Fight or flight: Study looks at potential losses due to negative impact on cattle following wolf encounters
March 31, 2014
Many discussions about wolf impact on livestock producers focus on depredation losses, both confirmed and unconfirmed. The rule of thumb is that for every confirmed kill there are probably eight more unconfirmed losses. This is a significant impact, but ranchers who have been dealing with wolves are reporting additional costs when wolves are present. These costs include weight loss, lower pregnancy rates, reduced gain for calves, and significant increase in management costs.
David Bohnert, Beef Extension Specialist and Ruminant Nutritionist, Oregon State University (Eastern Oregon Agricultural Research Center, at Burns, Ore.) was part of a research group that looked at the impact on cows from exposure to wolves. This was part of the larger ongoing study funded by the Oregon Beef Council, using GPS collars on cows and a few wolves, tracking their movements and interactions.
"Casey Anderson, manager of the OX Ranch in Idaho, and some of the ranchers in Oregon told us that cattle were coming home from the range different than they did before they had to contend with wolves. These ranches were experiencing lower pregnancy rates, lower number of calves, cows with less body condition, more sickness, and the cattle were just not doing as well. These things are hard to document, however, and difficult to get an economic number on," says Bohnert.
"Some of the work that Reinaldo Cooke and I did earlier was to come up with a model that would enable us to measure stress in cattle–looking at cattle temperament and using models regarding transport and various other stresses. Basically we look at chute score (to evaluate how stressed and agitated the cattle are) and measure exit speed to come up with a temperament evaluation. So this is one of the things we used in our recent study," he says.
"We also checked body temperature of the cows, and looked at blood variables, typically cortisol." This hormone is produced in larger quantities when the animal is stressed. When an animal or human is stressed, blood pressure and body temperature rise, and cortisol levels go up.
His research group received $30,000 from the Oregon Beef Council for the cattle impact study. "We wanted to use cattle that we know had documented wolf interaction and depredation. Cattle that came off the OX Ranch fit this requirement because the U.S. Fish and Wildlife has documented depredation events there. To say cattle were exposed to wolves and to be able to prove cattle were exposed are two different things, and we wanted to be sure we had proof," says Bohnert.
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"We got 50 cattle from the OX Ranch that were pregnant (mid gestation) in late fall. We had them shipped here to the Experiment Station at Burns, Ore. Then we chose 50 of our cows as a control group. We were confident they had not had any exposure to wolves. There is no documented evidence of wolves in our area. We ran those two groups of cows together for 3 months so they would get used to each other."
Once a week the whole group was brought into the corrals and working facilities. "We got them used to the people and the facilities here. Our own cattle were already used to it, but the OX cattle had to adapt." The 3 month break-in period was to minimize any affects of the environment, so the new cattle would not be stressed by the facilities or handling. They gained confidence from the calm "home" cattle that were already at ease with this environment.
The 100 cows were managed as one group, fed as a group, and handled the same. "We ran them through our facilities with people handling them quietly, once a week for 3 months," says Bohnert.
"When it came time to do the study, we used 3 German Shepherds as 'wolves'. We also obtained wolf urine and saturated cotton wicks with the urine so we could put those along the edge of the pens that we planned to put the cows in. We also had a howl box, to play recordings of wolf howls and wolf vocalizations (day to day 'wolf talk')."
Before the cows were exposed to simulated wolf presence, they were run through a working facility to get a temperament score on each cow—measuring how they acted in the chute and exit velocity. "We pulled blood samples to check the blood hormones, and put a temperature probe on them to measure temperature. This was our baseline data after getting the cows accustomed to our facilities," he says.
"We did the study on 5 groups of 20 head. Each group had 10 OX cows and 10 of our cows. We put them into two pens, side by side, that had the wolf urine, howl boxes, etc. We kept our cattle together in one pen, and the OX cattle together, in their separate side-by-side pens," he explains.
"It was amazing to watch. As soon as they got into the pen, even before the howl boxes began or the dogs were brought out, the OX group felt threatened because they could smell the wolf urine. They were a lot more reactive. Our cattle were wondering what was going on, but they weren't as upset. As soon as we turned the howl box on and turned the dogs loose, the OX cows went into a frenzied tight group. The OX cows were at least 3 months away from having any exposure to wolves, yet there was a dramatic visual difference in behavior of the two groups," says Bohnert.
"Ours, that had never seen a wolf, were interested in the dogs; they had their heads up and were watching the dogs, but they were not frightened. The OX cattle, by contrast, were sure that something bad was going to happen," he says.
"We exposed the cattle to simulated wolf presence for roughly 30 minutes. Then we took the cattle back to our working facility to measure temperament score, exit velocity, and how they acted in the chute. We measured the blood parameters and the cow's temperature. What we found was that the OX cattle responded differently than ours. In our group the cows' temperature went up a little, just because of normal activity, moving around. The temperature of the OX cattle went up at a higher rate, showing they were more stressed," he says.
"Their cortisol levels went up, whereas in our cattle it remained the same. Temperament score of the OX cattle also went up, due to being so agitated. We still had the howl box going in the working facility and the cows could see the dog, and then we pulled the dog away," he explains.
What was interesting was their exit velocity. "It didn't change, on our cattle. It didn't change much for the OX (for total time to leave the chute), except that when we opened the chute they didn't run out right away. They paused there for a few seconds, looking around to see if there was anything dangerous out there, and then they shot out like a rocket. The overall rate of exit time didn't change, but their behavior did," he says.
"We were able to measure temperature, cortisol and temperament score and know that those OX cattle responded to stress in a more adverse manner than our cattle that had never been exposed to wolves," says Bohnert.
"Now the challenge is to interpret what this means. We know they are more highly stressed, and when they are more stressed, our studies and other studies have shown that cows with higher stress have lower pregnancy rates, lower overall performance, and their calves do not perform as well. We can't quantify that number, based on the current research, comparing the drop in performance to unstressed cattle, but my guess is that it's somewhere in the 10 to 20 percent range. Further research may help accurately determine these numbers," he says.
"John Williams, OSU Extension Service, did an economic analysis after talking with Casey Anderson and other ranchers, and came up with a loss of $260 per head when cattle are impacted by wolves. This is a huge loss for ranchers," says Bohnert.
"These cattle are highly stressed in a fight or flight response. Our cattle at the research station had never been attacked by canines so they did not associate them with danger. Cattle that have been attacked and have seen others attacked and chased become very agitated. If this happens to them very often they don't spend much time grazing." They are too worried about survival–looking around, hyper and alert.
"Wolves are here now and we have to learn how to deal with this impact. This is information that our industry and other people need to know. The cost is more than just the actual depredation," says Bohnert.
"We need to figure out how we can manage wolves and manage cattle in ways that will minimize their interaction, so ranchers can survive. Our study was simply a first step to show the differences in how cattle react when they've experienced wolves. This fight or flight reaction makes it difficult for ranchers to use dogs when gathering and moving cattle. They attack the dogs and it's impossible to use dogs for herding."
The OSU group would like to do another study, looking at actual affects on pregnancy rate. "We have one ranch in northeast Oregon that raises their replacement heifers down here near Burns, and then takes them up there. If we could split those heifers into two groups, leaving half down here (without wolf interaction) and take half up there where they have to interact with wolves, we might be able to measure and document the differences," he says.