Sperm whales sleep in vertical pods, drifting tail-down near the surface in groups of five or six, completely motionless for about 15 minutes at a time, in one of the shortest sleep cycles of any mammal on Earth
Sperm whales rest in vertical clusters near the ocean surface, silent and motionless for roughly fifteen minutes at a time — the shortest sleep cycle of any mammal yet measured, and a posture marine biologists only confirmed in 2008.