Dreaming in Blue

Sperm whales sleep vertically in pods, a behavior first documented in 2008 and captured in high-quality photographs in 2017. They take huge breaths and enter deep sleep for short periods, typically around 10 to 15 minutes, but they can sleep for longer — up to two hours at a time — when undisturbed. Unlike some other cetaceans, sperm whales may shut down both hemispheres of their brains simultaneously, making them less responsive to external stimuli during sleep. Thus the pod for protection.