Press

ALBANY, NY (MAY 14, 2008) – A New York State Museum researcher has co-authored a new study published today in a British scientific journal, which sheds new light on sleep patterns in wild animals and will also help scientists understand the function of sleep in humans.

This study, the first-ever to use an electroencephalogram (EEG) to study sleep in wild animals, shows that animals in captivity may sleep more than they do in the wild, thus emphasizing the need for more study of animals in their natural conditions. In the past, a standard method for studying the purpose of sleep has been to compare EEG studies of different species, which required them to be in a laboratory setting because of the bulky equipment.

In this study a team of researchers fit free-ranging three-toed sloths with miniature EEG recorders and found that they were sleeping only 9.6 hours per day -- six hours less than captive sloths did. "Sloths in captivity don't really have anything to do so we weren't surprised that they sleep more," said Roland Kays, co-author and curator of mammals at the New York State Museum. "However, the six-hour difference was surprising. This was more than an extra little siesta in the middle of the day, and has real implications for our understanding of sleep in all animals."

Kays was part of a team of international researchers working on the Smithsonian Tropical Research Institute’s Barro Colorado Island in Panama. Their study was published online today in the Royal Society journal Biology Letters, a primarily online, peer-reviewed journal that publishes high-quality biology research.

“We are fascinated that some animal species sleep far longer than do others,” said first author, Niels Rattenborg of the Sleep & Flight Group at the Max Planck Institute for Ornithology. “If we can determine the reasons for variations in sleep patterns, we will gain insight into the function of sleep in mammals, including humans. But if animals behave differently in captivity, where all previous comparative studies were performed, than they do in the environments where they evolved, measuring their brain activity in captivity can lead to the wrong conclusions.

“We got around this problem by using a technique developed for monitoring brain activity in humans, in conjunction with a newly developed miniature recorder for neurophysiological data, in order to monitor sleep in the wild,” said Rattenborg.

In addition to the brain activity sensors worn as a cap on their heads, three adult sloths were also each fitted with radio-telemetry collars and accelerometers so that their exact locations and movements could be monitored over the following five days. The activity of two other sloths was monitored for a longer seven-month period, via radio-telemetry collar alone, using a unique Automated Radio Telemetry System in place on the island.

The placement of brain activity monitors on sloths, living among treetops 130 feet above the forest floor, demonstrates the feasibility of understanding a complex behavior, such as sleep, in the complex tropical forest environment and is expected to lead to more refined, comparative sleep research work.

“The beauty of the automated telemetry system is that it makes a new suite of animal behavior studies possible,” said Martin Wikelski, director of the Plank Institute, researcher at Princeton University and research associate at the Smithsonian.

The Smithsonian Tropical Research Institute, headquartered in Panama City, is a unit of the Smithsonian Institution. The Institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems.

The New York State Museum is a program of the New York State Education Department, the University of the State of New York and the Office of Cultural Education. Started in 1836, the Museum has the longest continuously operating state natural history research and collection survey in the United States. Located on Madison Avenue in Albany, the Museum is open daily from 9:30 a.m. to 5 p.m. except on Thanksgiving, Christmas and New Year's Day. Admission is free. Further information about programs and events can be obtained by calling (518) 474-5877 or visiting the museum website at www.nysm.nysed.gov.

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