Cows belonging to herds that have experienced wolf attacks show stress-related biological differences from cows in herds that have never encountered wolves, according to a study conducted by Oregon State University scientists.
Researchers compared the expression of genetic brain-blood biomarkers related to psychological disorders like post-traumatic stress disorder (PTSD) in cattle from herds that either had or hadn’t seen carnage caused by canids.
Wolf populations are increasing here in Oregon. A minimum of 112 wolves were known to be living in the state last year, according to the Oregon Department of Fish & Wildlife’s 2016 Annual Report. In 2015, there were nine incidents of wolf depredation of livestock. In 2016, there were 24 confirmed events. Wolves killed 11 calves, seven sheep, a goat, and a llama in Oregon last year.
“Wolf attacks create bad memories in the herd and cause a stress response known to result in decreased pregnancy rates, lighter calves, and a greater likelihood of getting sick,” said study lead author Reinaldo Cooke, OSU associate professor and beef cattle specialist.
Angus-crossbred cows from Council, Idaho that had witnessed several wolf-predation episodes from 2008 to 2015 and cows from the Eastern Oregon Agricultural Research Center (EOARC) in Burns that had never met a wolf were exposed to a simulated wolf encounter. None of the cows from the Idaho herd had been physically attacked by wolves previously. Gray wolves aren’t yet present in the area around Burns and the EOARC.
After a 60-day period for cows to adapt and commingle, scientists assigned them into either Group A or Group B. Both groups comprised 10 cows, five from Idaho that had scary wolf stories to tell, and five from Oregon that had never before been exposed to wolves. Blood samples were taken from Group A before they were immediately slaughtered. Samples of blood and brain tissue were taken and analyzed to evaluate the inherent differences between wolf- experienced and wolf-naïve cows.
The following day, pairs of Group B cows were exposed to simulated wolf encounters for 20 minutes. Simulated encounters included cotton balls soaked in wolf urine attached to fences, reproduction wolf howls, and leashed dogs walking around the fence’s perimeter. Group B cows were also slaughtered, then had their blood sampled and their brains removed for further study.
“The cows previously unfamiliar with wolves showed no signs of agitation and actually approached the dogs,” said Cooke. “They also didn’t have biological signs of PTSD, according to PTSD-related biomarkers evaluated in their blood or brain tissue.”
These findings add to previous research by Cooke and others demonstrating more fearful behavior in cattle that had been exposed to wolves, even if they had not previously been attacked. Despite an increase in wolf depredation events in the state, other statistical evidence found elsewhere might suggest beef cattle still have much more to fear from humans than from wolves.