Biologists have pondered the subject of why zebras have stripes for more than a century. Various universities like the University of California, University of St. Andrews, etc. have conducted research on this subject.
Numerous theories have been advanced on the function of their distinctive black and white stripes, including camouflage, social recognition, and body temperature control.
However, the most promising idea involves protection from biting flies.
Why Do Zebras Have Stripes?
Five plausible ideas have been proposed for why zebras are striped. However, none of these hypotheses have been conclusively demonstrated.
Repelling Biting Flies Like Tsetse Flies and Horseflies
Tim Caro authored an entire book about zebra stripes. The book had a lot of observations about the streaks.
According to the book, the stripes function as a natural barrier against tsetse flies.
Observations indicate that striping is most prevalent in regions where biting insects are prevalent.
The assumption is that these flies prefer to land on a single-colored hide, such as that of a wildebeest or buffalo.
The white and black lines of a zebra fool the flies and serve as camouflage. According to a new study conducted in 2019, when flies approach zebras, they either fly over the stripes or crash-land.
But data from all over the seven living species of equids’ range are the most convincing.
Some of these animals are completely striped (zebras), some are not (Asian asses), and others are partly striped (African wild ass).
Across species and subspecies, the severity of striping correlates closely with the discomfort caused by biting flies in Africa and Asia.
Thus, wild equids indigenous to regions where horseflies are a year-round nuisance are more likely to have distinct striping patterns.
However, zebras also inhabit regions where the flies are not present.
If stripes are sufficient, why don’t other animals like wildebeest have them? And why do zebras require distinctive lines?
Social Interplay and Attribution
Stripes are something that zebras do not share in common. Each and every zebra in the world has a unique pattern.
In short, zebra lines serve as a way of identification. A zebra can visually identify its friends in a herd by observing the others.
Others have suggested that these distinctive stripes may serve social functions. Nobody knows how this might possibly operate.
Thermoregulation
One of the earliest hypotheses suggested that a zebra’s distinctive stripes kept it cool.
White and black absorb light differently. Because black absorbs heat, air flows quicker when it encounters black stripes. When the air hits the white stripes, it slows down.
This generates air circulation. When these currents collide, they generate air vortices, much like a fan.
The stripes are therefore a method of thermoregulation. The further south in Africa plains zebras are found, the wider and more spaced apart their stripes become.
The argument is that the closer the stripes, the greater the need for cooling and the faster the natural fan operates.
It is true that equatorial zebras have the most closely spaced stripes. But what about Cape-dwelling mountain zebras with dense stripes?
This thermoregulation theory has been challenged by a number of researchers.
Instead of monitoring zebras in the wild, they draped zebra skins around oil barrels for four months and measured the temperatures.
Their result was that zebra stripes had no effect on barrel temperature, suggesting zebras do not require stripes for thermoregulation.
Disruptive Colors to Avoid Predators
The conventional belief is that stripes are a type of camouflage. Charles Darwin, who had extensive knowledge of animal evolution, was the first to propose it.
This notion is debunked by a 2016 study published in the journal PLOS ONE, which argues that “by the time predators get close enough to notice the stripes and be fooled by them, they would have already detected the zebra’s scent.”
The goal of distinctive stripes, however, is not a traditional disguise.
Darwin stated that stripes hinder predators from identifying individuals. They can see and smell the herds but have difficulty capturing one of them.
They generally congregate in tightly-knit herds. In contrast, wildebeest herds are dispersed over vast distances.
Black and white is not an effective camouflage for grass that is green. However, as the herd moves, a phenomenon known as motion blur occurs.
The black and white stripes combine into a single mass, making it challenging for predators to locate prey.
The patterns are perplexing and confusing. The stripes combine, overlap, and pulsate and create an optical illusion.
The confused predator has no idea in which direction a herd of zebras is running.
Most large predators prowl at night. So do predators detect unique stripes at night? The response may be unexpected.
A researcher claims that zebras become invisible at night. Dr. Anthony Sinclair states that while tracking wildebeest in the Serengeti, wildebeest would suddenly disappear.
He observed wildebeest as dark forms against the light grass. Zebras have the same light intensity as the background.
The reason for the disappearance of the wildebeest was zebras crossing their path.
Big cats have exceptional eyesight, so perhaps the stripes are a technique of compensating for this advantage.
How Do Zebras Get Their Stripes?
Their skin is black and tanned. Their fur is the only thing that is striped.
Zebras have white fur at birth. Special skin cells transfer the skin’s black pigmentation, resulting in lines.
This mechanism is comparable to that of other African mammals. Cheetahs from Africa have only spots on their fur, whereas tigers from outside of Africa have stripes.
Each species of giraffe has a distinct pattern on its coat, despite the fact that all giraffes have a similar pale tan.
This is observable in foals. Instead of striped coats, young zebras have soft brown patterns. The skin pigmentation does not entirely transfer until the zebra is 18 to 24 months old.