AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
Zebras stripes white black stripes or11/19/2023 Still, “I very much doubt zebra stripes do work in concealment,” adds Stevens.Ĭaro, who has been studying zebras for a decade and has written a forthcoming book about their stripes, thinks he knows the answer. Its only flaw is that the team didn't specifically measure how closely a zebra matches its background environment, in either color or brightness. “It’s the first proper test of a very longstanding and prominent idea,” says Martin Stevens from the University of Exeter, who studies camouflage. Zebras, being very noisy browsers, are hardly stealthy. “If the stripes are doing something exciting, they’ll be doing it close up, by which point the predators have probably realized the zebra is there, because they can smell or hear it,” says Caro. That rules out both the blends-among-trees idea and the breaks-up-outline one-neither can possibly be true if the predators can't see the stripes. “Those stripes are going to fuse together and be indistinguishable.” “At most distances, the zebras are going to look to a lion like a gray waterbuck,” says Caro. At dawn and dusk, lions, and hyenas can only resolve zebra stripes at 46 meters and 26 meters respectively. Those values get much worse for Grevy's zebra (the species with the thinnest stripes), for leg stripes (which are also thinner), and at darker times of day. By contrast, lions can only do so at 80 meters, and hyenas at 48 meters. They found that in daylight, humans with 20/20 vision can resolve zebra flank stripes from around 180 meters away. They then calculated how good those predators are at resolving zebra stripes at different distances and light levels. The team measured stripe widths from different body parts on all three zebra species, and used published data to estimate the acuity of lion and hyena eyes. So Caro, together with Amanda Melin from the University of Calgary worked out what zebras look like to these predators. By contrast, their main adversaries-lions and hyenas-have eyes with poorer resolution, but greater sensitivity at dawn, dusk, and darkness. Human eyes are exceptionally good at resolving detail in daylight, so “we have a very odd appreciation of the coat of a zebra,” says Tim Caro from the University of California, Davis. The problem is that we've always looked at zebras through the wrong eyes-ours. Both ideas have been around for a while, but neither has been tested well. Alternatively, the stripes break up the zebra's outline, making it harder to identify as a juicy piece of horse-shaped steak. First, the black stripes could match dark tree trunks while the white ones match shafts of light between the trunks. The idea that its black-and-white coat might help it blend in rather than, say, stand out seems preposterous, but there are two ways in which this could work. “The zebra is conspicuously striped,” wrote Darwin, on one of his less insightful days. (“In a world of confusion/ We all need a sign/ If only we could live side by side/ Like the stripes down a zebra’s spine.”) Which, honestly, makes about as much sense as the most commonly cited hypothesis about zebra stripes-that they're a form of camouflage. Comedy maestro Bill Bailey has a song about zebras, in which he casts their black and white stripes as a message of racial harmony.
0 Comments
Read More
Leave a Reply. |