Monday, December 24, 2007

Enviably cerulean males

Natalie Angier has a rather lovely piece in this week's Science Times concerning nature's own doping problem:
Like athletes who toy with drugs, animals are constantly, if unconsciously, performing the basic calculus: How much of my long-term health am I willing to sacrifice for the sake of short-term glory? Male cardinals and house finches become obsessed each fall with eating berries and other ruddy fruits, not for their nutritional value but for their carotenoids, the red and orange pigments the birds must acquire if their new crop of feathers are to beam brightly come spring. “Fruit is a poor-quality food in general, just a lot of sugar and water, and it would make more sense for the birds to ingest grain instead,” said Geoffrey Hill, an ornithologist at Auburn University in Alabama. But female birds are drawn to the most brilliant males, he said, so during the molting period, “if you don’t get carotenoids, you’ve got no hope.”

Moreover, colorful male birds may divert so much of their ingested carotenoid into their plumage that they have none left to act in the chemical’s other capacity, as an antioxidant vitamin — a resource allocation decision with possibly lethal consequences. Researchers monitoring bird populations around Chernobyl in Ukraine recently found that in highly radiated areas, brightly colored birds were significantly less abundant than drab birds. The scientists proposed that the drabber species, whose coloring relies on internally generated melanin pigment rather than consumed carotenoids, were freer to use their dietary vitamins to help mop up the cellular damage that radiation can spark.

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