Lizards Sunbathe for Better Health

Lizards and other cold-blooded critters bask in the sun to keep warm. But they also do it for the vitamin D, a new study finds.
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"The chameleons were as effective as mathematically possible by our methods at regulating toward optimal UV exposure for their vitamin D profile," he said. "We thought they were probably pretty good at regulating their UV exposure; we just didn't think they'd be this good."

It's not clear, however, by what mechanism they are able to sense their internal vitamin D levels, but Karsten thinks there may be a brain receptor sensitive to the vitamin.