Livestock Injury and Mortality Investigations: A Reference Guide for WDFW Field Personnel

1. What they did

The Washington Department of Fish and Wildlife (WDFW) wrote this guide for its staff who investigate reports of livestock injured or killed, possibly by large predators. It is a general reference, not step-by-step instructions, because each investigator is expected to develop their own techniques over time. It follows the order of WDFW’s investigation form, from general to specific:

• Initial report. Questions to ask the person reporting the incident, and a necropsy kit list.
• Site description and physical evidence. Tracks, hair, scat, blood, beds, signs of struggle, and whether the animal was moved or cached.
• Description and location of injuries. External examination, necropsy (opening and examining the carcass), and telling scavenging from predation.
• Source of injuries. A chart of the wounds and signs typical of each predator.
• Classification. WDFW’s criteria for classifying reported wolf depredation.

It then gives a “signature” page for each of seven predators (wolf, coyote, feral or domestic dog, cougar, bobcat, black bear and grizzly bear), a page of preventive techniques, a blank and a filled-in sample investigation form, and an equipment list. Many photos show the “classic” signs of predator attacks, with the warning that every investigation is different.

2. What they found

Site investigation first

• Where possible, the whole site should be investigated before the animal is examined. Good places to look for tracks and hair are creek banks, puddles, mud, cow pies, fences, trees and shrubs.
• Finding predator signs does not by itself mean a predator caused the injury or death.
• Photos should show the whole scene first, with close-ups after a wide view, and an object of known size next to tracks.

Scat

• Bears: highly variable, often with partly undigested food; often deposited in large piles and seldom covered.
• Cats: often segmented with blunt ends, may contain hair and bone; cats often scratch out a spot and may cover the scat. Cougar scats are often larger than bobcat scats.
• Dogs: often with a tapered end, may be twisted like rope; scrapes may come from kicking after defecating; seldom covered.
• After a meat meal, scat of any predator may be very dark and have little form.

Tracks

• Cat tracks are round, with a triple-lobed heel pad and two middle toes slightly offset; dog tracks are oval, with a double-lobed heel pad and middle toes nearly level.
• Wolf and dog tracks overlap in size and cannot be told apart by shape. Gaits and track patterns around kills are often confusing. Tracks were likely made by a wolf if the hind foot is 3½ inches or longer, or the front foot 4 inches or longer, without claws (82% of dogs have smaller feet). Some large breeds, such as Great Danes and mastiffs, fall in the wolf range.
• Grizzly bears have long, light front claws (2 to 4 inches), a dished face, smaller rounded ears and a shoulder hump; black bears have short, dark front claws (about 1½ inches), a straight face profile, larger pointed ears and no hump. The guide’s figure calls claws and toe alignment the key characters.
• Measuring tips: tell front from hind (both dogs and cats have slightly larger front feet), measure at the bottom of the track, average several prints, and leave out the claws.
• Approximate track sizes given (width by length): wolf 4 by 4.5 inches; coyote 2.5 by 2.5; dog about 3 by 3 (variable); cougar 3.5 by 3.5; bobcat 2 by 2; black bear front 4 by 4.5 and hind 3.5 by 7; grizzly bear front 5 by 5.5 and hind 6 by 10.

Signs of attack, moving and caching

• Cougars stalk, so there may be little sign of struggle; bears chase for short distances; wolves chase and bite, so an extended struggle may show, though not always.
• Cats usually drag or carry prey to dense cover and may cache it under carefully scraped debris. Bears may or may not move or cache prey; a bear cache can look “roto-tilled.” Dogs seldom move or cache prey.
• Wounds mostly on the front upper half (bears and cats): little chase, carcass may be dragged and covered. Long scrape marks (24 inches or more) suggest cougar, short ones (16 inches or less) bobcat.
• Wounds mostly on the back half (wolves, coyotes and dogs): chase and struggle, ragged wounds, feeding at or near the kill site, remains scattered. Dogs bite indiscriminately and seldom feed.

Scavenging or predation?

• Wolves, coyotes, dogs, cougars, bobcats and bears all scavenge.
• Bites made while the animal was alive show hemorrhaging (bruising) and tissue damage under the hide. To find them, the whole carcass should be skinned.
• Lividity (blood settling to the lowest side after death) can look like hemorrhage. In one example, a red spot in a typical wolf-attack place had no marks on the hide and no muscle damage: wolves had visited, but did not kill the animal.
• Dried hides can be soaked overnight and re-examined.
• Many livestock die of other causes. Predators caused 5.5% of cattle and calf deaths nationwide in 2010, and about 6.7% in five northwestern states. Photos show injuries from an enclosure, trampling, and birds feeding after death that could be mistaken for predator attacks.

Wolf depredation classes

WDFW uses six classes: confirmed wolf depredation; probable wolf depredation; confirmed non-wild-wolf depredation (another predator, a wolf-dog hybrid or a pet wolf); unconfirmed depredation; non-depredation; and unconfirmed cause of death. Confirmation normally rests on bite marks with hemorrhaging; tracks, scat, hair and canine tooth spacing may help identify the species or individual.

3. What they concluded

• Every investigation is unique, and what investigators see may be very different from the photos in the guide.
• Site evidence, the external examination and a full necropsy should be used together; the predation chart and attack-zone figure are for general reference only.
• Knowing the behaviour and habits of large predators, and recent confirmed sightings, can help even when there is little site evidence.
• When there is not enough evidence, “I don’t know” is a perfectly acceptable answer. If no large predator was involved, investigators should take great care in drawing any further conclusions.
• Preventive techniques suggested include removing bone piles and dead livestock, avoiding feeding ungulates near homes, range riders and more human presence, and fladry or electrified fladry (turbo-fladry), which work best in calving season and night pens rather than open range. Tethering goats and sheep, or not housing them at night, may make them more vulnerable.

4. How tracking was or was not used

Tracks and signs are a core part of the investigation the guide describes. Investigators are asked to search the site for tracks, hair, scat, blood, beds, trampled vegetation, broken branches, drag marks and scraped-up caches, to photograph tracks with a scale, and to measure them. The guide shows how to tell cat from dog tracks, wolf from dog tracks, and grizzly from black bear, and gives track sizes for each predator. It also reads the carcass itself as sign: bite and claw wounds, feeding patterns, cracked bones, plucked or sheared hair, and how remains are spread. The guide stresses that tracks, scat and hair alone cannot show whether an animal was killed or only scavenged. No trailing is described.

6. Other technologies, skills or innovations

• Field necropsy: skinning the entire carcass to find bite hemorrhages, and cutting into muscle to tell lividity from bruising.
• A standard investigation form with a body diagram for marking injuries, Global Positioning System (GPS) coordinates, land status and cover type.
• An equipment list including a skinning knife, tape measure, camera, GPS unit, a tarp and a bucket to cover tracks and scat in bad weather, coin envelopes for hair for DNA, and tubes with alcohol for tissue samples.

7. Implications for conservation (from the paper)

• Most livestock deaths are not caused by predators, so careful investigation matters before a predator is blamed.
• Removing attractants such as bone piles and carcasses, more human presence on the range, and fladry may reduce attacks.