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The Pitohui and the Frog

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Originally Published: North Bay Herpetological Society Newsletter

by Robert B. Hole, Jr.

One day in 1989, Jack Dumbacher caught a bird, called a Hooded Pitohui, in a net in New Guinea. The bird bit and scratched at Jack while he was removing it from the net. At some point, Jack put his finger in his mouth. Sometimes, from such things are scientific discoveries made.

Well, when Jack Dumbacher put his finger in his mouth, his tongue and lips went numb. After a little panic and a little investigation, it turned out that the pitohui (pronounced "pit-oo-eey," kind of like spitting) was poisonous. The Hooded Pitohui, and two close relatives, are the first documented poisonous birds.

What has all this got to do with a frog? The poison of the pitohui was identified, and it turned out that the poison is a very special one, and had only been seen once before -- in dart poison frogs of the genus _Phyllobates_ in the family Dendrobatidae. The specific toxin isolated from the birds is homobatrachotoxin, a steroidal alkaloid, and is chemically identical to the homobatrachotoxin produced by _Phyllobates_.

Pitohuis are much less toxic than _Phyllobates_ though I wouldn’t suggest eating one, though New Guinea natives will occasionally. They do say that it must be skinned and prepared very carefully. Distillation from a few milligrams skin of the Hooded Pitohui will kill a mouse in a few minutes. The three pitohui species vary in toxicity, the Hooded Pitohui is the most toxic, the Variable Pitohui is intermediate, and the Brown Pitohui is the least toxic.

Pitohuis and dart poison frogs are also somewhat similar in coloration. All three species of pitohui have red and black plumage - warning colors used by _Phyllobates_. Also, like the frogs, the less poisonous Brown Pitohui is the least strikingly colored being mostly brown, and the more toxic Hooded Pitohui is the most strikingly colored.

Though the pitohuis are the first documented case of poisonous birds, these are probably not the only birds with chemical defenses. Just as many species of amphibian are distasteful to potential predators while not being toxic, many birds taste terrible. Though this has not been thought of by most ornithologists as a chemical defense, it could easily be considered one.

Not much is known about pitohui biology. Major aspects of their life histories remain to be discovered. One of the most important unknown things is how they make homobatrachotoxin, and how the birds themselves survive the poison in their bodies. There is enough unknown to provide several people with lifetime research projects.

Acknowledgements:

I thank Dr. Bruce M. Beehler, who organized the expedition to New Guinea, and brought pitohuis to my attention through discussions about the bird.

References:

Dumbacher, John P., Bruce M. Beehler, Thomas F. Spande, H. Martin Garraffo and John W. Daly. 1992. Homobatrachotoxin in the Genus _Pitohui_: chemical defense in birds? Science, vol. 258, pp. 799-801.

Diamond, Jarad M. 1992. Rubbish birds are poisonous. Nature, vol. 360, pp. 19-20.

Wrangham, Richard. 1992. The taste of birds: _Pitohui_! Science, vol. 258, p. 1867.


Original contents of this and all linked pages produced by this author copyright © 1995-2005 Robert B. Hole, Jr. All Rights Reserved