5 ms·

"the source of the effect remains unexplained" They list several candidate explanations, but miss one I came up with immediately: maybe zebras are in some other

"the source of the effect remains unexplained" They list several candidate explanations, but miss one I came up with immediately: maybe zebras are in some other way less attractive targets for the flies -- their skin is thicker, their blood/fluids don't taste as good, etc. -- and the stripes are simply a visual indicator to the flies that they are zebras, and therefore less desirable. This sort of trait has evolved poison frogs, insects, and other plants and animals, so why not zebras?

gernb 4y ago
maybe zebra skin has a different oder. They said they used pelts.
Gys 4y ago
Seems easy to test? Just paint a horse or cow and keep count of the flies.
- qbrass 4y ago
  It doesn't differentiate the flies mistaking the cow for a zebra, compared to the stripes themselves doing something else to keep the flies away.
  - idlewords 4y ago
    It does when the flies are circling a cow in the UK or Japan.
- MonkeyMalarky 4y ago
  Check out this snazzy looking fellow: https://www.smithsonianmag.com/smart-news/scientists-dressed-horses-zebras-determine-purpose-stripes-180971540/ https://www.smithsonianmag.com/smart-news/scientists-dressed...
  - oblak 4y ago
    Is it repelling or camouflage?
    - toxicFork 4y ago
      Yes
- infotecht 4y ago
  Regardless of perceived ease, they cover this: "Controlled experiments have used various landing substrates, including striped and solid oil tray traps, sticky plastic, smooth plastic, cloth (Experiment 2 in [22]), horse blankets or sheets, and paint on live animals."
idlewords 4y ago
This is mentioned in the paper, and you can find citations there to previous experiments where the visual effect alone is tested and demonstrated to be very strong. Moreover, the researchers took steps to limit any olfactory effect by salt-curing the hides used in this experiment. Whatever other defenses a zebra has, it's been shown that flies really hate those stripes.
- zamfi 4y ago
  I think the parent is acknowledging that the stripes have an effect, they're whether the authors considered that some other property of zebras is unattractive and the stripes are a good indicator, leading to an evolved preference among the insects against stripes. Here's an analogy: people often fear and avoid insects that are yellow/black striped, not because the stripes are annoying, but because many such distinctively striped insects have a painful sting, and avoiding the stripes avoids the stinging insects.
  - idlewords 4y ago
    I understand what the parent (and you) are saying; what I was trying to diplomatically suggest is that they read the paper, where these issues are all addressed. Biologists who publish in Nature anticipate a surprising number of the objections that might occur to Hacker News readers in the first ten seconds of thinking about a topic.
    - gcanyon 4y ago
      I have read (quickly) the paper. I see nothing there that addresses the idea that the stripes might be simply an identifier the flies use. Rather, the paper seems focused on the effect the stripes have on the flies rather than the idea I suggested. For example: "If, as our results indicate, stripes that span the range of interspecific stripe width variation repel flies to the same extent, adaptive explanations for stripe width variation would have to pertain to some other selective pressure." The use of "would have to" completely ignores the potential of stripes to be an identifying feature. If my hypothesis were correct, there would not have to be any other selective pressure; since all stripes identify "zebra," any stripes would work. For example, to test my hypothesis, it might be sufficient to check whether, in those zebras where some of the hide is tan rather than striped, the tan portion of the hide is attacked by the flies disproportionately to the striped portion of the hide. In sum: the paper reflects on the mechanism of the stripes in repelling flies, and seems to disregard the possibility that the stripes simply allow the flies to identify "not a good target."
aaron695 4y ago

gernb 4y ago

maybe zebra skin has a different oder. They said they used pelts.

Gys 4y ago

Seems easy to test? Just paint a horse or cow and keep count of the flies.

qbrass 4y ago
It doesn't differentiate the flies mistaking the cow for a zebra, compared to the stripes themselves doing something else to keep the flies away.
- idlewords 4y ago
  It does when the flies are circling a cow in the UK or Japan.
MonkeyMalarky 4y ago
Check out this snazzy looking fellow: https://www.smithsonianmag.com/smart-news/scientists-dressed-horses-zebras-determine-purpose-stripes-180971540/ https://www.smithsonianmag.com/smart-news/scientists-dressed...
- oblak 4y ago
  Is it repelling or camouflage?
  - toxicFork 4y ago
    Yes
infotecht 4y ago
Regardless of perceived ease, they cover this: "Controlled experiments have used various landing substrates, including striped and solid oil tray traps, sticky plastic, smooth plastic, cloth (Experiment 2 in [22]), horse blankets or sheets, and paint on live animals."

idlewords 4y ago

This is mentioned in the paper, and you can find citations there to previous experiments where the visual effect alone is tested and demonstrated to be very strong. Moreover, the researchers took steps to limit any olfactory effect by salt-curing the hides used in this experiment. Whatever other defenses a zebra has, it's been shown that flies really hate those stripes.

zamfi 4y ago
I think the parent is acknowledging that the stripes have an effect, they're whether the authors considered that some other property of zebras is unattractive and the stripes are a good indicator, leading to an evolved preference among the insects against stripes. Here's an analogy: people often fear and avoid insects that are yellow/black striped, not because the stripes are annoying, but because many such distinctively striped insects have a painful sting, and avoiding the stripes avoids the stinging insects.
- idlewords 4y ago
  I understand what the parent (and you) are saying; what I was trying to diplomatically suggest is that they read the paper, where these issues are all addressed. Biologists who publish in Nature anticipate a surprising number of the objections that might occur to Hacker News readers in the first ten seconds of thinking about a topic.
  - gcanyon 4y ago
    I have read (quickly) the paper. I see nothing there that addresses the idea that the stripes might be simply an identifier the flies use. Rather, the paper seems focused on the effect the stripes have on the flies rather than the idea I suggested. For example: "If, as our results indicate, stripes that span the range of interspecific stripe width variation repel flies to the same extent, adaptive explanations for stripe width variation would have to pertain to some other selective pressure." The use of "would have to" completely ignores the potential of stripes to be an identifying feature. If my hypothesis were correct, there would not have to be any other selective pressure; since all stripes identify "zebra," any stripes would work. For example, to test my hypothesis, it might be sufficient to check whether, in those zebras where some of the hide is tan rather than striped, the tan portion of the hide is attacked by the flies disproportionately to the striped portion of the hide. In sum: the paper reflects on the mechanism of the stripes in repelling flies, and seems to disregard the possibility that the stripes simply allow the flies to identify "not a good target."

aaron695 4y ago