CBC News - NO SHUT-EYE FOR NEWBORN DOLPHINS, ORCAS
The following is a news item posted on CBC NEWS ONLINE
NO SHUT-EYE FOR NEWBORN DOLPHINS, ORCAS
WebPosted Wed Jun 29 17:48:45 2005
---Newborn dolphins and orcas don't catch any zzz's during the first few
months of their lives, a finding that scientists say raises questions
about the necessity of sleep.
To aid growth and development, most animals maximize rest and sleep after
birth, but the two sea mammal species seem to be an exception.
Researchers in California studied two adult orcas ( Orcinus orca ) and
their calves for five months at SeaWorld San Diego.
Young orcas stayed active 24 hours a day for at least the first month of
their development, the scientists report in Thursday's issue of the
Mothers also got little sleep during this period, the researchers found.
They based part of their sleep observations on whether the animals kept
at least one eye open.
"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," Jerome Siegel, a neuroscientist at the
University of California - Los Angeles, said in a statement.
Coping without sleep As the calves grew, their sleep levels gradually
reached adult levels of resting five to eight hours per day floating
at the surface or lying on the bottom of the pool, rising
occasionally for air.
Bottlenose dolphins ( Tursiops truncates ) at a research station in the
Black Sea region of Russia showed similar sleeping patterns.
The researchers don't know how the cetaceans cope with so little sleep,
but they say it may offer some advantages to the calves: By moving
continuously, the risk from predators is reduced. The young maintain
their body temperature while they develop insulating blubber. The animals
can swim to the surface more often, aiding respiration. Lack of sleep may
help the animals' brains and bodies to grow rapidly.
The findings suggest sleep isn't required for development, raising the
question of "whether humans and other mammals have untapped physiological
potential for coping without sleep," Siegel said.
The results run contrary to previous research on rats and flies that
suggests forced sleep deprivation for two to three weeks can be lethal.
Based on those results, scientists suspected sleep is crucial early in
life for land-dwelling mammals.
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