Cougars will become increasingly common visitors to Southwestern cities like Las Vegas in the next few decades as climate change drives their prey to greener urban pastures, a new study suggests.
The hot, dry Southwest is projected to become even hotter and drier as mounting fossil fuel emissions trigger more frequent, intense and long-lasting droughts. That change will reduce the cougar population, according to research presented Monday at the American Geophysical Union Fall Meeting in San Francisco—but it may also cause more of the animals to show up in well-watered towns.
David Stoner of Utah State University and his colleagues used satellite images measuring the food content of natural vegetation in Utah, Nevada, and Arizona to model how the extreme drought year of 2002—considered a taste of what’s to come in the Southwest—affected the population density of cougars and of mule deer, the big cats’ favorite prey.
In 2002, the researchers estimate, a parched landscape with fewer and less-nutritious plants yielded a 22-percent drop in the region’s deer population. Cougars, which depend on the long-eared deer for food, suffered an estimated 43-percent plunge.
In a drier future, Stoner says, deer will increasingly head for verdant, irrigated suburbs and farmlands. Cougars are sure to follow—and to encounter humans.
“As water in natural habitats dries up, it makes those human landscapes all the more attractive and appealing to animals,” Stoner says. “So we project that some of these conflicts related to animals will increase.”
END OF A REBOUND?
Cougars, also known as mountain lions or panthers, once lived all over the United States. By the early 20th century they’d been hunted to extinction in the East, except for a small population in Florida. But in recent decades they’ve been rebounding in the West. The big cats are so elusive, though, that their numbers aren’t well known.
The cats’ future is uncertain too. Their habitat is fragmented by a tangled web of roads and private lands, which isolates them and leaves them vulnerable to in-breeding, genetic defects and disease. It also compounds their trouble when drought decreases their food supply, forcing them to roam more widely to hunt.
“Climate and land-use forecasts for this region suggest two things: warming and drying, combined with increased fragmentation of habitat,” says Stoner. “These in conjunction are likely to lead to population declines in very large, wide-ranging migratory animals.”
Vertebrate ecologist John Benson of the University of Nebraska, Lincoln, who was not involved in the new study, finds it very plausible that cougars will start showing up more in settled areas. He and his colleagues have already found female cougars that appear to be hunting only about three-quarters of a mile from developed parts of the Los Angeles metropolitan area. (Check out these photos of cougars, including one under the Hollywood sign.)
“It’s not like any of their kills were right in back yards,” Benson says, “but they were closer than you would expect.”
Male cougars, meanwhile, hunted further away, in forested areas. Benson thinks females stayed closer to urban areas to avoid males that posed a danger to their kittens.
But as climate change pushes mule deer deeper into city landscapes, the cats face a dilemma. “Mountain lions have a natural avoidance of humans,” Benson says. “So they’ll need to balance that with their need to eat.”
For humans, the cost of cougars coming into town can include harm to livestock, collisions, and attacks on people. Stoner says the actual risk of attacks is extremely low—only one or two take place in North America every year. “But people who live on this urban-rural interface should manage their pets and livestock accordingly,” he adds. “And watch their children.”
He worries that people won’t tolerate an influx of cougars to urban areas. Just a few weeks ago, a Southern California cougar was given a death sentence after killing nearly a dozen alpacas and a goat on a ranch in Malibu. The state gave the rancher, Victoria Vaughn-Perling, a permit to kill the cat, known as P-45.
But she decided not to do it. Instead, the National Wildlife Federation paid for a fence that volunteers built to protect her remaining alpacas.