News in Science

Baby dolphins never sleep

Sleep-deprived mothers of newborn babies should spare a thought for bottlenose dolphins and killer whales.

An international study has shown the young of those two species don't sleep during the first month of life.

Unlike other mammals, they are active 24 hours a day, and their mothers have learned to cope.

Scientists from the US and Russia publish their findings in today's issue of the journal Nature.

"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," says author Dr Jerome Siegel, a neuroscientist at the University of California, Los Angeles.

Siegel and his colleagues say the developmental pattern they discovered in the dolphins and whales is different to other mammals.

All other mammals studied so far sleep the most as newborns, and need less sleep as they grow into adults.

But as the calves of dolphins and killer whales grow, they sleep more, until they reach adult levels.

"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," Siegel says.

The scientists believe the newborns' lack of sleep has several advantages.

Their constant movement reduces the danger from predators and helps to maintain their body temperature until they develop greater mass and blubber.

It also allows them to swim to the surface frequently to breathe and helps their body and brain to develop.