CALABASAS, Calif. — P-54 was only 4 weeks old when she became part of the National Park Service's ongoing study of mountain lions in the Santa Monica Mountains. Biologists have tracked her for more than five years now, as she matured, mated and had kittens. In June, just as she was about to give birth to another litter, a car on Las Virgenes Road struck and killed her.

J.P. Rose of the Center for Biological Diversity called the loss tragic.

“Given that there’s only a handful of adult mountain lions that inhabit the Santa Monica Mountains, the loss of a female with four unborn kittens is incredibly heartbreaking,” he said.

And sadly not isolated. P-54s mother, P-23, was killed by a car in 2018, just a few miles away from where P-54 would also lose her life. One of her offspring, P-97, was struck and killed on the 405 Freeway in April. Seth Riley, the wildlife branch chief for the National Park Service in the Santa Monica Mountains National Recreation Area, said it’s been a tough year for local mountain lions.

“We’ve had five different collared animals and actually another uncollared animal right in our study area that have died this year getting hit on roads,” he said. He points out that two years ago saw a baby boom in what was dubbed the “summer of kittens,” putting those kittens at the age where they would be trying to find their own territory.

“All young males try to disperse and get somewhere else,” Riley said. "When you have a situation like ours, where they’re surrounded by freeways and development and roads like PCH and Las Virgenes, then that mortality is certainly a possibility.”

What’s unique about P-54’s death, however, is that it illustrates the intersection of two of the biggest dangers facing urban wildlife — roads and rat poison. Researchers had a rare opportunity to study the four full-term unborn kittens and found multiple anticoagulant rodenticides in all of them. 

Riley said P-54 had been exposed to a total of five different compounds while each of the kittens was exposed to at least three.

“It just really shows that there’s still a lot of that exposure out there,” he said.

NPS researchers have now found these highly toxic compounds in 39 out of 40 local mountain lions tested, including these four fetuses. The National Park Service has been urging homeowners to avoid using these products.

“Whenever possible, just try not to use toxicants poisons of any kind, and especially try not to use these anticoagulants,” Riley said. “I think it’s really critical as much as possible to try to solve, you know, rodent issues without poisoning whenever you can.”

Rose agrees and offers some alternative suggestions for pest control.

“One of the best ways is simply to ensure that your house is properly enclosed, any holes are blocked up,” he said, also warning homeowners not to leave any food outside that might attract rats. “I think the bigger question is, what type of a world do we want to live in? Do we want to live in a world where the wild is still alive? And where we coexist with wildlife, or a world where we continue to kill indiscriminately native wildlife through the use of poisons?”

The Center for Biological Diversity co-sponsored a bill in 2020 that restricted the use of certain super toxic rodenticides. As for road deaths, they are currently waiting for the governor to sign another piece of legislation, AB 2344, which would require Caltrans to consider and incorporate wildlife connectivity into any road projects moving forward. This is essential, Rose said, to increasing genetic diversity among the local cougar population, which right now, the Center predicts faces a 99% chance of becoming extinct locally.

Rose said having mountain lions on the landscape keeps the ecosystem in balance. They help keep the deer population under control and their kill assists the California condors.

“If we don’t take steps to build wildlife crossings, control super toxic rodenticides and coexist with nature, we will lose Southern California mountain lions,” he said.

CORRECTION: The story has been updated to indicate the animals were collared. (Sept. 19, 2022)