Research reveals why the zebra got its stripes

Research reveals why the zebra got its stripes
Professor Tim Caro observing zebra behavior in response to biting fly annoyance. Credit: School of Biological Sciences, University of Bristol

Why do zebras have stripes? A study published in PLOS ONE today takes us another step closer to answering this puzzling question and to understanding how stripes actually work.

The evolution of the 's two-tone coat has intrigued scientists for over 150 years. Many theories have been proposed, including avoiding predators, better heat regulation and a social function, yet there is still no agreement between scientists.

Now, researchers from the University of Bristol and UC Davis, California, have added evidence to the theory that the primary purpose of zebras' stripes is for avoiding blood-sucking parasites.

Professor Tim Caro, Dr. Martin How and colleagues have been investigating the behaviours of tabanid horse flies around captive zebras and at a livery in North Somerset, using video analysis techniques.

Their new study has shown that stripes don't deter horse flies from a distance, with both zebras and domestic horses experiencing the same rate of circling from the flies. However, video analyses revealed differences in approach speed, with horse flies failing to slow down on approach to zebras, which is essential for a successful landing.

Professor Tim Caro, Honorary Research Fellow from the University of Bristol's School of Biological Sciences, said: "Horse flies just seem to fly over zebra stripes or bump into them, but this didn't happen with horses. Consequently, far fewer successful landings were experienced by zebras compared to horses."

Research reveals why the zebra got its stripes
Joren Bruggink (left) and Jai Lake (right) investigating how horse flies behave around horses wearing different colored coats. Credit: School of Biological Sciences, University of Bristol

Dr. Martin How, Royal Society University Research Fellow in the School of Biological Sciences, added: "This reduced ability to land on the zebra's coat may be due to stripes disrupting the visual system of the horse flies during their final moments of approach.

"Stripes may dazzle flies in some way once they are close enough to see them with their low-resolution eyes."

Their second experiment was to observe horse fly behaviour around the same horses wearing different coloured cloth coats: black, white or zebra striped livery. This excluded any differences in behaviour or smell between horses and zebras. Just as before, when horses wore coats with striped patterns, they experienced fewer horse fly landings compared to when they wore single-colour coats.

Horse flies are a widespread problem for domestic animals so mitigating techniques, such as the development of anti-fly wear designed to resemble zebra stripes, may, from this research, be an interesting outcome for animal health and wellbeing.

The research also directly observed zebra and horse behaviour in response to biting flies. Zebras exhibited preventative behaviour, such as running away and tail swishing at a far higher rate than horses. Consequently, any horse flies that did successfully land on zebras spent less time there compared to those landing on horses, with few staying long enough to probe for a blood meal.

In Africa where zebras are native, horse flies carry dangerous debilitating diseases such as trypanosomiasis and African horse sickness which cause wasting and often death. Therefore, it is unsurprising that zebras utilise both behavioural defences and morphological striping to avoid horse flies.

This research provides new evidence for the theory that zebras evolved dichromatic striped coats to evade biting flies and has considerable implications for the horse industry.


Explore further

Scientists solve the riddle of zebras' stripes

More information: Caro T, Argueta Y, Briolat ES, Bruggink J, Kasprowsky M, Lake J, et al. (2019) Benefits of zebra stripes: Behaviour of tabanid flies around zebras and horses. PLoS ONE 14(2): e0210831. doi.org/10.1371/journal.pone.0210831
Journal information: PLoS ONE

Citation: Research reveals why the zebra got its stripes (2019, February 20) retrieved 21 May 2019 from https://phys.org/news/2019-02-reveals-zebra-stripes.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
504 shares

Feedback to editors

User comments

Feb 20, 2019
I am surprised horse flies haven't adapted by now to negate the stripe's disruption of their ability to attack zebra's. After all, it must have taken a long time for zebra's to develop distinct banding, and the flies have a significant incentive to be able to attack them.

Feb 20, 2019
Big difference between "why do zebras have stripes" and "how did zebras get stripes". The latter is latter is only valid if you believe in evolution. The former is really what scientists should be studying.

Feb 21, 2019
The evolution of the zebra's two-tone coat has intrigued scientists for over 150 years. Many theories have been proposed, including avoiding predators, better heat regulation and a social function, yet there is still no agreement between scientists.

Well, if you go be the evolutionary fairy tale then of course it would be difficult to discern how it got stripes. The simple answer is that God designed them that way!
This research provides new evidence for the theory that zebras evolved dichromatic striped coats to evade biting flies and has considerable implications for the horse industry

This is the biggest load of non-science ever! Just because it appears that stripes have a way of putting off the navigation of flies does not in ANY way lead to a true conclusion that the stripes are the result of figuring out that flies can be outwitted in that manner. How does an un-striped zebra invent stripes in it's body? How did it begin to code the genes for that?

Feb 21, 2019
Stripes may be genetically easier to develop than a brain that doesn't have trouble with them. And there are plenty of other things for them to bite. It's not like horseflies are able to think, "Damn! Missed that one!"

Feb 21, 2019
"This is the biggest load of non-science ever! ... How does an un-striped zebra invent stripes in it's body? How did it begin to code the genes for that?"

Are you asking seriously? (If so, someone might bother to answer seriously.)

Feb 21, 2019
The zebra doesn't "develop" them. Common misconception about evolution by natural selection; it doesn't proceed by the action of intelligence. Traits happen; most unusual traits die out. The ones that provide advantage live on.

The mutations that lead to the traits have been conserved for a billion years in so-called "junk DNA." So blathering about how unlikely some trait is shows the ignorance of the poster. Many apparently unlikely traits are stored in DNA that isn't normally active- but that can be.

Feb 21, 2019
The mutations that lead to the traits have been conserved for a billion years in so-called "junk DNA." So blathering about how unlikely some trait is shows the ignorance of the poster. Many apparently unlikely traits are stored in DNA that isn't normally active- but that can be.


In some cases, but note prokaryotes who do not have much unused DNA, this is not in general how evolution works. Evolution is change in the population genome over generations, based on additive mechanisms (such as mutation, recombination, gene flow) and subtractive mechanisms (such as drift, selection, inbreeding).

The process model is simply analogous to a bathtub, not troll claims of "intertoobz" magically carrying "information". In information terms information is naturally channeled from the environment through selection, *we have known that for a century*.

FWIW, stripe patterning can reappear [ say, https://phys.org/...ral.html].

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more