What’s killing Southern California’s mountain lions?
"This population has one foot on the banana peel and one foot on the edge," says author of study on the cats’ declining numbers.
California, home to such a tremendous array of flora and fauna, is considered prime country for mountain lions, with a potential population of 5,000 statewide. And these gorgeous cats – also known as pumas, cougars, and catamounts – now have protection against hunting. Yet their annual survival rate, in Southern California at least, is considered significantly low, hovering at just 56 percent.
Until 1963, mountain lions were considered a “bountied predator,” meaning hunters were given a monetary reward for killing them. Their status was changed to "big game," and while hunters were no longer rewarded, they were still allowed to kill them. In 1990, almost all killings of mountain lions in California were banned. So why is their survival rate so low?
Most of the available mountain lion habitat in Southern California is nestled between the greater Los Angeles and San Diego areas. A comprehensive 13-year study from University of California, Davis looked at the population's mortality and survival in an area that extends from Orange County, south to the Mexican border and east to the Salton Sea.
Combining genetic and demographic data, they determined that even though hunting is prohibited, humans still managed to kill more than half the of the known deaths of the mountains lions studied. Sadly, this probably isn’t much of a surprise. They were killed by cars, depredation permits, illegal shootings, public-safety removals or human-caused wildfire.
Making the problem even worse is the I-15 highway, a major thoroughfare connecting the counties of San Bernardino, Riverside and San Diego counties. It is nearly impossible for the cats to cross successfully, but crucial in order to boost their declining genetic diversity.
The study's lead author, Winston Vickers, an associate veterinarian with the UC Davis Wildlife Health Center at the UC Davis School of Veterinary Medicine, said fragmentation of mountain lion populations by major roads is so serious in Southern California that there are significant concerns about the fate of these cats.
"Nowhere in the U.S., outside of the endangered Florida panther, have mountain lion populations been documented that are this cut off and with survival rates this low," Vickers said. "This means that the odds of an individual animal making it across I-15, surviving to set up a territory, successfully breeding, and then their offspring breeding so the genes are spread throughout the population is harder to have happen naturally than one would expect."
The situation is so bad that translocation may be required to save them, the study notes. However, more natural solutions to connect the population – like creating safe crossing areas on targeted highways – would be a much better option, says Vickers.
"This population has one foot on the banana peel and one foot on the edge," Vickers said of Santa Ana mountain lions. "Whatever we can do, we should do.”