Mountain lions have no concern for humans, or we enjoy built-up areas. But after the 2018 wildfires in California, local lions took more risks, crossing paths more often and turning more during the day, scientists reported on October 20. Current Biology. In another way, the effects of human development could make themselves vulnerable to wildlife – in this case, by potentially pushing them to our limits.
The Woolsey Fire started near Los Angeles on November 8, 2018, and has burned more than 36,000 hectares in the Santa Monica Mountains. About 30,000 people died, and three people died. The beasts also fled from the fire, including the local mountain lions (leopard leopard). The fire was a tragedy, but also a scientific opportunity, says Rachel Blakey, a global change biologist at UCLA. Many of the lions wore collars to track them, allowing scientists to learn how the fire changed their behavior.
Of the 11 cougars colliding in the area at the time, nine to protect the fire itself. “They have big houses, so nothing can make them cover many kilometers in a day,” says Blakey.
No matter how much they moved, the people avoided the mountains. One collapsing cat, P-64, initially evaded fire — until it got close to advanced range. Between the fire and the chosen people, the lion retreated into the burning area. “That’s where his movement stopped,” Blakey said. The park office later found the remains of the P-64. His feet were burnt, and it was possible that he was killed while hunting.
Using data from the nine lions that survived the fire and other conflagrations, the scientists showed that the cats generally avoided areas where their territories were severely burned. With the grass gone, the cats had little cover to catch and ambush prey.
But the cougars stuck to the unburnt areas and continued to avoid humans. But they took more risks around human infrastructure, increasing their road crossings from an average of about three times a month to five.
All these country roads were not two-lane. The first timer to successfully cross Interstate 405, which has 10 lanes in places, did it after the Woolsey Fire. And the big cats crossed US Route 101 once every four months, whereas before the fire they crossed once every two years. Their territories are also often encroached upon, increasing the potential for lethal fights between solitary cats. And in general, nocturnal animals increased their activity during daytime hours from 10 percent to 16 percent of their active time—a chance of a lion boosting the power bump into a human.
The transition is what Blakey calls “mismatch risk.” Lions in areas with many people appear to be at a greater risk of encountering humans. “But running across the aisle is more likely to be fatal,” he said. That risk, combined with the risk of running into other cats, can be fatal. The young man, a male contributor, died months after the fire. He was running away from a fight with an older, disorganized male.
Intense burns like the Woolsey fire heat up the resilience of mountain lions, says Winston Vickers, a wildlife research veterinarian at the University of California, Davis who was not involved in the study. “They have amazing mobility, they can usually escape from immediate fire, they usually survive,” he notes. Changes in risk, he said, could be thought of as a population confined to the mountains by human development.
Wildlife crossings, like the new Wallis Annenberg Wildlife Crossing 101, will hopefully give mountain lions a safer option for roaming, though the main goal is to promote species among the lion population, Blakey says (SN: 5/31/16). In a field where fire, people and roads are intertwined, it is good to run somewhere.
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