Sleeping with more than one eye open

Researchers have discovered that some whales and dolphins don’t sleep after birth. Both newborns and their mothers stay continuously active for about a month and then gradually build up their sleep to normal adult levels after four or five months. “What’s going on is very different than any animal ever encountered,” said Dr. Jerome Siegel, a professor of psychiatry at the University of California, Los Angeles, and an author of a paper describing the finding in Nature.

Siegel and his colleagues studied newborn killer whales and bottlenose dolphins, recording their activities in pools at Sea World in San Diego and in an aquarium in Russia. Dolphins had already been known to exhibit unusual resting behavior: They sleep with one eye open. At any time only one brain hemisphere shows activity that is characteristic of a certain kind of sleep. Dolphins have also never been shown to exhibit rapid-eye-movement sleep, Siegel said.

But when Siegel heard about another cetacean, a killer whale, being born at Sea World, he sent a student, Oleg Lyamin, to study it. “He reported that not only wasn’t there REM sleep, there didn’t appear to be any sleep at all,” Siegel said.

“Unquestionably, the amount of sleep is minimal at birth,” Siegel said. Why don’t these animals need REM sleep? “It may be that REM sleep has a function for stimulating the brain, and non-REM sleep is more of a rest state,” he said. “And because dolphins never have a brain in a rest state, there’s no need for it. But how they do without sleep in general,” he added, “I don’t have a clue.”

NYT