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Livestock Depredation Investigations

Domestic animals can die for a variety of reasons—due to disease, weather, injury, and predators. When a livestock owner believes wolves caused the loss or injury of their livestock, ODFW uses an evidence-based investigation process to determine if wolves were involved.  The goal is not to determine the livestock animal’s cause of death, as in some cases that could require a veterinary pathologist (e.g., illness, injury, age, poisonous plants).

When doing an investigation, ODFW closely examines the physical evidence (on the animal or the scene) to determine if the domestic animal was actually killed or injured by a predator—and not just scavenged by one after dying from another cause.  If the death or injury is determined to be predator-caused, further examination is needed to determine if wolves (rather than coyotes, cougars, bears, or domestic dogs) were responsible.  

Most confirmed wolf attacks show pre-mortem bite scrapes and severe tissue trauma in specific locations (rear hindquarters above the hock, elbows, and flanks) on the animal.  In some cases, livestock losses cannot be confirmed to be caused by wolves because there is not enough evidence. In others, an investigation finds the domestic animal died by an entirely different cause. More detail on the classifications used is below.

In some counties in Oregon, USDA Wildlife Services (WS) assists ODFW when wolves are suspected and is the lead agency to investigate when other predators such as coyotes, bear, or cougar are suspected.  In some counties, sheriff’s deputies also attend investigations.  ODFW (or WS, east of Highways 97/20/395) needs to make the determination for lethal removal of chronically depredating wolves to be considered or if the livestock producer wants financial compensation from the Oregon Department of Agriculture.

Recent Livestock Investigations (pdf)

Past Investigation Reports


Reported wolf incidents may be classified as either confirmed, probable, unknown, or not wolf, based on the following criteria.

CONFIRMED – Wolf depredation is confirmed when there is physical evidence that an animal was injured or killed by a wolf. Such evidence includes pre-mortem wolf-sized bite marks on the hide with associated hemorrhaging and tissue damage of sufficient severity in specific locations that are indicative of wolves. The evidence must indicate that the attack occurred while the victim was alive, as opposed to wolves simply feeding on an already dead animal. Or a depredation may be confirmed when insufficient carcass remains, if there is a kill scene indicating wolves killed the animal. An injured animal or carcass with evidence of predation but either 1) lacking sufficient evidence for confirmation (e.g., a carcass that is largely consumed) or 2) from events with too many animals to examine each one, may still be confirmed if associated with other confirmed injured or dead animal(s) at the same depredation event.

PROBABLE – Having physical evidence to suggest wolf depredation, but lacking sufficient evidence to clearly confirm predation by wolf, an injured or dead animal may be classified as probable if there are bite marks and hemorrhage and/or a kill scene that is not more likely indicative of a different predator species. A carcass that lacks sufficient evidence to determine probable (e.g., a carcass that is largely consumed) may still be determined probable if it is associated with another carcass determined probable at the same depredation event.

UNKNOWN – It is unknown if wolves were involved in the injury or death of the animal. A dead animal may be classified as unknown if the areas that wolves attack are missing or have deteriorated such that bite marks and/or hemorrhage cannot be observed. An injured animal may be classified as unknown if injuries on the animal have healed such that bite marks cannot be confirmed, or if the animal is not restrained or available for the examination. The presence or sign of wolves (tracks, scat, telemetry) is not evidence of predation.

NOT WOLF – Cause of animal injury or death should be classified as not wolf when physical evidence indicates that a wolf did not injure or kill the animal. The cause of death may be unknown, due to predation by a different species, or other causes such as injury, disease, birthing complications, etc.

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