Center for Biological Diversity

For Immediate Release, March 1, 2019

Contact: Jonathan Evans, (510) 844-7118,

Studies: Rat Poisons Harm Bobcats' Immune Systems, Genetics

Research Provides Support for California Bill Restricting Rat Poisons  

LOS ANGELES— Two studies by researchers at the University of California, Los Angeles and the National Park Service reveal that rat poisons are causing dramatic changes to the immune system and genetics of bobcats. The research provides further support for a bill introduced late last month to greatly restrict super-toxic rodenticides in California.

The researchers found that the damage to bobcats’ genes and immune systems can be linked to a range of health problems, such as a 2002 mange outbreak that killed dozens of the animals.

“Evidence continues to mount that California must ban these dangerous poisons to prevent the needless illness and death of wildlife,” said Jonathan Evans, legal director of the Center for Biological Diversity’s environmental health program. “There are safer, cheaper alternatives that greatly reduce risks to wildlife, pets and children.”

Assemblymember Richard Bloom (D-Santa Monica) has introduced AB 1788. The bill would ban super-toxic rodenticides — known as second-generation anticoagulant rodenticides — except for use in agriculture and in the case of public health and environmental emergencies. It would also limit other anticoagulant rodenticides on state lands.

“Virtually every mountain lion we test has rat poison in its system, and so do 90 percent of the bobcats,” said Seth Riley, a professor at UCLA and wildlife branch chief at Santa Monica Mountains National Recreation Area who co-authored the recent studies. “We’ve found three mountain lions that bled to death internally, but our studies show that even animals that don’t die can be harmed. This research pinpoints how the poisons affect cats in previously unknown, sublethal ways, which has important implications for management and conservation.”

California state regulators are also reevaluating rodenticides after a state analysis late in 2018 found super-toxic rat poisons in more than 90 percent of tested mountain lions, 88 percent of tested bobcats and 85 percent of protected Pacific fishers tested.

The harm caused by the super-toxic second-generation anticoagulant rodenticides in California is well documented. More than 70 percent of wildlife tested in California in recent years has been exposed to dangerous rodenticides. Officials have found poisonings in more than 25 different species of animals, including endangered wildlife such as the San Joaquin kit fox and Pacific fisher.

More than 4,400 children under age 6 were poisoned with long-acting anticoagulant rodenticides in the United States in 2016, according to the American Association of Poison Control Centers. The Environmental Protection Agency has found that children in low-income families are disproportionately exposed to the poisons. Thousands of incidents of pets being poisoned by rodenticides have also been reported, many resulting in serious injury or death.

Effective, affordable alternatives to rat poison include rodent-proofing homes and farms by sealing cracks and crevices and eliminating food sources; providing owl boxes in rural areas to encourage natural predation; and using traps that don’t involve these highly toxic chemicals. For more information on nontoxic rodent control methods, visit

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 1.4 million members and online activists dedicated to the protection of endangered species and wild places.

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