Monday, January 16, 2012

Pale penguins

National Geographic recently carried an account of tourists* on one of their sponsored expeditions to Antarctica spotting a mutant penguin - and thereby I learned a new word. These birds in less-than-formal dress are called "isabelline penguins" and they are rare, but not unheard of. "They do pop up from time to time, but they're not particularly common. They're very obvious when you do see them. Amongst all the black backs you suddenly see a white one,'' says Australian biologist Megan Tierney. Isabellinism affects approximately 1 in 50,000 penguins of most species, examples of which I have collected above: royal penguin (1st image), chinstrap penguin (2nd image, video here), gentoo penguin (3rd image), adelie penguin (4th image). The term refers to the light color, distinguishing isabellinism (a form of leucism in which all types of skin pigmentation are reduced) from albinism (in which just the melanin is reduced or absent). South African researchers spotted only 2 isabelline specimens among the king penguins on Marion Island. Magellanic penguins, which live on South American coasts, seem to have the lowest incidences of the condition, according to penguin expert P. Dee Boersma of the University of Washington. The Ornithological Society of New Zealand, clarifies that isabellinism has not been observed in the emperor penguin, Fiordland crested penguin, erect-crested penguin, Galapagos penguin, or little (blue) penguin. Although instances of ostracism have been documented among penguins with plumage aberrations, isabellines do not appear to experience "racism" and have been observed carrying out normal nesting behavior and living for years.

*More information on visiting Antarctica at Cool Antarctica and the United States Antarctic Program.

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