Zebra Stripes Has a Purpose; Monochrome Pattern Helps Protect Them From Horseflies [STUDY]

Zebra's monochrome patterned stripes are not just for aesthetics, they reportedly have a purpose. Their black and white coat repel horseflies.

How Does Zebra's Black And White Coat Work?

Researchers at the University of Bristol discovered that zebra fur has a purpose. Their fur is noticeably thinly striped and sharply outlined.

According to a new study, the monochrome pattern is effective in repelling and thwarting horsefly attacks. The team theorizes that the thin back stripes minimize the size of local features on zebra that attracts the biting flies.

Professor Tim Caro and Dr. Martin How from the University of Bristol's School of Biological Sciences led the study. According to Caro, several studies have already demonstrated that horseflies avoid landing on striped surfaces. However, it remains unclear exactly what stripes they find repulsive.

They weren't sure if the stripes' thinness, the contrast between black and white, or the polarized signal that they emit were behind the horseflies' reaction. Hence, they set out to investigate it by filming incoming horseflies while utilizing variously patterned cloths draped over horses.

The researchers discovered that tabanid horseflies are more drawn to massive, dark items in their surroundings than to dark, irregular patterns. The majority of landings were related with all-grey coats, then those with huge black triangles arranged irregularly, then, in no particular sequence, little checkerboard patterns. In a different experiment, they discovered that while more homogenous stripes were more appealing, contrasting stripes attracted relatively few flies.

This means that any hoofed mammal that lessens its overall black outline against the sky will benefit in terms of decreased ectoparasite attack, according to Professor Caro.

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No evidence was discovered for other problems the team studied, such as polarization or visual tricks that confuse precise landings, such as the so-called "wagon-wheel effect" or "barber-pole effect."

The research team is now trying to understand why only members of the horse family, or equids, exhibit stripes naturally whereas other hoofed animals do not.

Professor Caro noted that zebra pelage - fur - is short, allowing horsefly mouthparts to reach the skin and blood capillaries below, which may make them particularly susceptible to fly irritation. Also, horseflies carry fatal diseases to the horse family but less so to ungulates. Thus, Caro believes that more investigation is necessary.

The study titled "Why don't horseflies land on zebras" by Tim Caro, Martin How and their colleagues is published in the Journal of Experimental Biology.

Range of Theories Behind Zebra Stripes

There are several possible explanations behind the zebra stripes, according to Daily Mail. The outlet shared some of the theories divided into seven categories, which are as follows.

Apparent size increase
Visibility in poor light
Moving stripes may dazzle predators
Camouflage
Social benefits
Fitness indication
Protection from tsetse flies.

There are also speculations that the stripes offer social benefits like it helps zebras recognize each other due to their stripes, or it could help zebra moms communicate with their foals. There are also theories that the stripes are for anti-predation like helping them camouflage or offer visual confusion to prey.