Wild Things: Life as We Know It

Why do butterflies have two sets of wings? Not to stay aloft, it turns out. Scientists from Carnegie Mellon and Cornell found that cabbage white butterflies with their hindwings removed could fly as far and as high as before. But they were slower to turn. This suggests hindwings are the key to aerial agility, a trait that helps butterflies evade hungry birds.

Eland antelopes use their knees to get a leg up on rivals, according to researchers working in Kenya. When mature bulls walk, their knee tendons slip over their leg bones, making a clicking sound like castanets. The noise, which can be heard hundreds of yards away, may help maintain dominance hierarchies: the louder the tone, the bigger the bull. The downside? Lions can hear it, too.

Researchers studying the origins of deep-sea animals analyzed the family tree of octopuses that live in total darkness. The eight-legged creatures evolved from a common ancestor that lived 34 million years ago in the Southern Ocean. Its closest living relative is the yard-long Megaleledone setebos, which still lives in Antarctica. Other species were carried to new habitats on deep-sea currents called the "thermohaline expressway."

Name: Catharus ustulatus, or Swainson's thrush.
Summers: In Canada and the northern United States.
Winters: In Mexico and South America.
Flies: By night, at least when migrating.
Sleeps: Surreptitiously. Scientists have long wondered how migrating birds, after flying all night, apparently make it through the day without sleeping. A new study of brain waves among captive Swainson's thrushes suggests they drowse with their eyes open; nap for mere seconds; and doze with one eye open, resting one side of their brain at a time. They could be catnapping while watching out for the cat.

It was "long-standing dogma" that sea snakes subsist on saltwater, say researchers from the University of Florida and elsewhere. But when they tested venomous kraits in the lab, the snakes drank only freshwater or highly diluted saltwater. Conclusion: the sea-dwelling reptiles must drink river or spring water that flows into the ocean or rainwater that pools on the sea surface.