Rat and mouse poisons, or rodenticides, pose a serious risk to public health and the environment. These are toxic products that cause severe health damage and even death in nontarget wildlife, pets and people. Because of their toxicity and the weak safety standards for their use and distribution, rodenticides are a serious threat to any living thing that accidentally ingests them.
While there are several types of rodenticides, the most dangerous on the market are second-generation anticoagulant rodenticides, aka “super-toxic” rodenticides. Super-toxic rodenticides are slow-acting substances that block the synthesis of vitamin K necessary for normal blood clotting, causing their consumers to bleed uncontrollably and die slow and agonizing deaths. There are four types of these silent, super-toxic killers (brodifacoum, bromadiolone, difethialone and difenacoum), all of which have long half-lives that allow rodents to ingest them multiple times before dying. Through a secondary-poisoning process called bioaccumulation, rodenticide residues build up in rodent carcasses to levels many times the minimum lethal doses — exposing rodent-eating predators and scavengers to immense amounts of poison.
Cases of secondary poisoning are thus potentially disastrous for animals like hawks, owls, foxes and mountain lions, and they’ve been reported in numerous imperiled species, including various raptors (such as owls, hawks and eagles), endangered San Joaquin kit foxes and Pacific fishers. While some rodenticide-poisoned wildlife can recover if found and treated in time, many inevitably perish. And even humans — especially children — and household pets can suffer from contact with rodenticides. These toxics obviously pose risks unworthy of the suffering and biodiversity loss they cause.
Because of rodenticides’ widespread harm to many kinds of life, the Center for Biological Diversity is working hard for regulations that reduce their collateral damage.
In California’s San Francisco Bay Area, species at risk of poisoning by rodenticides include the endangered San Joaquin kit fox, Alameda whipsnake, Swainson’s hawk and salt marsh harvest mouse. After continuous legal pressure on the U.S. Environmental Protection Agency, including from a 2007 legal challenge, the Center was able to reach an agreement with the EPA to restrict the use of 74 toxic pesticides — including rodenticides — in Bay Area habitat for these and other species, until the agency formally completes a legally required consultation with the U.S. Fish and Wildlife Service and evaluates the pesticides’ harmful effects. In support of our case, the Center released a 53-page comprehensive scientific report outlining the harms pesticides inflict on these animals, as well as the EPA’s failure to address those harms as required under the Endangered Species Act.
The Center filed suit again in January 2011, specifically challenging the EPA’s failure to follow the Endangered Species Act’s requirements to consult with the Fish and Wildlife Service about the threats of registered rodenticides to listed species and their habitats. Then, in December of that year, we asked the California Department of Pesticide Regulation to ban the use of second-generation coagulants in the state of California, or at minimum to significantly restrict their use.
After 15 years of analyzing the problem and years of pressure from the Center, the EPA finally issued a decision in early 2013 to place new limitations on the use of toxic rat poisons in an effort to minimize the risk of their contact with children and pets in the home. Unfortunately the measure is inadequate to address rodenticides’ threats to nontarget wildlife, leaving imperiled species’ habitat unprotected from the deadly toxins. So second-generation anticoagulants continue to travel up the wildlands food chain, mercilessly poisoning and killing natural predators of rodents.
The Center will continue to push for stricter regulations of rodenticides to ensure that both people and wildlife receive strong protections from them.
For a full chronicle of the Center’s work on pesticides reduction, check out our action timeline.
Safe, Nontoxic Methods for Rodent Control
Prevention is fundamental in practicing safe, nontoxic rodent control. Removing sources of food, water and shelter to discourage the rodents’ presence is highly effective before and after rodent infestation breaks out. The following is helpful guidance on integrated pest management techniques to addressing potential rodent invasions and treating existing ones.*
PEST-CONTROL METHODS THAT ARE SAFE BETS FOR WILDLIFE
• Don’t leave pet food and water outdoors, especially overnight. Store pet-food supplies indoors in sealed containers.
• Seal gaps around air vents to building sub-areas and attics and any other openings that penetrate exteriors. Use sweep seals under doors. A rat can squeeze through a hole the size of quarter, a mouse through a hole smaller than a dime.
• Don’t plant ivy — it provides shelter and a food source for rodents: snails and slugs. Ivy on walls can form “rat ladders” to windows, attics and other interior spaces.
• Keep compost piles as far away from structures as possible.
• Keep grass cut and trees trimmed as far away from structures as possible.
• If you have a birdfeeder, use a squirrel guard at the base to keep rodents away. Keep the ground area clean of birdseed.
• Keep outdoor grills and cooking areas clean.
• Keep firewood off the ground and as far away from structures as possible to mitigate shelter opportunities.
• Use city-issue plastic trash bins. If cracked or missing a lid, contact the Department of Sanitation for a free replacement.
• Clean up trash in garden areas to remove shelter for rodents.
If the above methods aren't sufficient, you may be forced to take secondary-control steps. Note: The Center does not condone cruelty to rodents or any other living creatures; these techniques are mentioned in order to best combat the toxic dangers of rodenticides while also preventing or causing minimum harm to rodents themselves. Some of this content may be unpleasant to read.
* Pest-control methods suggested by Richard Stanley, director of the Los Angeles-based nonprofit Friends of Griffith Park. © The Griffith Reporter/Winter 2012-2013