Fur seals have two sleep modes: one for when they're hauled out, and one for when they're in the water. Scientists writing in the Journal of Neuroscience say they hope studying the physiological differences between the two states will give them insight into human sleep, reports CBC News.

Researchers from the University of Toronto and the University of California say that fur seals sleep with half their brain at a time. "The left side of their brain can sleep while the right side stays awake," said Professor John Peever, in a news release from the University of Toronto.

"Seals sleep this way while they’re in water, but they sleep like humans while on land. Our research may explain how this unique biological phenomenon happens."

The researchers are studying the chemicals active in seals' brains to help solve the mystery of how and why humans sleep.

Read more at CBC News: Seals offer glimpse into human sleep