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Scientists Solve the Mystery of Why Zebras Have Stripes

samzenpus posted about 7 months ago | from the leopards-took-the-spots dept.

Science 190

Hugh Pickens DOT Com (2995471) writes "There have been many explanations for the zebra's impressive stripes including Darwin who thought that the stripes help males and females make sensible choices about whom they mate with. Now Henry Nicholls reports at The Guardian that Tim Caro at the University of California, Davis, has taken a completely original approach, stepping back from one species of zebra and attempting to account for the differences in patterning across different species and subspecies of zebras, horses and asses to see if there is anything about the habitat or ecology of these different equids that hints at the function of stripes. To answer that question, Caro and his colleagues created a detailed map charting the ranges of striped vs. non-striped species and subspecies. Then they worked on a map for the bloodsuckers that targeted those species — specifically, abanid biting flies (horse flies) and tsetse flies.

'I was amazed by our results,' says Caro. 'Again and again, there was greater striping on areas of the body in those parts of the world where there was more annoyance from biting flies.' Where there are tsetse flies, for instance, the equids tend to come in stripes. Where there aren't, they don't. Biologists who buy into the bug-repellent hypothesis say that, all other things being equal, striped animals would have an evolutionary advantage because they wouldn't suffer from the loss of blood, reduced weight gain and lowered milk production that's associated with bug bites. Tsetse flies are also associated with the transmission of diseases. 'There are a lot of them, such as sleeping sickness, equine anemia and equine influenza,' Caro says. Why would zebras evolve to have stripes whereas other hooved mammals did not? The study found that, unlike other African hooved mammals living in the same areas as zebras, zebra hair is shorter than the mouthpart length of biting flies, so zebras may be particularly susceptible to annoyance by biting flies. 'It's clear that the flies can get through that hair and get to the skin.'"

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Cite your Refs (5, Funny)

Mr D from 63 (3395377) | about 7 months ago | (#46647741)

So, this is why very few referees suffer from fly bites? I always wondered.

Re:Cite your Refs (1)

rmdingler (1955220) | about 7 months ago | (#46647823)

Deepwoods Off clothing accessories coming soon to an aisle in your sporting & more store.

Re:Cite your Refs (0)

Anonymous Coward | about 7 months ago | (#46647929)

this would imply that referees are an evolved life form. Perhaps this is proof that God created the sports world in six days? He made referees with poor vision to provide a more entertaining environment. (Did Noah have two referees on board?) If there really is such a thing as "evolution" referees would have evolved from eagles and have better eye sight.

Re:Cite your Refs (0)

Anonymous Coward | about 7 months ago | (#46648653)

Referees ARE evolving.

Referees used to have 1 inch wide stripes on their shirts. Now from the NFL down, the referees are evolving to 2 inch wide stripes, therefore less stripes on their shirts.

Too many stripes weighed them down and made it harder for them to run to get into proper position to make the calls. With less stripes, the calls will be made properly. (Please trust me and do not do any critical thinking)

Re:Cite your Refs (-1)

Anonymous Coward | about 7 months ago | (#46648771)

I was trying to figure out what the OP thought referees [wn.com] had to do with the price of eggs, until I realised they were talking about the appearance of refs in their local game of handegg [thefootballgirl.com] ...

Terrible summary (5, Insightful)

timholman (71886) | about 7 months ago | (#46647767)

You know, if you're going to just copy and paste part of the article as your summary, you might as well post the last paragraph, and get to the actual explanation:

Zebras have stripes because biting flies have an aversion to landing on striped surfaces.

Re:Terrible summary (3, Insightful)

Joce640k (829181) | about 7 months ago | (#46647821)

biting flies have an aversion to landing on striped surfaces.

Biting flies can't evolve?

I found the whole thing very unconvincing.

Re:Terrible summary (0)

Anonymous Coward | about 7 months ago | (#46647965)

Biting flies can't evolve?

No, God made them that way, duhhhh.

Re:Terrible summary (4, Interesting)

Thanshin (1188877) | about 7 months ago | (#46647973)

biting flies have an aversion to landing on striped surfaces.

Biting flies can't evolve?

I found the whole thing very unconvincing.

If it's proven that biting flies have aversion to landing on striped surfaces, it makes no sense to say it can't be true because flies would evolve. One should rather ask "Why didn't flies evolve past this limitation?"

One could start with various hypotheses like:
- It's a behavior that protects them from something. Maybe the advantage of biting zebras has a lesser weight than the disadvantage of losing that protection.
- It's a behavior that's consequence of something they can't evolve past without not being flies anymore. Maybe their eyes are not able to know the distance of a striped surface with the required precision, for whatever physical reasons, and better eyes would be too expensive.

Re:Terrible summary (5, Funny)

davewoods (2450314) | about 7 months ago | (#46648181)

better eyes would be too expensive.

They simply ran out of evolution points when they were rolling their species.

Re:Terrible summary (4, Insightful)

Joce640k (829181) | about 7 months ago | (#46648239)

Biting flies can't evolve?

I found the whole thing very unconvincing.

If it's proven that biting flies have aversion to landing on striped surfaces, it makes no sense to say it can't be true because flies would evolve.

Correlation != causation.

To me it makes much more sense that biting flies have evolved to avoid landing on Zebras (eg. because Zebras have a secret anti-fly weapon we don't know about yet).

How do they know to avoid Zebras? Because of the stripes.

Carts and horses. Make sure you know which is which...

Re:Terrible summary (2)

ZahrGnosis (66741) | about 7 months ago | (#46648753)

I half agree and half don't. Asking why the flies did not evolve to adjust is a good question; most animals do evolve to exploit readily available food sources, not to have seemingly random phobias of them, so there seems to be a large unanswered question. My problem with any evolutionary theory, though, that uses the word "why" is that it's implying causality from correlation, which is a science no-no.

It could be, for example, that flies have some other aversion to zebras -- for example they may have a more effective swatting tail -- and therefore the flies evolved an aversion to zebra stripes. Since we don't have any good tests of ancient fly behavior we can't truly know which came first. It could be that there was some third related causal element... for example if zebras stripes were an evolutionary advantage allowing them to hide from large predators in some particular foliage that appeared striped, and that foliage also housed animals that ate tsetse flies, the flies could have learned not to go near the striped surfaces for reasons unrelated to zebra. Or the two things (stripes and aversion to stripes) could have evolved as a coincidence.

Don't get me wrong, it's a good use of animal demographic data and a very interesting result. I also tend to believe that the result is correct: that the zebra evolved stripes because those with particularly dominant stripes were less prone to disease and problems brought on by fly bites, and this led to a positive selection for those striped traits. I'm just saying it's always going to be a leap to say there's a "why" that any particular evolutionary advance happened, because "why" is vulnerable to the "why not" counterargument, and it's unprovable because no experimentation can (reasonably) be done.

Re:Terrible summary (1)

Joce640k (829181) | about 7 months ago | (#46648853)

I also tend to believe that the result is correct

Why?

All we have at the moment is a correlation.

that the zebra evolved stripes because those with particularly dominant stripes were less prone to disease and problems brought on by fly bites

Maybe the stripes just help zebras distinguish other zebras clearly in a world full of hoofed animals.

Re:Terrible summary (5, Insightful)

kruach aum (1934852) | about 7 months ago | (#46648003)

They can evolve, but they have evolved to a local maximum where they can't determine whether visual information received indicates a zebra, mud, or water. As they seem to be thriving at this level, there is no pressure for them to evolve the required discriminatory abilities.

Re:Terrible summary (2)

kruach aum (1934852) | about 7 months ago | (#46648023)

replace "mud or water" with "things they don't want to land on." I made a thinko.

Re:Terrible summary (0)

Anonymous Coward | about 7 months ago | (#46648407)

agree but would surmise, "they" are not all alike, they have evolved to a pool of variation that encompasses some more stripy biters and some less stripey biters, over some range of stripy and bitiness, and were all the zebras to get wiped out (by cancer of the stripes?) or stripe versa, the flypool would shift.

Re:Terrible summary (1)

asylumx (881307) | about 7 months ago | (#46648621)

Also, just because they haven't evolved to do this yet doesn't mean that they won't ever evolve to do that. People seem to think as "today" as if it's the pinnacle of evolution, but it's not. Who knows what kinds of species the Earth will be home to in 100,000 yrs? 1 million years?

Re:Terrible summary (4, Insightful)

rmdingler (1955220) | about 7 months ago | (#46648019)

Biting flies, like the zebra, certainly do evolve... typically at a much faster rate than large mammals.

That would make the idea of evolving insect repellent coloring even more amazing.

For proof like in the pudding, the biting flies would have to be shown to exert selection pressure on zebras that is not present where equines without stripes flourish.

It could be the striped coat offers an amalgam of advantages. Hindering attacks from predators trying to pick out a single quarry in a sea of seizure-inducing undulating stripes should not be considered mutually exclusive from hindering insect bites.

Re:Terrible summary (1)

Joce640k (829181) | about 7 months ago | (#46648317)

Biting flies evolve... typically at a much faster rate than large mammals.

...which makes it even less likely that strips would work to keep them away. They'd out-evolve the stripes before the stripes ever developed fully.

Re:Terrible summary (1)

jeffmeden (135043) | about 7 months ago | (#46648465)

Biting flies, like the zebra, certainly do evolve... typically at a much faster rate than large mammals.

That would make the idea of evolving insect repellent coloring even more amazing.

For proof like in the pudding, the biting flies would have to be shown to exert selection pressure on zebras that is not present where equines without stripes flourish.

It could be the striped coat offers an amalgam of advantages. Hindering attacks from predators trying to pick out a single quarry in a sea of seizure-inducing undulating stripes should not be considered mutually exclusive from hindering insect bites.

Predator logic...
A few stripes: bite like hell until my mouth has food in it
A shit-ton of stripes: bite like hell until my mouth has food in it

Re:Terrible summary (1)

Joce640k (829181) | about 7 months ago | (#46648695)

Hindering attacks from predators trying to pick out a single quarry in a sea of seizure-inducing undulating stripes should not be considered mutually exclusive from hindering insect bites.

Predator logic...
A few stripes: bite like hell until my mouth has food in it
A shit-ton of stripes: bite like hell until my mouth has food in it

Yep. If that's their strategy, it doesn't seem to be working: https://www.google.es/search?q... [google.es]

The 'camouflage' explanation doesn't hold up under scrutiny. eg. I don't recall seeing human soldiers wearing black/white stripy uniforms in Africa...

Me? I think other zebras just find stripes irresistible, ie. Zebra eyes have evolved to enjoy being surrounded by other zebras

Re:Terrible summary (1)

Anonymous Coward | about 7 months ago | (#46648079)

slashdot "science" strikes again. here are the rules
0. frame a hypothesis as a rule from good.
1. imply causality for mere correlation.
1a. bonus points for untestable (i.e. unscientific) theories.
(the way to test this one would be to evolve zebras without tsetse
files. there's no way to do the null hypothesis experiment.)
2. no natural phenomena can have more than one cause.
(i mean why didn't the zebra grow longer hair? how hard is that?)
 

Re:Terrible summary (1)

Joce640k (829181) | about 7 months ago | (#46648271)

Not just /.

This story is *everywhere* today. The level of uncritical thinking and mindless reposting is astounding.

Re:Terrible summary (0)

Anonymous Coward | about 7 months ago | (#46648313)

It's been pretty much accepted for decades. Heck, they sell fly covers for horses with zebra striping on them with that argument.

Ok, let's take on the "biting flies can't evolve" argument: the basic argument is that the zebra stripes mess with the visual system of flies (facette eyes connected to a simplistic visual cortex suitable for insects with a reasonable tolerance towards in-flight collisions). Now there is rather little variation in the principal apparatus involved here, and zebras are black-and-white, so there is not much potential to fix this with color or similar differentiation.

I would guess the effect to be basically that the insects make an evasive maneuvre in the last flight phase because the imagery, lacking depth, is pretty indistinguishable from the kind of moving stark contrast when getting swatted. So that would take rather fundamental changes (we are not talking "species" level but a much broader category of invertebrates) to the optics and connected synapses (calling it "brain" seems a bit excessive) of the otherwise successful tsetse fly.

Re:Terrible summary (1)

Charliemopps (1157495) | about 7 months ago | (#46648455)

biting flies have an aversion to landing on striped surfaces.

Biting flies can't evolve?

I found the whole thing very unconvincing.

Not only that, but wouldn't it be easier to just grow longer hair?

Re:Terrible summary (4, Insightful)

geekmux (1040042) | about 7 months ago | (#46648463)

biting flies have an aversion to landing on striped surfaces.

Biting flies can't evolve?

I found the whole thing very unconvincing.

For biting flies to evolve, there would likely have to be a considerable reason to, such as zebras being their only source to lay eggs. Chances are their ecosystem was hardly impacted at all by zebra evolution due to diversity.

As evidenced, zebras did evolve due to considerable reasons, as their short hair made them rather specific targets for the flies above many other animals.

Thankfully, evolution does require considerable justification. Questionable mutations would evolve otherwise, and we should be thankful it's not a knee-jerk reaction in nature, no matter how much we would like to prove it actually exists to those who refuse to acknowledge it on every level.

Re:Terrible summary (1)

Joce640k (829181) | about 7 months ago | (#46648903)

For biting flies to evolve, there would likely have to be a considerable reason to

The same argument applies to stripes. Maybe more so - stripes aren't food, they have a much more subtle evolutionary pressure (assuming they're the repel flies).

Longer, swishier tails to swat flies with seem much easier to evolve than stripes - there's already some genetic variation in tails.

Re:Terrible summary (1)

zerosomething (1353609) | about 7 months ago | (#46648485)

Biting flies can't evolve

Like most science this brings up more questions. Additionally why didn't Zebras evolve longer hair if the flies can't get through that as well, apparently other animals did evolve long hair and not stripes. Maybe for different reasons, maybe none of the explanations are any good. Isn't science fun!

Bad Hair VS Sexy Stripes (2)

DarthVain (724186) | about 7 months ago | (#46648655)

Just playing devils advocate (I am sure there is a joke in there somewhere)...

Anyway, as I understand it, evolution is about the selection of traits for survival, This usually involves environment, eating/not getting eaten, and procreation.

It very well could be that Zebra's with their short hair, developed stripes to hide from biting insects, as their survival was significantly impacted enough to warrant the change. While on the insect side of things, perhaps they have enough of a food source that missing out on the Zebra buffet isn't a significant survival issue, and thus never bothered to evolve any eyeballs capable to seeing them for lunch (or perhaps the Zebra evolution isn't all that effective anyway).

What is more interesting to me however, if this explanation is the case, then why didn't Zebra's just evolve longer hair? Then again, I suppose it is hot, so that might not work out so well. Then again not everything has a lot of hair or is striped in those parts either. I am pretty sure evolution isn't really all that exact anyway, which is partially why it takes so damn long to produce changes over generations. I liken it to randomly programming solutions to a problem, some are better than others, but some are pretty good and stick around for quite awhile, or are just good enough, though over time the best solution will get used more often eventually.

Also mixed into the mess is not only physical things like hot/cold, eat/eaten, procreation, but behavior based on those traits. Basically at which point is a stripey Zebra more sexy to another Zebra as that is perceived as better unconsciously. Oh baby, that's nice stripes you got there... I have to think there is also a significant lag time between physical evolution, and behavioral evolution, as the one pretty much has to occur before the other. Perhaps that is the point, if a trait sticks around long enough, it sort of proves itself a bit, which then kicks in the behavior modification, which further reinforces the trait...

Anyway interesting to try and figure it all out, even if only a thought experiment.

Re:Terrible summary (1)

bigrockpeltr (1752472) | about 7 months ago | (#46648813)

very unconvincing... wouldnt it be easier to grow your hair a few mm longer?

Re:Terrible summary (1)

O('_')O_Bush (1162487) | about 7 months ago | (#46648849)

Isn't it obvious? This is why Elephants, Rhinos, Spring bucks, Antelopes, Giraffes, and Buffalo all have stripes too.

And their stripe pattern has nothing to do with large, sight base feline predators like lions and tigers in Africa, or jaguars in South America. The selective pressure from being bitten by flies is way stronger than being eaten, especially since equines don't have to rely on camoflauge because they have armored skin, horns, and blazing speed like other potential prey species.

Re:Terrible summary (3)

Impy the Impiuos Imp (442658) | about 7 months ago | (#46648867)

Assuming the statistical analysis is correct, I will give the answer:

As the fly flies by, the alternate dark and light banding confuses the fly into thinking it is the moving shadows of some threat from overhead, like a hungry bird.

Go write a paper and list me as lead.

Re:Terrible summary (1)

shadowrat (1069614) | about 7 months ago | (#46648281)

I read other articles that said the scientists basically found a correlation between heavy populations of biting flies and intensely stripped zebras. All they have is some statistical analysis that says these populations overlap. They [the scientists] then say that this is intriguing and someone should figure out if the stripes actually protect the zebras.

that's fine. it's good science. It's the journalists that are claiming, that flies have an aversion to striped surfaces.

For all we know, the heavy fly populations could be because flies tend to really like landing on stripped hosts so the flies are heaviest where the zebras are.

Re:Terrible summary (1)

Joce640k (829181) | about 7 months ago | (#46648611)

I read other articles that said the scientists basically found a correlation between heavy populations of biting flies and intensely stripped zebras. All they have is some statistical analysis that says these populations overlap. They [the scientists] then say that this is intriguing and someone should figure out if the stripes actually protect the zebras.

that's fine. it's good science. It's the journalists that are claiming, that flies have an aversion to striped surfaces.

Or.... maybe the flies have a good reason to avoid zebras - Zebra blood tastes bad or something.

The 'camouflage' explanation isn't very good either. I don't see many African soldiers wearing black/white striped uniforms, do you?

My theory? Zebras live in a land full of hoofed animals and the stripes let them know which other animals they're supposed to hang out/mate with. ie. Zebra eyes find stripes irresistible.

Re:Terrible summary (1)

jeffmeden (135043) | about 7 months ago | (#46648297)

You know, if you're going to just copy and paste part of the article as your summary, you might as well post the last paragraph, and get to the actual explanation:

Zebras have stripes because biting flies have an aversion to landing on striped surfaces.

Yep, or put another way:
"Getting bitten by flies because your hair is too short? Fuck longer hair, let's get some stripes! Because evolution!"

Re:Terrible summary (1)

wonkey_monkey (2592601) | about 7 months ago | (#46648405)

Thank you. Bloody summary doesn't make sense without that nugget.

Re:Terrible summary (1)

Gothmolly (148874) | about 7 months ago | (#46648591)

You know, I was going to make a Roland Picquipaille joke, and then I looked, and lo it was Hugh Pickens, the second copypasta/clicktroll master.

Re:Terrible summary (0)

Anonymous Coward | about 7 months ago | (#46648671)

Zebras have stripes because biting flies have an aversion to landing on striped surfaces

The real question is- why didn't zebras just grow longer coats, like all the other animals? (FTFA: "...unlike other African hooved mammals living in the same areas as zebras, zebra hair is shorter than the mouthpart length of biting flies, so zebras may be particularly susceptible to annoyance by biting flies") Why did evolution push them toward that method of avoiding bites (grow stripes, cuz flies don't like stripes), rather than the tried-and-true method of 'don't let the flies close enough to bite'.

Re:Terrible summary (1)

Joce640k (829181) | about 7 months ago | (#46648941)

It's hot over there.

But what about the really important question (2)

OzPeter (195038) | about 7 months ago | (#46647771)

Are Zebras Black with White stripes or White with Black stripes?

Re:But what about the really important question (2, Informative)

Anonymous Coward | about 7 months ago | (#46647827)

Are Zebras Black with White stripes or White with Black stripes?

Black with white stripes. Their snouts are black making them their stripes white.

Re:But what about the really important question (1)

Anonymous Coward | about 7 months ago | (#46647831)

The former [wikipedia.org] .

Re:But what about the really important question (0)

Anonymous Coward | about 7 months ago | (#46647843)

That question has a really important and obvious answer:

Yes.

Re:But what about the really important question (0)

Anonymous Coward | about 7 months ago | (#46648355)

White usually is a secondary color in equines. Most white horses are born with different colors. They have a gene that makes their hairs gray much sooner than usual, so they turn white after several years.

True albinos or creame-white colors are quite rare and come at birth instead.

Important Quote from Article (5, Informative)

Grantbridge (1377621) | about 7 months ago | (#46647775)

Relevant quotes missing from summary:

"researchers built horse mannequins, painted them in a variety of patterns, coated them with sticky stuff, and found that horseflies seemed to avoid landing on the fake horses that were painted with black and white stripes."

"The proposed explanation was that the flies preferred to land on dark surfaces. Such surfaces reflect the kind of polarized light that reminds the flies of the water or mud where they breed. Light surfaces aren't as attractive, but dark-and-light patterns are even worse — perhaps because such patterns confuse the flies' navigational sense."

OK, but that still doesn't explain (1)

Anonymous Coward | about 7 months ago | (#46647813)

Why zebras always blow big calls at the end of playoff games.

Re:OK, but that still doesn't explain (0)

Anonymous Coward | about 7 months ago | (#46648235)

Why zebras always blow big calls at the end of playoff games.

I'm sure vegas has an answer. I wouldn't be surprised if a few of them have had some side bets here and there.

Other relevant quote (1)

Anonymous Coward | about 7 months ago | (#46647993)

Other relevant quote:

"Now Henry Nicholls reports at The Guardian that Tim Caro at the University of California, Davis, has taken a completely original approach, stepping back from one species of zebra and attempting to account for the differences in patterning across different species and subspecies of zebras, horses and asses to see if there is anything about the habitat or ecology of these different equids that hints at the function of stripes"

Reading TFA I can conclude that flies prefer biting asses. So, cover yours.

Re:Important Quote from Article (1, Troll)

Thanshin (1188877) | about 7 months ago | (#46647995)

the fake horses that were painted with black and white stripes."

Are we sure zebras are black with white stripes and not the other way around?

Re:Important Quote from Article (1)

lazarus (2879) | about 7 months ago | (#46648153)

I am totally trying this with body paint next time I go to the beach.

Re:Important Quote from Article (1)

RabidReindeer (2625839) | about 7 months ago | (#46648393)

Relevant quotes missing from summary:

"researchers built horse mannequins, painted them in a variety of patterns, coated them with sticky stuff, and found that horseflies seemed to avoid landing on the fake horses that were painted with black and white stripes."

"The proposed explanation was that the flies preferred to land on dark surfaces. Such surfaces reflect the kind of polarized light that reminds the flies of the water or mud where they breed. Light surfaces aren't as attractive, but dark-and-light patterns are even worse — perhaps because such patterns confuse the flies' navigational sense."

Flies don't like to land on moving surfaces from what I've seen. They prefer stationary targets which won't move while they're trying to land, are less likely to be able to swat them, whatever.

If you can't keep moving all the time (and in tropical regions, you'd really prefer not to), then the alternative is to provide the illusion of movement. As a fly approaches a striped object, those compound eyes are going to register a veritable pyrotechnic display of apparent movement, since the fly is moving relative to the stripes and is going to find it hard to tell how much of the movement is its own and how much is the target. Even humans, who have more precise vision and more brain processor power are routinely deceived by such illusions.

Hey, it's as good a hypothesis as any.

Completely original? (1)

Anonymous Coward | about 7 months ago | (#46647805)

The wikipedia article on Zebra's links to the following for a possible explanation to the origin of these stripes:

http://www.bbc.co.uk/nature/16944753

Notice anything similar?

Re:Completely original? (2)

Muros (1167213) | about 7 months ago | (#46647967)

The wikipedia article on Zebra's links to the following for a possible explanation to the origin of these stripes:

http://www.bbc.co.uk/nature/16944753

Notice anything similar?

There was a similar story a few months back, also from the BBC, about a study with slightly different conclusions than polarisation of light.It concluded that the stripes cause optical illusions when moving. Link [bbc.co.uk] .

Re:Completely original? (1)

wonkey_monkey (2592601) | about 7 months ago | (#46648573)

It's the approach that's completely original, not the hypothesis.

What's black and white and eats like a horse? (0)

badzilla (50355) | about 7 months ago | (#46647825)

Slashdot insists that I actually type the punchline, a zebra

I thought it's a common knowledge !? (0)

Anonymous Coward | about 7 months ago | (#46647829)

I remember reading about it as a kid - that zebra's stripes repel tsetse flies.

Re:I thought it's a common knowledge !? (0)

Anonymous Coward | about 7 months ago | (#46647939)

Orrr you've been bitten by a tsetse fly and you imagine you've read about it as a kid.

My idea of the stripes. (1)

Anonymous Coward | about 7 months ago | (#46647837)

Forget where I watched/read it, but I always believed the idea behind the stripes that it was more difficult for predators to single out one zebra.

I thought it was for predators... (3, Interesting)

YalithKBK (2886373) | about 7 months ago | (#46647841)

I thought the stripes broke up the outlines of individuals and made it harder for predators to single one out of a crowd? Or did no actual research go into that claim?

Re:I thought it was for predators... (1)

Joce640k (829181) | about 7 months ago | (#46647871)

I think flies are allowed to evolve to overcome things like this, but what do I know, right?

Re:I thought it was for predators... (1)

Jason Levine (196982) | about 7 months ago | (#46648273)

As other posters have pointed out, chances are that one of three things happened:

1) The flies were doing well enough even with the zebra's stripe-protection and so there wasn't a strong evolutionary pressure to get past this.

2) The stripe-aversion consisted of a benefit (e.g. kept them from landing on surfaces that could harm them) and this outweighed any benefit of being able to get past the zebra stripes.

3) The biological cost involved with overcoming the stripe-aversion (e.g. better eyes) was too great for the flies so that any benefit they gained was outweighed by the disadvantage of the "improvement."

Re:I thought it was for predators... (-1)

Lumpy (12016) | about 7 months ago | (#46647891)

Nope, it seems that predators are not a threat to zebras, and it's all about flies.

I cant wait for the next "science" article here on slashdot.

Re:I thought it was for predators... (3, Interesting)

wonkey_monkey (2592601) | about 7 months ago | (#46648539)

Nope, it seems that predators are not a threat to zebras, and it's all about flies.

There's no such implication in the article.

The question is not "Why are zebras camoflauged?" but "Why do zebras have stripes?"

As an AC below [slashdot.org] has suggsted:

as stripless equine species also had predators to deal with but not the flies the flies are the more plausible answer. the effects against predators are therefor likely to be a secondary benefit, and could have caused zebra's to have evolved into forming larger groups then most other animals their size to take advantage of that.

--

I cant wait for the next "science" article here on slashdot.

And I can't wait for the next hastily ill-informed, condescendingly dismissive post in reply to that article.

Re:I thought it was for predators... (0)

Anonymous Coward | about 7 months ago | (#46648703)

Yes, it would be totally impossible for an evolved trait to have benefits in more than one domain.

I thought it was for predators... (0)

Anonymous Coward | about 7 months ago | (#46648085)

the question here is what first caused strips to appear. what evolutionary pressure created and maintained them first.

as stripless equine species also had predators to deal with but not the flies the flies are the more plausible answer. the effects against predators are therefor likely to be a secondary benefit, and could have caused zebra's to have evolved into forming larger groups then most other animals their size to take advantage of that.

So, um (0)

Anonymous Coward | about 7 months ago | (#46647865)

why don't humans evolve this if tse tse flies are so deadly?

Evolved!? (1)

Anonymous Coward | about 7 months ago | (#46647889)

Wouldn't it have been easier to "evolve" longer hair?

Re:Evolved!? (1)

pahles (701275) | about 7 months ago | (#46647913)

hmm, you beat me to it, while I was trying to log in...

Re:Evolved!? (0)

Anonymous Coward | about 7 months ago | (#46648021)

You login, you lose

Re:Evolved!? (2)

g0bshiTe (596213) | about 7 months ago | (#46647947)

Evolution is like government, sometimes progress or in this case evolution makes little sense.

Re:Evolved!? (0)

Anonymous Coward | about 7 months ago | (#46647975)

Or pray to the zebra gods to make the flies go away? lolrite? Maybe growing longer hair takes too much energy? They'll have to eat more, which means they have to forage further out and expose themselves to predators more?

Nah, too complicated, I want a simple story so I'll put evolve in quotes!

Re:Evolved!? (2)

MiniMike (234881) | about 7 months ago | (#46648047)

Longer hair might have other disadvantages, such as worse heat dissipation and (slightly) more weight. Longer hair might also make them more susceptible to burrs, ticks, lice, or other bugs.

Re: Evolved (0)

Anonymous Coward | about 7 months ago | (#46648147)

that would have increased isolation(heat retention), hampering the zebra's ability to run for longer distances, making it more vulnerable to predators and less able to migrate. with the stripes it could keep both at bay.

(for comparison, humans likely lost almost all hair to be able to jog for longer distances then any other creature. allowing us the catch pray through sheer exhaustion under the hot African sun. (our jogging pace is also finely tuned to be the most annoying to outrun, too slow for a sprint, to fast for walking away forcing the creature to keep changing speed increasing exhaustion)

Re: Evolved (1)

Jason Levine (196982) | about 7 months ago | (#46648295)

our jogging pace is also finely tuned to be the most annoying to outrun

I knew it! I knew people evolved to be annoying!

Re:Evolved!? (1)

wonkey_monkey (2592601) | about 7 months ago | (#46648553)

I dunno. Try it and get back to me.

Hypothesized in 1982 (4, Interesting)

DarwinSurvivor (1752106) | about 7 months ago | (#46648069)

Zebra stripes have traditionally been thought of as an adaptation against detection by vertebrate predators such as lions and hyaenas. A different hypothesis is suggested: that the stripes are an adaptation against visually orienting biting flies and act by obliterating the stimulus presented by a large dark form, which is important in host-finding by many Diptera. This hypothesis is supported by some indirect evidence, and by a field experiment in Zimbabwe in which biting fly catches were compared on moving and stationary black, white and striped models. Striped models caught significantly fewer tsetse (Glossina morsitans) Westwood and other flies (including tabanids) than solid black or white models, but this difference was much reduced in the presence of olfactory attractants.

~Waage, J. K. (1981) [lifedesks.org]

Maybe people studying zebras should start by reading the zebra wikipedia page [wikipedia.org] .

Re:Hypothesized in 1982 (1)

wonkey_monkey (2592601) | about 7 months ago | (#46648597)

I don't think the article's particularly clear about this, but these guys aren't necessarily claiming to be the first with the idea. They've just done the work to back it up.

Re:Hypothesized in 1982 (1)

BitZtream (692029) | about 7 months ago | (#46648765)

No, they didn't. They didn't do anything other than look at the number of flies in relation to number of zebras in a particular area and made some random guesses.

Hypothesized in 1982 - more proof in 2014 (2)

DavidMZ (3411229) | about 7 months ago | (#46648791)

AFAIK the Waage study did not map the respective habitats of zebras and flies; that is what is actually new in this study, and it supports the Waage hypothesis.

Greater Mysteries Remain (0)

Anonymous Coward | about 7 months ago | (#46648105)

Like why Marketing insists on ruining every useful functional design on the planet...

disproof of evolution! (-1)

Anonymous Coward | about 7 months ago | (#46648129)

This is just proof of the Intelligence of the Designer! How wise of God to foresee that if He put horses in areas with biting flies, He would have to give them striped protection! God is Great! Leviticus 17:13-14!

Genesis 30:37-39 (1)

Anonymous Coward | about 7 months ago | (#46648243)

37 Then Jacob took fresh rods of poplar and almond and plane trees, and peeled white stripes in them, exposing the white which was in the rods. 38 He set the rods which he had peeled in front of the flocks in the gutters, even in the watering troughs, where the flocks came to drink; and they mated when they came to drink. 39 So the flocks mated by the rods, and the flocks brought forth striped, speckled, and spotted.

Re:Genesis 30:37-39 (0)

Anonymous Coward | about 7 months ago | (#46648721)

Amen.

Solved? (2)

jclarker6 (3402799) | about 7 months ago | (#46648349)

Why does the title claim this is solved? Even the summary calls it a hypothesis

Not "solved" (0)

Anonymous Coward | about 7 months ago | (#46648387)

Please do not title an article as scientists "solved" something, when they merely present a good theory as to why. Sigh...

The obvious answer (1)

Nidi62 (1525137) | about 7 months ago | (#46648391)

Zebras evolved to hide from German U-boats [wikipedia.org]

So why not evolve longer hair? (1)

140Mandak262Jamuna (970587) | about 7 months ago | (#46648439)

All other hooven animals in Africa found it easier to evolve longer hair to thwart the flies. Why Zebra did not choose that path? It is easier for the fly to adapt to landing on striped surfaces (change a few neurons reconnection in the brain, more like software update) than to evolve longer proboscis (more tissue, weight limit on flying organisms, more like hardware refit).

Using painted fake horses and sticky glue is does not mimic a real zebra skin that emits sweat & odors. Real skin has subtle temperature variation patterns etc. A badly designed experiment, unwarranted conclusions, not a complete literature study to be aware of other prior explanations, no attempt to design the experiment to bolster the new explanation against existing explanations ...

Will give a B for undergrad project, C for a masters project, D for masters thesis, and an F if it is part of any PhD level work.

Re:So why not evolve longer hair? (1)

Mysticalfruit (533341) | about 7 months ago | (#46648987)

Likely the stripes give the animal multiple advantages. Predators and biting insects. Possibly the long hair might also confer some negatives in terms of being able to disparate heat, etc.

Successful mutational adaptations that benefit an (0)

Anonymous Coward | about 7 months ago | (#46648451)

Successful mutational adaptations that benefit an organism may do so for multiple reasons, as those mechanisms cannot be known by the DNA, only the effect of the benefits, mutations that successfully accomplish multiple beneficial adaptions will be likely to highly adapt to the population within only a few generations. Similarly multiple overlapping beneficial adaptations will sometimes have compound effects that benefit an organism specifically against one aspect of the environment can evolve independently if each adaption is beneficial enough so as to give the organism an advantage.

confused flys? (0)

Anonymous Coward | about 7 months ago | (#46648615)

Does this mean that the stripes confuse or repel the flies. Is this a visual resistance mechanism?

Traffic Zebras (0)

Anonymous Coward | about 7 months ago | (#46648645)

In Bolivia, Zebras are used to manage traffic in the streets! I even saw a Zebra flash mob in a fried chicken place. A very versitile animal.

Break out the stripes... (1)

freak0fnature (1838248) | about 7 months ago | (#46648719)

I'll be wearing my striped shirts this summer. It's the best defense against mosquitoes!

Alternate evolution (1)

Lodlaiden (2767969) | about 7 months ago | (#46648801)

Too bad they didn't evolve longer hair.

Not true (1)

gurps_npc (621217) | about 7 months ago | (#46648803)

The zebra hid from leopards among forests and developed stripes to make it easier to hide among the "stripy, speckly, patchy-blatchy shadows".

I was told 'Just So' by Rudyard Kipling:

How the Leopard got his spots [gutenberg.org]

Bar code (1)

NapalmV (1934294) | about 7 months ago | (#46648919)

Those stripes are actually some very evolved bar codes. No one would admit that though since it would establish prior art and invalidate all the lucrative bar code patents. :-)

Striped horses (1)

T.E.D. (34228) | about 7 months ago | (#46648975)

Why would zebras evolve to have stripes whereas other hooved mammals did not?

I don't think that's true. I distinctly remember seeing a shot of a mustang (not the car, the horse) with stripes on its hindquarters. These are wild horses descended from escaped Spanish horses in the western US. I distinctly remember the announcer saying their wild ancestors probably had stripes, and after half a millennium of independent evolution, some were regaining stripes.

According to this link [aaanativearts.com] the horses the Blackfeet used often had these stripes. Despite what their legends may say, Native Americans like the Blackfeet got their horses by taming them from this same pool of the descendants of escaped Spanish horses.

Wikipedia does say that the ancestor of the domestic horse, Equus Ferrus Ferrus, often had stripes [wikipedia.org] on its shoulders.

So it sure looks like there's probably some kind of genetic usefulness for stripes in non-domesticated horses, both in ancient Asia and the modern American West as well.

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