Largest toothed mammal

The largest toothed mammal alive today is the sperm whale Physeter macrocephalus, also known as the cachalot. Mature males can attain a total length of 20.5 m, although they average 16 m. Adult females are smaller. It occurs in temperate and tropical oceans and seas worldwide, but the distribution of males includes higher latitudes than that of females. Functional teeth only occur in the lower jaw (there are 18–26 on each side), and fit into slots in the upper jaw. Conversely, teeth in the upper jaw are only tiny and rudimentary; indeed, they often do not actually emerge into the mouth. Each lower jaw tooth weighs up to 1 kg.

Although the lower jaw's teeth are functional, they do not appear to be essential for the capturing and consuming of squid and other prey, because well-fed sperm whales have been found that lack these teeth. Consequently, some authorities have suggested that they may be used for aggression, at least between rival males, especially as specimens have been found that bear scars seemingly made by sperm whale teeth.