Written by Jonathan Evans, Center for Biological Diversity

Sure, who wants to live with rats—but have you considered the impact to other creatures when using rodenticides?

Listen to this Green Divas Heart Wildlife podcast segment to learn how to handle rodents without the use of common poisons. Then read on for more…

Rat and mouse poisons pose a serious risk to public health and the environment. These highly toxic rodenticides cause severe health damage and even death in non-target wildlife, pets and people.

Because of their toxicity, and the weak safety standards governing 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 uncontrollable bleeding that leads to slow and agonizing deaths.

Four types of silent, super-toxic killers…

There are four types of these silent, super-toxic killers (brodifacoum, bromadiolone, difethialone and difenacoum). 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, eagles, foxes and mountain lions, and they’ve been reported in numerous imperiled species, including endangered San Joaquin kit foxes, Pacific fishers and northern spotted owls.

Famous wildlife species have also succumbed to rodenticide poisoning. P22 is a mountain lion well known in Los Angeles ever since it graced the cover of National Geographic in December 2013 in a striking night photograph that captured it below the Hollywood sign.

In the spring of 2014, P22 was caught in order to replace the battery in his radio-tracking collar. Biologists discovered that he has been exposed to rodenticides and was severely ill with mange, a parasite of the skin and hair that is also known to affect large wild cats such as bobcats and mountain lions in southern California.

Researchers with the National Park Service and the University of California, Los Angeles have demonstrated a strong correlation between mange and anticoagulant rat poison exposure in the Santa Monica Mountains of Southern California. Studies have documented a new outbreak of mange associated with rodenticide exposure. Two mountain lions found dead from rodenticide poisoning in Southern California also suffered from mange.

P22 had perilously managed to cross two of the busiest freeways in the country, the 405 and the 101, only to suffer from poisons put out by his new neighbors near Griffith Park. National Park Service biologists treated him with topical medications and vitamin K injections to offset the poisoning, and released him back into the park. Fortunately, P22 appears to be doing well: He has recovered from mange and even put on a few healthy pounds.

While some rodenticide-poisoned wildlife can recover if found and treated in time, many inevitably perish.

Humans—especially children—and household pets can even be hurt by rodenticides.

These toxics clearly pose risks unworthy of the suffering and biodiversity loss they cause.

There are many safe, nontoxic ways to prevent rodent infestations in order to limit sanitation and disease problems. Removing sources of food, water and shelter to discourage the rodents’ presence is highly effective before and after rodent infestation breaks out. Many safe, affordable and effective strategies for addressing rodent problems can be found here.

Three guiding principles to address rat and mouse infestations: Prevent, identify and treat.

First, prevent the problem from starting. Seal entry points to prevent rodents from entering your home and buildings using metal mesh or expanding foam with a bittering agent that rodents dislike. Remove rodent attractions such as food, water or shelter by ensuring that food is securely stored, pipes are not cracked or leaking, and that surroundings are clean.

Second, identify signs of rats or mice in your home, such as rodent droppings or nesting materials around food, inside cabinets, under sinks or under the house.

Finally, treat the problem. Remove rodents by using snap or electronic traps, and not rodenticides. If you live in rural or open suburban areas, install barn owl boxes. You can also hire a pest control company, but make sure that they don’t use rodenticides.

Jonathan Evans is the Toxics and Endangered Species Program Director at the Center for Biological Diversity. He works to protect imperiled wildlife from the threats of environmental contamination and reduce the toxic threats of pesticides, heavy metals and chemical pollution in our environment. Jonathan received his law degree from the University of Oregon School of Law and a bachelor’s degree in conservation and resource studies from the University of California at Berkeley. Prior to joining the Center, Jonathan worked at the National Fish and Wildlife Foundation managing ecosystem restoration grants. He also brings to the Center a background in the field of outdoor education as a naturalist and guide throughout California.

~Asst. Ed. Green Diva Christine