2015-12-11 / Front Page

Rodenticide debate heats up in wake of wildlife deaths

By Sylvie Belmond


A SLOW DEATH—A coyote sick with mange. Animals with the skin disease have often been poisoned by rodenticides. “As you poison the rodents, you’re also killing their predators,” said Duane Tom of CWC. 
Courtesy of CA Wildlife Center A SLOW DEATH—A coyote sick with mange. Animals with the skin disease have often been poisoned by rodenticides. “As you poison the rodents, you’re also killing their predators,” said Duane Tom of CWC. Courtesy of CA Wildlife Center When people use anticoagulants to get rid of unwanted critters, they don’t just kill rats and mice. They also imperil wildlife, pets and children.

After the death of P-34, a young female mountain lion that was found dead on a trail in Sycamore Canyon Sept. 30, local animal advocates and park agency representatives are renewing their efforts to educate the public about the dangers of anticoagulant rat poisons.

The National Park Service had been tracking P-34 since she was 3 weeks old. In December 2014, the juvenile cougar was photographed by Newbury Park resident Sherry Kempster as the animal crossed a backyard wall with a mountain as a backdrop.

Biologists say the mountain lion was killed by anticoagulants used in rat poison.


ILL HEALTH—A coyote affected by rodenticide poisoning prowls behind a fence. 
Courtesy of California Wildlife Center ILL HEALTH—A coyote affected by rodenticide poisoning prowls behind a fence. Courtesy of California Wildlife Center Nearly all mountain lions, coyotes, bobcats, hawks, owls and other wild animals in the Santa Monica Mountains and Simi Hills are exposed to rodenticides.

These poisons inhibit blood from clotting and weaken the immune system, making animals and birds of prey less able to resist disease and vermin.

“I am surprised still at how many people don’t know about it,” said Cathy Schoonmaker, wildlife biologist for the National Park Service.

While the state of California has made it illegal for retailers to sell some rodenticides to the average consumer, the products are still being used by professional exterminators and farmers.

First- generation rodenticides require repeated intake of the poison bait to kill, but the second-generation poisons, also known as superwarfarins, are much more deadly.

In 2014, state legislators banned consumer use of products containing brodifacoum, bromadiolone, difenacoum or difethialone. Local cities also passed resolutions urging residents and business owners to stop buying and using anticoagulant rodenticides.

Yet scientific studies show that such poisons are still a leading cause of death among local predators.

“Animals suffer; they bleed internally and lose all their blood,” said Duane Tom, director of animal care at the California Wildlife Center.

When carnivores feed on rodents that have ingested anticoagulants, they accumulate the poison in their system.

Many animals brought to the wildlife clinic have bruising and excessive bleeding due to repeated exposure to the poisons.

“ Without doubt, anticoagulants are a big concern for wildlife and also for pets. The poison is also a problem for young children. It’s not a benign thing that people just put out to get rid of mice and rats. As you poison these animals, they don’t die right away,” said Tom, who has worked at the wildlife rehabilitation facility south of Calabasas for nine years.

Rodenticides are indiscriminate killers, and the bait boxes that contain them attract all kinds of animals.

After eating a poisoned rodent, a bobcat or coyote begins a long, painful, suffering decline, said Donna Mahan, a volunteer at the California Wildlife Center.

Most coyotes, bobcats and cougars that die from mange—a skin disease caused by parasitic mites—also test positive for rodenticide exposure.

The parasites make big cats and coyotes itch and scratch continuously, causing them to lose their fur and develop sores. And because their eyes may become swollen shut, the animals can no longer hunt so they slowly starve to death.

Wild predators are essential to regulate the rodent population.

If poisoning mice and rats also kills off large cats and canines, the rodent population will proliferate.

A breeding pair of rats can result in about 15,000 rats in a year, and a pair of mice can produce up to 1 million offspring in just over a year, Mahan said in a wildlife center newsletter.

“Anticoagulants will worsen rodent infestation. As you poison the rodents, you’re also killing their predators. If you kill off the predators, then rodents can multiply uncontained,” Tom said.

How to help

A new park service program called Nature Neighbor aims to show people the kind of changes they can make at home and at work to deter rodents from coming to their properties while also protecting the local wildlife.

“No matter where homes or businesses are in (the region), wildlife is using that area,” said Schoonmaker, who helped park service biologists track and study local mountain lions and other large carnivores for 10 years.

“Part of my passion for wanting to work with people is what I saw while working on this project,” said the woman, who obtained a grant to fund the Nature Neighbor program.

Controlling rodents without anticoagulant poisons may not always be easy but it is vital to protect the health of native wildlife, she said.

“People are not powerless; there are changes they can make where they don’t have to use anticoagulants.”

Residents, homeowners associations and business owners should remove trash and food that attract rodents to their property instead of using bait boxes or hiring a pest control company to kill rodents.

Trimming shrubs and branches, plugging holes and cracks leading to the interior of homes and outbuildings, and cleaning up wood and junk piles that provide shelter to small animals will also go a long way toward reducing rodent problems.

If all else fails, an electric trap is an option. Unlike oldfashioned snap traps, which may break the back of the rat and cause suffering, the electric devices provide an alternative way to kill and dispose of rodents.

For more information about rodent prevention and local wildlife, visit the Nature Neighbor website at http://go.usa. gov/3W5Xz.

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