by removal of litters as opposed to removal of the adults actually killing sheep. Anderson (1969:513514), among others, believes predation should cease when pups are destroyed. Absence of quantitative data leaves these questions unanswered. Cain et al. (1972) recommended costbenefit analyses of predator control methods, stating that such information was yet to be collected. Because most depredation control programs consist of several methods applied simultaneously, the effectiveness of a single control method is difficult to determine (U.S. Dep. Inter. 1978a). Because no other control methods were in effect during the present study, except winter removal for fur, the opportunity 1018 J. Wildl. Manage. 47(4):1983 This content downloaded from 157.55.39.78 on Mon, 20 Jun 2016 07:22:30 UTC All use subject to http://about.jstor.org/terms EFFICACY OF DENNING * Till and Knowlton 1019 was available to measure the cost and effectiveness of denning alone. Cooperation by the Palm Livestock Company and V. E. Dorn is appreciated. B. Gilbert provided helpful counsel and guidance. This study was supported by U.S. Department of Agriculture/SEA Research Grant 59-2491-02-112-0.