and molars Both male and female African elephants have tusks that grow from deciduous teeth called tushes, which are replaced by tusks when calves are about one year old. Tusks are composed of dentin, which forms small diamond-shaped structures in the tusk's center that become larger at its periphery. Tusks are primarily used to dig for roots and strip the bark from trees for food, for fighting each other during mating season, and for defending themselves against predators. The tusks weigh from and can be from long. They are curved forward and continue to grow throughout the elephant's lifetime. The dental formula of elephants is . Elephants have four molars; each weighs about and measures about long. As the front pair wears down and drops out in pieces, the back pair moves forward, and two new molars emerge in the back of the mouth. Elephants replace their teeth four to six times in their lifetimes. At around 40 to 60 years of age, the elephant loses the last of its molars and will likely die of starvation which is a common cause of death. African elephants have 24 teeth in total, six on each quadrant of the jaw. The enamel plates of the molars are fewer in number than in Asian elephants. Size The African bush elephant is the largest terrestrial animal. Cows are tall at the shoulder and weigh , while bulls are tall and weigh . Its back is concave-shaped, while the back of the African forest elephant is nearly straight. The largest recorded individual stood at the shoulder, and is estimated to have weighed . The tallest recorded individual stood at the shoulder and weighed . The African forest elephant is smaller with a weight of up and a shoulder height of in females and in males. It is the third largest terrestrial animal. Distribution and habitat African elephants are distributed in Sub-Saharan Africa, where they inhabit Sahelian scrubland and arid regions, tropical rainforests, mopane and miombo woodlands. African forest elephant populations occur only in Central Africa. Behavior and ecology Sleeping pattern Elephants are the animals with the lowest sleep times, especially African elephants. Their average sleep was found to be only 2 hours in 24-hour cycles. Family Both African elephant species live in family units comprising several adult cows, their daughters and their subadult sons. Each family unit is led by an older cow known as