Evolution of Stripes in Zebras: Complex Mix of Purposes


Why do zebras evolve to sport such black and white, striped coat, has made experts curious. There are many theories that explain the reason behind zebra stripes. One of the theory suggests that these stripes help zebras to camouflage in tall grasses, exceptionally well during dawn or the dusk time. While another one says, the strips assist zebra to escape from the bites of troublesome flies or social cohesion. While the last one advocates that, these stripes create an optical illusion, which dazzles the hunter that eventually misses its target. 

However, according to a latest study, researchers from the University of California proposes that zebra adaptation of such unique monochrome pattern tends to regulate body temperature thus keeping zebra cool in hot environments of Africa. The research team carried out a very extensive study to understand the reason behind sporting such stripes. It involved a thorough analysis of 29 various environmental variables such as vegetation, weather, and presence of predators & flies that may affect the stripe styles of zebras at 16 distinct locations ranging from south to central Africa.

Regulating body temperature

The findings revealed that zebra’s stripes have a clear relation with the temperature and precipitation in the surrounding. Team noted that zebras found in the hottest region like Kenya or Uganda sport wider, well defined, saturated stripes on the torso and the hind legs. On the contrary, zebra from relatively colder regions such as South Africa had minimal stripes.

A possible justification for association stripes with temperature could be that heat absorbing black stripes and heat reflective white stripes regulate body temperature of the zebra by creating a micro fan.

Lead researcher Brenda Larison explains that black or dark surface tend to get heated more than a lighter or white surface and this lead air currents to arise from black stripes at a higher rate, intensity and volume than the white stripes. And these two distinct air flows that flow much faster that the other might result in the development of convective currents at the point between white and black stripes that perhaps be cooling.

Creating optical illusion

The study could not find any evidence to support the theory that zebra striping may have emerged to dazzle predators or avoid flies. Had this been the case, there would have been more lions in the region saturated with fewer stripe zebras. On the contrary, lions are seen hunting the zebras or would there be a possibility that the lions are unaffected by the stripes dazzling effect; not too sure!

Whatever be the case, the stripes does come along with many benefits that enhance the animal. They have to graze continuously even in extreme temperature of the savannah and so they require a very effective thermoregulation mechanism. Nevertheless, taking this, as the only consideration does not look convincing enough. Evolution of zebra stripes is quite a complex problem, which require more in depth research as of now.

Source: Live Science

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