New guidelines may make it more difficult to fault Mexican gray wolves in the Southwest for livestock depredations.
USDA’s Wildlife Services has released a new set of standards for attributing livestock deaths in Arizona and New Mexico to Mexican gray wolves. Conservation groups have rallied for stricter standards to ensure the wolves aren’t “unfairly blamed for depredations they didn’t commit.”
The new guidelines require evidence that livestock were alive during wolf encounters, such as subcutaneous hemorrhaging and underlying tissue damage, and additional indicators of wolf involvement.
“The over-reported incidence of wolf involvement in cattle deaths in the Southwest has had negative impacts on the wolf recovery program, including the killing and capture of wild wolves,” claimed Greta Anderson, deputy director of Western Watersheds Project in a statement. “We’re hoping the new standards help prevent that from happening again.”
Wildlife Services says subcutaneous hemorrhaging is the best physical evidence available to field investigators to directly associate depredation by a carnivore. A carnivore attack will cause heavy or uncontrolled bleeding from the blood vessels under the skin layer and/or in the muscle tissue, the agency said. The hemorrhaging is found only if the skin and damage tissue occurred while the animal was still alive. Animals that die from other causes typically do not show external or subcutaneous bleeding, according to Wildlife Services.
Bite mark measurements and other physical evidence can also help distinguish Mexican wolves from other carnivores, as all four canines should be present in a set of bite marks due to the general size of the wolf’s mouth.
Other physical observations include chewed and broken large bones, tracks and scat, significant damage to underlying muscle, attacks on the hindquarters and flanks, and multiple kills in one event, among others.
Determination categories
The updated standards have separate requirements in determination categories for large and small livestock, as wolves tend to consume much of the carcasses of smaller animals. There are four levels of determination categories: confirmed, probable, unknown and other.
A confirmed determination leaves little doubt that livestock was killed by a Mexican gray wolf. In large livestock, confirmation is found through subcutaneous hemorrhaging and tissue damage, proving the animal was alive when attacked. Other physical observations can help make the determination but are insufficient on their own.
In smaller livestock, confirmation can be reached by either documenting hemorrhage and tissue damage, or comingled blood and wolf tracks indicating the animal was alive when it was killed and moved by wolves. Again, physical observations on their own will not be sufficient to prove a wolf kill.
For injured livestock, bite marks or rake marks that have the appropriate canine spacing for Mexican wolves will be adequate to confirm wolf injuries.
A probable determination is based on the suggestion that the livestock were more likely than not killed by the wolves, but there is insufficient physical evidence to support a confirmed determination.
An unknown determination is made if physical evidence is inadequate to suggest the wolf predation is more likely than not. Physical evidence of wolf presence could be found near or on the carcass, but this is inadequate evidence. In addition, Wildlife Services will not determine wolf depredation in the case of missing livestock without the presence of any other physical evidence.
An “other” determination is made if physical evidence suggests the cause of death was from something other than wolves. This could include depredation from other species, lightning strike, shooting, etc.
“It’s appalling that the U.S. Department of Agriculture blames endangered Mexican gray wolves for killing cows that died of something completely different,” said Michael Robinson, a senior conservation advocate at the Center for Biological Diversity. “I’m glad they’re tightening standards for determining causes of cattle mortality, but the government should go further and require that ranchers properly dispose of dead cattle to protect both wolves and livestock.”
The new standards in the Southwest are already followed in other states, such as Montana, Wisconsin, Oregon and Idaho, according to the groups. — Anna Miller, WLJ managing editor
