When it comes to feather lice, the name fits well: the lice live on birds, feeding on feathers as well as dead skin. The birds try to get rid of them, of course, and succeed part of the time.
Lice have “evolved” camouflage to help them hide from their unwelcoming hosts.
But ScienceNOW reports that the lice have “evolved” camouflage to help them hide from their unwelcoming hosts—a conclusion that comes from a new study appearing in The American Naturalist. Scientists compared twenty-six pairs of related, but different-colored, birds, looking at the color of their feather lice. As the scientists suspected, the color of each lice population tended to match the color of its host’s feathers—dark lice on dark-feathered birds, and light lice on light-feathered birds.
That makes sense, the researchers say, because birds can more easily spot—and remove—lice that stand out against their feathers as they preen. One exception was the color of the birds’ head lice, which was always dark. But this also makes sense; the birds are unable to see their heads as they preen, so the color of a louse doesn’t make it more likely to get “picked off” (literally).
Once, peppered moths were a leading icon of evolution. As the story goes, the presence of dark moths resting on dark trees and light moths resting on light trees proved the populations were “evolving” to their environment. But neither peppered moths nor feather lice are evolving at all; the force at work is natural selection, the result of which is a decrease in a population’s diversity and (potentially) its amount of genetic information.
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