Provided here are links to information and access to two studies completed recently that both show that for cows that have previously experienced an attack, by wolves, on a herd they were a part of, their reactions, including increased stress levels, led to weight loss in calves and reduction of pregnancies.
From a study of Oregon State University: (Links provided in this release)
“When wolves kill or injure livestock, ranchers can document the financial loss,” said Reinaldo Cooke, an animal scientist in OSU’s College of Agricultural Sciences. “But wolf attacks also 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. It’s much like post-traumatic stress disorder – PTSD – for cows.”<<<Read More of this Press Release>>>
The photograph below, one from the OSU study, shows the reactions by cows that had previously been subjected to wolf attacks, during a simulated exposure to wolves. They bunched into a corner and former a circle. The report stated that cows who had never seen a wolf were “curious” and mostly not phased by the experiment.
Photo by Reinaldo Cooke
From a study conducted by Joseph P. Ramler, Mark Hebblewhite, Derek Kellenberg, and Carolyn Sime – Crying Wolf? A Spatial Analysis of Wolf Location and Depredations on Calf Weight.
Combining a novel panel dataset of 18 Montana ranches with spatial data on known wolf pack locations and satellite-generated climatological data from 1995-2010, we estimate the spatial impact of changing wolf pack locations and confirmed wolf depredations on the weight of beef calves. We find no evidence that wolf packs with home ranges that overlap ranches have any detrimental effects on calf weights. Other non-wolf factors, notably climate and individual ranchspecific husbandry practices, explained the majority of the variation in the weight of calves. However, ranches that experienced a confirmed cattle depredation by wolves had a negative and statistically significant impact of approximately 22 pounds on the average calf weight across their herd, possibly due to inefficient foraging behavior or stress to mother cows. For ranches experiencing confirmed depredation, the costs of these indirect weight losses are shown to potentially be greater than the costs of direct depredation losses that have, in the past, been the only form of compensation for ranchers who have suffered wolf depredations. These results demonstrate a potentially important and understudied aspect of economic conflict arising from the protection and funding of endangered species recovery programs.