According to new information from the California Department of Fish and Wildlife, the biggest threat to mountain lions in California is being hit by cars, and more than 100 mountain lions died in 2016 on California's roads and highways. This loss is in addition to the 100 cats that die each year as a result of depredation permits.
Andrew Hughan, CDFW public information officer, told Public News Service that roadkill isn't uncommon and that vehicle collisions are an unfortunate side effect of habitat erosion.
"Mountain lions are probably killed a couple times a week," said Hughan. "They're killed all the time across the state."
According to the Public News Service by article by Logal Pollard published December 27, 2016, state officials say that despite the increasing number killed by cars, the mountain lion population remains stable. But the Mountain Lion Foundation notes that the department provides no evidence to support that claim. CDFW's estimates of the California mountain lion population range from 4,000 to 6,000, but these estimates are the result of habitat assessments made during the early 1980's and fail to take into account the habitat loss, increasing traffic, and growing human population that has occurred in the 40 years since.
Hughan's statement doesn't go far enough to illuminate the pressures on lion populations. He said that "There's no hunting, so the population's allowed to thrive. The only thing, really, that keeps the population in check is getting hit by cars." This however, fails to take into account the continuing threats of depredation kills, poisons, and habitat loss.
Mountain lion populations are self-regulating based on the availability of prey species like deer, and deer populations have dropped since the 1980's when forest practices including clear-cutting and fire suppression changed. Deer suffer from habitat loss too, but not as much as mountain lions, because deer are tolerated by people living in habitats fragmented by human development, but mountain lions often are not.
This means that the threats to lions are only likely to grow worse, as human population grows, and passages for wildlife across roads and highways become fewer as they are plugged by development.
In Temecula, California the Mountain Lion Foundation is working with a coalition of groups and individuals to halt two developments that would cut off the last remaining corridor across the I-15 freeway, which separates the more genetically diverse mountain lions of San Diego County from the highly threatened population of lions in the Santa Ana Mountains of Orange and Riverside Counties.
In the Santa Anas, with fewer than 25 mountain lions remaining, the number one cause of death is roadkill, particularly on the 241 Toll ROad. As a result, few lions in the Santa Ana Mountains reach adulthood.
In addition to the wildlife crossing contemplated for the Santa Monica Mountains near Los Angeles, home to another isolated population of lions, a lion crossing is being considered for the Santa Cruz mountains. Such infrastructure is a costly substitute for good planning.
Recent studies show that by reducing auto collisions with deer, mountain lions actually save lives. 2016 research published in the journal Conservation Letters demonstrates that if mountain lions were fully restored to their historic range, the cats could prevent 155 human deaths and 21,400 human injuries, and save $2.3 billion over the course of 30 years.
Improving wildlife corridors is a cost-effective way to increase human health and safety.
Fraser Shilling, co-director of the UC Davis Road Ecology Center and director of the California Roadkill Observation System has pointed out that "Since the cost of wildlife-vehicle conflict equals about 2 percent of California's transportation budget, it would seem reasonable to earmark 2 percent of that budget for efforts aimed at preventing incidents that threaten the safety of both animals and people." A map at the end of the Center's 2016 report Wildlife-Vehicle Conflict Hotspots along California Highways (2009-2015) provides a sense of the number and location of such collisions that take place in the State.
California should do more to protect it's apex predator.