Zebra stripes work as an elaborate cooling system 

The difference in temperature between black and white zebra stripes creates a convection current
The difference in temperature between black and white zebra stripes creates a convection current  Credit: Moment RF 

The mystery of how and why the zebra acquired its stripes has puzzled scientists for centuries.

But now zoologists believe the alternating black and white markings act as an elaborate cooling system, creating a convection current of air which behaves like a natural fan, helping to evaporate sweat.

Former biology technician, Alison Cobb and her zoologist husband, Dr Stephen Cobb of the University of Nairobi, measured the temperature of black and white stripes of two wild-born plains zebra at 15 minute intervals on a sunny day in Kenya.

They found that through the day the absorbent black stripes rose to temperatures between 111F (44C) and 132F (56C) but the more reflective white ones stayed between 96F (36C) and 107F (42C).

The Cobbs believe the differing strip temperatures cause a small-scale convective air movement which disturbs the air and helps beads of sweat helps to evaporate more speedily.

Zebras also carry a special protein called laterhin in their hair which makes their sweat frothy, lowering the surface tension and allowing for quicker evaporation.

During the field research, the pair also discovered that zebras can raise the hair on their black stripes while the white ones remain flat, probably to further help evaporation.

These three components– convective air movements, frothy sweat and hair-raising – work together as a mechanism to enable zebras to wick the sweat away from their skin to help them cool down, they conclude.

Mrs Cobb, lead author of the new paper said : "Ever since I read Kipling's Just So Stories at bedtime when I was about four, I have wondered what zebra stripes are for.

“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.

"It was not until years later that we got the opportunity to collect some field data from zebras in Africa, when we also noticed their ability to raise the hairs of their black stripes, while the white ones lay flat.

“It was only much more recently, when the role of latherin was discovered in helping horses sweat to keep cool, that it all began to fall into place. The solution to the zebra's heat-balance challenge is cleverer, more complex and beautiful than we'd imagined.”

Zebras are able to raise their black stripes to make evaporation even quicker  Credit: Alison Cobb

Previous studies have suggested the stripes serve as camouflage, yet zebra spend large parts of their time in the open.

Earlier this year Bristol University found the alternating monochrome wave forms disorientate bloodsucking horse flies.

The British team found that although flies circled and touched horses and zebras at similar rates, they landed on zebras 25 per cent less often

The Cobbs also speculate that the unstable air associated with the stripes may play a secondary role in deterring biting flies from landing on them.

“Of course, there is much more work to be done to gather evidence and fully understand how the stripes help zebras control temperature, but I am 85 now, so that's for others to do,” added Mrs Cobb.

The research was published in the Journal of Natural History.