EMBARGOED UNTIL 2 P.M. February 3, 1999
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STUDENT'S RESEARCH MAY BE KEY TO DECIPHERING STRANGE BIRD BEHAVIOR
BIRDS WHO SLEEP WITH ONE EYE OPEN MAY BE ON THE LOOK-OUT FOR PREDATORS
TERRE HAUTE, Ind. -- Many of us often wish that we could have eyes in the backs of our heads, but wouldn't it be equally advantageous if we could keep one eye open while still getting restorative sleep?
Niels Rattenborg, an Indiana State University graduate student, has conducted research on birds which shows that they can do just that.
"There has been little research in this area," said the 34-year-old Rattenborg, who studied sleep disorders in humans for more than 10 years prior to coming to ISU in 1996.
But there's been enough research conducted to show that birds often sleep with one eye open and with half of their brain awake (unihemispheric sleep).
The Madison, Wis., resident and primary investigator for this research is working on his doctorate in behavioral physiology at Indiana State University. An article detailing his results will appear in the Feb. 4 issue of Nature magazine. Steven Lima, an ISU professor of life sciences, and Charles Amlaner, chairperson of the ISU department, serve as co-authors for his study.
In fact, it was because of Amlaner that Rattenborg chose to study at ISU.
"Dr. Amlaner was essentially the only person in the United States studying sleep in birds," said Rattenborg, who met his professor at a national sleep society's annual meeting several years ago.
Rattenborg theorized that birds sleep with one eye open to remain on guard against predators and that their levels of unihemispheric sleep increase as the chances of potential predator attacks increase.
"My interest is in predator-prey interactions made me very interested in this research," said Lima. "One problem prey animals have is that they have to sleep and are very vulnerable to predators. It was obvious to me that unihemispheric sleep probably had an anti-predator function.
"A lot of animal behaviors are flexible in response to changing levels of danger," Lima added, "but now we know that unihemispheric sleep is one of those behaviors."
To prove his theory, Rattenborg studied four groups of mallard ducks (each group containing four ducks). Video recordings were made with the birds arranged in a row. Those birds on the ends of the row were more exposed to a threat than those in the center of the group.
What Rattenborg found was that the birds on the outside edges (those at greater risk of attack) were more often in a state of unihemispheric slow-wave sleep (USWS) than were those nestled in the middle of the group -- about 150 percent more. Also, the birds in USWS at the edge of the group were found to have their open eyes facing away from the group and in the direction of any potential predators at least 85 percent of the time.
"In other words, birds are able to control whether they sleep with one or both hemispheres of the brain based on the degree of risk perceived," said Rattenborg, who upon completion of his degree next year, plans to teach or work in a human sleep center and to continue his research.
"This research shows how very important sleep is," said Rattenborg, who earned his bachelor's and master's degrees at Washington University and St. Louis University, respectively.
"Usually, when days get busy, the first thing we sacrifice is sleep," he said. "The fact that birds have adapted to their environments in this way shows us that there is a true value to sleep and that birds are able to control in what form they get it.
Although humans are not able to control whether they sleep with one or both halves of the brain, Rattenborg's research could one day shed light on human sleep disorders such as sleep walking or persons' productivity levels in sleep-deprived states.
As a matter of fact, Rattenborg is taking his research with unihemispheric sleep to new heights. He is working with pigeons to discern whether each hemisphere of the brain needs a certain amount of sleep. By depriving one hemisphere of sleep for an extended period of time, he hopes to observe whether or not that hemisphere will sleep longer as a means of "catching up."
"Through our research, we've shown that each hemisphere of a bird's brain works independently of the other - both in wakefulness and in sleep. Not always is a sleeping duck a sitting duck," he said.
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