Zebra Stripes


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Post by jesperbaitianlong » Mon Nov 19, 2007 5:50 pm

Yes I find all this info very interesting too. Thanks

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Post by AstusAleator » Thu Nov 22, 2007 10:15 pm

the picture of the elephant is fascinating, showing all of the capillary beds in its skin. It's also interesting to compare that to the picture of the Giraffe, who's heat-pattern looks similar, but may have more to do with it's coloration. I wonder if the giraffe's patterning has to do with the locations of its dermal capillary beds?
What did the parasitic Candiru fish say when it finally found a host? - - "Urethra!!"

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Zebra Stripes

Post by Mascarell » Wed Dec 19, 2007 12:06 am

Some 2 Mya (ending the Miocene) the Bering passage between Alaska and Asia was present and becoming cooler and ice covered. The first members of the equid family crossed that passage into Asia and radiated across Asia to Europe (as the E. caballus) and to Africa (where the different zebra species evolved).

Some think that the first member of this family was the Hyracotherium, a striped (not like a zebra, but more like a Tragelaphini tribe member). And so they think that it was a camouflage for their jungle adapted living style. But, modern zebras prefer open plains, arid zones and mountain biomes instead of that woodlands and jungle biomes (where the hyroctherium used to live back 54 Mya).

The striped patterns so, are not rare or uncommon to the equid family. But, what we have to ask ourselves, is that where or when the zebras chose to maintain or even remark their striped fur, in front of becoming more unicolored like Kiangs, Przewaskis or Onagers. And we can do it now by looking the biome where zebras live, their distribution, their origin and evolution, and of course, their behavioural adaptatations.

So, Zebras as I said, prefer open plains (E. burchelli and E. grevyi), arid zones and mountain or rocky biomes (E. zebra). So, in this habitat, their coat has to make a difference to their predators. Some theories explain that a striped object looks bigger than a unicolored object. Others say that breaking the silhouette can be distractive to the predators. Others say that stripes make the predators to fail to calculate the distance to the prey (the military stuff back in the first world war was painted in stripes thinking in that theories).

Living in groups is a social adaptation to predation prevention that many mammals do. Zebras live in large groups raging from 15 to 100 individuals, and forming groups of thousands during the migration. Others, more sedantary like the Ngorongoro cratter populations, do not reach these numbers. Living in group is a defense, but being striped among a group prevents the isolation of the prey. But, zebras prefer to move in groups among gnus. The play to probability games. The more animals in the plains, the less possibilities to be chosen. They wander in small families among gnu groups. So, probably the disruptive pattern to prevent isolation, would work out in migrating groups and not in feeding groups.

Distribution of the zebra match probably the most part of the distribution of the Tse tse fly (Glossina sp.). So, the possibility to find a tse tse fly and a zebra, is high in plains zebra and grevy's zebra, low to nule in mountain zebra. But, experiences on tse tse flies demonstrated that flies choose by a high 75% more a unicolored object rather than a striped one. Is this concluded?... I don't think so. Reading articles about the incidence of the nagana desease in bovid families, something breaks out some of the theories out there. There are 3 animals that don't use to be biten by flies, and they are, zebras, gnus and some small antelopes. And rarely, they bite Impalas or waterbucks. So... why zebras don't get biten? the stripes?... and what about gnus?... yes, probably gnus entered in Africa some 40 Mya and developed ressistance to the virus. But, this remains highly dubted.

My point, is that something (the stripes) are maintained because they are energetically favourable. There isn't a single reason to their stripes, but many. All valid, all favourable. All positive for their ecology. And it is so, that they have been maintained and they haven't disapeared.

What breaks out my mind is not why they have stripes, but why lions prey more in zebras than gnus (in proportion).

See you guys!
Alex Mascarell

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