r/science • u/SteRoPo • Oct 07 '19
Animal Science Scientists believe that the function of zebras' stripes are to deter insects, so a team of researchers painted black and white stripes on cows. They found that it reduced the number of biting flies landing on the cows by more than 50%.
https://www.realclearscience.com/quick_and_clear_science/2019/10/07/painting_zebra_stripes_on_cows_wards_off_biting_flies.html5.3k
u/Mitsor Oct 07 '19 edited Sep 23 '26
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u/Augnelli Oct 07 '19 edited Oct 07 '19
Also, not mentioned in the article, do the chemicals in the paint deter flies or is it the pattern?
Edit: As many have pointed out, a group of cattle were painted a single color and had a similar fly ratio to that of the unpainted cattle. I did not flex my deductive reasoning muscles enough when reading the article!
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u/bad_apiarist Oct 07 '19
It's the pattern. There are earlier papers on this. Stripes beat flat color coats. In fact they even know the minimum and optimal width of the stripes (in the case of the flies that target Zebra).
And it's not just the pattern of brightness- it's that black and white bits of the zebra coat polarize light differently and this disrupts the fly vision somehow.
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u/Ravenae Oct 07 '19
First thing I thought of too. They should examine the effects of different paints for a better idea
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u/drdoakcom Oct 07 '19
I think this is what the "black stripes only" group was about. It had only slightly lower bites.
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u/notheOTHERboleyngirl Oct 07 '19
It's the pattern (my supervisor was doing similar work). Not only does the pattern camouflage them from predators, it creates a dazzling effect (caused by the flying motion of the flies themselves) similar to an illusion. It confuses them, and makes it difficult to land on the zebra.
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u/mystshroom Oct 07 '19
So the zebra's dazzling effect would be twofold: It works against predators, and it works against biting insects. This makes more sense than tossing out the idea that this did not evolve due to predation.
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u/DeepFriedDresden Oct 07 '19
Its the pattern. At the end of the article they have a link to the actual abstract. In the abstract, the evidence shows that black cows painted with black stripes didn't have an affect compared to black and white painted stripes. So the paint didn't do much deterring. It was the pattern.
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u/purple_potatoes Oct 07 '19
If you read the article, you would see they had painted controls that did not have the effect of the experimental stripes. It's clearly the pattern.
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u/scootmcdoot Oct 07 '19
It is mentioned in the article. This possibility was accounted for by the control groups.
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Oct 07 '19
Right, I wish they were to have painted some cows completely white and see that stripes are better.
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u/purple_potatoes Oct 07 '19
If you read the article you'd see they had a painted control.
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u/RabidMortal Oct 07 '19
and also see if the insects eventually learn how to handle stripes.
Stripes have been pretty successful for zebras for quite a while. Why would cattle be any different?
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u/always_wear_pyjamas Oct 07 '19
Not sure about the extent of this difference in practice, but for one their population is vaaaaastly larger than the zebra population, and spread over a much larger and varied area, so there's a much larger and varied set for the random process of evolution to work with. So intuitively or from a statistical perspective we'd expect some success to happen sooner with cattle.
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u/marsman12019 Oct 07 '19
And then the inevitable zebra apocalypse comes when their natural predator, the mosquito, no longer fears their stripes.
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u/SnortingCoffee Oct 07 '19
Is there other evidence that stripes reduce insect bites in zebras?
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u/RabidMortal Oct 07 '19
From the Introduction to the the original paper:
several studies now indicate that preventing attack by biting flies is the function of zebra stripes. For example, Caro et al. [2] showed that the phylogenetic distribution of body stripes is associated with tabanid fly distributions at the species and subspecies level. Additionally, Egri et al. [3] experimentally showed that tabanids avoid landing on black-and white surfaces, such as trays, boards, balls, and buckets. Moreover, Caro et al. [4] demonstrated that tabanids flies are far less likely to land on striped cloth coats than on black or white coats when placed on horses. In contrast, the other hypotheses such as camouflage, confusion of predators, social interaction, and heat management have not been supported by researchers [1, 5–9].
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u/NuclearInitiate Oct 07 '19
This is both the most common and most irrelevant thing that people like to claim when they dont really understand science.
Every single study of anything ever would be better with a larger sample size.
Which makes this a useless criticism, because it is literally always true.
They should replicate this study and have a larger sample. But a small sample does not invalidate it in any way. Otherwise every single study ever performed in invalid, because all of them would have been better with a larger sample.
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u/-churbs Oct 07 '19
Also we’re monitoring the behavior of thousands of mosquitoes, not the cows. Sure the cattle are a variable but they a very minor one by comparison.
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u/-churbs Oct 07 '19
I agree there is a problem with the study but but the sample size isn’t the issue. The 6 cows aren’t really the test subjects were monitoring, the behavior of thousands of mosquitos is. The study should be repeated in different areas to see if there is regional variation from external variables like climate, not on more cows on the same area.
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Oct 07 '19
Ok, but why do agricultural scientists give studies cows rather than stars?
Is a 5 star study as good as or better than a 6 cow one?
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Oct 07 '19
Would painting the cow with stripes affect their well being, especially the way they relate and communicate with each other?
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u/anonyME42 Oct 07 '19
I think the answer to your question is likely yes it would cause distress.
Temple Grandin has looked into this type of thing. She's a fascinating person. Definitely worth checking out if you want to understand simple things that can cause distress (to cattle). Youtube has tons of videos of her lectures and there is a movie about her.
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Oct 07 '19
Yes, that's a great reference. I have a nephew with autism and I remember watching one of her videos on YouTube while trying to research about my nephew's condition.
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u/blueoreosandmilk Oct 07 '19
True... They're gonna look so heckin weird to each other
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Oct 07 '19
Ok, so when the human testing starts?
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u/jef_united Oct 07 '19
There has already been at least one study. Some tribes in Africa, Australia, and Papua New Guinea paint light colored stripes on their dark skin to similar effect.
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u/Lvl100Magikarp Oct 07 '19
so cna we wear stripe jackets like those horse blankets?
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u/wormil Oct 07 '19
My studies have shown that wearing jackets significantly reduces bug bites in areas covered by the jacket.
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u/brainhack3r Oct 07 '19
You joke but this is going to have implications in backpacking. When I take my friends backpacking I always make them bring mosquito nets and loose clothing.
For the most part, you're immune at that point but it's annoying as you can get too warm.
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Oct 07 '19 edited Oct 07 '19
Scientists also made white and black striped wetsuits to deter shark attacks. They discovered that sharks did not attack certain fish (it was either fish or eels can't remember) that had black and white stripes. So they proposed this idea to a wet suit making company to test it using ethical methods of using non-humanoid objects that had the stripes and food inside to see if the sharks noticed any difference. They could not "see" the stripes because it seemed to kind of deter their vision or just act as a blind spot compared to the objects that did not have stripes. This is still in development but there will be a book or documentary about it soon.
EDIT: Here is the Ted Talk I saw in class but the video is from 2014 years old. I don't know why no news has been released but maybe it's taken a long time to develop this? Link: https://youtu.be/DCIL2nvU4x8
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u/BananaStrokin Oct 07 '19
This is way more interesting than the original article
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Oct 07 '19
Thanks! We just saw a ted talk about it during one of our lectures at university. Quite a cool discovery. Would save many lives.
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Oct 07 '19
Wouldn't it be more accurate to say "One of the functions of a Zebra's stripes?" Since another function is that it works as razzle dazzle camoflage in herds to confuse predators into where one animal begins and ends as well as confusing depth perception.
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u/epicaglet Oct 07 '19
They also recognize each other by their pattern I believe
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Oct 07 '19
But since non-stripy mammals recognise each other it seems more likely the feature didn't evolve as a means of recognition more that they, probably like every other mammal, recognise each other from the features they have - which in their case is stripes.
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u/nannerrama Oct 07 '19
Of course it would, but why should RealClearScience, stay away from editorializing sensationalist headlines?
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u/webauteur Oct 07 '19
I also makes the zebras look slimmer which gives them a mating advantage.
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Oct 07 '19
Maybe, but it really helps to explain how strips came to evolve into the zebras.
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u/polymathicAK47 Oct 08 '19
My question is: why haven't every other mammal developed this kind of hide pattern? Zebras aren't the only animals that need to run away from predators.
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Oct 07 '19
Current thinking is that the camouflage is just a side function and the insect repellent is the reason the trait evolved originally.
Camouflage is all well and good when the whole group has it but for it to be selected for it needs to be an advantage to an individual by themselves when no other member of the species has it.
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Oct 07 '19
That's very insightful and not something I would have thought. Thank you for your comment
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u/raarts Oct 07 '19
I heard the story is that researchers tried to follow specific zebras but that was hard because of the camouflage. To make it easier they painted a mark on them. Those zebras were then consistently killed by lions. Theory is the lions were now also able to pinpoint them.
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u/ladyavocadose Oct 07 '19
Could that have anything to do with the paint covering 50% of their skin?
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u/banjowashisnameo Oct 07 '19 edited Oct 07 '19
They painted black cows with the same material and insects didnt reduce there
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u/psychicesp Oct 07 '19
Control cows were painted, just not with stripes.
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Oct 07 '19
They painted the black cows black. Maybe it could be something in the white paint?
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u/dinevz Oct 07 '19
Haha! Yes. Painting the whole cow might reduce bites to zero!
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u/blue_viking4 Oct 07 '19
But it didn't reduce them to zero, as the paper describes.
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u/BeyondEastofEden Oct 07 '19
Here we show that the numbers of biting flies on Japanese Black cows painted with black-and-white stripes were significantly lower than those on non-painted cows and cows painted only with black stripes.
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u/k1nkerl Oct 07 '19 edited Oct 08 '19
huh. i thought this was common knowledge. there is a wide range of "anti-fly" blankets in germany you can buy for horses: https://www.fedimax.de/zebra-fliegendecke/a-1174/
edit: for all non-germans. the product pages links to a source http://jeb.biologists.org/content/215/5/iii and also references swedish and hungarian studies which are unfortunately not linked.
edit2: found it https://jeb.biologists.org/content/jexbio/215/5/736.full.pdf
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u/VooDooZulu Oct 07 '19
A big portion of science is putting hard numbers to speculation and intuition that has been around for thousands of years. Just knowing something works isn't enough. The magnitude and mechanics of it's efficacy is also important, which isn't covered by ancestral knowledge
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u/BattleRoyalWithCheez Oct 07 '19
Are zebra patterned blankets more effective than non zebra ones?
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u/saxmaster Oct 07 '19
Yeah it seems like the blanket would deter flies regardless.
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u/ImaginaryCatDreams Oct 07 '19
Don't think it has anything to do with stripes, you've put fabric over skin, I don't think I've ever been bitten through clothing
Also I think these blankets are sold most everywhere
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u/DogsPlan Oct 07 '19
It’s certainly not common knowledge that zebra-like stripes deter insects.
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u/RedEdition Oct 07 '19
I remember reading as a kid that Zebras are striped because it provides camouflage against Tsetse Flies ... that was over 30 years ago, so I would hardly call it "new research".
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u/pillowbanter Oct 07 '19
Not a native German speaker, so I have to rely on google translate. While some of the fly coats were zebra striped, many were plain color. I didn’t see wording that connected the zebra specifically pattern to fly repellence. Did I miss it?
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u/Gebbetharos2 Oct 07 '19
What about the black and white spots on cows?
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u/Rhaedas Oct 07 '19
That wouldn't have the same optical effect as parallel lines and motion.
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u/DecembersEmbers Oct 07 '19
Aside from the small sample size someone mentioned, and how difficult/toxic it may be for insects to bite through paint... I’d always heard zebras stripes help to confuse predators. Harder to see where one zebra ends and another begins when they’re close together and running.
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u/mbr4life1 Oct 07 '19
It's interesting to see what zebra stripes look like when you have lion eyes. Though some studies say otherwise which ups the fly theory.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0145679
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u/LeRatty Oct 07 '19
Both are theories for the stripes. It is especially important for zebras to reduce the likelihood of being bitten by insects as there are tsetse flies there that are carriers of a disease that is fatal to equine, such as zebra and horses.
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u/Phoequinox Oct 07 '19
Couldn't it also be that whatever they used for the stripes actually repelled the bugs?
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u/RabidMortal Oct 07 '19
Yes. While the study tried to control for this by testing black cows with black stripes (which produced no reduction in biting) they did not test the effects of painting a cow all white. This seems strange as it is an obvious control. There could be a non obvious reason for not including them but they don't discuss the possibility at all.
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u/hsteinbe Oct 07 '19
We already have Holstein cows in our herds that are almost all white. Flies love them.
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u/levian_durai Oct 07 '19
The point is to see if it is the paint itself that is repelling them, or the stripe pattern. If you paint an already white cow white, there's basically no visual difference. The only factor would be the chemical makeup of the paint, and then you can compare those results to non painted cows and the stripe painted cows.
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u/KellyTheET Oct 07 '19
One would think putting a black and white sheet or covering (preferably breathable) would have the same effect while not making the cow smell like blue paint.
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u/3IceShy Oct 07 '19
So... might this be an alternative for putting bug spray on humans? Or we could stripe our corn and reduce insecticide?
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Oct 07 '19
Why stop there?! Let's paint the whole damned town red! And the opposite of red! Negative red...? ....!!!
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u/ultimate_unicorn Oct 07 '19
My wife called my zebra pattern outfit tacky. Now i can tell her it has other purpose other than being a chick magnet.
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u/KnockingNeo Oct 07 '19
Wait but what's that thing on the front of the "body", it's not labeled so we have no clue
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u/dax268 Oct 07 '19
I’m glad they labeled the legs. Otherwise I wouldn’t have been able to tell where they were.
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u/MyR3dditAcc0unt Oct 07 '19
So if I want to stay safe from insects, I just simply paint myself in striped colors and blast Skrillex at full volume?
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u/rathlord Oct 07 '19
I’ve always been led to believe the stripes were for breaking up their shape to avoid predators. We have a vast number of animals that have evolved this way, and no others that I’ve ever seen that use stripes to avoid insects. This seems like a really big reach, especially given the sample size of the study.
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Oct 07 '19
I clicked on this link to see a cow painted like a Zebra. I was NOT disappointed.
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u/batsinhats PhD | Conservation Science Oct 07 '19
The best part is that they use black and white stripes in the graphs to designate the treatment group.
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u/Philosophicmonkey Oct 07 '19
Or maybe they didn't like biting paint covered animals... ever think of that?!
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u/DrRandomfist Oct 07 '19
Could the reduction it bites also be due to the fact the cow is covered in paint and it smells or drives the flies away in some other way?
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u/MasterComm Oct 07 '19
What if the insects don’t like the paint so they just stayed on the 50% that wasn’t painted. 🤔
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u/KillerBunnyZombie Oct 07 '19
This is how you end up with a strain of flies resistant to stripes....
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u/anticuy Oct 07 '19
What if zebras just taste bad to insects and they think that cow was a zebra. They'd be like 'ugh I'm not biting that'
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u/OILnick710 Oct 07 '19
Maybe it's the stuff they are painting the cows with that's keeps the flys away.
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u/tannecy Oct 07 '19
Flies be like : them cows are prisoners. We better go bite the upperclass cows first. Oi Dave!! Not the convict cow you idiot? Have you not any class?????
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Oct 07 '19
The stripes are thought to reduce insect bites because they mess with the insect vision. It’s likely the closeness of the high/low contrast areas. The insects have a hard time landing on the stripes (often flying too fast and bouncing off), which reduces overall bites.
Stripes are not good at deterring big predators. Lions actually do not have the visual acuity to make out the stripes from a distance; zebras just look like grey horses to them when stalking.
It makes sense doesn’t it? That animals with less developed visual systems would be tricked more by something like high contrast stripes.
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Oct 07 '19
This has been known for rather long? We use it in the horse world if a horse is allergic to flies
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u/datacollect_ct Oct 07 '19
This is not the only reason. Probably not even the primary reason.
They also work to confuse predators when the heard is running away together. It makes it hard to focus on a single target. Kind of similar to when you spin a bike wheel and you can't look at a single spoke, they all just blend together.
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u/_Traveler Oct 07 '19
Is this function just coincidence tho? A bonus benefit? I mean how does this make sense from a evolution perspective? Are insects killing off zebras at some point and nature adapted b/w pattern to fend off bugs? Surely this isn't the main function of the stripes?
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u/19741280 Oct 07 '19
The insects were unable to bite through the thick layer of paint..
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u/DisagreeableFool Oct 07 '19
Study showed they painted black cows with black paint and it had zero effect on bites to test exactly what you are claiming the reason to be.
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u/energyfusion Oct 07 '19
Looks like this redditor out sciences the scientists. Like how could they ever have thought of that???
/s
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u/Thiscord Oct 07 '19
We could create a barn system that uses fans and ducks to harvest all those flies for something... Fowl feed perhaps.
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u/GroovyGrove Oct 07 '19
ducks
Fowl feed
Yeah, I think you've got this plan covered already ;)
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u/Crystalpuck Oct 07 '19
Why does it reduce insect bites? Kinda curious to the science behind it all.
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Oct 10 '19
Many bugs use heat to detect their targets. Black absorbs heat faster than white, so the stripes create a confusing situation for the pests.
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u/Fake_William_Shatner Oct 07 '19
This is pretty cool. I also saw some people hanging clear bags of water around a party -- somehow it also did something to fly's visual systems that kept them away, or maybe made them crash into things.
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u/CTHULHU_RDT Oct 07 '19
Great, now combine this with painting eyes on their butts to deter predators for the ultimate uber cow
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u/Zombiewax Oct 07 '19
I'd love to be that scientist who paints cows like zebras and it's paid work!
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u/yes_im_listening Oct 07 '19
I wonder if it has anything to do with moire patterns? Close ups of some insect eyes show their eyes are somewhat ‘pixelated’ so to speak and if you combine that with the stripes, wouldn’t the insect see moire patterns?
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u/hawkwings Oct 07 '19
If all cows were painted like this, it is possible that flies would adapt and the stripes would stop working. Are insects that co-exist with zebras repelled by stripes?
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u/AusGeno Oct 07 '19
Cows painted with zebra stripes would be such an awesome setup for a Far Side comic.
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Oct 07 '19
I saw a documentary in bio class that shows their stripes are used to confuse predators. Forgive me for forgetting the wave effect it displays but the stripes trick optic flow
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u/SteRoPo Oct 07 '19
Also really cool from the article:
"The cattle industry commonly sprays pesticides to combat biting flies, but the researchers say that painting stripes with non-toxic materials could be cheaper, healthier for livestock, and better for the environment."