The West’s growing wolf population is significantly impacting ranchers and livestock, but to what extent hasn’t been well-documented. That need is being addressed by a 10-year study funded by the Oregon Beef Council (OBC), with help from USDA; some of the early results are surprising.

Begun in 2008, the study uses GPS collars on cattle in the study area — and on a few wolves. The collars allow researchers to monitor movements of these animals, and when and where they interact. 

Pat ClarkRange scientist Pat Clark of USDA’s Northwest Watershed Research Center in Boise, ID, has been involved with the study since its inception. Clark attracted the attention of OBC, which learned he was using GPS collars to collect data on the wolf-livestock issue in central Idaho. Doug Johnson from Oregon State University had also been doing GPS collar work on range cattle in northeast Oregon with a collar design of his own. 

Figuring it was only a matter of time before wolves extended their range into Oregon from Idaho, OBC wanted to evaluate how wolves would impact rangeland cattle production in Oregon. So OBC asked Clark and Johnson to extend Clark’s wolf-cattle interactions research to northeastern Oregon (where there were no wolves yet), and western Idaho (where wolves were common).

Thus, the Oregon/Idaho Wolf-Cattle Interactions Project began with three study areas each in western Idaho and in eastern Oregon.

“We selected Idaho study areas from the western part of the state, where range-cattle grazing is the dominant land use, and where wolves were common. We searched for sites in Oregon with similar topography, vegetation types, soil types, cattle breeding, calf age at turnout, grazing schedules, etc.,” Clark explains. Wolf presence was the main differing factor between the Oregon and Idaho sites.

“This type of experimental design is called a BACIP [before-after/control-impact, paired] design. The Idaho study areas served as the control, since wolves were already present. What would eventually change [and create impact] was wolf presence in Oregon. Wolves were expected to travel from Idaho into Oregon and establish packs in the Oregon study areas,” Clark says.

The researchers wanted to collect at least two years of data in Oregon before wolves arrived in sufficient numbers to exert a true impact. They could then contrast that data to data collected after wolves extended their range into Oregon.

“We put GPS collars on at least 10 cows in each study area. Herd sizes in these areas ranged from 300-450 cows. The sample size was limited by available funds from OBC,” Clark says. The study was later expanded to two more ranches, giving enough sample size for adequate data to detect differences in cattle range use and other behaviors.


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GPS data track the location of collared cows and determine how fast they travel. “From this, we can calculate how much time a cow spends foraging during the day, vs. standing looking around, or resting. A hyper-vigilant animal spends a lot of time standing watch, rather than foraging, which could impact nutritional status. With GPS data collected every five minutes, we can detect changes such as increase in vigilant behavior and decreases in foraging time,” Clark says.

One of the Idaho study sites is the OX Ranch near Council, ID, managed by Casey Anderson, where data have been collected since 2008. The ranch experienced wolf predation before the study started, but had no documentation. “In 2009, we were able to confirm more of the wolf kills — 18 animals. But five cows, two yearlings, a bull, and about 70 calves also were unaccounted for,” Anderson says.

There were few wolves in Oregon when the study began — just those passing through and returning to Idaho. Within two years, however, the wolves established packs in northeastern Oregon, and the study moved into the “after” phase: comparing high wolf pressure with low wolf pressure (rather than no wolf pressure).

wolf control and predatation