Spotlight on Zoo Science
November 29, 2004
The Birds and the Beetles
New Guinea traditional naturalists helped National Zoo scientists unearth the bugs that make the skin and feathers of some birds sting.
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| Crested pitohuis (P. cristatus) from New Guinea have mildly toxic feathers and skin. |
In 1992, the National Zoo’s Jack Dumbacher and his colleagues stunned the scientific community with the surprising first report of birds with poisonous skin and feathers. Equally surprising was the poisonous agent: a chemical called homo-batrachotoxin. Batrachotoxins are among the most toxic natural substances known—nanogram for nanogram, batrachotoxins are 250 times more toxic than strychnine.
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| Hooded pitohui (P. dichrous). |
Previously known only from the skin of South American poison-dart frogs in the genus Phyllobates, here they had turned up in passerine birds in the genus Pitohui, found only on the island of New Guinea on the other side of the world. Later, Dumbacher found them in another New Guinea bird genus known as Ifrita. The scientists believe that the birds’ toxins may provide protection from parasites, such as lice, and from predators, including people.
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| The South American bicolor poison-dart frog (Phyllobates bicolor) secretes the same poison as New Guinea pitohui and ifrita birds do. |
The discovery of batrachotoxins in birds raised the same question: How do the birds obtain them? As with the frogs, scientists suspected the toxin came from their food, but with Pitohui birds eating a wide variety of insects, spiders, and other arthropods—potentially thousands of different species—even narrowing down the list of suspects to test was a daunting task.
Then, New Guinean traditional naturalists came to their rescue, enabling Dumbacher (now at the California Academy of Sciences), the Zoo’s Scott Derrickson, and their colleagues to find the likely source of the batrachotoxins in Pitohui and Ifrita in some little-known tiny beetles in the genus Choresine, family Melyridae.
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| New Guinea villages call Cheosine beetles (above) nanisani, the same name they give to the toxic blue-capped ifrita (below). |
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Villagers from Herowana, in the Crater Mountain Wildlife Management Area in the Eastern Highlands Province of Papua New Guinea, identified the beetles, which they call nanisani—the same name they give to the blue-capped ifrita (Ifrita kowaldi)! The word nanisani is also used to describe the tingling and numbing sensation of the lips and face that results from contacting both beetles and bird feathers.
Armed with this intelligence and aided by local people, the scientists collected beetles from the vicinity of Herowana for laboratory analysis, and yes, found batrachotoxins in most of their samples of four different species of Choresine. Moreover, they examined the stomach contents from birds in the five different species of toxic Pitohui and in one species of Ifrita and found that they do eat Choresine-sized insects, and one Pitohui stomach actually contained a Choresine beetle.
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| A Cheosine beetle. |
This discovery may also help solve the mystery of the dart-poison frogs’ source of batrachotoxins. Beetles in the family Melyridae are found around the world, so it is possible that relatives of Choresine living in South America give these frogs their toxic punch.
For more information: "The Intoxicating Birds of New Guinea" from ZooGoer magazine.
Reference
Dumbacher, J.P.; Wako, A.; Derrickson, S.R.; Samuelson, A.; Spande, T.F.; and Daly, J.W. Melyride beetles (Choresine): A putative source for the batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds. Proceedings of the National Academy of Sciences, 101(45): 15857-15860.
Photos by Jack Dumbacher except the bicolor poison-dart frog by Jessie Cohen/NZP.
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