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Public Radio's Environmental News Magazine (follow us on Google News)

Hawaiian Frogs

Air Date: Week of

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CURWOOD: It's Living on Earth. I'm Steve Curwood.

TOOMEY: And I'm Diane Toomey. Hawaii officials have a new hotline, but it's not for reporting crimes or UFOs. It's for reporting frogs. The targeted amphibians are native to the Caribbean. They're commonly known as the coqui and the greenhouse frog. They got to Hawaii in potted plants about a decade ago and they've been spreading rapidly ever since. The frogs are putting pressure on native bugs and birds, but it's people who are starting to crack. In chorus, the ear-piercing creatures produce a noise that's causing some Hawaiians to lose sleep. Earl Campbell is a biologist for the U.S. Department of Agriculture. He's been trying to reign in the ruckus. Dr. Campbell, what's it like to be out in the field with these frogs?

CAMPBELL: It's pretty astonishing. I never thought that frogs could get that loud. It's basically a wall of sound. We have people complaining because they can't sleep at night or they can't show their houses at night, because it's so loud nobody would buy the property.

TOOMEY: How loud can it get?

CAMPBELL: At its loudest, the frog calling can be at a level that, if a staff member and I are standing about eight feet apart, we basically have to yell at each other to carry on a conversation.

TOOMEY: But no earplugs.

CAMPBELL: No earplugs.

TOOMEY: I understand that you have a tape of a recording of these frogs. If you could play that for us now, so we can hear what these guys sound like.

(Loud frogs)

TOOMEY: Okay. I had to take my headphones off. That's pretty piercing. (Laughs) Okay. Dr. Campbell, if these creatures are native to the Caribbean, why aren't people in places like Puerto Rico being made deaf?

CAMPBELL: One of the things to make clear is, we have no native amphibians in Hawaii. So our ecosystems developed without having amphibians as a component. Essentially, the things that hold the frogs in check to some level or keep their populations at a certain level, many of those mechanisms, for instance predation, competition, or disease, aren't present in Hawaii.

TOOMEY: Over the past few decades there have been more and more invasions of non-native species into areas around the world. And for the most part, attempts to stop them have been pretty unsuccessful. But you're trying something new. It's a spray made from caffeine.

CAMPBELL: Yeah. The population levels are so high that hand-capture is absolutely ineffective. The traps that have been used for these things aren't effective. We worked with state and federal agencies to screen, what about chemicals that we know may effect frogs? We tested 30 different chemicals that have been known to potentially have effects. And it turns out that nothing that's registered works well on frogs. The only thing that worked was caffeine.

TOOMEY: Tell me how the caffeine works. Why is caffeine a poison to frogs?

CAMPBELL: We don't know the actual mechanism that causes mortality in frogs from caffeine. If you look at the literature on caffeine and its effects, for instance, on human beings, the few cases where there have been human mortality from somebody that just drank absolutely too much coffee, one of the things that's seen is heart failure. So that could be one of the ultimate causes of an application of caffeine.

TOOMEY: Dr. Campbell, do you have any stories that you've heard from residents who live near these areas of infestation that might help us understand just how bad things can get?

CAMPBELL: We've had people try to light their yards on fire. You know, one or two cases, where an individual basically doused her yard with something that would light on fire.

TOOMEY: So this person was so desperate that they set their back yard on fire?

CAMPBELL: They attempted to set their yard on fire, yes.

TOOMEY: Did it work? Did it get rid of the frogs?

CAMPBELL: No. (Laughs)

TOOMEY: Earl Campbell is a biologist with the U.S. Department of Agriculture. Thanks for joining us today.

CAMPBELL: Thank you very much.

(Music up and under)



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