Zebra

Pearls Before Swine

Pearls Before Swine, My favorite comic

Zebra’s are pretty strange critters if  I do say so myself.

Photo: Zebra herd vocalizing

Here is a bit of basic Zebra knowledge as found on Natgeo:

“No animal has a more distinctive coat than the zebra. Each animal’s stripes are as unique as fingerprints—no two are exactly alike—although each of the three species has its own general pattern.

Why do zebras have stripes at all? Scientists aren’t sure, but many theories center on their utility as some form of camouflage. The patterns may make it difficult for predators to identify a single animal from a running herd and distort distance at dawn and dusk. Or they may dissuade insects that recognize only large areas of single-colored fur or act as a kind of natural sunscreen. Because of their uniqueness, stripes may also help zebras recognize one another.

Zebras are social animals that spend time in herds. They graze together, primarily on grass, and even groom one another.

Plains (Burchell’s) zebras are the most common species. They live in small family groups consisting of a male (stallion), several females, and their young. These units may combine with others to form awe-inspiring herds thousands of head strong, but family members will remain close within the herd.

Zebras must be constantly wary of lions and hyenas. A herd has many eyes alert to danger. If an animal is attacked, its family will come to its defense, circling the wounded zebra and attempting to drive off predators.”

We realize they are very different, at that those stripes are unique to them….but how did they get their stripes?

Science Daily has the answer.

How the Zebra Got Its Stripes

ScienceDaily (Feb. 9, 2012) — If there was a ‘Just So’ story for how the zebra got its stripes, I’m sure that Rudyard Kipling would have come up with an amusing and entertaining camouflage explanation. But would he have come up with the explanation that Gábor Horváth and colleagues from Hungary and Sweden have: that zebra’s stripes stave off blood-sucking insects?

 

The team publishes their discovery that zebra stripes is the least attractive hide pattern for voracious horsefiles in theJournal of Experimental Biology at http://jeb.biologists.org/.

Horseflies (tabanids) deliver nasty bites, carry disease and distract grazing animals from feeding. According to Horváth, these insects are attracted to horizontally polarized light because reflections from water are horizontally polarized and aquatic insects use this phenomenon to identify stretches of water where they can mate and lay eggs. However, blood-sucking female tabanids are also guided to victims by linearly polarized light reflected from their hides. Explaining that horseflies are more attracted to dark horses than to white horses, the team also points out that developing zebra embryos start out with a dark skin, but go on to develop white stripes before birth. The team wondered whether the zebra’s stripy hide might have evolved to disrupt their attractive dark skins and make them less appealing to voracious bloodsuckers, such as tabanids.

Travelling to a horsefly-infested horse farm near Budapest, the team tested how attractive these blood-sucking insects found black and white striped patterns by varying the width, density and angle of the stripes and the direction of polarization of the light that they reflected. Trapping attracted insects with oil and glue, the team found that the patterns attracted fewer flies as the stripes became narrower, with the narrowest stripes attracting the fewest tabanids.

The team then tested the attractiveness of white, dark and striped horse models. Suspecting that the striped horse would attract an intermediate number of flies between the white and dark models, the team was surprised to find that the striped model was the least attractive of all.

Finally, when the team measured the stripe widths and polarization patterns of light reflected from real zebra hides, they found that the zebra’s pattern correlated well with the patterns that were least attractive to horseflies.

“We conclude that zebras have evolved a coat pattern in which the stripes are narrow enough to ensure minimum attractiveness to tabanid flies,” says the team and they add, “The selection pressure for striped coat patterns as a response to blood-sucking dipteran parasites is probably high in this region [Africa].”

Zebra. If there was a ‘Just So’ story for how the zebra got its stripes, I’m sure that Rudyard Kipling would have come up with an amusing and entertaining camouflage explanation. But would he have come up with the explanation that Gábor Horváth and colleagues from Hungary and Sweden have: that zebra’s stripes stave off blood-sucking insects? (Credit: © davy liger / Fotolia)
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