Zebras have stripes to keep them cool

Zebras' thick, black stripes may have evolved to help them stay cool in the midday African heat, a new study has found.

Researchers have long struggled to explain the purpose of the zebra's unique black-and-white coat.

It has been suggested that the stripes may help zebras camouflage themselves and escape from lions and other predators; avoid nasty bites from disease-carrying flies; or control body heat by generating small-scale breezes over the zebra's body when light and dark stripes heat up at different rates.

Researchers at the University of California, Los Angeles (UCLA) examined how 29 different environmental variables influence the stripe styles of plains zebras at 16 different sites from south to central Africa.

The scientists found that the definition of stripes along a zebra's back most closely correlated with temperature and precipitation in a zebra's environment, and did not correlate with the prevalence of lions or tsetse flies in the region.

These findings suggest that torso stripes may do more to help zebras regulate their body temperature than to avoid predators and tsetse flies, 'Live Science' reported.

Other animals also need to regulate body temperature, or thermoregulate, said study co-author Ren Larison, a researcher in the Department of Ecology and Evolutionary Biology at UCLA, but zebras may especially benefit from an extra cooling system because they digest food much less efficiently than other grazers in Africa.

As such, zebras need to spend longer periods of time out in the heat of the midday sun, eating more food.

The team found that the plains zebras with the most-defined torso stripes generally lived in the Northern, equatorial region of their range, whereas those with less-defined torso stripes were more common in the Southern, cooler regions of the range - a finding that supports the thermoregulation explanation.

The researchers plan to test the thermoregulation hypothesis, either by studying the behaviour of air currents over zebra pelts, or by implanting wild zebras with temperature sensors, if they are granted permission to do so, Larison said.

The study is published in the journal Royal Society Open Science