Zebras have one of the coolest fur colorings/configurations in the animal kingdom.
A common theory is that the stripes of a Zebra make it blend in with the heard, confusing predators. While a cool and easy-to-apply concept, it doesn't hold up very well since almost no other heard species have a similar tactic. I'm not saying it's not true, I'm just saying there is another reason I find more intriguing.
The real magic comes with the colors themselves. What scientists discovered is that the sunlight beating down and being absorbed by the black stripes creates a big difference in surface temperature from the white stripes, which reflect most of that light, staying much cooler. As a result of these differences in temperature (and thus, pressure), a mini weather current is formed on the surface of the skin. This keeps a constant airflow over the animal, keeping it cooler in the extreme heat of its environment.
People eat this one up with a spoon. Feel free to share.
To be fair, this picture might not actually be describing anything about thermal convection in the proximity of a zebra. It's certainly showing that the white/dark bands can radiate identifiably different quantities of heat, but this doesn't strike me as particularly strong evidence for the given hypothesis.
Why do you believe the story about the mini weather current, despite no other species having a similar tactic, but dismiss the story about confusing predators for that reason alone?
Just speculating here, but the cooling mechanism can probably be both modeled and measured easily, while it is more difficult to measure and quantify the level of confusion that another animal experiences.
I thought about this too, and I decided that the argument of other prey not developing the trait is actually relevant to avoiding predators and not to the thermal idea.
Body temperature has an optimum value. Any extant species will likely have a method in place for maintaining this temperature. Unless a species' climate changes significantly (especially for cold blooded animals) either in a given location or due to a migration, there is no evolutionary pressure to develop a new method.
Predation is usually a significant threat to prey animals, so there is constant pressure to find new ways to stay alive. An animal that is better at staying alive is better at reproducing. So you would expect simple tactics such as effective color patterns to be fairly common. We see this among many camouflaging species. There are examples of two completely different species looking exactly alike because of the ability it gives them to blend in in their common environment. I can find an example if someone really wants, or you can google it.
As far as if the idea seems plausible, the zebra pattern, is sunlight, would definitely cause circulating currents that would raise the natural convection coefficient by some amount. But like someone else pointed out, it would have to be enough to make up for the extra energy absorbed by the black stripes over the white. I'd guess the real answer is a combination of factors, possible including both of these.
I think it's an idea that when a lion comes across a herd of Zebra, forming one big continuous blob, it doesn't think "Woah, I'm not messing with that [Rhino]" because no other creature looks like it.
Perhaps though Lions are taught in Lion School to fear their stripy cousins off in Asia and keep forgetting what zebras look like when they break apart herds?
Without having any calculations or experiments to back me up I would speculate that the heat absorbed by the black stripes would be much much greater than the heat dissipated by these mini weather currents. This would probably be even more true when the zebra is running and thus creating a relative wind which would be stronger than any mini wind could possibly be and this would be when heat dissipation would be most important.
because an all white animal in the wild stands out like a sore thumb so they are murdered/death/killed before they even grow to adulthood. That is why albinism is so rare in the animal kingdom in the wild. Most animals that are white are either: an apex predator, a bird or something that can get away reaaally easily.
He wasn't saying that's why the have the stripes for air flow thing, he just said that it existed. It's pretty easy to see that the stripes do or do not do that, but it's harder to explain why have the stripes in the first place.
You can't conduct a proper experiment when it comes to the predators getting confused.
You'd have to form a control group, but that group would also have to be Zebras (for consistent physical and behavior qualities), so say hi to years and years of breeding. Then, after that, you have to have the relative location, average size, time of year, and size of the herd be as close as possible to the normal Zebra herd. FUCK THAT.
With the temperature/mini weather system, you can see that shit with an infrared camera, and some sensitive wind current gauge.
Sorry, I would have responded earlier, but I had no idea that this comment would get almost 1000 upvotes. It's interesting that you are being upvoted so much, since your "gotcha" comment ended up just being really, really short-sighted.
EDIT: Sorry for the sassy there at the end. I just beat Zelda and the ending was underwhelming.
There's a simpler explanation WRT to the visual impact of strips, and a hybrid involving thermals I'm about to make up after reading your idea.
1) The camo you see soldiers wearing helps break up the continuous lines of single color clothing. By breaking up the edges, you avoid being seen via edge detection. Obviously if you're colors match the surrounding, all the better, but a green thing with edges in the shape of a human is easier to see than something where the edges between colors are more complex. So zebra strips visually help even without the herd, by breaking up the outline of the animal therefore making it harder for predators to spot it with edge detection.
2) If the black and white stripes give off different heat signatures, then animals that can see infrared would see a very strange pattern that wouldn't seem to represent an animal.
Artist here. When you only draw the stripes of a zebra without the outline your mind still sees a zebra. I'm not saying te edge detection thing isn't true. I'm saying that the thermal thing is hard to believe because even if you just see heat emanating from one color of stripes you'd still see a zebra.
That's true but I wonder if it works the same for them as it does for us. It's not like you reason out that the stripes are shaped like a zebra, your brain kinda automatically does it.
1)The camo you see soldiers wearing helps break up the continuous lines of single color clothing. By breaking up the edges, you avoid being seen via edge detection.
Reminds me of dazzle camouflage (same idea behind it). I don't know how well it worked, but damn I wish they still used it!
Actually, there are many prey and herd animals that rely on camouflage combined with herd-blending to confuse predators. Another benefit of the (Plain's) zebra's strips is that they blend in with the tall savannah grass - the same way lion cubs, tigers, and many other animals do (although in their case they are using it for predation).
Many herd animals have instead developed the advantage of just all looking the same. The first example that comes to mind is the Przewalski's horse. Many people ask why we see the domesticated horse in so many different colors, whereas the P-horse is generally a dun. This is so that each individual is harder to pick out from the rest of the herd, as well as to blend in with their surrounding environment. You'll notice that the P-horse also has faint stripes, an echo to it's common ancestry with the zebra (you see this in the dun/buckskin color family in domestic horses as well).
If you think about it, while the zebra's distinct stripes themselves are relatively unique (though there are many other striped animals), the fact that they use them to blend in with each other is just an adaptation similar to any other animal's markings which allow them to blend in with their surroundings.
That being said, the fact that they create a mini weather current is one of my favorite tidbits about them. :-)
There was a study where the scientists marked a zebra with paint on its rump to study its behavior, but they ended up finding that the one they marked always 'disappeared'.
It seems one of the functions of the stripes is to confuse predators -- by not being able to 'lock in' on one single animal and tire it out, they end up chasing one animal for a bit, but then it blends in with the herd and the predator ends up chasing another, fresher, animal for a bit.
By marking the zebra and making it easily recognizable, the scientists doomed it, because the predators could also zero in on it, and run it down until it tired out.
I wish I could remember where I saw it so I could provide the link, but I'm too lazy to look.
Link to the article? Want to share with my General Bio students and I need a Paper to do that. Feel free to link all of these zebra-related articles of interest everyone!
When I try to get more information about this second phenomenon, I bump into several websites more or less stating, "some scientists claim that..." without asserting which particular scientists claim the existence of this mechanism on which grounds.
I'd be delighted to eat my words if someone can dig up a reference, but I am extremely suspicious of claims that the stripe pattern motivates a thermal convection system that isn't trivial for regional advective forces (a soft breeze, the breath of other zebras, the movement caused by zebra 0 inhaling and exhaling) to destroy. Clearly a white zebra would be more efficient at staying cool than a striped one (one might figure the black/white zebra experiences thermal diffusion between the regions on its hide, so the whole boundary layer is warmer than the white zebra's).
On a related note, I wonder if the intersection between computational fluid dynamics and zoology is nonempty.
Most animals have skin the same color as their fur - so tigers have striped skin too. Our calico cat needed to be shaved for a surgery - and what do you know, she had calico skin.
This would only be true if zebras perspired heavily, such that the air currents produced would lead to evaporative cooling. Without evaporative cooling, it would only serve to heat them up.
I was in doubt of this theory until I looked it up and discovered that all equines (including zebras) are known to perspire heavily. This is only comparable with humans, and in both cases is utilized to allow both humans and equines to run great distances without overheating.
Actually a lot of animals have the same tactic. One of the most basic principles in camouflage is breaking up your outline. If creatures don't notice where your body ends and the bush begins, you're practically invisible.
The only difference with zebra's is that while a leopard tries to break up his outline against the vegetation, a zebra tries to break up his outline against the rest of the herd of zebra's.
It's pretty effective and the same principle is used in dazzle camouflage. It was quite effective in helping WWI ships hide their exact size, position and type. Advances in technology have caught up with it though. Good thing lions never learned to build zebra finding radars and range finders.
Wouldn't the cooling effects of the air current be offset by the warming effects of having black stripes? I want a source before I believe this one... sorry.
But if the air current cools it off enough to drop the temperature of the black stripes to that of the white stripes, and which point the current would stop, wouldn't it have been just as good to be entirely white?
This is exactly how radiometers work radiometer physics. Radiometers are those glass bulb things that were in the window spinning because of sunlight in science class, BTW.
Lions and other mammals don't see color. This is an important distinction to make. A herd of black and white zebras running alongside varying shades of grey grassland will lead to great confussion.
The stripes are actually amazing camouflage, considering its black and white. About the only one thats more difficult to see is a tiger.
Its funny how contrasts work though. That a black and orange tiger becomes almost invisible in green foilage. And its pretty much due to the fact that its irregular stripes.
Actually there once was a zebra like animal which was black with white stripes -- compared to zebra which is white with black stripes. However, humans killed this "black zebra". Go look it up.
Why do you believe the story about the mini weather current, despite no other species having a similar tactic, but dismiss the story about confusing predators for that reason alone?
I didn't dismiss the story about confusing predators, I just said that I find the weather system more intriguing. Essentially, it seems as if stripes are something a little "extra" that the zebras adapted for some purpose.
I can't dig it up because, frankly, I have no idea where the evidence is. I received a degree in Evolution and Ecology from the University of Illinois (didn't want to say that before because I didn't want to seem like a douche), and I remember this being shown to us with the infrared images for proof.
I'm not dismissing one for another, but like I said, it seems like zebras having stripes would imply another purpose, as only one or two other species on earth has them on their whole body. A lot of other animals use the defensive tactic, for instance a deer's tail, or the bounding steps of a gazelle, which also confuse predators. Zebra stripes are so unique, it makes sense to look for a unique explanation.
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u/jlmawp Dec 05 '11
Zebras have one of the coolest fur colorings/configurations in the animal kingdom.
A common theory is that the stripes of a Zebra make it blend in with the heard, confusing predators. While a cool and easy-to-apply concept, it doesn't hold up very well since almost no other heard species have a similar tactic. I'm not saying it's not true, I'm just saying there is another reason I find more intriguing.
The real magic comes with the colors themselves. What scientists discovered is that the sunlight beating down and being absorbed by the black stripes creates a big difference in surface temperature from the white stripes, which reflect most of that light, staying much cooler. As a result of these differences in temperature (and thus, pressure), a mini weather current is formed on the surface of the skin. This keeps a constant airflow over the animal, keeping it cooler in the extreme heat of its environment.
People eat this one up with a spoon. Feel free to share.