The study is challenging the view that wild horses and burros on Western public lands have no natural predators, prompting the nation's largest wild horse and burro protection organization, the American Wild Horse Campaign (AWHC) to call for a re-evaluation of the Bureau of Land Management’s (BLM’s) wild horse management policy, a recommendation echoed by the study’s authors. 

“Our data suggest that cougars may be an effective predator of feral horses and that some of our previous assumptions about this relationship should be reevaluated and integrated into management and planning,” the study, led by researcher Alyson Andreasen of the University of Nevada, Reno, stated.

"Andreasen's excellent work dispels a long pervasive myth that wild horses 'have no natural predators', and raises a myriad of new questions,” says Erick Lundgren, a postdoctoral researcher at Aarhus University in Denmark. “My own preliminary research has found that wild burros change their behavior in response to mountain lion predation, leading to altered effects on ecologically important desert wetlands.”

“Given that mountain lions, and other predators, are heavily persecuted, perhaps it is time for us to reconsider how we treat both wild equids and their predators,” Lundgren, who has studied the ecological role of wild burros in the Mojave Desert, concluded.

“The fact that mountain lions prey on wild horses is known to anyone who has studied this iconic species. But the extent of this predation has been denied by those pushing for the removal of wild horses from public lands based on a false narrative that horses are invasive species with no natural predators,” said Meredith Hou, science and policy counsel for AWHC. 

“We challenge the Biden Administration to live up to its promise of science-based governance by using this latest scientific information to re-evaluate federal wild horse roundup and predator elimination policies, both of which are driven by the livestock industry at the expense of wildlife, wild horses, and American taxpayers,” Hou added.

The research studied thirteen cougars in the Great Basin and a control group of an additional eight in the Sierra Nevada mountain range in the western part of Nevada. The results revealed that 60 percent of the mountain lion diets in the Basin were made up of wild horses of varying ages and that ten of the 13 cats tracked were predominantly choosing horses for kill. 

The new findings add to the latest research debunking the BLM’s claim that wild horses and burros must be removed from their federally-designated habitat in order to protect public lands.

In spring, a groundbreaking study published in the journal Science uncovered that wild burros are actually boosting the availability of water in desert landscapes across the American West, and the preliminary results out of the University of California’s Santa Cruz Paleogenomics Lab have further cemented paleontologists’ view of wild horses as a native, reintroduced North American wildlife species. 

According to AWHC, while mountain lions are found in many areas where federally-protected wild horses and burros roam, their populations are kept unnaturally low due to government-issued hunting tags and federal kill programs that eradicate the apex predators for preying on privately-owned cattle and sheep grazing on public lands.

In addition, the group notes that the agency has never attempted to understand the place of wild horses in the western ecosystem and instead manages them as if they are livestock that needs to be periodically “harvested” (rounded up and removed). 

In 2013, the BLM commissioned a scientific review of its Wild Horse and Burro Program which was conducted over an 18-month period by the National Academy of Sciences.

The scathing report stated that the continuation of “business as usual” practices will be expensive and unproductive for BLM and the public it serves and found in part, that the population limits the BLM sets for wild horses were, “not based in science,” and that roundups and removals could be directly contributing to large population growth on the range due to a biological phenomenon called compensatory reproduction.

The agency ignored the findings and continues to spend hundreds of millions of tax dollars on the roundups. 

Key Findings of the Research 

Based on GPS Collars and evaluation of over 1,300 “kill sites,” researchers documented that: 

• Diets of cougars in the Great Basin were composed predominantly of horses (460 horses killed by 13 cats).
• Ten cougars regularly consumed horses, and horses were the most abundant prey in the diet of 8 additional individuals in the Great Basin.
• Differences in predation on horses between the sexes of cougars were striking; Great Basin females killed more horses across all age classes year-round, whereas male cougars tended to prey on neonatal young during spring and summer before switching to deer during winter. 
• The likelihood of predation on horses compared to other prey species increased with elevation, horse density, and decreasing density of mule deer on the landscape, and was more likely to occur in sagebrush than in pinyon-juniper forests.

About the American Wild Horse Campaign

The American Wild Horse Campaign (AWHC) is the nation's leading wild horse protection organization, with more than 700,000 supporters and followers nationwide. AWHC is dedicated to preserving the American wild horse and burros in viable, free-roaming herds for generations to come, as part of our national heritage. In addition to advocating for the protection and preservation of America's wild herds, AWHC implements the largest wild horse fertility control program in the world through a partnership with the State of Nevada for wild horses that live in the Virginia Range near Reno.

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Press release by Grace Kuhn and  Amelia Perrin