Zebra Stripes

Earlier this year the BBC reported on a study that some scientists did regarding Zebra stripes (http://www.bbc.co.uk/nature/16944753).

The experiment is fascinating and a great example of how to do good science.

Scientists are not sure exactly why the Zebra got its stripes. Although, from reading other commentary on the subject, it does seem to be more a case of other related animals lost their stripes because the common ancestor was apparently striped.

That aside, the Zebra stands out as being striped while all those around it are not. The standard idea is its camouflage related; in the tall grass of the African plain the striped zebra is harder to see in the tall grass and long shadows. Certainly I can testify to the effectiveness of this when, many years ago, I went on safari with a video camera stuck to my face and a B&W screen in the viewfinder. However, with the benefit of colour vision, the black and white zebra can be quite easy to see when all around is green or brown.

When you consider that most other hoofed herbivores on the savannah are some form of beige, its easy to see why they are that colour because it makes them very hard to spot. So the Zebra stands out as being different.

Aha! The creationist would say, proof that God created the world as it is. This is certainly the view that I would once of taken.

Well, the study referenced above took a different tack and tested the effect of the stripes on flies. Out in the African bush, where Zebras live alongside many forms of deer and antelope, flies are a major problem and it seems the study shows clearly that the Zebra stripes are an effective disincentive to the flies.

This would certainly be an advantage to the Zebras. Especially when you consider that when you see Zebras in the wild they are very rarely on their own. By that I mean, you don’t just see a heard of Zebra. You tend to see a large heard of another prey animal, typically one similarly sized to the Zebra, alongside the Zebras. Its as though the conspicuous Zebra if using the greater numbers of another species to give it some form of predator protection and the stripes serve to ward discourage flies so that they bother the host herd animals more than the Zebra itself.

Now, I am of course speculating there, but that’s how science is done. You speculate, devise a test and see how right or wrong you are. No doubt more study will be done on this and its certainly unclear how the fly repellent features of the stripes would be strong enough to be a positive selective criteria.

Maybe there is another source to the stripes and the fly bit is merely a coincidental benefit which is now proving to be a great advantage.

Either way, the study shows an example of great science and I for one hope that more study will be done and published in the coming years.

And on a personal note, this is the kind of science that I love to read about.

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