Sperm whales are easily recognized by their massive heads and prominent rounded foreheads.
They have the largest brain of any creature known to have lived on Earth. Their heads also hold large quantities of a substance called spermaceti. Whalers once believed that the oily fluid was sperm, but scientists still do not understand the function of spermaceti. One common theory is that the fluid—which hardens to wax when cold—helps the whale alter its buoyancy so it can dive deep and rise again. Sperm whales are known to dive as deep as 3,280 feet in search of squid to eat. These giant mammals must hold their breath for up to 90 minutes on such dives.
These toothed whales eat thousands of pounds of