Question: When Does an 800-Pound Predator Sleep? Answer: Any time it wants to! Sleep patterns vary widely across species. For example, sleep duration in mammals varies from a low of 3 hours a day in horses to up to 20 hours a day in bats (Siegel, 2005, 2009). One explanation is that sleep patterns result from evolutionary adaptation to a particular ecological niche. Thus, animals with few predators, like polar bears, have the luxury of sleeping long hours out in the open and even taking daytime naps after a meal. In contrast, giraffes take short naps throughout the day, often keeping one eye open to stay alert for predators.

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