Damage and Damage Identification

Left, Bald eagle, Haliaeetus leucocephalus; right, golden eagle, Aquila chrysaetos

Golden eagles are more likely to prey on livestock than are bald eagles. Both species readily feed on livestock carrion and carcasses left by foxes and coyotes, although some individuals prefer live prey to carrion. Eagles are efficient predators and can cause severe losses of young livestock, particularly where concentrations of eagles exist. Generally, they prey on young animals, primarily lambs and kids, although they are capable of killing adults. Eagles also take young deer and pronghorns, as well as some adults. Eagles have three front toes opposing the hind toe, or hallux, on each foot. The front talons normally leave wounds 1 to 3 inches (2.5 to 7.5 cm) apart, with the wound from the hallux 4 to 6 inches (10-15 cm) from the wound made by the middle front talon. On animals the size of small lambs and kids, fewer than four talon wounds may be found, one made by the hallux and one or two by the opposing talons. Talon punctures typically are deeper than those caused by canine teeth and somewhat triangular or oblong. Crushing between the wounds usually is not found, although compression fractures of the skulls of small animals may occur from an eagle’s grip. Bruises from their grip are relatively common.

Eagles seize small lambs and kids anywhere on the head, neck, or body, frequently grasping from the front or side. They usually kill adult animals, or lambs and kids weighing 25 pounds (11 kg) or more, by multiple talon stabs into the upper ribs and back. Their feet and talons are well adapted to closing around the backbone, with the talons puncturing large internal arteries, frequently the aorta in front of the kidneys. The major cause of death is shock produced by massive internal hemorrhage from punctured arteries or collapse of the lungs when the rib cage is punctured. Eagles also may simply seize young lambs, kids, or fawns and begin feeding, causing the prey to die from shock and loss of blood as it is eviscerated.

Eagles skin out carcasses, turning the hide inside out while leaving much of the skeleton intact, with the lower legs and skull still joined to the hide. On very young animals, however, the ribs often are neatly clipped off close to the backbone and eaten. Eagles frequently do not eat the breast bone, but some clip off and eat the lower jaw, nose, and ears. Quite often, they remove the palate and floor pan of the skull and eat the brain. They may clean all major hemorrhages off the skin, leaving very little evidence of the cause of death, even though there may be many talon punctures in the skin. Ears, tendons, and other tissues are sheared off cleanly by the eagle’s beak.

Larger carcasses heavily fed on by eagles may have the skin turned inside out with the skull, backbone, ribs, and leg bones left intact, but with nearly all flesh and viscera missing. The rumen normally is not eaten. Eagles may defecate around a carcass, leaving characteristic white streaks of feces on the soil. Their tracks may be visible in soft or dusty soil. Small downy feathers often are evident on vegetation where eagles have fed.

Legal Status

Both bald and golden eagles and their nests and nest sites are protected by the federal Bald Eagle Protection Act and state regulations. In June 1940, legislation was passed that outlawed killing, possessing, selling, or trading any live or dead bald eagle, or any part of a bald eagle, including feathers, eggs, and nests. In 1962, the same protection was afforded the golden eagle. Provisions in these laws allow specific permits to be issued by the US Department of Interior for the taking of eagles or their parts for scientific research, for exhibitions and Indian religious purposes, and for control of predation to domestic livestock (50 CFR, Part 22). Permits for control of eagles to prevent or reduce predation on livestock, how-ever, have not been issued by the US Department of Interior since 1970. Also, regulations promulgated by the Secretary of Interior under authority of the Endangered Species Act of 1973 (as amended) prohibit “taking” of an endangered species, such as bald eagles. Because golden eagles also are protected, they too cannot be “taken.” Congress has defined the term take as follows: “to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct.”

A depredation permit from the US Department of Interior is required to carry out any eagle damage control activities. This requires a formal consultation and biological assessment under Section 7 of the Endangered Species Act for bald eagles. At present, permits to take, harass, or scare depredating golden eagles are issued routinely to the western Regional Director of the USDA-APHIS-ADC by the USFWS. Only USDA-APHIS-ADC personnel are permitted to engage in eagle damage control activity under such permits.

Economics of Damage and Control

Although eagles may benefit producers by preying on rodents and rabbits and feeding on carrion, they may have a major adverse impact on individual producers by preying on young lambs, kids, exotic game species, and other game animals. Losses are most severe where nesting eagles prey repeatedly on the same flock or where migrant eagles concentrate in an area and cause major losses over a short period of time.

Whether eagle damage control is necessary and beneficial depends on the levels of loss, the costs of control, and the effectiveness of control efforts for each damage situation. The severe restrictions on the application of any type of eagle control and the long delays in securing the necessary permits and/or assistance from the US Department of Interior are major constraints to the protection of livestock.