The administration of Gavin Newsom, the California governor, is moving to loosen restrictions around the most toxic rat poisons, even as a new state report shows the rodenticides are unintentionally poisoning wildlife across the state, including endangered species.
Blood-thinning, anticoagulant rodenticides were significantly restricted when a 2024 state law approved after 10 years of legislative wrangling required the California department of pesticide regulation to limit the substances’ use unless data showed species collaterally harmed or killed by it had rebounded.
A new report from the California fish and wildlife service, also part of the Newsom administration, shows widespread poisonings of dozens of species, including mountain lions, hawks, owls, bears and bobcats. About 83% of bald eagles tested showed levels of the rodenticides in their blood, and endangered California condors also showed high levels.
Still, the Newsom administration is moving forward with the plans to undo many of the regulations in the new law, a move that points to industry influence, said Jonathan Evans, a senior attorney with the Center for Biological Diversity.
“You have the agency that has really tracked this issue for decades putting forward this data that shows continued harm to wildlife, but then you have another agency that’s literally trying to roll back laws that the legislature and governor put in place and includes tight restrictions, which is very, very concerning, to say the least,” Evans said.
The pesticides department proposal allows use of the most toxic rat poison to be used at more than 100,000 new locations, including grocery stores, restaurants, highways, roads, and even parks and wildlife areas.
The anticoagulant poisons cause a “gruesome” death, Evans said, because they slowly kill an animal by effectively causing it to bleed out internally. It sometimes can take days for an animal to die. The anticoagulants have a long half-life compared with other rat poisons, meaning they stay in rodents for longer, and accumulate in larger predators up the food chain that eat them.
Evans said there was little credible scientific research showing that the anticoagulants are more effective than other poisons, like strychnine, that cause less harm to predators. Still, industry claims the anticoagulants are highly effective, Evans said.
Even when the poisons do not kill the predator, it sickens them, which makes them less likely to survive later. The anticoagulants thin blood, so an animal that sustains wounds in a fight, for example, would have a difficult time healing.
The poisons also cause predators to grow disoriented, and advocates say the rodenticides have been especially hard on mountain lions, which are already under major stress from development pressure, habitat loss, car strikes and other issues.
The “Hollywood Mountain Lion” that lived in Los Angeles captured the public’s attention when he was poisoned by anticoagulants and – disoriented from the toxic substance – was then hit by a car. He died from his injuries.
River otters have also showed poisoning, highlighting the threat to aquatic animals, and the poisons have been especially harmful for great-horned owls and red-shouldered hawks, which are “some of our best natural rodent-controllers”, said Lisa Owens-Viani, director of Raptors Are the Solution, said in a statement.
“Now is hardly the time to relax restrictions when, in fact, our state department of pesticide regulation should close the loopholes in the law to truly protect these animals,” Owens-Viani added.
In part led by efforts from Newsom, whose father was one of the state’s original mountain lion conservationists, the state passed the nation-leading Poison Free Wildlife Act of 2024. Evans said he suspected Newsom was not aware of the proposal.
The pesticides department was largely funded by proceeds from sales of pesticides, Evans added, so it is incentivized to send substances to the marketplace.
Some anticoagulant rules had also gone into effect a few years earlier, but the latest state wildlife department data from 2024 shows little decrease in the amount of anticoagulant found in predators, though data from 2025 is not yet available.
The data may also show very little progress because the law includes a loophole that allows the rodenticides to be used on agricultural land, Evans said. Regardless, the data must show an improvement before the pesticides office can act, Evans added.
A spokesperson for the pesticides department did not immediately respond to a request for comment, and a powerpoint presentation used to solicit public input on the proposed rule changes provided little explanation of the rationale.
Lawmakers who helped craft the 2024 law sent a letter to the pesticides agency encouraging it to rescind the proposed rule change, stating that the justification was “flimsy and unclear”.
The governor’s response would be revealing, Evans said.
“We know Governor Newsom is concerned about this issue and has taken steps to reduce exposures, so it’s an interesting moment in which we will see if he will continue to back wildlife, or the narrow interest of the pesticide industry,” Evans said.
