The early bird may get the worm, but the sleepless sandpiper gets the chicks.
Male pectoral sandpipers that sleep less than their counterparts during the bird's intense three-week breeding season mate with more females and sire more offspring — and don't appear to be impaired whatsoever by their sleeplessness, according to a study published today (Aug. 9) in the journal Science.
These results are surprising since humans and many other animals handle sleep loss poorly, with decreases in memory, attention and hand-eye coordination, said study co-author John Lesku, a researcher at the University of Western Australia.
Eyes wide open
During breeding — when the sun over the Arctic tundra never sets — males must defend their territory, fight with other males and impress potential mates by flying over them and hooting, chest puffed out. All of this requires a lot of energy, and the picky females, it appears, keep their eyes open for champs that are able to stay ahead of the competition. [ The Animal Sex Quiz ]
The finding runs counter to the notion that regular sleep is always necessary to function well. "There's plenty of evidence suggesting that how our brain performs during wakefulness depends on sleep," said co-author Niels Rattenborg, a scientist at the Max Planck Institute for Ornithology in Seewiesen, Germany. "But here we have sandpipers sleeping very little in a very competitive real -world environment and the ones that are sleeping the least do the best."
Not only do the supermales sire more baby sandpipers, but they don't appear to "sleep it off" afterward, and more of them come back to the site the next year compared with the better-rested birds, Rattenborg said. Also, it's not like the birds rested before breeding: They'd just migrated to the Alaskan tundra from the Southern Hemisphere, where they winter.
Adaptive sleep loss
Jerome Siegel, a sleep researcher at UCLA who wasn't involved in the research, said the study supports the view that sleep is best understood as a way to conserve energy. "What's adaptive is to be asleep when you don't need to be awake," Siegel said.
Across the animal kingdom, there's a wide variety of sleep habits and duration, and environmental conditions seem to be the most important determining factor. Animals that sleep in the open or have to migrate don't sleep much, he said. Newborn killer whales and dolphins don't sleep for more than a month after birth, during which time they are migrating, he said.
The researchers outfitted birds with motion-sensitive sensors to determine when they were sleeping. Earlier, small brain-wave-measuring devices found that when the birds stay still for more than a few minutes they are indeed asleep. The scientists also collected DNA from the tagged animals and their newborn chicks to see who fathered whom.
At the extreme end, one male slept for less than 23 hours over the course of 19 days and sired four chicks. And all the sandpipers that mated with more than one female were active for more than 90 percent of the breeding season.
Studying such a sleepless bird is a challenge. U.S. Fish and Wildlife Service bird researcher Richard Lanctot, who wasn't involved in the study but has researched a similar species called the buff-breasted sandpiper, said staying up around the clock quickly takes a heavy toll on scientists. "I've always wondered how they stay up so long, because we [humans] certainly cannot."
How do the birds stay awake so long? They scientists don't know, but they hope to find out. They have plans to look at what's going on inside the bird's brains and search out genes that could help withstand sleeplessness, which could help better understand the function of sleep.