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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 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 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 should be classified as either confirmed, probable, possible/unknown, or other, based on the following criteria.

CONFIRMED – Depredation is confirmed in those cases where there is reasonable physical evidence that an animal was actually attacked and/or killed by a predator. The primary confirmation factor would ordinarily be the presence of bite marks and associated subcutaneous hemorrhaging and tissue damage, indicating that the attack occurred while the victim was alive, as opposed to simply feeding on an already dead animal. Spacing between canine tooth punctures, feeding pattern on the carcass, fresh tracks, scat, hairs rubbed off on fences or brush, and/or eye witness accounts of the attack may help identify the specific species or individual responsible for the depredation. Predation might also be confirmed in the absence of bite marks and associated hemorrhaging (i.e., if much of the carcass has already been consumed by the predator or scavengers) if there is other physical evidence to confirm predation on the live animal. This might include blood spilled or sprayed at a nearby attack site or other evidence of an attack or struggle. There may also be nearby remains of other victims for which there is still sufficient evidence to confirm predation, allowing reasonable inference of confirmed predation on the animal that has been largely consumed.

PROBABLE – Having some evidence to suggest possible predation, but lacking sufficient evidence to clearly confirm predation by a particular species, a kill may be classified as probable depending on a number of other factors such as: (1) Has there been any recently confirmed predation by the suspected depredating species in the same or nearby area? (2) How recently had the livestock owner or his employees observed the livestock? (3) Is there evidence (telemetry monitoring data, sightings, howling, fresh tracks, etc.) to suggest that the suspected depredating species may have been in the area when the depredation occurred? All of these factors, and possibly others, should be considered in the investigator’s best professional judgment.

POSSIBLE/UNKNOWN – Lacking sufficient evidence to classify an incident as either confirmed or probable predation, the possible/unknown classification is appropriate if it is unclear what the cause of death may have been. The investigator may or may not have much of a carcass remaining for inspection, or the carcass may have deteriorated so as to be of no use. The investigator would want to consider if the area has been frequented by a predator, or if the habitat is one which the predator is likely to use. Possible predation may include cases where counts show that abnormal numbers of livestock are missing or have disappeared above and beyond past experience, and where other known cases of predation have occurred previously in the area.

OTHER – Cause of livestock deaths should be classified as other when it is discovered that the cause of death was not likely caused by the animal originally reported to Wildlife Services during a request for assistance. Examples of other may include cases where the cause of death is confirmed or is likely due to predation by some other animal or cause determined at the time of the investigation such as red fox instead of coyote or other causes such as, bloat, poisonous plants, stillborn, disease, lightning strike, vehicle collision, etc.

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