Poisons Used to Kill Rodents Have Safer Alternatives

Poisons Used to Kill Rodents Have Safer Alternatives

A second generation of ultra-potent rodenticides creates a first-class crisis for people, pets, and wildlife.

By Ted Williams
Published: January-February 2013

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 Galapagos 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.

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Ted Williams

Ted Williams is freelance writer.

Type: Author | From: Audubon Magazine



Hi Don:
It's second generation. Don't use it. Not that I'm in favor of using first generation.

Poisons and Glue Traps

Thanks Maggie:
I agree that it’s preferable to use no poisons. But if one insists, at least use the first-generation poisons you mention that have been cleared by the EPA. I can’t agree that glue traps should be avoided because of urination, defecation, and cruelty. First, mice and rats urinate and defecate all over the place when they’re NOT in glue traps. In my camp, for example, they’ll even defecate in the ice-cube trays if we forget to turn them over. At least in the glue traps, they urinate and defecate for the last time. They also defecate and urinate in snap traps and in electrocuting traps. I am having trouble grasping why everyone thinks glue traps have to be inhumane. If you use them only indoors, tend them regularly and dispatch the critters, they are no more inhumane that snap traps which often catch rodents by the legs.

Anticoagulants in wildlife

A property that makes second generation anticoagulants so dangerous to non-targets is their resistance to metabolic degradation. Levels build up in the liver (where clotting factors are produced). Multiple sublethal exposures can put predators in the danger zone over time. I supect many incidents of raptor mortality are the result of multiple exposures over time. With an array of 2nd generation products now in use, it is now common to detect 2 or 3 different anticoagulants per raptor.

Thanks Joe

Good point, Joe. I found your necropsy reports very helpful.

To quote the Lorax: Unless

To quote the Lorax:

Unless someone like you cares a whole, awful lot, nothing is going to get better. It's not.

We are connected to the environment, like it or not

We are connected to the environment, like it or not, so we can't really elect to sacrifice some species to benefit ourselves. Poisoning one species and having it end up poisoning more, not only makes a mess of the environment but these poisons can end up in us, too. Humans are part of this ecosystem and doing destructive things to it, only harms us, too.

Spreading Poisons

Well said, Cindy.

The person writing this

The person writing this article seems to know a lot about different species of birds. As far as treating and eliminating rats however not so much.

Snap traps- very good for mice. They are curious to anything new to their environment. Roof rats and Norway rats however are not. Leading to a very ineffective treatment method.

Glue boards- probably the most in humane of them all. I On numerous occasions have seen glue boards with nothing but a rodent leg attached. The rat will literally gnaw its own leg off to free itself.

Electrocuting rodent stations- work but the chances of being able to eliminate a family nesting in an attic very slim.

Soup cans attached to a rod?- I have yet to try but damn I want to lol.

1st generation rodenticides- very ineffective over time hence the reasoning for having such products that work such as 2nd generation rodenticides. Using 1st gen takes far longer to eliminate problems often leading to the rodents destroying expensive wiring which can cause fire. Rodents are said to be the primary cause of about 20% of fires. So as for me as much as I hate what the effects to wildlife are. I will trade birds for human life.

I had friend who stayed in a

I had friend who stayed in a nice hotel in Moscow once. There was a mouse in the room so they called the front desk. Within a couple of minutes a man knocked on their door. When they opened it he handed them a cat. When they came back to the hotel at the end of the day, the mouse and the cat were gone.

Egypt had it right. Europe in the middle ages (and the USA now) got it wrong. Sometimes the tried and true way just might still be the best way. But Ted and the Audubon Society have lost all objectivity and are therefore dangerous. IMHO

Chad, will you trade pets for human life too?

What is the threat to human life from rodents? The threat is very mild in most places! I myself had a horrible problem when rat mites infested my house - probably because of a dead rat in the attic. As soon as a rat dies in your home, its parasites jump ship and go looking for new warm bodies - including yours and your pets. The mites were horrible, and took me months to get rid of, but I didn't get sick or die. Poisoning rodents in your house means they can end up in the walls, which can create a major problem for a homeowner. Poisoned rats don't just get eaten by wildlife, there are thousands, perhaps millions of documented cases of pet dogs and cats being poisoned - are you ok with that? I don't feel that pest control operators or companies are a good source to listen to on this issue. I myself, in my volunteer work with wildlife, have heard many times that a pest control operator out and out lied to a consumer by telling them the poisons they use are "safe." That is simply an oxymoron. There is no such thing as a safe rat poison. The only product that came close was called Rodetrol, it uses non-poison, to kill rats by affecting their metabolism. This product was from the UK and they could never get EPA approval in the US. Wonder why? I suspect major corporate bad guys like Reckett-Beckieser - maker of d-Con, who use their corporate power to influence agencies and politicians so they can keep making billions from the poisoning of childen, pets and wildlife. Our small grassroots effort of education people is making progress and RB can't stand it! They are the only company refusing to follow the EPA's recommendations. You can do a lot to eliminate the possibly of rodents starting fires but investing in an exclusion process of a building. Costs more up front, and deprives PCOs of their lucrative monthly fees, yet more and more offer it because their customers are wising up and demanding it as an alternative to poison. We are a small group, but we are not going away.

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