Why zebras have their stripes is one of the oldest mysteries in evolutionary biology.
A team of UK researchers now claims it has uncovered evidence that the stripes are used by the African equines to dazzle predators.
The markings, they claim, work as an optical illusion that conceal a zebra’s movements and protect it from being attacked.
Scientists from Royal Holloway, University of London and the University of Queensland used computer models in an attempt to test their theory.
‘The stripes don’t just confuse big predators like lions – pests and flies are affected too,’ said Professor Johannes Zanker from the Department of Psychology at Royal Holloway.
‘The highly visible oriented stripes on a zebra’s flank and the narrower vertical stripes on its back and neck give unexpected motion signals that confuse viewers, particularly in a herd of zebras.’
Humans and many animals have something known as a ‘motion detection mechanisms’ which processes the direction in which something is moving.
An example of an illusion that can override this mechanism is the barber-pole effect, where the spiral of stripes on a vertical pole appears to move upwards as the pole spins.
Zebra stripes capitalise on this type of illusion to help protect the animals.
Broad diagonal stripes on a zebra’s flank and the narrower vertical stripes on its back can also confuse this mechanism.
‘Our research suggests that these illusions cause pests and predators to mistake the zebra’s movement direction, which would cause biting insects to abort their landing manoeuvres and chasing predators to mistime their attacks,’ said Professor Zanker.
Last year researchers from Lund University in Sweden argued that the characteristic markings on zebras are there to keep horse flies at bay.
They said that the stripes, which are unique to each animal, are unappetising to the hungry pests, which have a nasty bite and spread lethal blood diseases.
The reason they find the stripes so unattractive is because they reflect light in a certain way.
Horse flies, it turns out, prefer the ‘flat’ light produced by darker coats.
Other theories for the function of these stripes include social communication signals as well as their use as camouflage at dusk or dawn in grassy habitats.
