Cougars have no interest in people or the built-up areas that we enjoy. But after a California wildfire in 2018, local lions were put at further risk. cross streets more often and move more during the dayscientists report on October 20 in current biology. It’s another way that the effects of human development could be putting pressure on vulnerable wildlife, in this case potentially pushing them onto our bumpers.
The Woolsey Fire started near Los Angeles on November 8, 2018, and burned more than 90,000 acres in the Santa Monica Mountains. About 300,000 people were evacuated and three people died. Animals also fled the fire, including local cougars (cougar concolor). The fire was a tragedy, but also a scientific opportunity, says Rachel Blakey, a global change biologist at UCLA. Many of the lions wore tracking collars, which allowed scientists to study how the fire changed their behavior.
Of the 11 cougars in the area at the time, nine made it to safety during the fire. “They have really big home ranges, so they don’t mind being able to cover a lot of miles in a day,” says Blakey.
No matter how much they moved, the cougars avoided people. A collared cat, P-64, initially fled the fire, until he approached a built-up area. Faced with a choice between fire and people, the lion retreated into the burning area. “That’s where his movement stopped,” says Blakey. The park service later found the remains of P-64. He had burned his legs and it is possible that he was unable to hunt and starved to death.
Using data from the nine lions that survived the fire and others that were later collared, the scientists showed that the cats generally avoided severely burned areas of their territories. Without vegetation, the cats had little cover to stalk and ambush their prey.
Instead, the cougars stayed in the unburned areas and continued to avoid people. But they took more risks around human infrastructure, increasing their road crossings from an average of three times a month to five.
These were not all two-lane country roads. The first collared lion to successfully cross Interstate 405, which is 10 lanes in places, did so after the Woolsey fire. And big cats crossed US Route 101 once every four months, up from once every two years before the fire. Their territories also overlapped more frequently, increasing the potential for deadly encounters between the lone cats. And the generally nocturnal animals increased activity during daylight hours to 10 to 16 percent of their active time, which increased the chances of a lion running into a human.
The road crossing is what Blakey calls a “risk mismatch.” Lions in crowded areas seem to weigh the risk of encountering humans as more dangerous. But “running down a freeway is much more likely to be fatal,” she says. That risk, combined with the risk of running into other cats, can be deadly. A young man wearing a collar ended up dead on a highway in the months after the fire. He was running away from a fight with an older man, without a collar.
Intense burns like the Woolsey Fire highlight the resilience of cougars, says Winston Vickers, a wildlife research veterinarian at the University of California, Davis, who was not involved in the study. “They’re incredibly mobile, they can mostly escape immediate fire, they mostly survive,” he notes. Changes in risk taking, he says, could reflect how confined the population is, penned into the mountains by human development.
wildlife crossingslike the new Wallis Annenberg Wildlife Crossing on the 101, will hopefully give cougars a safer option to roam, though the main goal is to promote gene flow between lion populations, says Blakey (Serial number: 05/31/16). In a landscape where fire, humans, and roads combine, it’s nice to have a place to run.