Sheep Depredation by Golden Eagles in Montana

A limited study on two ranches near Dillon, Montana, near the end of the lambing season in 1974 revealed that 44 domestic lambs were killed by golden eagles (Aquila chrysaetos). This was 76 percent of all deaths recorded during the short study. Using an average docking percent of 90 (based on years before severe eagle problems developed), the 76 percent eagle predation, and the 1974 docking percentages, the ranchers estimated an eagle kill of 1,092 lambs valued at about $38,000. The U.S. Fish and Wildlife Service livetrapped and removed 249 golden eagles from the ranches during the next three springs. During 1975, when 145 eagles were removed, docking percentages were even lower than in 1974, and the ranchers estimated a loss of $48,000. During 6 hours on one ranch in 1975, I found 15 fresh eagle kills. Less severe eagle problems occurred during 1976 and 1977, and the docking percentages improved. The effect of the trapping program on predation could not be evaluated. Lamb losses were greatest during the years of greatest trapping success. Decreasing lamb losses in 1976 and 1977 may have resulted from increasing populations of jackrabbits (Lepus spp.) throughout the West. Juvenile and subadult golden eagles caused most of the predation. A decline of jackrabbits may have caused these young birds, which had no established territories, to concentrate on the lambing grounds. As numbers of sheep decline on western ranches, eagles may take a greater percentage of lambs from the remaining herds. With golden eagles totally protected, increasing predation on lambs should be expected, especially when natural prey is scarce. Because of the expense and the relative scarcity of qualified personnel, the trapping and moving of depredating eagles is not a practical operational procedure. Non-lethal methods of eagle management show little promise for alleviating lamb losses. Experiments should be conducted combining scare tactics, including shooting near the birds, with limited killing for reinforcement. Illegal control may endanger juvenile bald eagles (Haliaetus leucocephalus) and result in the killing of many golden eagles if ranchers are not assured of aid when a serious depredation problem occurs. The extent, or even existence, of predation by golden eagles on livestock is controversial. In fact, for many admirers of this majestic bird, simply discussing it at a pest conference is sheer heresy. However, the hunting of golden eagles, from the ground and air, was common throughout the West until the Bald Eagle Act of 1940 was amended in 1962, providing protection for the golden eagle. The Act allows the shooting or trapping of golden eagles when serious depredations to the livestock industry are determined but forbids shooting from aircraft and poisoning, except for research purposes. Until 1970, governors could, at the discretion of the director of the U.S. Fish and Wildlife Service (USFWS), obtain "blanket" permits for taking golden eagles in specified areas (usually a county or block of counties) for a specified period of time. The occasional shooting of juvenile bald eagles, mistaken for golden eagles, was feared and added to public sentiment against killing any eagles. Awareness of a general threat to birds of prey from pesticides during the 1960's heightened public concern for all raptors. On 5 March 1970, then Secretary of Interior W.J. Hickel sent a memorandum to the director of the USFWS. Excerpts follow: The several staff papers, studies, and reports relating to the question of controlling golden eagles to prevent livestock depredations have been studied very carefully. The studies referred to indicate that depredations are not widespread and that they do not threaten either the local economies or the livestock industry generally. . . . In processing applications from the Governors of the several western States, you are instructed to make a detailed investigation into the question of economic hardship and to exercise the most careful judgment regarding the question of whether or not the situation is so critical that extraordinary measures must be taken for the protection of any particular domesticated flock or herd in said States. "Blanket" permits as such will no longer be issued. This action is not intended to preclude the issuance of necessary permits for scientific exhibition, or religious purposes, or the issuance of individual permits where, after investigation and report to me, I conclude that such individual permit is necessary. [Emphasis mine.] Some idea of the resistance to eagle control can be gathered from the following. In 1976, the Governor of Texas requested a depredations control order for the purpose of taking golden eagles. The director of the USFWS denied the request partly on the following basis: 1) Relying, as the March 5, 1970, order does, on scientific knowledge about the behavior of eagles, there is no cause to reconsider the said order unless data are presented demonstrating the fallacy of currently accepted knowledge on the behavior of eagles or demonstrating a change in the actual behavior patterns of golden eagles. No such data have been submitted... .......................................................................................... The U.S. Fish and Wildlife Service, The Montana Fish and Game Department, The University of Montana, and the Wildlife Management Institute, cooperating.