It’s almost impossible to spend time with a herd of zebra and not notice the constant rippling of their skin. From a distance, the movement looks subtle, almost like a shimmer passing across their black and white coats. But sit closer for a while and you’ll see just how relentless it is. A flick of the ear, a shiver down the shoulder, a ripple across the flank – an unending dance against an equally persistent adversary: flies!
The Panniculus Reflex
Zebra skin is equipped with a specialised sheet of muscle, the panniculus carnosus, which lies just beneath the surface. This muscle contracts in response to the lightest touch – a largely automatic reflex. When a fly lands, the skin ripples to dislodge it before it can pierce through. Horses and cattle share this ability, but zebras seem to utilise it almost continuously, living as they do in regions across Africa where tsetse flies, mosquitoes, and horseflies are abundant. Add to that the whip of a tail and the stamping of hooves, and you begin to appreciate just how much of their daily rhythm is devoted to keeping insects at bay.
The striking black and white stripes of a zebra do more than just stand out. They disrupt the way biting flies see, making zebra a less inviting landing site compared to other large mammals. Still, the endless twitching reminds us that the battle is never entirely won.
Why Flies Target Zebra
Flies target zebras because they are after blood. The flies use a mix of cues to find a host: the warmth radiating from the body, the carbon dioxide released in every breath, and subtle odours from the skin and coat. Large, moving animals in open habitats are easy to detect, and in a herd, there are multiple targets close together, making zebras especially appealing. The stripes help reduce landings, but they don’t stop the insects from trying.
Zebra are certainly not the only target of pestering flies!
Stripes as a Defence
The black and white coat plays a surprisingly important role in this story. Research has shown that biting flies are drawn to large, dark, uniform surfaces. The alternating stripes appear to disrupt the polarised light that insects use to orient themselves. In effect, the stripes make it harder for flies to recognise a zebra as a landing site.
Studies comparing zebras to uniformly coloured horses in the same habitat found that horses are bitten far more frequently by biting flies than zebras are. Stripes don’t eliminate the problem altogether – hence the constant twitching – but they make zebras less appealing to an insect that relies heavily on vision.
Beneath the skin lies a thin sheet of muscle, the panniculus reflex, that ripples at the slightest touch – a built in reflex to shake off flies.
Stripes and Heat
There’s also a thermoregulatory angle. Dark stripes absorb more solar radiation than light ones, creating slight temperature gradients across the skin. This difference sets up small-scale convection currents, which may help lift heat away from the body. The effect is subtle and still debated in scientific circles, but it adds another possible layer of evolutionary advantage to the zebra’s coat. In an environment where shade is often scarce and temperatures soar, even minor cooling mechanisms are crucial.
Twitching and Stress Relief?
While twitching is primarily an involuntary response to insect irritation, there is some evidence that animals, including zebras, also use body shakes and shivers in moments of release after stress. Ethologists studying mammals often note a “shake-off” after a chase, fight, or other heightened event. In these cases, the movement serves a neurological reset, helping the body transition from a state of high alert back to calm. For zebras, the line between insect defence and stress release may blur, but the constant twitching itself is more mechanical than emotional.
Although these two painted dogs had clearly had their meal for the morning and the zebra is and unlikely target for the dogs, the twitching and ripple of their skin could be more than a defence for the flies – it can also mark the body’s shift from tension back to calm.
A Survival Strategy
So, the restless flickering of zebra coats is far more than a nervous habit. It’s a finely tuned combination of muscle reflexes, patterning, and physics – a way to endure the irritation of flies and the extremes of African heat, while perhaps even providing an outlet after stressful encounters.
Next time you sit with a herd and notice the shimmer moving across their flanks, it’s worth remembering that what you’re seeing is a quiet but essential survival strategy, honed over millennia.
The final moments of the day with a small dazzle of Zebra and a herd of Impala
Fascinating information, Kelsey. Did you Japanese scientists painted cows in zebra stripes to test whether this reduced the number of flies landing on them? And it did, by 50%!
I grew up with black and dark bay horses, and the constant twitching, swishing, shaking and stomping to rid themselves of flies (even after the assistance of fly spray) made me irritated for them, but I suppose they don’t know any different. There is a particular species of fern that we’d pick and prop on our horses heads during trail rides in the woods to help deter them. It seemed to work, but perhaps it was just wishful thinking? I’m surprised buffalo haven’t evolved striped coats to aid them in their fly deterring methods.
Hi Kelsey, the picture of the zebra “parliament ” is absolutely fantastic! Do you know why they were gathering like that? I would be very interested in your answer. Zebra are extremely beautiful animals, spectacular, I love the fact that, like leopards, they are untamable. I guess buffalo are the favourite prey of those pestering insects! I knew all the reasons why Zebra bore stripes, you described it in a perfect and charming way. I knew wild dogs are sometimes after Zebra foals, but the relentless defence of the herd, les by the stallion or a guiding matriarch female makes it hard to reach the goal. Luckily! Nature is nature, maybe we tend to be more emotionally struck by animals that remind us our domestic companions. None the less, they are incredible animals.
Great info, thank you Kelsey.
Hi Kelsey, it must be so irritating for the zebras being bitten all day long. Those flies and mosquitoes and horse flies bite quite sore. They are also always fighting with each other and you can see they are irritated.
Those twitches make them even more dazzling!
Really interesting, new information for me, Kelsey. Thanks!
I’ve always wondered why zebras twitch so much whilst feeding or just standing, and now I know thanks to your informative post. After reading this, it makes more sense that wearing black in hot climates,that are prone to many of the biting insects, is not recommended and that it’s better to stay with white or light colors.
Hi Kelsey, Thanks for this great information on zebras and their ability to fight flies and other insects. At the moment I am in a very fly-intensive area. The trick here is to wear some gauze net over your head otherwise one would get crazy. Luckily the zebras have this twitching ability and their tails.
I love your photos and also Reece‘s one, the zebras at sunset