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Alison has a new slant on zebras' stripes

August 2nd, 2019 7:05 AM

By Brian Moore

Alison's data revealed a temperature difference between the black and white stripes on the zebra that increase as the day heats up. (Photo: Shutterstock)

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HAVE you ever wondered why zebras have stripes?

Alison Cobb, an 85-year-old resident of the Sheep’s Head peninsula, has and she’s written an academic paper, which has for the first time proposed that the stripes are designed to keep the Zebra cool under the hot African sun.

Alison, who lives for much of the year in the only house on the Sheep’s Head without electricity, and her husband Dr Stephen Cobb, spent many years in sub-Saharan Africa, where Stephen directed environmental research and development projects.

Alison’s study is the first-time that zebras have been assessed in their natural habitat to investigate the role of stripes in temperature control.

‘Ever since I read How the Leopard Got His Spots in Kipling’s Just So Stories when I was about four, I have wondered what zebra stripes are for,’ she said.

‘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,’ Alison told The Southern Star.

In December 2003, as a 70th birthday present from her husband, Alison went with him to Kenya to measure the temperatures of zebras at the equator. ‘It was while we were collecting some field data from zebras in Africa, that we noticed their ability to raise the hairs of their black stripes, while the white ones lay flat,’ she recalled.

‘It was only much more recently, when the role of latherin (a protein in horse sweat) was discovered in helping horses sweat to keep cool, that it all began to fall into place,’ Alison said.

Alison’s data revealed a temperature difference between the black and white stripes that increases as the day heats up, with the black stripes becoming 12-15 degrees celsius hotter than the white.

Also Alison and Stephen speculate that the unstable air associated with the stripes may play a secondary role in deterring biting flies from landing on them.

This insect behaviour has been observed in recently published studies about zebra stripes and could confer an additional advantage for zebras.

‘The solution to the zebra’s heat-balance challenge is cleverer, more complex and beautiful than we’d imagined.

‘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.’

• The journal article is available online at www.tandfonline.com.

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