Study quantifies high value of indirect losses to livestock producers by wolves
A team of interdisciplinary researchers at University of California, Davis have used research to quantify the cost of wolves shouldered by ranchers. Tina Saitone, a University of California, Davis, professor and Cooperative Extension specialist in livestock and rangeland economics centered her research on three California wolf packs to put a number on both direct and indirect losses after the California Department of Fish and Wildlife launched a pilot program to compensate ranchers for wolf-related losses. She said it became quickly apparent that there is little research on the costs of indirect losses to livestock producers, especially in states like California and Colorado, where wolves haven’t been present for centuries.
“It’s hard to inform policy or advocate for compensation when critics claim there’s no evidence that there’s even a problem,” she said. “We hope this will be helpful and we keep stepping through and building the fort, if you will, with more evidence.
In California, wolves were believed to be extinct until a single wolf migrated into the state from Oregon in 2011. A pack was identified in Siskiyou County in 2015, and at the end of 2024, seven wolf packs were established in the state with evidence of wolves in four other locations. According to California Department of Fish and Wildlife, most of the packs are in northeastern California, though one is in the southern Sierra Nevada.
WOLF-LIVESTOCK COMPENSATION
According to CDFW, in 2021, the California State Legislature appropriated $3 million to CDFW to develop a Wolf-Livestock Compensation Pilot Program to help minimize the impact of wolves on livestock producers based on direct livestock loss, nonlethal deterrents and pay for presence. The pilot program for compensation of all three areas of need launched in June 2023 and ran until funds were exhausted in March 2024.
Eligible livestock producers received 100% of the $3 million allocated by the legislature. A total of 109 grants were awarded to producers with livestock in areas of known wolf activity in Siskiyou, Lassen, Plumas and Tulare counties.
Saitone said the study took a village. She pitched the study to her husband, Ken Tate, a UC Davis professor and Cooperative Extension specialist in rangeland sciences. Ben Sacks, director of the Mammalian Ecology and Conservation Unit in the UC Davis Veterinary Genetics Laboratory, joined to analyze wolf scat. Brenda McCowan, a professor of population health and reproduction at UC Davis Veterinary Medicine, examined cortisol levels.
The study is still working its way through the peer review process, but Saitone said releasing some results has become important as the wolf issue in places like California and Colorado intensifies and becomes more complicated and increasingly controversial.
“Producers we were working with out here (in California) are really anxious for us to share some of our work, even though it hasn’t gone fully through the peer review process just yet, to be able to inform things like the compensation program funding in particular and to document things they’re experiencing,” Saitone said.
OUTREACH
She said they have done significant outreach to livestock producers who are ranching with wolves and are beginning to release findings and engage with producers and media through the university.
The team found that:
One wolf can cause between $69,000 and $162,000 in direct and indirect losses from lower pregnancy rates in cows and decreased weight gain in calves;
Total indirect losses are estimated to range from $1.4 million to $3.4 million depending on moderate or severe impacts from wolves across the three packs;
72% of wolf scat samples tested during the 2022 and 2023 summer seasons contained cattle DNA; and
Hair cortisol levels were elevated in cattle that ranged in areas with wolves, indicating an increase in stress.
“There’s a few different pieces to this study,” she said. “As you know, the wolf problem is incredibly complex and range-based cattle operations are also incredibly complex as you think about working with ranchers and cattle, to some extent, as collaborators.”
The approach taken, she said, was a preponderance of evidence approach, a term familiar to those who have undergone the process of confirming wolf depredation losses with a state wildlife agency. Multiple smaller studies contribute to the larger conversation, with the first being the systematic collection of wolf scat during the summers of 2022 and 2023 within the study area.
The scat samples were taken to the UC Davis veterinary genetics laboratory where Sacks first determined that the scat samples belonged to wolves as a host species. Sacks also genetically assigned the host an identity within the sample population. At that point, the prey was delineated to determine the wolf’s diet.
“Our results across the two years indicated that 72% of the scat we collected — there were 101 confirmed to be wolf across the two years — contained cattle DNA,” she said. “So, that is obviously a substantial portion of their diet and uncharacteristic when you compare it to places where wolves have been present for a long period of time, like Montana and Wyoming and Idaho.”
The reason for this, she said, is due in part to California’s lack of large native ungulate herds. She said there is a small recovering population of Rocky Mountain elk in the state, and the elk and wolves don’t overlap geographically.
“Really, besides cattle on the landscape, mule deer would be their next option but those are dwindling in terms of population in the state,” she said.
Those results, she said, indicate that cattle are significantly contributing to wolf recovery in the state and it suggests that, as ranchers would tell you, that the confirmed depredations in the state and other states, underscore the degree to which cattle and wolf conflict exists on the landscape.
CAMERAS
The second portion of the larger picture depended upon motion-activated field cameras. When the study began, the wolf pack’s alpha female was collared, but the collar stopped functioning about six months into the study. CDFW is unable or unwilling to share wolf GPS data with researchers, so cameras were utilized to ensure that the treatment cattle herds did have wolves present, and the control herds did not have wolves present.
“We also wanted a way to essentially create a heat map or a measure of intensity of wolf pressure on cattle,” she said. “Like many wildlife-based studies, we laid a 4-km. by 4-km. grid over our study area and then identified key grazing areas like large meadows and key watering areas where cattle and potentially wolves would interact.”
Using the cameras, they were also able to capture videos of wolves chasing cattle and stalking events, where wolves are bumping cattle and dogging them throughout the night.
“A picture is worth a thousand words, obviously, and those pictures are another piece of evidence when critics of the scat analysis question whether the cattle were killed by wolves or merely scavenged,” she said. “Our results can’t speak directly to whether a particular animal was killed or scavenged, but we don’t believe wolves are chasing cattle around for fun. They are predators. It is their instinct and their need to kill things to survive, so it’s another piece in that preponderance of evidence puzzle to quantify indirect costs.”
CORTISOL LEVELS
The third portion of the study utilized cattle tail switches, which continue to grow, compared to cattle body hair which sheds seasonally. She said this made it possible for the tail switch hair to be used to measure cortisol levels of cattle during summer grazing.
“If you want to capture a measure of cortisol through time, you want to use that continually growing hair,” she said.
Before cattle were turned out on summer grazing allotments, much like in Colorado, the researchers clipped a portion of the cows’ tail switch hair to the skin. Then, the hair was allowed to grow back all summer while she was out grazing in either the treatment or control group. At the end of the summer grazing season, the same area was clipped, and the regrowth was tested.
“That hair would encompass the stress of her summer experience,” she said.
The 2022 data is available, and the preliminary data suggests that cattle grazing in the presence of wolves have 37% higher cortisol levels than cattle that grazed without wolves.
“This is another piece of the puzzle when we start thinking about reductions in conception rates and lower body condition scores,” she said. “You would expect to see those sorts of outcomes in animals that are exposed to consistently stressful situations. Another piece of the puzzle was documenting that stress.”
Saitone said the cortisone level measurements allowed stress level data without having to put the cattle through additional handling to pull blood or saliva for testing, thereby exposing them to additional stress and requiring testing immediately following stressful experiences.
“It is clear the scale of conflict between wolves and cattle is substantial, expanding and costly to ranchers in terms of animal welfare, animal performance and ranch profitability,” Saitone said. “This is not surprising given that cattle appear to be a major component of wolf diet and the calories drive their conservation success.”
