[Reading Science] Are Zebra Stripes for Camouflage?

A herd of zebras. When you look at them, an optical illusion occurs. Are the white and black stripes really camouflage?
[Photo by YouTube screen capture]

[Asia Economy Reporter Kim Jonghwa] Zebras are called zebras because of their distinctive stripes. Like horses, they have excellent hearing and eyesight, can run at speeds of up to 56 km/h, and can injure predators with powerful hind kicks.

But why do zebras have stripes? Zebras live in herds led by a dominant male. When predators approach, the leader alerts the herd to danger, and the male at the rear defends the group with strong hind kicks to fend off the predators. Meanwhile, the females and young use this time to escape.

The zebra’s sturdy hooves can support its heavy weight and allow it to run easily over rocky terrain. At night, one member of the herd stands guard against predator attacks while the others rest, repeating this cycle.

Zebra stripes are generally considered camouflage. Usually, they have black stripes on a white background, but occasionally, a mutation produces white stripes on a black background. This is thought to be a form of camouflage using an optical illusion. However, recent theories have proposed other explanations.

When a herd of zebras gathers, humans may be confused by the optical illusion, but predators like lions hunt by scent and are not easily confused. In fact, the stripes may make zebras more visible and thus more likely targets.

On the other hand, if a lion attacks a zebra and that zebra blends back into the herd, the lion may be unable to distinguish which zebra it was and may hesitate to attack again, retreating instead. This suggests that the optical illusion and herd behavior provide an advantage.

Another role of the stripes is to repel flies. The flies in Africa, where zebras mainly live, transmit diseases such as equine influenza and sleeping sickness, so it is beneficial to drive them away immediately. Other horses constantly swish their tails to chase flies.

Zebras reportedly have far fewer flies landing on them than ordinary horses. Experiments covering horses with zebra-like stripes showed a significant reduction in the number of flies landing on their backs. The optical illusion caused by the stripes makes it difficult for flies to accurately identify landing spots, causing them to collide instead.

One other hypothesis is that the stripes help lower body temperature during the hot summer. While grazing under the intense African sun, the stripes may help regulate body temperature. It is suggested that the contrasting black and white stripes create air currents that cool the skin.

A lion getting kicked by a zebra's hind leg.
Photo by YouTube screenshot

Measurements of zebra skin temperature showed that the black stripes were about 12?15℃ warmer than the white stripes. The temperature difference between adjacent stripes could generate air currents. This hypothesis is supported by the fact that zebras living in hotter regions have more distinct stripe patterns.

However, some scientists argue that this hypothesis is incorrect because when water containers with and without stripes are placed outdoors, their temperatures are the same.

Whether this hypothesis is true or false remains unclear, but zebras, like humans and ordinary horses, regulate their body temperature by sweating. If the natural cooling effect of stripes is real, zebras could stay much cooler than ordinary horses simply by sweating.

Although zebras are more visible than other animals and thus targeted by large predators, the optical illusion helps them avoid smaller predators like African horseflies, and they can cool down faster than ordinary horses. This provides a significant survival advantage. It seems clear that zebra stripes are the result of long-term evolution.