October 11, 2012
Hair Plays Important Role In Keeping Elephants Cool
Alan McStravick for redOrbit.com - Your Universe Online
Our ancestors and other species were pretty hairy. They had to be. Body hair on mammals has long been thought of as an evolutionary requirement for survival in cold climes that prehistoric man and the woolly mammoth inhabited. Even today, with the hair on top of your head, you are insulating your body trying to maintain that magic number: 98.6.Or are you? A new study suggests it may do the opposite. Well, where pachyderms are concerned, at least. Conor Myhrvold of Princeton University and his colleagues believe epidermal hair may have evolved to help the animals keep cool in the hot regions they live in. They published their research yesterday in the open access journal PLOS ONE.
The study focused on African and Asian elephants and the density of their epidermal hair. Elephants, though generally considered hairless, have many interactions with hair in their life cycles. The fetus is covered in lanugo during gestation but sheds most of it before birth. Elephants have hairs on their tail that can grow to a length of 33 1/3 inches and smaller sensory hairs on their trunk. Hairs around the eyes and in the ears are protective, working to stave off an invasion of unwanted particles.
Until this study, the idea that low surface densities of hair could help dissipate heat only found fame in the field of engineering. While theories have existed, the biological and evolutionary significance of sparse skin hair really has not made itself known to the scientific community.
The authors wanted to study the effects of skin hair densities in elephants on the thermoregulation for the animals. Their research shows that while the denser body hair of furry animals does play a part in insulation, as skin hair grows more sparse there is a thermoregulation tipping point. A point where, for an animal such as the elephant, skin hair can actually play an active role in helping to release heat from the body rather than retain it.
Though the idea that low surface densities of hair can help dissipate heat is a popular concept in engineering, the biological and evolutionary significance of sparse skin hair is not well known. The authors studied the effects of skin hair densities in Asian and African elephants on thermoregulation in these animals, and concluded that elephant skin hair significantly enhances their capacity to keep cool under different scenarios, such as higher daytime temperatures or less windy days.
Taking into account their large size and the heated climate in which these elephants live, according to the authors of the study, they have the greatest need for such heat loss in order to maintain a constant body temperature. The results of this study are the first time there has been a suggestion that animal hairs could play such a role in heat dissipation that could prove beneficial to certain mammals, like elephants.
Corresponding author of the study, Elie Bou-Zeid commented, “Sparse hair increases heat dissipation from the skin of the elephants and help the largest terrestrial mammal meet its thermoregulation needs.”