![]() In the many years we spent living in Africa, we were always struck by how much time zebras spent grazing in the blazing heat of the day and felt the stripes might be helping them to control their temperature in some way." Zebras are also smallest near the equator, providing a large surface area to volume ratio which assists the animals' ability to dissipate heat through evaporation.Īlison Cobb, lead author of the new paper says: "Ever since I read 'How the Leopard Got His Spots' in Kipling's Just So Stories at bedtime when I was about four, I have wondered what zebra stripes are for. It has been demonstrated that the zebra stripes become remarkably more pronounced on animals living in the hottest climates, near the equator. There is evidence from other recent studies that backs up the idea that heat control may be key to why zebras have their striking coats. This insect behaviour has been observed in recently published studies about zebra stripes and could confer an additional advantage for zebras. The authors also speculate that the unstable air associated with the stripes may play a secondary role in deterring biting flies from landing on them. These three components- convective air movements, latherin-aided sweating and hair-raising-work together as a mechanism to enable zebras to wick the sweat away from their skin so it can evaporate more efficiently, to help them cool down. ![]() The authors propose that the raising of black hairs during the heat of the day, when the stripes are at different temperatures, assists with the transfer of heat from the skin to the hair surface and conversely, when the stripes are at the same temperature in the early morning, and there is no air movement, the raised black hairs will help trap air to reduce heat loss at that time. The researchers propose that the differential temperatures and air activity on the black and white stripes set up small-scale convective air movements within and just above the stripes, which destabilise the air and the water vapour at the tips of the hairs.ĭuring the field research, the authors also observed-probably for the first time-that zebras have an unexpected ability to raise the hair on their black stripes (like velvet) while the white ones remain flat. ![]() This makes the sweat frothy, increasing its surface area and lowering its surface tension so it evaporates and prevents the animal overheating. Recent research reveals that the passage of sweat in horses from the skin to the tips of the hairs is facilitated by a protein called latherin which is also present in zebras. Like all species in the horse family, zebras sweat to keep cool. It is therefore the way the zebra stripes are harnessed as one part of their cooling system, rather than just their contrasting coat colour, that is key to understanding why these animals have their unique patterning. This indicates there is an underlying mechanism to suppress heating in living zebras. Whilst this difference stabilises on living zebras during the middle seven hours of the day, with the black stripes 12-15oC hotter than the white, the stripes on a lifeless zebra hide continue to heat up, by as much as another 16oC. The data revealed a temperature difference between the black and white stripes that increases as the day heats up. The researchers collected field data from two live zebras, a stallion and a mare, together with a zebra hide draped over a clothes-horse as a control, in Kenya. ![]() This study is the first-time zebras have been assessed in their natural habitat to investigate the role of stripes in temperature control. ![]() Together, they have spent many years in sub-Saharan Africa, where he has directed environmental research and development projects. The findings have been published this month in the Journal of Natural History, the scientific publication of the British Natural History Museum, by amateur naturalist and former biology technician, Alison Cobb and her zoologist husband, Dr. These three elements are key to understanding how the zebras' unique patterning helps them manage their temperature in the heat. The authors argue it is the special way zebras sweat to cool down and the small-scale convection currents created between the stripes which aid evaporation, while the previously unrecorded ability of zebras to erect their black stripes is a further aid to heat loss. ![]()
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