Sleep. It's an essential biological function that has long intrigued scientists. Researchers have studied everything from mice to fruit flies in the lab to get a better understanding of what happens when animals sleep — and why so many do it. This week, scientists finally added one piece to the elusive sleep puzzle: How wild chinstrap penguins sleep amid their noisy colony. Turns out, they do it over 10,000 times in seconds-long bursts throughout the day — totaling 11 hours when all is said and done.