Zebra stripes could be used to control their temperature, study reveals – ScienceDaily

The authors argue that it is the special way that zebras sweat to cool and small-scale convection currents created between bands that facilitate evaporation, while the then unrecorded ability of Zebras to erect their black stripes also contributes to heat loss. These three elements are essential to understand how the unique structure of zebras helps them manage their temperature in hot weather.

The results were published this month in the Journal of Natural History, the scientific publication of the British Natural History Museum, by Alison Cobb, amateur naturalist and former biology technician, and her husband zoologist, Dr. Stephen Cobb. Together, they spent many years in sub-Saharan Africa, where he led environmental research and development projects.

This study is the first time that zebras are evaluated in their natural habitat to study the role of rays in controlling temperature. The researchers collected field data from two live zebras, a stallion and a mare, as well as a zebra skin draped over a clothesline as a witness, in Kenya.

The data revealed a temperature difference between the black and white bands that increases as the day warms up. While this difference stabilizes on living zebras in the middle of the seven hours of the day, with black bands 12 to 15 ° C warmer than white, strips of lifeless zebra skin continue to heat up. up to 16 ° C. This indicates that there is an underlying mechanism for suppressing heating in living zebras. So it's the way zebra stripes are exploited as part of their cooling system, rather than just the color of their coat, which is fundamental to understanding why these animals have their unique pattern.

Like all species of the horse family, zebras sweat to stay cool. Recent research shows that the passage of sweat in horses from the skin to the tips of the hair is facilitated by a protein called laterine, also present in zebras. This makes the sweat foamy, increasing its surface and lowering its surface tension so that it evaporates and prevents overheating of the animal.

The researchers propose that differences in temperature and air activity on the black and white bands create small scale convective air movements in and just above it. bands, which destabilizes the air and water vapor at the tips of the hairs.

During the field research, the authors also observed – probably for the first time – that zebras had an unexpected ability to bristle their black streaks (such as velvet), while whites remained flat. The authors propose that the lifting of black hairs during the heat of the day, when the stripes are at different temperatures, assists the transfer of heat from the skin to the surface of the hair and vice versa, when the stripes are at the same temperature in the skin. body. early in the morning and in the absence of air movement, the raised black hairs will help to trap the air to reduce heat loss at that time.

These three components – convective air movements, perspiration and latherin-helping hair – work together to allow zebras to wick away perspiration from the skin to evaporate more effectively and help it cool down. .

The authors also assume that the unstable air associated with scratching may play a secondary role in deterring biting flies from landing there. This behavior of insects has been observed in recently published zebra studies and could confer additional benefit on zebras.

Other recent studies show that heat control may be the reason why zebras wear a striking coat. It has been shown that zebra stripes are remarkably more pronounced in animals living in the warmer climates near the equator. Zebras are also the smallest near the equator, providing a significant surface / volume ratio that helps animals dissipate heat by evaporation.

Alison Cobb, lead author of the new paper, said: "Since I've read" How the leopard does it's stains "in Kipling's Just So Stories at bedtime, towards the l & # 39; When I was four years old, I wondered what zebra stripes are all about, we've spent our lives in Africa, and we've always been amazed by the time zebras graze in the overwhelming heat of the day. felt that scratches could help them control their temperature one way or another. "

"My first attempts, forty years ago, to test this hypothesis were to compare water temperatures in oil drums with different colored markers, but it seemed to me that this was not the case. was not enough experience and I wanted to see how the stripes behaved, live the zebras. "

"Steve, the man who later became my husband and co-author, teaching conservation biology at the University of Nairobi, had a student who was working with zebras, who said that he was the only one to be a student. he could calm them in their crush by brushing them with a long-handled broom In 1991, it even gave me the courage to ask permission to go to the orphanage of the animals of the Nairobi National Park to see if I could tame one of the wild zebras of the paddock by brushing it with a dandy brush.I found this tickle very nice and, over the days, it got me Gradually allowed to brush it (see photo) .Two years later, I returned to Nairobi and entered the paddock with the brush.The same zebra mare raised her head, stared at me and looked at me. is approached from me so that we brush me again. "

"It is only years later that we had the opportunity to collect field data from zebras in Africa, when we also noticed their ability to haul their black bands, while The white ones were flat.It's only so much more recently, when the role of latherine was discovered to help the horses to sweat to stay cool, that everything started to come into place. "

"The solution to the thermal equilibrium problem of the zebra is smarter, more complex and more beautiful than we had imagined, and of course there is still a lot of work to do to gather evidence and understand how stripes help the zebras control the temperature, but I'm 85 now, so it's up to others to do it. "