No sleeping on the job for mothers of baby dolphins



This was published 17 years ago

No sleeping on the job for mothers of baby dolphins

New parents tormented by sleepless nights should count themselves lucky not to be dolphins, new research suggests.

Scientists have discovered that baby bottlenose dolphins do not sleep at all during their first month of life. Their mothers hardly get a moment's rest, either. They begin to sleep normally again only after several months, as their calves become less active.

The findings surprised scientists because sleep had been thought to be vital both to growing offspring and adults.

The same pattern was noted in killer whales. Experts know of no other mammals that go without sleep to the same extent.

The leader of the study, Jerome Siegel, from the Semel Institute for Neuroscience and Human Behaviour at the University of California, Los Angeles, said: "Somehow these seafaring mammals have found a way to cope with sleep deprivation, facilitating rather than hindering a crucial phase of development for their offspring.


"Their bodies have found a way to cope, offering evidence that sleep isn't necessary for development, and raising the question of whether humans and other mammals have untapped physiological potential for coping without sleep."

The scientists observed two female killer whales with young at SeaWorld in San Diego, California. Normally, the adult whales would rest for five to eight hours a day, by drifting at the surface of the pool or along the bottom.

But this pattern was not seen in the new mothers. For the first month after their offspring were born, they remained active 24 hours a day.

Similar behaviour was seen in four captive bottlenose dolphins at the Gelendgik Dolphinarium and the Utrish research station in the Black Sea region of Russia.

In both groups, the newborns needed to surface to breathe every three to 30 seconds, while their mothers kept swimming. Sustained sleep was impossible for either, though the mothers managed to rest more than the infants.

The scientists reported their findings this week in the journal Nature.

They believe there may be advantages to newborn whales and dolphins being so busy after birth. Movement and wakefulness reduce danger from predators and help maintain body temperature before the young cetaceans have acquired an insulating layer of fat. They also allow frequent surface breathing and facilitate rapid growth of the brain and body, as well as behavioural development.

"The dolphin and killer whale are the only mammals that show this complete suppression of sleep," Dr Siegel said. "It is unclear if any similar behaviour exists in other kinds of animals."

Press Association

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