Hacker News

Someone said 3 months ago:


”The treatments were black-and-white painted stripes, black painted stripes, and no stripes (all-black body surface)”

Weird that they didn’t have a fourth group with white painted stripes. Now, the group with black-and-white painted stripes is the only one that has white paint applied, so it could as well be that the white paint causes the difference.

anw said 3 months ago:

Very interesting article.

I would love to drive by fields of zebra-painted cows, however it does make me wonder if there were other elements at play.

From the plos.org article above: "Biting flies are attracted to their host animals by odors, shape, movement, brightness, color, polarization and body temperature"

By painting on an animal, you are now changing not just the color (and perceived shape, which affects perception of movement), but also the odor (due to the paints) and perhaps interfering with how the flies will perceive the body temperature of the animal, too.

It would also be interesting to see how these specific data points compare between zebras and the cows used for these kinds of tests.

anon1m0us said 3 months ago:

If that's the case, then the flies will evolve to ignore the changes and adapt to the new zebra cows.

This is a short term fix at best.

Eric_WVGG said 3 months ago:

if that was the case, flies would have evolved to adapt to zebras by now.

anon1m0us said 3 months ago:

It only repels 50% of the bites though. Thus, those that bite, will survive and make babies. Some of them will be able to bite, others not.

Eventually, only those that can bite will survive.

I don't see how it can go the other way. Where eventually since only half of them bite, that ratio declines to zero. Can that happen with evolution?

I suppose there is a tipping point where if enough of the population can't find each other then they all die alone. Like rats in Alberta.

lurquer said 3 months ago:

50% less bites does not imply only 1/2 of flies are biting. It's more likely that each fly bites only 1/2 as much.

Someone said 3 months ago:

You’re likely also changing their temperature (white paint reflects better).

Another element at play could be that (I’m making this up, but it doesn’t seem impossible to me) zebras have thicker skin than cows, so that only half the fly species (or perhaps even only older, larger flies) can extract blood from them.

lurquer said 3 months ago:

Moreover, if there is something about the color white that affects the flies biting, the expirement boils down to this: "If you cover 1/2 a cow with a substance that flies dislike, the cow receives 1/2 as many bites!"

sgt said 3 months ago:

I think the sample size is too low. I am willing to bet that once you start doing this, the flies will start adapting and learning - eventually completely ignoring the stripes after a few generations.

rudolph9 said 3 months ago:

With enough time I 100% agree but considering the flys have not adapted for centuries to biting zebras with their stripes I’m skeptical this will happen any time soon.

sgt said 3 months ago:

I think you underestimate fly intelligence. There's been a lot of research done on e.g. fruit flies, and they are pretty intelligent compared to their neuron count, showing a simple thought process before acting.

Gene_Parmesan said 3 months ago:

But the point is, the theory with the most current support for why zebras have stripes is that they help the zebras avoid biting flies. As far as I understand it, it's not about intelligence, it's about confusing the flies' ability to detect movement. That's where this idea came from -- from research on zebra striping.

edoo said 3 months ago:

As a kid I was taught zebra stripes throw off the depth perception of lunging predators leading to increased survival rates. It is similar to the dazzle camouflage of old ships. https://en.wikipedia.org/wiki/Dazzle_camouflage

jonshariat said 3 months ago:

Ditto but I remember reading that they were uncertain if it was even effective. Anyone know if this is proven in other circumstances? It seems to make sense intuitively.

Eric_WVGG said 3 months ago:

there was a recent study where striped “jackets” were given to horses, and were found to be very effective.


edoo said 3 months ago:

Biologically speaking pigmentation is expensive so they'd lose it if it didn't serve some significant survival purpose.

raducu said 3 months ago:

Zebras only existed for centuries?

msla said 3 months ago:

If you've existed for a million centuries you've existed for centuries.

airstrike said 3 months ago:

At which point you remove the paint and instead paint zebras with cow-like patterns!

elliekelly said 3 months ago:

I wonder if you could then remove the stripes and start the confused fly cycle over again?

wmil said 3 months ago:

I doubt it's that simple. The trick is taking advantage of a limitation in flies eyes. They can't just choose to ignore the stripes.

Angostura said 3 months ago:

The problem I have with the paper is regarding the nature of the controls.

They painted black and while stripes on the cows. But they don't say what the controls were that I can see. Unpainted cows? Or cows painted a single colour.

I'd want to see all white and all black painted animals - perhaps the makeup of the paint put off the flies?

iicc said 3 months ago:


>Six Japanese Black cows were assigned to treatments using a 3 × 3 Latin-square design. The treatments were black-and-white painted stripes, black painted stripes, and no stripes (all-black body surface).

So apparently flies don't like white paint.

throwaway66920 said 3 months ago:

Seems like they’re missing a critical all white painted cow group

reportgunner said 3 months ago:

Also is being painted healthy for the cows ?

pvaldes said 3 months ago:

Most probably not; Cows would eventually lick and ingest the painting. There are several types of white pigments, some are poisonous and permanent using several metallic salts, other non durable, calcium and chalk based, and would be washed with the first rain.

The idea of a blanket is better, but the problem is that the blanket would act as a tick sanctuary then.

Sometimes, it seems that everybody is trying to solve the wrong problems, in any case.

maury91 said 3 months ago:

the article says is water-based paint, so it isn't toxic

darknoon said 3 months ago:

The comment above is indicating issues with the pigment, rather than the solvent used to disperse it. You can have very toxic water-based paint, see watercolors with cadmium etc. That being said, it's completely plausible to mix eg chalk with something non-toxic that also doesn't wash off so quickly.

kevin_thibedeau said 3 months ago:

Peroxide cow printer?

Angostura said 3 months ago:

Thank you. I missed that part. But yes, odd about the missing white paint :)

scotty79 said 3 months ago:

I think the article doesn't mention that but this is inspired by previous research on zebras, done to explain why zebras have evolved this kind of pattern.

steamer25 said 3 months ago:

I've heard that the stripes make it difficult to track an individual zebra against the backdrop of the whole herd. I.e., a lion might start chasing zebra A, but become disoriented and move onto zebra B who hasn't been worn down from direct pursuit. Researchers have supposedly observed that individual zebras marked with red paint smears tend to get eaten sooner.

said 3 months ago:
protomyth said 3 months ago:

Somehow driving through South Dakota looking out over a vast field of seaweed eating, zebra striped cows was not the future I anticipated as a youth.

I'd like some more research given that cows come in black / white patterns, pure white, and pure black. Is stripes really a thing and how about the other patterns? Do we start breading for color now?

k_sze said 3 months ago:

6 cows doesn’t seem like a significant enough sample.

Anecdotally, I tend to attract mosquitoes a lot more than some other members of my family. I would imagine the same phenomenon is true among cows.

JoeAltmaier said 3 months ago:

I know of that phenomena! I had a Scout, after 6 days on Isle Royale and we were joking about our mosquito bites and how we looked like we all had rickets, calmly said "Mosquitoes don't bite me."

We all looked at him, and he didn't have a bite/blemish on him. Nothing. Not one.

I told him, you put that in a bottle and you'll be an instant millionaire.

openasocket said 3 months ago:

I know that the swelling and itching from a mosquito bite is actually an allergic reaction to the mosquito's saliva. It's possible he was getting bitten, but was one of the few that doesn't have that allergic reaction.

JoeAltmaier said 3 months ago:

Always the skeptic! Most of us know instantly when we get bit by a mosquito.

Falling3 said 3 months ago:

I've been bitten by a lot of mosquitoes and never once been aware of it happening. I don't think anyone I know has ever claimed to know when it was happening either.

newman8r said 3 months ago:

I'm one of those people who doesn't seem to get attacked by mosquitoes when camping or backpacking. I haven't thought about it until now, but I've NEVER actually felt myself getting bitten by them. If they're really thick I will end up getting maybe 1 or two bites, but I can't ever recall the feeling of actually getting bitten.

danans said 3 months ago:

This Veritasium video explores the links between genetics and attractiveness to mosquitos.


One of the craziest phenomena it reveals is that once you've had malaria, you become more attractive to mosquitos than you were before!

mywacaday said 3 months ago:

My dad, my brother and I react badly to any king of insect bites, we get large 1-2 inch marks that swell and weep. I thought it was that we attract more bites but then wondered if that belief was because we react so badly. If a person didn't get the reactions would they even recall the bite. Anybody know if there is any research on this?

newman8r said 3 months ago:

I just answered someone above with something similar but... I go camping a lot but very rarely get a mosquito bite. Sometimes if they're really bad I will end up getting a couple of bites, but the bumps are highly delayed, and I cannot recall the feeling of ever actually being bitten.

Until this post, I didn't even realize people actually "felt" the bite as it was happening.

leni536 said 3 months ago:

This is a great Veritasium video on the subject:


ordu said 3 months ago:

> 6 cows doesn’t seem like a significant enough sample.

It would matter if we propose that different cows might have different traits that could bring such differences in bites counts. So it is not paint causes differences but cows themselves. It seems highly unlikely for me.

fiedzia said 3 months ago:

I can't wait for "april fools" announcement after thousands of farmers will paint their cows.

Gpetrium said 3 months ago:

It would be interesting to see whether certain flies evolutionary traits may develop if we start painting cows. It is entirely possible that Zebra stripes serves as a 'radar jammer' to flies and that it could help decrease fly bites, further studies may be of interest in this area.

If evolutionary traits are likely to occurs, it is worth noting that the size of cow (1,400,000,000) [1] and zebra (800,000)[2] population may have an impact on how fast these traits evolve to cope with the new normal.

[1] https://www.economist.com/blogs/dailychart/2011/07/global-li... [2] https://www.worldatlas.com/articles/where-do-zebras-live.htm...

spiderfarmer said 3 months ago:

This knowledge has already resulted in products like this horse blanket: https://www.boeren.nu/b_picture/6926/

L_226 said 3 months ago:

Do you think that the blanket itself might have some kind of influence on preventing biting insects? /sarcasm

spiderfarmer said 3 months ago:

Well, you can't comfortably cover their legs with a blanket so if flies are more attracted to regular blankets they still get bit more.

patall said 3 months ago:

It would be awesome if you could do this is a cowshed. Add a stripe projecting light source in the resting area so cows can ruminate with less disturbance.

lonelappde said 3 months ago:

It seems a different group did the same research last year: https://news.ycombinator.com/item?id=19212086

And if I recall this was also in the news several years ago.

orblivion said 3 months ago:

This sounds like an episode of Looney Tunes.

I wonder how long before the flies evolve to bother zebras?

ChuckMcM said 3 months ago:

Clearly the disruptive startup idea here is yoga pants for cows. Well, yoga body suits. /s

I love the result. Given the farm automation for feeding, perhaps an automatic paint job could be added to that system as well.

Ensorceled said 3 months ago:

So covering the cows half in white paint, halved the number of bites?

Seems like a large number of flaws in this study:

1. This wasn't 100% so maybe flies avoided the painted cows and just went to bite the non painted cows in the study. Would this work if the whole herd was painted? I know from personal experience that the best mosquito repellant is to bring a "city slicker" as bait but you need DEET if one isn't available.

2. Maybe it's the paint and if you cover the entire cow the flies stay away entirely?

3. How long did this experiment run? Once they horseflies get hungry or ending their season, they get more aggressive (they are getting aggressive right now in Ontario)

clnhlzmn said 3 months ago:

They did paint some of the cows with black paint to rule out the effect coming only from the paint itself.

oh_sigh said 3 months ago:

Seems like a large number of flaws in this post. Usually it's helpful to read a study before pointing out flaws in it.

Ensorceled said 3 months ago:

1 flaw. Missed the part where the also had black painted cows. Still doesn't cover the other 2 issues.

oh_sigh said 3 months ago:

Point 3 is also covered in the study.

csunbird said 3 months ago:

or maybe flies simply do not like the smell of paint and went to bite the ones without paint. Maybe if you paint all cows they continue biting the same, since they will rather bite cows with paint smell instead of dying of starvation

svennek said 3 months ago:


lqet said 3 months ago:


arkitaip said 3 months ago:

I wonder if a poncho would with the same pattern would have the same effect...? brb registering ponchos4cows.com

Gys said 3 months ago:

If covering the cow helps, the pattern on the cover will not make much difference? I assume covering itself is problematic and therefore (too) expensive.

OJFord said 3 months ago:

Or, less bizarrely, presumably it also works if painted like a Friesian?

softwaredoug said 3 months ago:

Could this be applied to cut down on the drugs we need to give cattle?

buryat said 3 months ago:

Will it work for humans?

axegon said 3 months ago:

Camouflage for cows?

pvaldes said 3 months ago:

Nature always in the middle of our way. Is so annoying that we can't turn Africa in a huge cow field... (roll eyes).

On the other way, milk fortified with Antimony white, or even better the sweet white lead paint, would do surprising things to children health...