Witnessing an attack can be traumatic. The images of violence, perhaps the memories of death or destruction can come back to plague witnesses in the future. And that goes for cows, too.
Oregon State University has released findings that show cows that have witnessed wolf attacks display physical signs associated with post-traumatic stress disorder. PTSD is a psychological disorder that develops in some people who have experienced shocking, frightening or dangerous events. This is the first study to reveal PTSD biomarkers in cattle.
The findings were published in a recent issue of the Journal of Animal Science, and Reinaldo Cooke, an animal scientist at Oregon State University, led the study. "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," Cooke says.
Gray wolves are back in the wild in bigger numbers. After being reintroduced to Yellowstone National Park in the past two decades, the wolves have moved throughout the West and have hunted in livestock grazing areas. Oregon's wolf population has grown steadily since wolves migrated to the northeastern part of the state. The state has documented 112 wolves visually in 2016. Wolves west of U.S. 385, U.S. 95 and Oregon Route 78 are protected by the Endangered Species Act.
OSU researchers had heard stories from ranchers that cows that have come in contact with wolves eat less, and are more aggressive and sickly.
Simulated wolf encounter
In the study, cows at the Eastern Oregon Agricultural Research Center in Burns, Ore., were exposed to a simulated wolf encounter. Their brains and blood were analyzed for biomarkers looking for genes associated with stress-related psychological disorders, including PTSD.
This work builds on Cooke's research from 2014 showing cows that had been exposed to wolves exhibited more fearful behavior — even when they had not been attacked. These latest findings confirmed the researchers' hypothesis: The cows' stress response was expressed in certain biomarkers in their blood and brain cells linked to PTSD in humans and other mammals.
In their latest 2016 study, researchers simulated a wolf encounter with 20 Angus crossbred cows to evaluate the stress of a wolf attack. Half were raised at the EOARC and had never seen a wolf, and the other half had been part of a commercial herd in Idaho that was previously attacked on the range. None of the Idaho cows had been directly attacked, or injured, by wolves.
Both sets of cows were gathered separately for 20 minutes in a pen scented with wolf urine, while pre-recorded wolf howls played over a stereo. Three trained dogs — two German shepherds and one adult border collie-Alaskan malamute mix — walked outside the pen.
Cooke noted: "The cows previously unfamiliar with wolves showed no signs of agitation and actually approached the dogs. They also didn't have biological signs of PTSD, according to PTSD-related biomarkers evaluated in their blood or brain tissue." Multiple studies from Cooke and other researchers have established a link between cow stress and poor performance traits that can cost ranchers. The researchers call for further research into ways of successfully managing both wolves and livestock so they can co-exist.
The Oregon Beef Council funded this study.
Source: Oregon State University