The Case of the Skinny Calves
By Jacob Baynham
Montana’s ranchers had noticed it for years. When a wolf killed one of their cows, the rest of the herd lost weight. It seemed a strange correlation, but ranchers saw the evidence before their eyes. When it came time to sell their calves at the end of the season, they weighed less than years before.
They had some theories to explain why. When a herd experiences a wolf attack, they get a little jumpy. They tend to group together, rather than spread out. They stay in terrain that is safe but not necessarily fertile. They spend more time with their heads up, alert and away from the grass. They spook easier and run more. And stressed cows produce less milk for their calves.
Ever since the gray wolf was reintroduced into Yellowstone National Park and Idaho in 1995, Montana Fish, Wildlife and Parks has put plenty of thought into how to reconcile the alpha predators’ impact on the local ranching economy. In 2007, the Montana Legislature formed the Livestock Loss Reduction and Mitigation Board, which compensates ranchers for each calf that is killed by wolves. In 2010, 87 cows were reported killed by wolves around the state, and ranchers were reimbursed about $900 per cow. But until recently, no one had looked into the ranchers’ concerns on how wolf attacks affect the weight of their calves. It was a compelling question that got the attention of Joe Ramler, a graduate student in economics at UM, and his associate professor, Derek Kellenberg.
“We really didn’t have any prior information other than anecdotal stories from ranchers that seemed to suggest when they had wolves on their property, their calf weights were coming in lower,” Kellenberg says.
Kellenberg and Ramler enlisted the help of Mark Hebblewhite, an associate professor in UM’s College of Forestry and Conservation, and Carolyn Sime, a UM law student. In order to gather enough data, Ramler spent a summer driving across western Montana interviewing 18 longtime cow-calf producers who were willing to participate in the study. He gathered data on their calf weights from 1995 to 2010.
Meanwhile, Kellenberg and the team were wondering about the other variables that contribute to calf weight – geography, climate, breed and growth hormones. Would they be able to determine that wolves were responsible for the calves’ weight loss?
Most Montana ranchers run cow-calf operations. Mature female cows are bred in summer and give birth in early spring. The cow-calf pairs are let out to pasture for the summer and fall. The calves are then sold to feeder ranches once they are weaned in late fall. Ranchers sell the calves by the pound, so their profit relies heavily on the calves’ healthy weight gain. An average calf in the study weighed about 650 pounds by the time it was sold.
When Kellenberg and his team looked at the data on calf weight and compared it to radio-collar data on wolf locations from Montana Fish, Wildlife and Parks, they learned something straight away. “There is no statistical evidence that wolves being on the same landscape as cows had an effect on calf weight,” Kellenberg says. “But if there was a confirmed wolf kill in a particular year, then the average weight of calves fell by 22 pounds on that ranch.”
The team reported their findings in “Crying Wolf? A Spatial Analysis of Wolf Location and Depredations on Calf Weight,” which was published in the American Journal of Agricultural Economics in 2014. The paper makes clear that wolves are just one factor affecting a calf’s weight gain, and geography, climate, breed and growth hormones have a far larger impact.
“The wolf effect, in the grand scheme of things, is fairly small,” Kellenberg says. “But for ranches that have experienced depredation, it’s not insignificant, either.”
An average weight loss of 22 pounds per calf adds up when you’re selling 250 of them at a time. Using the 2010 sale rate of $1.15 per pound, Kellenberg says ranchers who experienced a wolf depredation lost an average of $6,679 due to the skinnier calves. That’s more than seven times the usual $900 ranchers receive from the Livestock Loss Reduction and Mitigation Board when a wolf kills one of their herd.
The figures are valuable scientific evidence that verifies what the ranchers have been noticing all along. It’s also added some fuel to the controversy of wolf conservation.
“There are some ranchers who think wolves just shouldn’t be out there,” Kellenberg says. “Other ranchers think wolves are here to stay. They’re willing to come up with ways to coexist with wolves, but they also want to be treated fairly.”
The paper doesn’t attempt to explore the full cost-benefit analysis of wolves in the Western landscape, nor does it make any recommendations for ways the state could more accurately reimburse ranchers who experience wolf depredations.
“A scheme like that would be difficult,” Kellenberg says. The state could set up a compensation formula to account for all the variables beforehand, for example, or tailor the compensation rate to each specific ranch after a cow is killed.
Kellenberg points out that compensating ranchers isn’t the only way to use economics to mitigate cow-wolf interactions. Many ranchers in Montana already are using some sort of system to deter wolves from encroaching on their cattle. The Blackfoot Challenge, a group of landowners in the Blackfoot Valley, employs a trained spotter to move from pasture to pasture looking for signs of wolves. Other ranchers set up electric fences around fields or rig fladry systems – ropes rigged with brightly colored flags that wave in the wind and deter wolves.
“The basic idea,” Kellenberg says, “is if you can spend some money on the front end to subsidize mitigation techniques, it may be cheaper than after a wolf attack occurs.”
Kellenberg has sent the paper to the Livestock Loss Reduction and Mitigation Board, to U.S. Fish and Wildlife, to Montana Fish, Wildlife and Parks, to the Stockgrowers Association and to the Cattlemen’s Association. Oregon, Washington and California have all been eager to read it as they prepare their own state wolf plans. He’s done interviews with Montana and Wyoming public radio.
A study on wolves and cattle is novel material for Kellenberg, an environmental economist who usually looks into transnational environmental agreements or international pollution issues. But he appreciates the chance to study something a little closer to home.
“I really enjoyed it,” he says. “It was fun to work on a project that had local interests.”
The paper won’t resolve the controversy of wolves in the West. Indeed, each side of the debate could probably find conclusions in it that support their beliefs. But Kellenberg is content to add some data to the discussion.
“Whether or not wolves should be on the landscape is a complex issue,” he says. “People have different views on the subject. The purpose of this paper was to look at one specific issue that hadn’t been researched: Do wolves have an indirect effect on calf weight?”
Three years after Kellenberg and his team first pondered that question, they now have an answer, and the data to prove it: When depredations occur, Montana’s ranchers aren’t just crying wolf.
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Better at Counting Wet Noses
When the gray wolf was reintroduced in 1995, they were relatively easy to count. There weren’t many of them, and they could be tracked with radio collars. But by the time they were delisted as endangered in 2011, the population had grown and the money to count them had dwindled. Wildlife agencies needed an alternative to their old model of “counting wet noses.” It was going to be tough.
“Carnivores are really difficult to monitor,” says Mike Mitchell, who directs the Montana Cooperative Wildlife Research Unit at UM and is also a wildlife biology professor. “They live at low densities over huge areas. Some of those areas in the northern Rockies are really difficult to get into.”
So in 2006, Mitchell and his team – research associate Dave Ausband, post-doc Betsy Glenn and graduate student Lindsey Rich – turned to a technique called occupancy modeling, which uses all available data and statistical probability to estimate animal populations. It had never before been applied to an entire state.
Mitchell’s crew, working with Montana Fish, Wildlife and Parks researchers, started by dividing Montana into about 600 “patches” roughly the size of a wolf pack’s territory. Then they turned to the data on wolf sightings collected by FWP hunter surveys. Each sighting helped them determine the probability of a pack’s presence in a particular patch. They added up the probabilities and multiplied that number by the average pack size to get a total statewide population.
The results? The latest estimate, from 2012, puts Montana’s wolf population at about 804. The number has leveled off lately. This could be because of wolf hunting and trapping seasons, Mitchell says, or because the population is approaching carrying capacity. Whatever the case, the number is too many for some, and not enough for others.
“What constitutes a lot of wolves,” Mitchell says, “is very much a matter of opinion.”