Poisons Used to Kill Rodents Have Safer Alternatives

But second-generation rodenticides do have a legitimate use—ecosystem restoration on rat-infested islands. These projects are tremendously expensive, and you get only one shot, so you need weapons of mass destruction. There’s no “almost”; you kill every rat save non-pregnant ones of the same sex or you fail.As if in a ghoulish recast of The Nutcracker Suite, Norway rats had ruled aptly named Rat Island in the Aleutians since they’d disembarked from a wrecked Japanese ship in 1780. They’d eradicated songbirds, seabirds, native plants, and even the island’s original name—Hawadax. Biologists described the island as “eerily quiet.” Then in 2008 the U.S. Fish and Wildlife Service and its partners (The Nature Conservancy and Island Conservation) deployed two helicopters to saturation-bomb 6,424 acres with 46 metric tons of brodifacoum bait. Cost: $2.5 million.

There can be no better example of the deadliness of second-generation rodenticides than collateral damage on Rat Island. Found dead along with the rats were 46 bald eagles, at least 320 glaucous-winged gulls, one peregrine falcon, and 53 other birds representing 24 species. Despite the heart-breaking nontarget mortality, the project succeeded from a species perspective. Today the island (renamed Hawadax) is rat free, and native species rarely, if ever, seen are surging back—among them burrow-nesting seabirds, giant song sparrows (found only in the Aleutians), black oystercatchers, pigeon guillemots, rock sandpipers, common eiders, red-faced cormorants, and gray-crowned rosy finches.

Collateral damage on Rat Island taught the partners valuable lessons. In 2011 they took on the black rats thought to have been introduced by the U.S. Navy in World War II to Palmyra Atoll, a national wildlife refuge between Hawaii and American Samoa. Again they applied brodifacoum by helicopter. And because of an enormous population of land crabs known to eat rat bait like candy and with impunity the partners had to use far more poison than would otherwise be necessary. But they applied it when birds weren’t migrating through the area, and they captured resident birds, mostly bristle-thighed curlews, maintaining them in an aviary for two months. At a cost of $2.7 million and a few nontarget mortalities (but very few) the island is now rat free, and what had been a biological desert is exploding into a vibrant native ecosystem. Seedling pisonia trees, all but eliminated by rats, now carpet the ground. Other plants thought to have been extirpated are back. Dragonflies and crickets have reappeared. Fiddler crabs patrol the beaches in numbers biologists had never imagined possible. Now instead of a few hundred sooty tern fledglings there are thousands; similar nesting success of other seabirds is imminent.

“It’s really hard to argue against the overwhelming benefits of rodenticiding rats off seabird islands,” comments Canada’s Pierre Mineau, who has experience with these projects. “But I really question, as does your EPA, whether every homeowner needs a sledge hammer when a flyswatter will do. The companies don’t see it that way; once they have a product, they need to sell a certain volume to make it profitable. If they have to sell it only on a strictly needed basis for island rat eradication, it’s probably not worth it.”

The questioning Mineau refers to percolated within the EPA for years. Finally, in 2008, the agency declared that second-generation rodenticides brodifacoum, bromadiolone, difethialone, and difenacoum posed an “unreasonable risk” to children, pets, and wildlife, and gave manufacturers three years to cease selling directly to residential consumers—a standard procedure. But it left a gaping loophole by exempting large-quantity sales (presumably to farmers) and tamper-proof bait boxes used by exterminators. Predators, scavengers, and pets are no less poisoned if they eat rodents that consume bait from sealed boxes or bait set out by farmers.

Of the 29 rodenticide manufacturers receiving the EPA’s directive for new safety requirements, 26 complied. Among these was Bell Laboratories, honored by the Wisconsin Environmental Working Group, its home-state neighbor, for designing the specialized bait formulation for Rat Island. (Bell also designed formulations for Palmyra Island and similar successful projects on the Galápagos Islands, South Georgia Island, Channel Islands National Park off California, and Canna Island off Scotland.)

But in a nearly unprecedented move, three companies have refused. They are Spectrum Group, which, ironically, makes pet-care products along with the rat and mouse poison Hot Shot (whose active ingredient is brodifacoum, especially deadly to pets); Liphatech, which produces rodenticides Generation, Maki, and Rozol—the strictly regulated but still-registered prairie-dog poison that has killed raptors and predatory mammals, probably including endangered black-footed ferrets (see “Doggone”); and Reckitt Benckiser, the $37 billion-a-year multinational company that markets popular household products like Woolite, Lysol, French’s Mustard, and brodifacoum-laced d-Con.

In January 2011 Reckitt Benckiser, the most intransigent of the three, prevailed in its legal complaint that the EPA lacked the authority to enforce its order unless it had already canceled registration of a pesticide. That doesn’t mean the company won’t have to stop general consumer sales of its second-generation rodenticides if EPA pulls that registration, as it claims it will do. But formal cancellation proceedings can take years, and that’s what Reckitt Benckiser wants. Meanwhile, species that don’t have that kind of time will keep dying.