It’s been nearly four years since the Woolsey Fire ripped through Southern California, burning nearly 100,000 acres and destroying hundreds of homes in Ventura and Los Angeles counties. Now, new research finds that human communities weren’t the only ones to suffer.

An elusive population of mountain lions living in and around Los Angeles also found their habitats scarred by the fire.

The big cats were forced to adjust their behavior in dangerous ways to avoid the burn zones after the blaze, the study finds. They crossed major roads more often; trespassed on one another’s territories; and moved around in the daytime, risking encounters with humans.

The findings, published Thursday in the journal Current Biology, suggest yet another way worsening wildfires may threaten natural ecosystems in the western U.S. They can force wildlife into closer contact with human communities and urban landscapes.

For the mountain lions of Los Angeles, that’s an extra challenge on top of an already serious suite of threats.

The population is small to begin with—there are likely around 100 cats in the Santa Monica mountains north of the city, and perhaps a dozen or so in and around urban Los Angeles. And they’re threatened by expanding urbanization, which is carving up their habitat into smaller and smaller pieces.

Mountain lions are solitary, territorial animals. They need large spaces to themselves, ideally in wooded areas with lots of cover to help them stalk mule deer, their favorite prey. Fragmented, urbanized landscapes can support fewer individuals over time.

Research has found that the small population is beginning to suffer from inbreeding. A 2016 study warned that a lack of genetic diversity could put the population in danger of extinction within 50 years.

“That was the context when the Woolsey Fire happened,” said Rachel Blakey, the lead author of the new study and a scientist at California State Polytechnic University, Pomona. "We have already a population that has a lot of barriers to dispersal and is experiencing a lot of stressors.”

Scientists had already been monitoring the urban cats for years, tracking them using GPS collars. The wildfire gave them an opportunity to investigate how the animals responded to a major environmental disturbance. The fire transformed large swaths of the area into “pretty much a moonscape,” according to Blakey, making it unusable habitat for the cats.

The researchers found that the mountain lions still made a major effort to avoid humans after the fire, steering clear of urban areas as much as possible. But avoiding the burned areas as well presented a challenge for the cats.

The researchers found that they began crossing roads more often, including the area’s busy 101 highway. They also began dipping into other cats’ territories more frequently.

The researchers haven’t yet determined whether these behavioral changes have led to an increase in fatalities. But it’s a concern. Being killed on roadways is the population’s leading cause of death. And altercations with territorial adult males is another major cause of death in adolescent male mountain lions.

The combination of urbanization and worsening wildfires may present a growing threat to the Los Angeles mountain lions as time goes on. As the climate warms, stronger and more frequent fires run the risk of transforming the landscape, destroying native forests and turning them into shrublands—poor habitat for the cats.

Mountain lions are currently listed as a “specially protected species” in California while the state conducts a review to determine whether they should be classified as a threatened species. In the meantime, construction is underway on a new wildlife bridge across Southern California’s 101 highway. The bridge could help mountain lions safely disperse into new territories, potentially increasing the population’s genetic diversity and addressing at least one threat to the population’s survival.

The Woolsey Fire is believed to have killed at least two mountain lions directly, the new study notes. But the event’s aftermath is a reminder that these events can have even more insidious effects in the long run.

“I do think we need to think more about what those disturbances do in a longer-term fashion,” Blakey said. “Our study was only 15 months after the fire, but we did see these ongoing behavioral changes, which cause a great deal of concern for a population that was already struggling to maintain resilience into the future.”

Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2022. E&E News provides essential news for energy and environment professionals.