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The Honolulu Advertiser
Posted on: Wednesday, November 12, 2003

Frog find fuels snake concern

By Timothy Hurley
Advertiser Staff Writer

The tiny greenhouse frog, one of two Caribbean frogs that has been spreading across the Islands, has been discovered on Guam, and scientists say that's bad news for Hawai'i.

The greenhouse frog, recently discovered on Guam, is an ideal food source for the brown tree snake.

Haldre Rogers • USGS

The frogs are an ideal food source for the brown tree snake and could fuel a population explosion of the slithery invader that has decimated bird populations and created other problems on Guam.

"This is an issue for Hawai'i because more snakes on Guam mean a greater chance of snakes getting to Hawai'i," said Earl Campbell, Pacific Islands invasive species coordinator with the U.S. Fish and Wildlife Service.

The federal government has spent millions trying to eradicate the brown tree snake and prevent it from spreading to Hawai'i and other Pacific islands.

Legislation introduced in Congress last week called for spending as much as $18 million annually between 2005 and 2010 in an escalation of Guam's brown tree snake control program.

The accidental introduction of brown tree snakes to Guam in the 1940s became one of the world's worst biological catastrophes caused by an invasive species. The brown tree snake wiped out nine of Guam's 12 native bird species and reached a high of 30,000 snakes per square mile in some areas by the 1980s.

Because the snake has exhausted much of its food supply, its numbers have leveled off to about 12,000 snakes per square mile in certain forested areas.

But the greenhouse frog, discovered last month in north Tumon, threatens to send the numbers soaring again.

"It's like throwing fuel on the fire," Campbell said.

Both frogs have characteristics that will allow them to proliferate on Guam, he said. They are highly reproductive, have no tadpole stage and forglets hatch directly from eggs.

Fred Kraus, a former state invasive species coordinator and now a scientist at Bishop Museum, said it's likely that greenhouse frogs hitchhiked to Guam on landscape materials originating from Hawai'i. That's how they are believed to have spread across this state.

Greenhouse frogs are smaller than the coqui, another Caribbean frog that has been spreading across Hawai'i. While the coqui fits on top of a quarter, the darker greenhouse frog fits on top of a dime. Both species need a moist environment, but they do not need standing water.

The coqui's distribution in Hawai'i has been relatively easy to track because of its noisy chirp, but that is not the case for the quieter greenhouse frog. While wildlife officials are working to eradicate greenhouse populations on Kaua'i, their distribution on the other islands is unclear.

Hawai'i has no native frogs, and biologists fear these animals may prey on native insects and spiders, spread plant diseases and increase the population of rats and mongooses by serving as a food source. They may also serve as a food source for any snakes allowed into the state.

Hawai'i wildlife scientists welcomed legislation introduced Friday by Reps. Madeleine Z. Bordallo (D-Guam), Neil Abercrombie (D-Hawai'i) and Ed Case (D-Hawai'i), saying it would bring badly needed stability to Guam's brown tree snake control program, which currently relies on year-to-year money.

"It's a good step in the right direction," Kraus said.

And with the greenhouse frog arriving on Guam, there may be even more urgency to step up the program, scientists said.

Reach Timothy Hurley at (808) 244-4880 or thurley@honoluluadvertiser.com.