Back in 2019, a peculiar equine trend took the horse world by storm. A new study claimed that zebra-striped fly rugs could confuse horseflies into aborting their landings. Naturally, the media latched onto the story with humorous headlines and striking images of horses dressed like escaped zoo animals. Riders and owners rushed to the tack shops, and suddenly, it seemed every field had its own equine zebra.

Fast forward to 2025, and while the initial buzz has calmed, zebra fly rugs are still very much on the shelf. So now seems a perfect time to revisit this study—not just for a dose of scientific curiosity, but because it reveals something deeper about how we interpret “science” in our horsey world.

What the Study Said

The original study was conducted on a UK farm housing both horses and captive zebras. Researchers set out to examine three things:

• Horsefly behaviour toward equines (zebras and horses),
• Equine behaviour toward horseflies,
• Horsefly behaviour toward horses wearing different rugs—black, white, and zebra-striped.

Their main conclusion? That stripes “confuse horseflies into aborting their landings.” A punchy headline, certainly. But let’s dig a little deeper.

A Closer Look (and Some Red Flags)

Firstly, it’s worth noting the observational data showed that while horseflies behaved similarly near both species, they approached zebras faster, made fewer landings, and spent less time on the skin.

However… It’s just as plausible that horseflies behaved this way not because they were confused, but because zebras were more effective at removing them. In fact, the study itself observed that zebras reacted much more strongly—briskly walking or running away, tail swishing—compared to horses, who mostly managed a twitch.

If an insect is highly motivated to feed, it won’t linger politely. It’ll fly faster, land quickly, and act more aggressively. These behaviors were only seen toward the zebras. That, to me, suggests greater motivation to bite—not confusion.

But Wait, There’s More (or Less, Actually)

The intervention part of the study—the one where horses were dressed in zebra, black, or white rugs—should have been the clincher. But it lacked one critical element: a control group. No group of unrugged horses was used to compare baseline fly interactions.

Why does this matter? Because without that control, we don’t know whether zebra rugs reduced fly activity, or whether black and white rugs increased it. The “Zebra looks better” result could simply be the illusion of contrast. As Dr Veronica Fowler wrote:

“This would give the illusion that the Zebra fly rug reduced horsefly interactions, when in fact, it just had no effect.” 

Further, the authors themselves noted that horseflies are most interested in parts of the horse that aren’t covered by rugs—like the face and legs. On those areas, no reduction in fly landings was seen. In fact, the data suggests zebra rugs might have made things worse.

So, Do Zebra Rugs Work?

Dr Fowler concluded that there was no robust evidence to suggest zebra stripes actively deter horseflies. A more plausible explanation is that the stripes are simply less attractive than solid colours.

And that distinction matters.

If zebra stripes truly deterred flies, they would consistently result in low interaction rates—regardless of other horses nearby. But if they are merely less attractive, horseflies may still choose to land on them when no better options (like a solid-coloured horse) are available.

In support of this, the study found that a dapple-grey horse—a coat pattern closer to mottled camouflage—was avoided more than both zebras and solid-colour horses. Perhaps the real answer isn’t zebra stripes, but something closer to nature’s own dappled grey.

Welfare Implications

Dr Fowler raised some compelling welfare questions as well:

• If zebra rugs are “less attractive” than standard rugs, are we increasing fly attraction by using common white or black rugs?
• Could zebra rugs actually divert flies to unrugged horses in the same field, reducing their welfare?
• If zebra rugs leave the face exposed, are we simply focusing all bites on the most sensitive and poorly-defended area?

In essence, the zebra rug might change where the flies land, but not how many flies there are.

A Final Thought

Dr Fowler also offered a caution against what she called the “post-purchase rationalisation” bias—that psychological quirk where, once we’ve bought something, we unconsciously convince ourselves it was a good idea. If you’ve bought a zebra rug, it’s tempting to overlook the flaws in the science.

The lesson here? Don’t believe every headline. Be critical, ask questions, and don’t let fashionable science drive your spending without evidence to back it up.

And perhaps keep an eye out for dapple-grey pyjamas—science might not be finished with that idea just yet.

What Has Research Told Us Since?

Since the 2019 study, researchers have developed a growing body of work exploring how and why zebra striping appears to deter horse‑flies. Many results are compelling — but it’s worth asking: how strong is the evidence, and are we ready to declare the case closed? Here’s what recent research suggests — and where open questions remain:

High-Contrast, Thin Stripes Are Key (2023)

University of Bristol studies tested domestic horses wearing rugs with different patterns. Rugs with sharp black-and-white stripes — especially thin ones — seemed to reduce horse-fly landings more than plain or low-contrast designs.

Caveat: Sample sizes were limited, and results may vary in real-world, outdoor farm conditions.

Close‑Range Landing Disruption Confirmed (2022)

In Kenya, flies approached zebra and impala pelts similarly, but avoided landing on zebra stripes at close range. This suggests stripes don’t stop flies from flying near — they disrupt landing behaviour within about 30 cm.

Caveat: Laboratory vs. field behaviour might differ, and not all pelts were tested under identical lighting or movement conditions.

Stripe Width Doesn’t Matter Within Natural Range (2022)

Studies found that variation in stripe width — from thin to wide — didn’t significantly change fly behaviour. This implies the presence of stripes, not their size, is what matters most.

Caveat: “No significant difference” can sometimes mean “not enough data to detect a small effect.”

Thermal False‑Vessel Hypothesis (2022)

Sunlit barrels painted with thin black lines attracted flies, who appeared to mistake them for warm blood vessels. Flies then failed to feed, suggesting thermal misdirection could play a role.

Caveat: This is a creative model — but horses are not barrels, and thermal gradients in real fur might differ.

Visual Aliasing Less Significant Than Contrast

Earlier theories proposed that zebra stripes confuse flies’ motion-detection systems via “aliasing.” More recent work, however, found that contrast and patch size — rather than optical illusions — were stronger predictors of deterrence.

Caveat: These findings haven’t ruled out optical effects entirely; multiple mechanisms might be in play.

So, Are We Sure Yet?

While the evidence is growing, most studies use lab conditions, limited sample sizes, or synthetic patterns. Rather then high quality evidence on actual equine populations. The trend is promising — but before we make broad recommendations, it may be time to take stock.

Time for a Follow-Up Review?

We’ve seen a surge in zebra-stripe studies since 2019 — but how consistent are the findings? How robust are the methods? And how well do these effects scale to varied horse breeds, environments, and fly species?

Maybe its time for a follow-up review? I’d certainly be interested in knowing if a zebra print fly rug is the answer to pesky horse flies!

Summary of Key Points

Finding	Supported by
High-contrast, thin stripes most effective at reducing landings	Studies 2, 3, 4
Stripe pattern disrupts landing (not attraction) at ~30 cm range	Original (1), follow-ups
Stripe width (within natural variation) irrelevant to efficacy	Studies 2, 3
Thermal/“false vessel” hypothesis confirmed in cattle	Study 4 (cows), background nods from Blahó et al.
Visual aliasing/aperture not primary mechanism; contrast matters more	Study 3

Full Reference List

1. Caro, T., Argueta, Y., Briolat, E.S., et al. (2019). Benefits of zebra stripes: Behaviour of tabanid flies around zebras and horses. PLoS ONE, 14(2): e0210831.
   – This original study recorded horse- and zebra-wearing coats and analyzed flight patterns, showing stripes prevent controlled landings newatlas.com+6sciencedaily.com+6journals.plos.org+6smithsonianmag.com+15journals.plos.org+15researchgate.net+15.
2. Caro, T. & How, M. (2023). Why don’t horseflies land on zebras? Journal of Experimental Biology.
   – University of Bristol experiments across various patterned rugs confirmed that high-contrast, thin stripes minimize fly landings; optical illusions were ruled out kpax.com+11bristol.ac.uk+11bristol.ac.uk+11.
3. How, M.J., Gonzales, D., Irwin, A., & Caro, T. (2020). Zebra stripes, tabanid biting flies and the aperture effect. Proc. R. Soc. B, 287:20201521.
   – Demonstrated that both striped and checked rugs deter flies equally, indicating visual “aliasing” effects are less significant than contrast and patch size theguardian.com+14researchgate.net+14nature.com+14royalsocietypublishing.org+1journals.plos.org+1.
4. Kojima, T., Oishi, K., Matsubara, Y., Uchiyama, Y., Fukushima, Y., Aoki, N., et al. (2019). Cows painted with zebra-like striping can avoid biting fly attack. PLoS ONE, 14(10): e0223447.
   – Cows painted with black-and-white stripes experienced significantly fewer fly landings and defensive behaviors than controls wral.com+5journals.plos.org+5nature.com+5.
5. Blahó, M., et al. (2013). Stripes disrupt odour attractiveness to biting horse flies: Battle between ammonia, CO₂, and colour pattern for dominance in the sensory systems of host-seeking tabanids. Physiol. Behav., 119:168–174.
   – Earlier work supporting the effect of broken patterns in reducing fly attraction sciencedaily.com+15nature.com+15researchgate.net+15.
6. Additional background sources include:
   • Connock, W.M. (2020). Behavioural measures of ectoparasitic burdens in plains zebra — Bangor Univ. nature.com.
   • Egri, Á. et al. (2012). Polarotactic tabanids avoid brightness/polarization modulated stripes, J. Exp. Biol. nature.com+1researchgate.net+1.
   • Waage, J.K. (1979) and Brady & Shereni (1988) — foundational lab studies using artificial targets documenting landing avoidance researchgate.net+1nature.com+1.