Three years ago, P-22 — an iconic mountain lion in the Hollywood area — died after a fatal vehicle collision, the Los Angeles Times reported. While it may have been a car that killed him, it was something of a miracle that he was alive at all.

After chronic exposure to rat poison throughout his life, only regular medical attention from scientists at the National Park Service kept him going — and now more animals are in danger of the same exposure.

What's happening?

In 2021, the California Department of Pesticide Regulation set new limits on the most dangerous poisons used to control rodents. Anticoagulant rat poisons — toxins that kill pest species by thinning their blood — don't just harm the target rodents, but also affect all other species across the food chain that prey on these species or the ones that eat them. Such was the case with this rescued baby bobcat.

Unfortunately, the department is now looking to roll back these regulations and once again allow the public to use these toxic substances for pest control.

That will affect the more than 7,500 species living in the Los Angeles area, including 52 endangered species and more distinct bird species than any other county in the United States. California's Department of Fish and Wildlife even proposed in December that mountain lions should receive the protection afforded to threatened species under the state's Endangered Species Act. All of these animals are vulnerable to rat poison exposure.

At the same time that California is looking to roll back measures against anticoagulant rat poison, Connecticut is considering stricter regulations.

Why are regulations controlling pesticide use important?

When a rat eats poison and dies from it, the poison remains. Predators and scavengers that come across the body of the rodent — or that hunt exposed rodents before they have time to die — then ingest poison themselves. 

What happens next depends on several factors. Predators are usually larger than their prey, so it takes a larger dose of poison to kill them, but they typically eat many prey animals — this means that if poison is being widely used in the area, they may be exposed to a fatal dose.

The type of poison also matters. Some toxins break down in the body, while others build up over time. Some are targeted and only affect rats, such as a class of poisons that sterilize the animal and prevent it from multiplying. Others can also harm the predator.

Anticoagulant poisons are the worst kind. They remain deadly as they spread through the food web. According to the Los Angeles Times, 95% of mountain lions, 100% of golden eagles, and 69% of general wildlife that have been tested in California have been exposed to these poisons. The more widely the poisons are used, the greater the collateral damage.

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What do experts recommend?

Data from multiple public and environmental health departments suggest there was no significant increase in rodent problems after the restrictions on the anticoagulant rat poisons were put in place. Options that are less harmful for the wider environment can be just as effective, and experts recommend that the public use them.

Meanwhile, according to the Los Angeles Times, state regulators will play a vital role in setting guidelines that protect our planet.

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