Chow time in Death Valley
Mountain lions are munching on burros. Scientists say it’s good for the ecosystem.
An apex predator has been quietly hunting interlopers in Death Valley, and for the first time, one of the deadly encounters has been captured on camera.
A mountain lion can be seen via nighttime images pouncing onto the back of an in-stride wild donkey.
The cougar easily wins the fight: A photograph taken seven minutes later shows it standing over the dead donkey, eyes glimmering as it stares into a wildlife camera.
“It’s extremely rare to get a predation on camera,” said Erick Lundgren, the biologist who captured the images. “I guess that just goes to show that [this] predation is really not [that] rare in Death Valley.”
The cougar-donkey dynamic has been the focus of little research, but it might illustrate a developing relationship between the two animals that could benefit the ecosystem, according to a recent study.
The feral donkeys, also known as burros, have long been considered invasive and major disrupters of native species and habitats in Death Valley, pillaging wetlands and destroying vegetation that other animals rely on. But Lundgren is hoping this study could shift how conservationists and researchers view the donkeys.
“I was interested in the wild donkeys not just as a pest ... but as wildlife,” said Lundgren, the lead researcher of the report, published in the Journal of Animal Ecology. “Which is, I think, how you should study them if you want to understand them.”
The study found that the donkeys were the “primary recorded prey” of mountain lions in certain areas of the national park and that the presence of the cats changed how and when the donkeys fed, roamed and congregated, with their interaction forming an “emerging ecological network.”
The increased predation “was associated with altered donkey activity patterns and rates, and with reduced herbivory and disturbance-related effects on desert wetlands,” the study found. This limited damage caused by donkeys in these areas.
“There’s a prevailing narrative that wild horses and wild burros are problems ... at some kind of biological level,” Lundgren said. “And I think that’s really nonscientific.”
However, in areas where the mountain lions were not as active, donkeys continued to wreak havoc, the study found.
Although the wild donkeys are not native to North America — they descended from the domesticated African wild ass, which was brought west by pioneers during the Gold Rush — the region was home to different horse-like species before the last Ice Age that lived alongside prehistoric mountain lions, Lundgren notes.
“Mountain lions co-occurred with equids [horse-related species], just like wild donkeys, for several million years,” he said. “So it’s kind of neat that they’re together again and that these new relationships are unfolding, which in many ways mimic old relationships that were around for millions of years.”
For Mairin Balisi, a paleontologist and co-author of the study, the images of the mountain lion kill were the “return of an extinct interaction.”
“Fossil ecosystems are useful for providing baselines of conservation,” said Balisi, a curator at the Raymond M. Alf Museum of Paleontology in Claremont.
She said this evolving relationship in Death Valley has the potential to be a natural experiment in how the two species can benefit each other and the surrounding habitat. She likens the interaction to the successful reintroduction of the gray wolf in Yellowstone National Park, which had a positive effect on the food chain.
But Death Valley officials remain committed to their goal of zero burros, given how a consensus of prior research shows that the animals “denude vegetation at springs (sometimes completely), foul water with their excrement and prevent native wildlife, such as native bighorn sheep, from using springs,” park spokesperson Abby Wines said.
“Mountain lion predation is not sufficient to control the burro population in the park,” Wines added.
There are an estimated 4,000 feral burros on parkland, a dramatic increase from about 400 in 2005, she said. National park leaders have worked in recent years to humanely remove the burros from Death Valley.
Kate Schoenecker, who studies wild burros for the U.S. Geological Survey at the Fort Collins Science Center in Colorado, said it’s unlikely Death Valley will be able to eliminate the animals, given their protected status on nearby Bureau of Land Management and U.S. Forest Service land.
She didn’t question the park’s efforts to remove the donkeys through trapping efforts but said she was excited that the new research gave a more in-depth look at the understudied animals. Specifically, she pointed to how the research documented the donkeys’ “predator-risk avoidance behavior,” which can positively affect ecosystems.
“This is really cool, because it’s never been studied for burros,” said Schoenecker, who notes that questions remain given the study’s small sample size and limited data.
“I think there’s a lot we still don’t know,” she said. “We’re just still learning about basic demographic rates of burros.”
Lundgren and Balisi agree that there should be more research on the donkeys and their broader effects on the ecosystem.
“Ecologically important predator-prey interactions can emerge rapidly in novel ecosystems,” Lundgren said, adding that he is concerned that total removal of the burros could have unintended consequences for the larger food chain and that continued threats to mountain lions could stunt this potentially beneficial relationship.