In Guam, U.S. Drops Dosed Dead Mice To Stem Snake Infestation

Brown tree snakes are causing a problem in Guam. And now, efforts being used to reduce the brown tree snake population by using dead mice, a common pain killer and aerial drops. Robert Siegel speaks with Dan Vice, a wildlife biologist with the USDA, for more on this process.

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According to the U.S. Department of Agriculture, sometime after World War II, one reptile stowaway, a female brown tree snake, possibly pregnant, probably slithered off a ship and onto the island of Guam. Over the next 60 years, the offspring of that founding mother snake, in the absence of natural predators, have flourished to excess. Guam today is evidently awash in brown tree snakes - one to two million of them. And while the problem is interesting, it's the solution to this problem that caught our attention, the plan that USDA and other agencies are using to pull a St. Patrick and rid the Pacific island of its snakes. Dan Vice is a biologist with Wildlife Services - it's a USDA agency. He's in Guam and has worked on this project for over a decade. Welcome to the program.

DAN VICE: Thank you very much, Robert.

SIEGEL: And, first, before you describe how you hope to exterminate thousands, if not hundreds of thousands of tree snakes, first, why is it necessary?

VICE: Well, a little bit of history. When the snake arrived on Guam, there were not predators on the island. The snake arriving here was able to quickly exploit the relatively defenseless birds to the point that today there are virtually no birds left in the forest. And this now super-abundant snake has a tendency to get into cargo and into aircraft and onto ships and move around.

SIEGEL: OK. Well, let's move on to the solution to this, which involves huge quantities of dead mice.

VICE: For an unknown reason, the brown tree snake on Guam very readily consumes dead prey - things that it hasn't killed itself. And once researchers discovered this, we were able to combine the attractiveness of the dead mouse with a very effective but very low-risk toxicant, acetaminophen, which is a very common over-the-counter painkiller and fever reducer for people.

SIEGEL: Now, the idea here is that the acetaminophen - essentially Tylenol, to use the brand name - that's toxic to the tree snakes, and the tree snakes would eat dead mice, if they came upon them. So, the idea is to somehow make the mice the delivery vehicle of the acetaminophen.

VICE: Absolutely. And what makes acetaminophen such a good choice for this work is that it's highly toxic to snakes but it's very low toxicity to virtually everything else. And so we've developed a system where the bait, mice, are affixed to a floatation device. It's basically two pieces of thin cardboard with some accordion-folded tissue paper attaching the two pieces together.

SIEGEL: The mice effectively are parachuted down into the treetops.

VICE: Yes, you could say that but it's not literally a parachute. But the concept is the same. We're trying to float them down gently.

SIEGEL: You're a wildlife biologist. As an example of evolution, this scheme, as it has evolved, the notion that somebody would have come up with the idea of acetaminophen to kill the snakes, dead mice to deliver the acetaminophen and then these little tissue paper and cardboard sort of parachutes to be dropped out of helicopters to fall into the trees where the snakes would get them, that's an extraordinary scheme.

VICE: It is. It's trying to solve a problem when you can't Google the solution. There's nobody that'd done anything like this before.

SIEGEL: Well, Dan Vice, good luck to you.

VICE: Thank you so much, Robert.

SIEGEL: And thanks for talking with us.

VICE: You're welcome.

SIEGEL: That's Dan Vice, a biologist with the USDA's Wildlife Services in Guam.

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