Black and white stripes of a zebra ‘dazzles’ blood-sucking flies

Why zebras have stripes: Black and white pattern ‘dazzles’ blood-sucking flies and makes it harder for them to land on the animal’s skin

  • Flies land on zebras only 25 per cent as much as they do on horses 
  • Scientists dressed up horses in zebra-striped coats on a Somerset farm  
  • Review of video footage found flies were hesitant to land on the stripes 
  • Experts now believe the stripes actively ‘dazzle’ the flies and prevent landing  
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The mystery of why zebras have black and white stripes may have been solved as scientists find the pattern ‘dazzles’ blood-sucking flies. 

Flies approach the animal with the intention of landing and eating the zebra’s blood. 

An unusual experiment dressed horses up in stripy coats in the fields of Somerset to conduct the research. 

They found that horse flies gathered around domestic horses and zebras at a similar rate – but landed on zebras a quarter as often. 

When uniformly coloured horses were dressed in ‘zebra coats’ the flies made far fewer landings on the striped areas but were not kept away from the uncovered head. 

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Flies approach zebras animal with the intention of landing and drinking the zebra’s blood. They found that horse flies gathered around domestic horses and zebras at a similar rate – but landed on zebras a quarter as often (stock)

Video footage showed that the flies made uncontrolled approaches when faced with a striped landing strip. 

Typically they came in too fast, often crashing into their prey or aborting the landing altogether. 

Study leader Professor Tim Caro, from the University of California at Davis, said: ‘This indicates that stripes may disrupt the flies’ abilities to have a controlled landing.’ 

Dr Martin How, a member of the team from the University of Bristol, said: ‘Stripes may dazzle the flies in some way once they are close enough to see them with their low-resolution eyes.’ 

WHAT ARE THE THEORIES BEHIND WHY ZEBRAS HAVE STRIPES?

There are several possible explanations as to why zebras have black and white stripes, but a definitive answer remains to be found. 

There are a number of theories which include small variations on the same central idea, and have been divided into the main categories below.

The areas of research involving camouflage and social benefits have many nuanced theories.

For example, social benefits covers many slight variations, including:

  • Zebras recognise each other on the basis of their stripes
  • This is especially important in the visual communication between mothers and their foals
  • Stripes might also be visual markers for group bonding or to direct companions to particular parts of the body for grooming.

Anti-predation is also a wide-ranging area, including camouflage and various aspects of visual confusion.   

These explanations have been thoroughly discussed and criticised by scientists, but they concluded that the majority of these hypotheses are experimentally unconfirmed.

As a result, the exact cause of stripes in zebra remain unknown.

In a similar way, human pilots can be dazzled when attempting to land into the sun. 

The study took place on a UK horse farm in Somerset that keeps both domestic horses and zebras. 

The purpose of zebra stripes has long been a mystery. 

Theories about their function have included camouflage, a means of confusing predators, a method of signalling other zebras, and a system of heat control. 


 The purpose of zebra stripes has long been a mystery. Theories about their function have included camouflage, a means of confusing predators, a method of signalling other zebras, and a system of heat control (stock)

More recent research has suggested that somehow the stripes reduce the chances of a zebra being bitten by flies. 

As additional protection, zebras swish their tails almost continuously to keep flies off, the study found. 

If the flies are particularly persistent, they will stop feeding or attempt to flee from them. 

In contrast domestic horses chiefly twitch to flick away flies and only occasionally swish their tails. 

The research is reported in the journal PLOS ONE. 

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