Why Do Elephants Have Hair?
October 19, 2012
Scientists at Princeton University reported in mid-October that they had finally determined why elephants have hair: to help them cool down. The result was surprising, because for most mammals, hair helps the body to stay warm.
Many people may be surprised to hear that elephants have hair at all. Actually, elephants have hair all across the head and back. Both African and Asian varieties have hair, though Asian elephants have more of it. Young elephants have noticeably more hair than older elephants do. Granted, elephant hair is rather sparse. The scientists analyzed the density of elephant hair and found that elephants have about 1 hair per square inch (0.16 hair per square centimeter) of skin. The head of a human being has about 1,290 hairs per square inch (200 hairs per square centimeter).
Elephants, like all mammals, have hair at some time in their lives. However, the hair of elephants is very sparse. (World Book illustrations by Jean Helmer)
Because they live in some of the warmest places in the world–countries in Africa and Asia–it is very important for elephants to be able to cool off. Their own body structure, however, makes it very difficult for them to do so. An elephant’s body has a large volume (the space it occupies) compared to the surface area of its skin. So it is difficult for an elephant’s body to shed heat. Elephants typically perform certain behaviors to cool off. They flap their ears, cover themselves in dust and mud to repel sunlight, and use their trunks to spray water on themselves. However, all of these behaviors are still not enough for an elephant to shed the amount of body heat it produces. Apparently, the elephant’s wiry hair also plays a part.
Elephants cool off in several ways, including bathing in water or using their trunks to spray water on themselves. (copyright C. Haagner, Bruce Coleman, Inc.)
The Princeton scientists used data they already had about how animals shed heat. By varying such details as amount of skin surface, width and density of the hair, wind speed, and texture of the skin, they concluded that elephant hairs can enhance the animal’s heat loss from between 5 and 20 percent. They also found the density at which hair on an animal begins to have a cooling effect–about 195 hairs per square inch (30 hairs per square centimeter).
The Princeton research may help to explain why animals developed hair when they did, about 100 million to 300 million years ago. At that time, Earth was much warmer than it is today, and animals needed to be able to cool off. The scientists speculated that animal hair may have evolved into a way to keep bodies warm as the climate cooled.
Even as scientists are learning more about elephants, conservationists are concerned about the ability of the animals to survive. WWF (World Wildlife Fund) officials reported in March 2012 that in Africa, elephants are being hunted virtually to extinction as poachers kill the animals for their ivory tusks.
Additional World Book articles:
- Climate
- Conservation
