Newborn dolphins don't sleep

Newborn dolphins and whales stay awake for a whole month after their birth - a finding researchers say is 'extraordinary' since newly born mammals and their mothers stay asleep for as long as they can after birth.

Newborn whales and dolphins are continually active, surfacing for air every 3 to 30 seconds. They also keep at least one eye open to track their mothers who seemed to set the frenetic pace by always coursing ahead of their offspring, a report said.

Researchers studied the surprising sleeping patterns of captive killer whales - Orcinus orca - and bottlenose dolphins - Tursiops truncates - in the early months of life, says NewScientist.com.

Jerome Siegel of the University of California at Los Angeles, who conducted the research, said sleep patterns observed in

newborn whales and dolphins were in contrast with that seen in adult cetaceans.

Adults normally 'sleep' for 5 to 8 hours a day - either floating at the surface or lying on the bottom before rising periodically for air.

Siegel and his colleagues found that over the months mothers and offspring gradually increased the amount of rest until it approached that of normal adults.

Measurements of the stress hormone - cortisol - showed that the levels were normal, the researchers said, an indication the animals were not apparently stressed by their insomnia.

The ability for cetaceans to keep on the go after birth has several advantages. It makes it harder for predators to catch them because 'in the water, there's no safe place to curl up', Siegel notes.

It also keeps their body temperature up while their layer of insulating blubber builds up.

'Unlike all animals previously studied, which maximise rest and sleep after birth to optimise healthy growth and development, the cetaceans actively avoided shut-eye,' says Siegel.

'It's an extraordinary finding,' says Jim Horne, director of the Sleep Research Centre at the University of Loughborough, Britain.

Horne says that humans sometimes fall asleep with their eyes open, so it is conceivable that nature allows the dolphins and whales to do the same.