Poisons Used to Kill Rodents Have Safer Alternatives

In New York rodenticides were found in 49 percent of 12 species of necropsied raptors. For great horned owls the figure was 81 percent.

Similar contamination is seen around the world. In Great Britain necropsies revealed the poisons in 92 percent of red kites, 91 percent of barn owls, and 80 percent of kestrels. In Denmark rodenticides were found in 73 percent of all necropsied raptors. In just a six-week period ended on January 23, 2012, second-generation rodenticides killed about a dozen spotted eagle owls in Port Elizabeth, South Africa. Rodenticides are also blighting raptors in Australia, New Zealand, Ireland, and Canada.

Canada doesn’t have near the rodent problems we do, but raptors there carry as much rodenticide as anywhere—a fact that puzzles Pierre Mineau, a leading ecotoxicologist who retired from Environment Canada’s National Wildlife Research Centre in 2012. “There are high levels of exposure in every species we’ve looked at,” he says. “Not just in the rodent eaters but in the accipiters [which eat mostly birds]. I wouldn’t have expected that. It’s still a mystery how this stuff is moving through terrestrial food chains. Insects may be picking it up and passing it to the songbirds that eat them. That might account for the accipiter [poisoning] connection.”

While the California data is quite recent, monitoring has essentially ceased there and in New York, and it never really began anywhere else. “If you look back at the incidence reports, there are big peaks, and then the funding gets cut off by California and New York,” remarks Nancy Golden, a contaminants specialist with the U.S. Fish and Wildlife Service.

But at least in California and New York, nontarget rodenticide poisoning is a public issue. New York City is much enamored of a 22-year-old red-tailed hawk named Pale Male (“How the Nest Was Won”). In February 2012 Pale Male’s mate, Lima, was found dead shortly before she would have laid eggs. The inside of her mouth was pale, as were her heart, lungs, liver, spleen, kidneys, and brain. The necropsy turned up fatal doses of three rodenticides, including brodifacoum, in her liver. Pale Male then took another mate, his sixth—Zena. In 2012 the pair fledged three chicks, one of which is thought to have been killed by rodenticides and two of which were gravely sickened by rodenticides but treated with vitamin K and released. The city, of course, has lost many less famous birds.

New York City Audubon entreats the public never to use the two second-generation rodenticides most toxic to birds (brodifacoum and difethialone) and not to use others except as a last resort and never during nesting season, when adults can feed poisoned rodents to their young and each other. But some bird lovers are scolding the organization for not demanding a complete ban. Director Glenn Phillips offers this defense: “Our city has a huge rat problem. We can’t ban all use of rodenticides; it’s never going to happen. If we were to advocate that, we couldn’t get the support of a single city agency. If you want to tilt at windmills, you can try. If you want to actually make things better for birds, you have to do what you can to reduce rodenticides, even if you can’t eliminate them.”

I have to side with Phillips because his organization has no choice. It’s making the best of a bad situation. But that doesn’t mean second-generation rodenticides have a legitimate place in or around New York City dwellings or in or around dwellings anywhere—not even when set out by farmers or licensed exterminators. Both tend to be just as clueless about collateral poisonings as the general public.

Consider the experience of Jeannine Altmeyer, a retired opera singer from the small south-coast town of Ojai, California. She had a major rat infestation because her 2.5-acre property is surrounded by orange and avocado farms. So in 2009 she hired a licensed exterminator. “These guys came every month for three years,” she told me. “There were far fewer rats for the first two years, but last winter we had a horrible infestation. Every night I’d see at least five rats crawling on the chicken coop. The company put out these tamper-proof boxes. Then on August 3, 2012, my beautiful, five-year old golden retriever, Franz, was acting strange. His gums were snow white; back then I didn’t know what that meant. He weighed 90 pounds. We had to carry him downstairs on a sheet, and he died on the way to the vet’s. Franz was a wonderful dog. I had a necropsy done; they found brodifacoum.”

Altmeyer paused, then continued, her voice cracking. “The pest-control people told me the bait wasn’t dangerous, that there was no secondary poisoning. I used to throw the dead rats over the wall; I would never do that now. The local vets see lots of poisoned dogs because the farmers indiscriminately put the stuff out in their orchards. One woman didn’t have the money to pay for treatment for her poisoned dog so she was going to sell her washer and drier. The vet had to tell her, ‘Keep your machines; I can’t save your dog.’”