Why Do Zebras Have Stripes? What the Latest Research Shows

The question that puzzled Darwin and Wallace

The stripes of zebras have been debated since the 19th century. Alfred Russel Wallace thought they might make zebras harder to see at dusk, while Charles Darwin doubted that camouflage explained them. For more than a century the question stayed open, mostly because it is hard to run experiments on wild zebras.

Modern research has tested each theory against real data: how zebra stripes vary across Africa, what predators can actually see, and how insects behave around striped surfaces. Much of this work was led by the biologist Tim Caro and colleagues, who summed it up in the book Zebra Stripes (2016).

The fly theory: the strongest evidence

Africa is home to many blood-sucking flies, including horseflies and tsetse flies. They carry diseases that can be deadly to members of the horse family, such as trypanosomiasis (sleeping sickness) and African horse sickness. Zebra hair is short and thin, so a fly’s mouthparts can easily reach the skin.

Several lines of evidence point to flies:

• Range maps. A 2014 comparison of all wild horses, asses and zebras found that the strongest striping occurs where biting flies are most active for most of the year. Factors such as predators or tree cover did not match the pattern nearly as well.
• Landing tests. In 2019, researchers filmed horseflies around zebras and horses on a farm in England. Flies approached both equally, but they failed to land on zebras far more often. Flying near a zebra, they did not slow down properly and simply overshot or bounced off.
• Horses in zebra coats. When ordinary horses wore black-and-white striped coats, flies landed much less on the coated parts of the body, while landings on the uncovered head stayed the same. The pattern itself, not the zebra, made the difference.
• Painted cattle. In Japan, black cattle painted with white stripes received roughly half as many fly landings as unpainted animals.

Why flies struggle is still being studied. An early idea that stripes confuse the polarized light flies use to find targets has been challenged. Recent work suggests that the high-contrast, narrow stripes break up the outline that a fly needs to judge distance and slow down for landing. Another proposal is that warm black and cooler white stripes create small temperature differences that mask the blood vessels flies seek.

Do stripes confuse lions and hyenas?

A long-standing idea is “motion dazzle”: a running herd of striped bodies might make it hard for a lion to pick out one target or judge its speed. Computer models show that moving stripes can create optical illusions, such as the wagon-wheel effect.

In the field, though, there is little support. Lions usually ambush zebras from close range, where stripes do not stop them, and zebras are one of their favorite prey. Researchers have found no link between how strongly zebras are striped and how many large predators live in an area. Fleeing zebras also scatter rather than bunching tightly, which works against the confusion idea.

Are zebra stripes camouflage?

The oldest theory says stripes help zebras blend into tall grass or the dappled shade of woodland. The problem is that zebras live mostly on open plains, are noisy and social, and do not freeze or hide when danger is near.

A 2016 study modeled what lions and spotted hyenas can see. In daylight, they probably cannot resolve individual stripes beyond about 50 m (160 ft), and at night the distance is even shorter. At those ranges a zebra looks uniform gray, and it is no harder to see than a plain-colored antelope. By the time a predator is close enough to see stripes, it can usually hear and smell its prey anyway.

Do stripes help zebras stay cool?

Black surfaces absorb more heat than white ones, so a striped coat has hot and cool bands side by side. Some researchers proposed that this sets up tiny air currents that cool the skin, and a 2019 field study reported such effects. Zebra striping is also stronger in hotter parts of Africa.

Other experiments disagree. A 2018 study wrapped water-filled barrels in zebra, horse and cattle hides and found no cooling benefit from stripes. Zebras also do not appear to run cooler than other grazers sharing the same plains. Cooling may play a small part, but it does not explain the pattern well on its own.

Do zebras use stripes to recognize each other?

Every zebra’s pattern is unique, and foals do learn their mother’s stripes, smell and voice in the first days of life. That led to the idea that stripes act as name tags or social signals.

However, horses and donkeys recognize each other perfectly well without stripes, and studies have found no link between the amount of striping and group size or social behavior across horse-family species. Stripes may help with recognition, but they probably did not evolve for that purpose.

Is the mystery fully solved?

Not quite. The fly-deterrence theory has the most experimental support, but scientists still debate why other African grazers that face the same flies, such as antelopes and buffalo, never evolved stripes. It is possible that several benefits combine, with flies being the most important.

The stripes themselves are made by pigment cells in the skin, which switch on or off along each band. Are zebras black or white? explains how the pattern forms. For more on the most common zebra species, see the plains zebra profile.