California Forum

Californians love their mountain lions. Why do we keep poisoning them?

California mountain lion P-55 rubs its cheeks against a rock, possibly to mark territory

A Southern California mountain lion who managed to cross the 101 freeway twice, was found dead recently at 3 years old, according to Santa Monica Mountains National Recreation Area officials. This video shows him rubbing his cheek against a rock.
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A Southern California mountain lion who managed to cross the 101 freeway twice, was found dead recently at 3 years old, according to Santa Monica Mountains National Recreation Area officials. This video shows him rubbing his cheek against a rock.

Californians voted almost 30 years ago to ban the hunting of mountain lions. In fact, no part of a mountain lion hunted in another state can be brought within our state’s boundaries.

We feel protective of our mountain lions — so much that when Dan Richards, then the president of the state Fish and Game Commission, hunted and killed a cougar in Idaho seven years ago, he was forced out.

For a state that loves its top land predators, though, we’re doing a remarkably good job of poisoning them, along with bobcats, fishers and owls and other wildlife.

In the past four years, three Southern California mountain lions have died with rat poison in their systems, the latest in March. In two of those cases, the poison was confirmed as the cause of death; in the third, it’s suspected. Scientists have been discovering cases of mange in cougars and bobcats and, though they can’t be absolutely sure, they believe the culprit is rat poison that weakens the cats’ immune systems and renders them more vulnerable to the disease.

An ongoing study by the National Park Service in the Santa Monica Mountains tested the blood of 19 mountain lions and found rat poison in 18 of them, the Los Angeles Times reported.


And state tests continually find large numbers of animals with various levels of rodenticide in their bodies. In 2018, a state report said that, of the animals tested, measurable levels of second-generation rat poisons were found in 90 percent of mountain lions, 88 percent of tested bobcats and 85 percent of protected Pacific fishers, a forest-dwelling relative of weasels and otters.

That doesn’t necessarily translate to such high levels of poisoning in all animals in the state; these animals were largely tested because they were already ailing. Still, it’s a lot of poison in treasured species. Similar numbers have been found in owls, eagles and other birds of prey.

About 15 years ago, scientists examining an outbreak of mange in bobcats, which killed dozens of the cats in the Santa Monica Mountains area, identified rat poison as the probable cause.

And here’s a possible reason: A 2018 study from a 20-year collaboration between UCLA and the National Park System found that exposure to rodenticide appeared to actually change bobcats’ immune systems. Bobcats exposed to rodenticides had fewer neutrophils, the white blood cells that are the first to respond to an infection.

The term “second generation” is especially meaningful here because it indicates a bigger environmental problem than the older poisons, such as warfarin.

Both types of rat poison involve anticoagulants that cause internal bleeding. But the newer poisons are more toxic and stay in the rat’s body for longer, which means they’re more likely to be ingested by animals that eat the corpse, or eat the still-live rats, which are easier to catch than other prey because they’re left woozy by the poison.

Of course we have to protect humans from rat infestations, but it’s unclear that anticoagulants are going to get us there in the long run. The existence of warfarin-resistant rats has been recognized for decades, and by 2014, scientists were reporting emerging signs of resistance to second-generation rat killers.

Karin Klein
Karin Klein

We Californians might feel noble about our bans on hunting cougars and trapping bobcats. The Legislature is considering a bill to ban trophy hunting of bobcats as well. But that’s all a little futile when we’re poisoning them for our own convenience.

And this is happening despite a state law that several years ago banned the consumer sale of second-generation rodenticides to consumers. In other words, you can’t stop at the local home and garden store for it. It’s only supposed to be available to professional exterminators.

Either those pest control companies are too fast to reach for their most intense chemical weaponry, or homeowners and landlords and various businesses are buying bulk quantities of the stuff online.

A new bill, Assembly Bill 1788, aims to turn this around with new restrictions on the use of anticoagulant rodenticides. Commercial pest control operators would not be able to use them except in cases where they are needed to protect public health.

They would have to file paperwork with their counties to get permission for each case, which means they are more likely to try other means first: ensuring that trash bins aren’t overflowing, sealing off entryways, using traps and turning to first-generation anticoagulants. Agriculture wouldn’t be included. Neither would certain kinds of businesses, such as food warehouses.

The main threat to wild animals has been where development butts up against open land. This means cougars and bobcats in the L.A. area, and owls, eagles and other raptors in the Bay Area, says Guy Strahl, chief of staff for Assemblyman Richard Bloom, D-Santa Monica, author of AB 1788.

So, this measure, even though it leaves out large swaths of land, ought to stave off the worst of the problem. The state itself would be banned from using even first-generation anticoagulants on its own property, an important concession, especially in parks, where wildlife are more likely to find poisoned rodents quickly.

It’s an incremental approach, but it may be enough to start turning things around. In any case, it’s the least the state can do for its wildlife. It’s folly to think that allowing animals to be poisoned into ill health and death is somehow more humane than hunting them.

Karin Klein is a freelance journalist in Orange County who has covered education, science and food policy. She can be contacted at Follow her on Twitter @kklein100.