Wolf Depredation Trends and the Use of Barriers to Protect Livestock in Western North America MARCO MUSIANI, * §§ CHARLES MAMO,† LUIGI BOITANI,‡ CAROLYN CALLAGHAN,§ C. CORMACK GATES, * LIVIA MATTEI, ** ELISABETTA VISALBERGHI,†† STEWART BRECK,‡‡ AND GIULIA VOLPI† * Faculty of Environmental Design, The University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada †Southern Alberta Conservation Cooperative, Box 314, Cremona, Alberta T0M 0R0, Canada ‡Department of Animal and Human Biology, University of Rome, Viale dell’Universita’ 32, Rome, Italy §Central Rockies Wolf Project, 713 Main Street, Canmore, Alberta, Canada ** Corpo Forestale dello Stato, Ministero delle Politiche Agricole e Forestali, Pescara, Italy ††ISTC, National Research Council, Via Aldrovandi 16b, 00197 Rome, Italy ‡‡U.S. Fish and Wildlife Service, National Wildlife Research Center, 4101 La Porte Avenue, Fort Collins, CO 80521, U.S.A. Department of Animal and Human Biology, University of Rome, Viale dell’Universita’ 32, Rome, Italy §§email mmusiani@ucalgary.ca Abstract: In Alberta, Canada (1982–2001), and in Idaho, Montana, and Wyoming, United States (1987– 2001), wolves ( Canis lupus) killed various domestic animals, among which the major prey were sheep in the United States (68%, n = 494) and cattle in Canada (95%; n = 1633). Under recovery programs, the wolf Q1 population increased in the United States, and depredation events increased proportionately. In both countries, the number of domestic animals killed each year was correlated with the number of wolves killed by government authorities for depredation management. We tested the ability of antiwolf barriers made of flags hanging from ropes to impede wolf access to food and livestock. In 18 experiments, barriers prevented captive wolves (n = 9) from accessing food for up to 28 hours and allowed daily separation of wolves to administer contraceptive pills to a female wolf. Barriers prevented access by wild wolves to 100-m 2 baited sites during two 60-day tests. We also set barriers around three cattle pastures. In Alberta during two 60-day trials on 25-ha pastures, wolves approached barriers on 23 occasions but did not cross them, and no cattle were killed. Wolves killed cattle on neighboring ranches during the trials and before and after the trials on the tested ranches. In Idaho, four radiocollared wolves crossed barriers and killed cattle in a 400-ha ranch after 61 days of barrier exposure. Our results suggest that antiwolf barriers are effective in deterring captive and wild wolves for >1 and ≥60 days, respectively, and that wild wolves switch to alternative livestock when excluded from one herd of livestock. Our depredation data indicate that protecting livestock from wolves reduces the necessity for killing wolves. Barriers could play a role among the limited set of preventive measures available and offer a cost-effective mitigation tool for the problem of livestock depredation on a local scale. Tendencias en la Depredaci´ on por Lobos y el Uso de Barreras para Proteger Ganado en Norte Am´ erica Occidental Resumen: En Alberta, Canad´ a (1982 a 2001) y en Idaho, Montana y Wyoming, Estados Unidos (1987 a 001), lobos ( Canis lupus) mataron a varios animales dom´ esticos entre los que la mayor´ ıa fueron ovejas en Estados Unidos (68%, n = 494) y ganado vacuno en Canad´ a (95%; n = 1633). La poblaci´ on de lobos in- crement´ o en Estados Unidos bajo programas de recuperaci´ on y los eventos de depredaci´ on incrementaron proporcionalmente. En ambos pa´ ıses, el n´ umero de animales dom´ esticos depredados cada a˜ no se correlacion´ o con el n´ umero de lobos matados por autoridades gubernamentales de gesti´ on de depredaci´ on. Probamos la efectividad de barreras contra lobos hechas de banderas colgando de cuerdas para impedir el acceso de lobos a alimento y ganado. En 18 experimentos, las barreras previnieron que lobos cautivos (n = 9) ac- cedieran a alimento por hasta 28 horas y permitieron la separaci´ on diaria de lobos para administrar p´ ıldoras Paper submitted February 3, 2003; revised manuscript accepted May 18, 2003. 1 Conservation Biology, Pages 1–10 Volume 17, No. 6, December 2003