"The idea that sleep is essential for development of the brain and body is certainly challenged," said research team leader Jerome Siegel.
Adult cetaceans normally sleep for 5 to 8 hours a day, but the newborn whales and dolphins were observed to be continually active, surfacing for air every 3 to 30 seconds. They also kept at least one eye open to track their mothers, New Scientist reported.
The research suggests the ability is an inbred defense mechanism, as "in the water, there's no safe place to curl up," Siegel said.
Siegel and his colleagues found that, over 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 levels were normal, so the animals were not apparently stressed by their insomnia.