Elephants grow throughout most of their lives, and can usually be aged fairly accurately using their shoulder height or the size of their feet. However, once fully adult, elephants grow more slowly and are therefore harder to precisely age by size alone. Elephant teeth are a far more reliable indicator of age.
With their busy feeding schedule and diet of tough vegetable matter, elephants need durable teeth. In their lifetime, they work their way through six sets of molars. As one set wears out, another moves up from the back of the mouth to replace it until the final set wears out and the elephant dies of starvation, no longer able to chew up plants.
At any given time, both upper and lower jaws usually have one molar tooth in place on each side, and possibly part of another molar. Each set of teeth is a slightly different size, with the sixth and final set having the most ridges criss-crossing its surface. By looking at the tooth surface and its position in the elephant's jaw, an expert can age an elephant.
The last set of molar teeth usually begins to erupt by the age of 30, and these teeth may last for as many years as the preceding five sets of teeth, with elephants usually living to just over 60 years old in the wild, although a captive elephant lived to the age of 81.