Toxic Frogs, Birds May Get Their Poison From Beetles

Cameron Walker
for National Geographic News
November 9, 2004

The Colombian poison-dart frog and six Papua New Guinea birds, mostly jay-sized songbird species commonly known as pitohui, live almost at opposite ends of the Earth. But the animals share one thing in common: They use batrachotoxin, a rare neurotoxin that is 250 times more potent than strychnine.

Researchers believe the creatures use the poison, which laces their skin and/or feathers, as a type of biodefense that protects the animals from predators and parasites.

One enduring mystery, however, has been the source of the poison: Scientists suspect the birds and amphibian can't manufacture batrachotoxin naturally.

Now researchers say they may have discovered how the animals obtain the toxin: They eat beetles riddled with the stuff.

In a study published last week in the Proceedings of the National Academy of Sciences, researchers report that they have found batrachotoxins in a little-known group of beetles from the Choresine genus. The discovery marks the first time the toxin has been found in an insect.

Biologists found the same beetles in the stomachs of the Papua New Guinean birds, which they say suggests that eating Choresine beetles provides the South Pacific animals with the key ingredient for their toxic defense against predators and parasites.

The discovery hinged on the work of local naturalist Avit Wako. Wako, from the village of Herowana in Papua New Guinea's eastern highlands, spent two years collecting biological samples to reveal a possible natural source of the bird-feather toxin.

"The big breakthrough was really his," said Jack Dumbacher, an ornithologist at the California Academy of Sciences in San Francisco and lead author of the study. "It speaks very highly of native naturalists and the value of traditional knowledge," he added.

Tracking Toxins

Batrachotoxin has been known to Western scientists since the mid-1960s, when chemist John Daly and colleagues at the United States National Institutes of Health first identified it in the skin of Colombian poison-dart frogs (Phyllobates spp.). Daly is also a co-author of the new study.

For far longer, however, traditional South American hunters have known about the poison and used it to coat the tips of their lethal blow darts.

Continued on Next Page >>




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