Contrary to popular belief, ostriches don't sleep with their heads in the sand. In fact, to all appearances, they never sleep at all: their eyes stay open, although they appear to doze off from time to time. To learn more about the sleep patterns of this unusual bird, researchers captured six ostriches in South Africa and measured their brain wave patterns with data loggers while they slept They expected the brain waves to look like those of other birds and mammals, which cycle between two patterns: deep sleep and rapid eye movement (REM). When the loggers showed that the ostriches were in deep sleep, the birds looked entirely alert. But when they entered another sleep cycle, their heads started to droop. This second brainwave pattern wasn't classic REM, but a unique hybrid of REM and deep sleep patterns, the researchers report this week in PLoS ONE. The only other animal to show this pattern is the platypus, a member of an ancient group of egg-laying mammals known as monotremes. As ostriches are an ancient type of bird, this similarity suggests that the separation between REM and deep sleep may have evolved recently in birds and mammals. One can only speculate on whether ostriches and platypuses have similar dreams, too.
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