The Dive Reflex

A deep-diving whale does not just hold its breath. Its whole body switches into power-saving mode. The heart rate drops sharply, and blood is pulled away from the skin and limbs to protect the brain and heart.

Whales also pack oxygen where land animals cannot. Their blood and muscle are extra rich in oxygen-carrying proteins, and the spleen releases a stored reserve of red blood cells right when a dive begins. Together these tricks stretch a single breath into a journey lasting more than an hour.