Sperm whales are the biggest living things with teeth, and they seem to "talk" to each other. To decipher their messages, scientists are free-diving with them. Then, in , he went on a sailing trip to the island of Mauritius, where something happened that would change the course of his life. As his boat approached the coast, giant towers of steam began exploding out of the water. One by one the columns closed in, until they surrounded the whole boat.

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, feet in search of squid to eat. These giant mammals must hold their breath for up to 90 minutes on such dives.

The sperm whale or cachalot [a] Physeter macrocephalus is the largest of the toothed whales and the largest toothed predator. It is the only living member of the genus Physeter and one of three extant species in the sperm whale family , along with the pygmy sperm whale and dwarf sperm whale of the genus Kogia. The sperm whale is a pelagic mammal with a worldwide range, and will migrate seasonally for feeding and breeding.

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