sábado, 27 de octubre de 2007

Sleeples Dolphins

Sleepless in SeaWorld: Some newborns and moms forgo slumber

Naila Moreira

Orca-whale and dolphin mothers and their newborns appear not to sleep for a month after the pups' birth, researchers report. Neither parent nor offspring shows any ill effects from the long waking stint, and the animals don't later compensate with extra sleep.


UP WITH THE BABY. An orca-whale mother and her newborn pup may forgo sleep for several weeks before adopting a normal pattern. Dolphins also exhibit this behavior.
SeaWorld, San Diego

No previously studied mammal stays awake for so long, says Jerry Siegel of the University of California, Los Angeles (UCLA), an investigator in the study.

In the months following their wakeful period, baby whales and dolphins—and their mothers—ramped up slowly to sleep amounts typical of normal adults, Siegel and his colleagues report. The infants' sleep pattern contrasts with that of other mammals, which need extra sleep during infancy and gradually sleep less as they age.

Oleg Lyamin, also of UCLA, started observing an orca mother and her baby just after it was born at SeaWorld, San Diego. Orcas usually snooze for 5 to 8 hours a night, closing both eyes and floating motionlessly.

The SeaWorld orca mother and baby, Lyamin found, neither shut their eyes nor remained motionless. Instead, the animals were constantly active, with the infant surfacing for a breath every 30 seconds. The researchers made similar observations of another SeaWorld orca mom and baby.

The team also watched dolphins at the Utrish Dolphinarium in Moscow. Dolphins sleep with one-half of the brain at a time, closing one eye while floating or swimming about. The team observed no sleeping behavior in the first month after birth among four dolphin mom-baby pairs.

The findings, reported in the June 30 Nature, challenge prevailing notions of the purpose of sleep, some researchers say. "We're under the belief that if you don't get sleep, you can't perform, and you're at risk for developing all sorts of disorders," says Paul Shaw of Washington University in St. Louis. For instance, rats die after being deprived of sleep for just 2 weeks.

The UCLA data are "the beginning of a change in the way we view sleep," says Shaw.

Scientists have commonly hypothesized that people and other animals require sleep for brain development and learning (SN: 6/1/02, p. 341: http://www.sciencenews.org/articles/20020601/fob6.asp). "Here we have a developing [whale or dolphin] youngster with no evidence of sleep," says Irene Tobler of ETH-Zurich in Switzerland. "It will revolutionize many people's ways of thinking."

Siegel argues that sleep is not required for brain development in these and other young animals and instead plays some role as yet unknown.

Alternatively, whales and dolphins may have evolved unusual compensatory mechanisms that permit them to develop without sleep, while other animals still require sleep for brain development, Tobler says.

Robert Stickgold of Harvard University suggests that mother and baby whales and dolphins may have evolved an unusual form of sleeping. "A sleepwalker makes it down the stairs, into the kitchen, into the refrigerator quite well while a [brain wave] recording says they're in deep sleep," he notes.

Stickgold says that such recordings from the animals could help determine whether the orcas and dolphins are awake.

Siegel speculates that mothers and babies of both species need constant activity to survive. The mother pushes the baby to the surface to breathe at regular intervals. Also, the baby must stay warm in cold water while it develops its blubber coat.

"The mystery is that they're ... dispensing with sleep behavior when so many sleep researchers have assumed that sleep has a vital function," Siegel says.


Why should the whale study lead scientists to "change the way we view sleep"? Among whales, the priority is that babies not drown in the first weeks of life. Maturational processes thought to occur during sleep, such as brain development, might have to be put on hold while this critical lesson is learned. Our neonatal sleeping pattern, 4-to-6-hour periods interspersed with bouts of feeding, is dictated by a critical need for rapid, overall physical development to achieve mobility. To live, the already mobile baby whale must first learn to breathe.

Brenda Marion Gray
Glen Burnie, Md.


2005. No sleep in the deep: Unlike other mammals, newborn dolphins and killer whales stay active 24/7 during first months of development. University of California, Los Angeles press release. June 29. Available at http://www.newsroom.ucla.edu/page.asp?RelNum=6274.

Lyamin, O. . . . and J. Siegel. 2005. Animal behaviour: Continuous activity in cetaceans after birth. Nature 435(June 30):1177. Abstract available at http://dx.doi.org/10.1038/4351177a.

Further Readings:

Bower, B. 2002. Snooze power: Midday nap may awaken learning potential. Science News 161(June 1):341. Available at http://www.sciencenews.org/articles/20020601/fob6.asp.

Brownlee, C. 2005. Losing sleep: Mutant flies need less shut-eye. Science News 167(April 30):275. Available at http://www.sciencenews.org/articles/20050430/fob2.asp.

Hesman, T. 2000. Fly naps inspire dreams of sleep genetics. Science News 157(Feb. 19):117. Available at http://www.sciencenews.org/articles/20000219/fob4.asp.

Milius, S. 2004. Sparrows cheat on sleep: Migratory birds are up at night but still stay sharp. Science News 166(July 17):38. Available at http://www.sciencenews.org/articles/20040717/fob7.asp.

A version of this article written for younger readers is available at Science News for Kids.


Paul Shaw
Anatomy and Neurobiology
Washington University School of Medicine
660 S. Euclid Avenue
Campus Box 8108
St. Louis, MO 63110

Jerry Siegel
Psychiatry and Biobehavioral Sciences
Center for Sleep Research
Neurobiology Research 151A3
VA GLAHS Sepulveda
16111 Plummer Street
North Hills, CA 91343

Robert Stickgold
Center for Sleep and Cognition
Harvard Medical School
Beth Israel Deaconess Medical Center E/FD861
330 Brookline Avenue
Boston, MA 02115

Irene Tobler
Institute of Pharmacology and Toxicology
University of Zurich
Winterthurerstrasse 190
CH-8057 Zurich


From Science News, Vol. 168, No. 1, July 2, 2005, p. 3.

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