The return of the wolf to California has been met with joy by conservationists, who rejoice in an unlikely population increase, and anger by ranchers who complain about the toll on their cattle.
Now, new research into the diet of gray wolves suggests that the population’s resurgence is the result of predators, as their natural animal sources remain relatively scarce.
Researchers at UC Davis found cattle DNA in 72% of wolf scat samples collected in the summers of 2022 and 2023.
By comparison mule deer, the primary natural prey of wolves in California, appeared in 45% of the samples, while small mammals appeared in 51% of the samples.
“Whether it is food or destruction, [cattle are] a large part of the wolves’ diet,” said Tina Saitone, lead author of the study and professor in the Department of Agriculture and Resource Economics at UC Davis. “Their conservation success is due to the livestock producers in the state.”
The study confirms fears that many wolves have become dependent on cattle as a source of staple food as it is easier to feed on slow, fat cattle than on the dwindling game in the state. Other unusual foods such as chicken and pork were also found in the samples, suggesting that wolves also scavenge human waste.
Beckwourth, Calif., rancher Dan Greenwood holds up a calf’s leg to show a bite from an animal that was attacked by wolves.
(Andy Barron / For The Times)
The results of the study, although limited to the Lassen and Harvey wolf packs over a period of several months, underscore the challenges of humans living alongside wolves.
There were 267 investigations opened by California wildlife officials into wolf predation by 2025, up from 74 last year. In an investigation launched last year, there were 198 confirmed livestock losses possibly due to wolves – causing outrage among ranchers in the Sierra Valley.
The high kill rate prompted the California Department of Fish and Wildlife to take the unprecedented step of removing four gray wolves from the Beyem Seyo pack that had killed 70 livestock in less than six months.
Wildlife officials have warned of the danger that wolves tend to overeat cattle as opposed to their natural prey of elk or deer.
“These changes not only undermine efforts to restore species in California but also risk altering feeding patterns, reproduction and broader ecosystem dynamics,” Fish and Wildlife said in a statement. “Furthermore, domestication brings wolves closer to human communities, increasing the likelihood of conflicts despite their natural avoidance of humans.”
The problem of cattle slaughter is also expensive, with each animal lost to ranchers who return several thousand dollars. The state has established a program to compensate ranchers for each lost cow, and last week the Department of Fish and Wildlife allocated $2 million to continue compensation efforts and to fund non-lethal methods to prevent wolves from attacking cattle.
Another recent study by UC Davis researchers shows that wolves increase stress levels in cattle herds that feed on them, which can have additional economic consequences for ranchers.
By analyzing tail hair samples, the researchers found that herds living among wolves had 58% higher cortisol levels than those living in areas without wolves.
“This really confirms that death or destruction is not the only impact here,” Saitone said in a statement. “Living among cattle wolves is a stressful experience, and that can have a related impact on productivity in the short and long term.”
The presence of wolves in California poses a new and complex challenge to wildlife authorities after hunters and trappers pushed the population to extinction over the past century.
Lupines have re-emerged within the past 15 years, originating in Oregon and forming new, highly concentrated pockets in the northeastern part of California. There were 55 wolves confirmed alive and nine wolf packs at the end of 2025, according to Fish and Wildlife’s annual wolf report.
Despite the challenges posed by ranchers, wolves play an important role in maintaining the balance of the ecosystem. As apex predators, they maintain a population of intermediate level predators, allowing vegetation and other wildlife species to move down the food chain to thrive.
