Rodenticides (rat poisons) designed to kill rodents are poisoning California’s native wildlife. These persistent poisons are first consumed by rats, who in turn are consumed by other wildlife, resulting in secondary poisoning and contamination of the food chain. Poisoned animals frequently suffer slow and very painful deaths. In addition to harming wildlife, children and companion animals are also vulnerable to rodenticides, accidentally consuming the poison intended for rodents.
The California Ecosystems Protection Act, authored by Assemblymember Richard Bloom, and co-authored by Senator Henry Stern and Assemblymember Laura Friedman, placed safeguards on the use of the most toxic rat poisons — second-generation anticoagulant rodenticides (SGARs) — except in cases of public health emergencies, until their re-evaluation by the Department of Pesticide Regulation determines they will have no significant adverse effect on non-target wildlife.
How Anticoagulant Rodenticides Work
While all anticoagulant rodenticides have a harmful impact on wildlife, SGARs, such as difenacoum, brodifacoum, bromadiolone, and difethialone, are particularly dangerous because they have higher potency than prior generations of poisons. A single dose has a half-life of more than 100 days in a rat’s liver.
Anticoagulant rodenticides disrupt normal blood clotting by interfering with the vitamin K cycle. Animals who consume first-generation anticoagulant rodenticides (FGARs) or SGARs suffer from uncontrolled bleeding and ultimately may die. FGARs require rodents to consume the bait for several consecutive feedings before receiving a fatal dose. SGARs are more potent – a rat can die after just one feeding. But both generations of rodenticides pose a serious danger to children, wild animals, and companion animals.
California’s Wildlife Imperiled
Anticoagulant poisoning has been found in numerous California wildlife species, including coyotes, San Joaquin kit foxes, black bears, raccoon, mountain lions, bald eagles, great-horned owls, skunks, and bobcats. Some of these include endangered and threatened species. The California Environmental Protection Agency documented rodenticide residues in 27 avian species and 17 mammalian species. There is no way to determine the exact number of animals who have been killed, in part because animals typically retreat to dens or other hiding places in the final hours of their lives.
However, a 2018 analysis of 11 studies determined that more than 85% of California mountain lions, bobcats, and Pacific fishers have been exposed to rodenticides. The California Department of Fish and Wildlife’s database of mountain lion deaths also revealed anticoagulant rodenticides were found in the livers of 63 out of 68 deceased mountain lions between 2015 and 2016.
Considering the harmful impact of these poisons on ecosystems, the California Department of Pesticide Regulation banned the use of SGARs by consumers, limiting their use to just professional pest control applicators, in 2014. But the impact of SGARs on wildlife has not decreased since then, meaning further action was urgently needed.
Children and companion animals are particularly vulnerable to rodenticide poisoning. Young children routinely consume poison intended for rodents, confusing the bait for food. Similarly companion animals either consume the bait directly or consume poisoned rodents. Between 1999 and 2009, the American Association of Poison Control Centers (AAPCC) received reports of an average of 17,000 humans exposed to rodenticides annually. The vast majority, roughly 15,000, of these exposures involved children younger than six. The AAPCC reported more than 50,000 dog poisonings from rodenticides in 2014.
The Animal Legal Defense Fund led the coalition to pass the California Ecosystems Protection Act in conjunction with the Center for Biological Diversity and Raptors Are the Solution (RATS).