Researchers Discover Why Zebras Have Stripes (phys.org) 56
According to research published in the Journal of Experimental Biology, zebra fur is thinly striped and sharply outlined to thwart horsefly attacks. "These characteristics specifically eliminate the outline of large monochrome dark patches that are attractive to horseflies at close distances," adds Phys.Org. "The team theorizes that the thin back stripes serve to minimize the size of local features on a zebra that are appealing to the biting flies." From the report: The team found that tabanid horseflies are attracted to large dark objects in their environment but less to dark broken patterns. All-gray coats were associated with by far the most landings, followed by coats with large black triangles placed in different positions, then small checkerboard patterns in no particular order. In another experiment, they found contrasting stripes attracted few flies whereas more homogeneous stripes were more attractive. [...]
The team found little evidence for other issues that they tested, namely polarization or optical illusions confusing accurate landings such as the so-called "wagon-wheel effect" or "the barber-pole effect." Now the team want to determine why natural selection has driven striping in equids -- the horse family -- but not other hoofed animals.
The team found little evidence for other issues that they tested, namely polarization or optical illusions confusing accurate landings such as the so-called "wagon-wheel effect" or "the barber-pole effect." Now the team want to determine why natural selection has driven striping in equids -- the horse family -- but not other hoofed animals.
Everything old is new again (Score:4, Informative)
Re: (Score:3)
This ^
I thought "why" of the patterns was already common knowledge. We should all upvote the parent, and just end the "non story" here.
Re: (Score:3)
What's interesting about this is the "why" is not the one I heard before which also makes me conclude the evolutionary adaptation can have multiple reasons.
I remember hearing the stripes can work as a herd defense. that seeing the strips wiggle as a herd of zebra run, can cause a predator to be confused about the exact position of a prey. Thus to defeat this, when zebra are prey, they must be isolated from a herd.
The conclusion that evolution doesn't find solutions for multiple threats with a single adaptat
Re: (Score:2)
Because we all know that zebras don't smell and can't attract flies by their smell.
Re: (Score:2)
The conclusion that evolution doesn't find solutions for multiple threats with a single adaptation, in my mind would be a great weakness of linear thinking with respect to studying biology and ecology.
I thought the stripes played a critical role for the protection of their offspring, which imprint on their mother's pattern when they are born. That is how the foal knows who its mother is.
Re: (Score:2)
Zebras, A.K.A. nature's barcodes.
Re: (Score:2)
Obviously not, since non-striped herd animals also have young that imprint on their mother shortly after birth. Cattle, horses, and sheep come to mind.
Re:Everything old is new again (Score:5, Informative)
They cite the 2019 paper by Caro et al, as well as several others, several times even in the introduction. Just because someone has done some work on a topic at some point, doesn't mean it's done and dusted, and there's nothing left to learn. This paper wasn't about establishing the fact of zebra stripes deterring horseflies, which it acknowledges in the introduction, it's about digging into the mechanisms of the effect, and the interpretation of their and previous findings. From the introduction: Nonetheless, the mechanism by which stripes deter biting flies from landing is still poorly understood and lack of knowledge of a mechanism can reduce the credibility of trait function., and Since one of the salient features of zebra pelage is highly contrasting black and white stripes, we wanted to understand the importance of differences in contrast between stripes for tabanids., etc. Exactly how important this work is, I'm not in a position to say, but it's not simply repeating previous studies.
Re: (Score:2)
Re: (Score:2)
Re:Everything old is new again (Score:5, Funny)
Re: (Score:2, Informative)
Re: (Score:1)
Don't know why, but that sounds like something that will offend conservatives.
Uhh (Score:1)
to ward off horseflies? Oh come on that seems silly. It seems fishy that none of the other animals in Africa seem to have evolved black and white striping, yet they too face the same evolutionary pressure.
Re: (Score:3, Funny)
Re: (Score:1)
Re:Uhh (Score:5, Funny)
Re: (Score:2)
Re: (Score:2)
Your argument doesn't make sense, because the same thing could be said for ANY reason why zebras have stripes. E.g. if the reason was to provide protection from the sun, you'd still be saying, "to provide protection from the sun? Oh come on that seems silly. It seems fishy that none of the other animals in Africa seem to have evolved black and white striping, yet they too face the same evolutionary pressure."
Beyond that, there are lots of possible reasons why zebras have stripes while others don't:
Re: (Score:3)
Your argument doesn't make sense, because the same thing could be said for ANY reason why zebras have stripes. E.g. if the reason was to provide protection from the sun, you'd still be saying, "to provide protection from the sun? Oh come on that seems silly. It seems fishy that none of the other animals in Africa seem to have evolved black and white striping, yet they too face the same evolutionary pressure."
Beyond that, there are lots of possible reasons why zebras have stripes while others don't:
Thank you! Good to see someone has some understanding of evolution.
The fish cited were not in the same environment. Horseflies are not in their environment, so any mutation that impeded horseflies is superfluous. Wouldn't have any effect on their preproduction success.
Other animals never got the random mutation that would create stripes in the first place
Zebras, due to other aspects of their physiology, are more susceptible to damage caused by horse flies, so experience a stronger evolutionary pressure.
Other animals previously developed other evolutionary approaches that work for them, so stripes didn't offer them any extra benefit.
And finally, some other African animals DO have stripes. Google image search for wildebeests for an example.
Yes Wildebeest is a good example. What is more, there are many animals that might be considered to have intermediate striping, like the oryx and the eastern Oryx https://en.wikipedia.org/wiki/... [wikipedia.org] https://en.wikipedia.org/wiki/... [wikipedia.org]
Pronghorn
Horseflies are Nasty Buggers. (Score:2)
A few years ago I was holding my child around the pool. Horsefly got me on the leg. It Hurt, But you can't drop your child.
Ended up with 2 bleeding holes down my leg.
Re: (Score:2)
A few years ago I was holding my child around the pool. Horsefly got me on the leg. It Hurt, But you can't drop your child. Ended up with 2 bleeding holes down my leg.
Yup, we had a horse at one time, and those damned horseflies are nasty. Horses often stand head to butt to allow their tails to brush the little jerks away from their face.
Re: (Score:2)
Because ... (Score:1)
Researchers Discover Why Zebras Have Stripes
Otherwise that saying, "When you hear hoof-beats, think horses not zebras." wouldn't make any sense. ...
The zebras know this
That Zebrastripes serve multiple purposes ... (Score:5, Informative)
... like pattern-breaking camo against predators when moving in a herd (which Zebras usually do) and against flies and insects has been know for a few decades.
The new insight here is exactly why and by what mechanism Zebrastripes repell the flies. This detail now seems to have been clarified. Bug-eyes apparently look for patches that don't reflect a certain spectrum of light but emit/reflect heat/infrared to find blood to suck. The stripes are smaller than such patches and thus flies pester Zebras less.
Evolution is fascinating.
Re: (Score:1)
Dazzle painting (Score:2)
Zebra crossings (Score:3)
Re: (Score:2)
Now explain to them what a Pelican Crossing is. :-)
The real reason (Score:5, Funny)
This study is bogus. It doesn't come close to the real reason zebras have stripes.
It's common knowledge those stripes help break up its shape against the background, thereby making it difficult for German U-boats to calculate their range, speed, and direction [imgur.com].
Do the flies kill zebras? (Score:3)
Re: (Score:2)
If not, there's not a lot of evolutionary pressure to develop stripes.
What is a real effect, is that when standing in a herd, the high-contrast vertical stripes make hard for a predator to focus on a single zebra.
Well the flies are literally feeding on the zebras so it's hard to imagine they don't have an effect on Zebra mortality and reproductive success.
I don't know of Zebra specific studies, but for cattle [oup.com]:
The 200,000 stable flies emerging from an average sized winter hay feeding site reduce annual milk production of 50 dairy cows by an estimated 890 kg and weight gain of 50 preweanling calves, stockers, or feeder cattle by 58, 680, or 84 kg.
(I think "58, 680" is some kind of livestock specific measuring system)
evolution speed (Score:3)
Re: (Score:2)
I would have thought that horseflies would be able to evolve to defeat the stripes more quickly than a large animal could evolve to implement them
I suspect it has to do with the prevalence of prey who are big dark blobs, particularly since zebras often graze in company with other large herbivores.
Horseflies are pretty simple creatures, given the choice of keeping a simple filter and losing out on some zebra snacks vs evolving a more complicated filter and snacking on everything, the fancy filter might not be worth the extra calories.
lot's of horses under a zebra blanket here (Score:2)
https://www.amazon.de/s?k=pfer... [amazon.de]
Common Knowledge (Score:2, Informative)
I forget the exact explanation, but it has something to do with black and white TV. Read it on the web around 1994 that it's been known since at least 1961.
Fruit Stripe Zebra for the win! (Score:1)
Idiots (Score:2)
No others? Um - gnu [bing.com], antelope [bing.com], okapi [bing.com].
And in case anyone thinks all zebras were heavily striped b&w, the quagga [bing.com].
Teleological reasoning about evolution? (Score:2)
As I understand it, mutations happen at random. A mutation makes the organism "fitter"(*) if it increases the chance of survival, but this is also dependent on random circumstances - a mutation which would be good in some situation might be bad in others (e.g. developing gills is only good for an organism living in water).
I have a fundamental problem with "why did some kind evolution happen" explanat
Re: (Score:1)
I think it's less about sloppy language than it is about a linguistic shorthand. Evolutionary biologists are taught about how wrong teleological thinking about evolution is from t
Re: (Score:2)
I can understand biologists using shorthand when talking informally among themselves, and being hand-wavy while developing ideas.
However, we are talking about a published peer-reviewed paper here, using formal language and notation. The main target public of the paper may be other biologists, but here we are: lay people (on
Re: (Score:2)
Type another four seconds.
Zebra Crossing (Score:2)
“The argument goes something like this: ‘I refuse to prove that I exist,’ says God, ‘for proof denies faith, and without faith I am nothing.’ “ ‘But,’ says Man, ‘the Babel fish is a dead giveaway, isn’t it? It could not have evolved by chance. It proves you exist, and so therefore, by your own arguments, you don’t. QED.’ “ ‘Oh dear,’ says God, ‘I hadn’t thought of that,’ and promptly vanishes in a puf
Kipling explained this a century ago (Score:2)
The zebra, of course, got his stripes by standing half in the shade and half out of it.
https://www.gutenberg.org/file... [gutenberg.org]
Cause vs. effect (Score:2)
The researchers claim that zebras developed stripes "because" this helps them thwart horseflies. Perhaps it's true that the stripes confuse horseflies. But that's far from establishing a causal link.
Why don't all horses have stripes? All horses do suffer from horsefly attacks. If there is a causal link, then we might expect to see more kinds of horses develop stripes.
Establishing a causal link would require an understanding of how horsefly stings leads to a genetic preference for striped patterns. There's n
Re: (Score:2)
Re: (Score:2)
Nobody said zebras are alone. I certainly didn't. Your google search certainly doesn't establish a causal relationship.
Re: (Score:2)
The search laid false that claim.
Should be Scientists make good guess why Zebras... (Score:2)
They did not discover squat. It's a good theory, interesting and may even be true... but it's not what I would call a discovery.
I guess it does get more clicks but Maybe it's just me, the increased trend of sensationalist titles all over the place is really annoying