Black on white, or white on black?
By Lesley Thomson
It’s a favourite question whenever one sits watching zebra grazing … but do we know the answer?
Recent research shows that not only do zebra stripes help with their temperature control, but they help protect them from predators and disease-carrying biting flies.
An individual Burchell’s (plains) zebra will have about 26 stripes on each side, with few or much lighter stripes on the legs. A Mountain zebra will have in the region of 43 stripes per side with the stripes going all the way down to the hoof.
It is the Burchell’s zebra you are most likely to see, as the Mountain zebra live in the stony and hilly areas of Namibia and southern Angola, while in South Africa they occur in the western and Eastern Cape.
Each stripe is unique, like a human’s fingerprint. Stallions have a very narrow vertical stripe between the buttocks, about 2-3cm wide, while the female stripe is thicker, about 5-8cm wide. Some stripes have a “shadow”.
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However, zebras have black skin under their white stripes! The embryo of a zebra is black, but a newly born zebra is brown, not black, and white. The white is thought to be a strip around the main black background, while the skin under the white remains black.
A theory is that the stripes make a zebra unattractive to small predators and the motion of a group of zebras standing or moving close together confuses the larger predators such as lions. To a lion, the moving zebras appear as a flickering mass, rather than one target.
Ongoing research is investigating whether the stripes deter biting and bloodsucking disease carrying flies, and the consensus appears to be that they do. It is thought that once flies come close to zebra, the stripes dazzle them so much that they cannot manage a controlled landing. They either fly in too fast, or bounce off.
Researchers are coming to the conclusion that the contrasting black and white stripes may confuse the fly’s low-resolution vision, which relies on sensing movement.
The most common theory of the purpose of a zebra’s stripes is that of temperature control – thermoregulation.
Black stripes become warmer than white, creating small vortexes where hot and cold air meet, thus acting as a cooling fan. Zebra, like horses, sweat to cool down.
Barking, snorting or whinnying
Communication among zebra is by barking, snorting or whinnying. If a zebra’s ears are standing upright it means it is feeling calm. However, that does not mean you can approach it! Zebra can be very temperamental and are very strong. They have been known to kill fully-grown lion, kick each other to death and will viciously bite or kick any human they see as a threat.
– Lesley Thomson: firstname.lastname@example.org
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Main picture, top: Jeff Griffith/Unsplash