‘Ig Nobel’ prize winners prove why flies prefer dark-coated animals

December 01, 2017

A group of prize-winning researchers are at it again with a new study. Though they aren’t Nobel Prize winners, they’re kind of close: winners of the Ig Nobel Prize.

While the Nobel Prize is bestowed upon people whose scientific advances benefit the world, the intent of the Ig Nobel Prize is a little more modest. Prize organizers say that Ig Nobel Prize winners — of which there are ten each year — should “first make people laugh, then make them think.” Winning research is often interesting and entertaining, but relatively trivial.

In 2010, Swedish and Hungarian researchers received the Ig Nobel Prize in Physics for their work showing that dark-coated horses are plagued in greater numbers by blood-sucking flies than light-colored horses are. As it turns out, when sunlight hits dark coats, polarized light is reflected. Guess what? Horseflies like polarized light, so they gather around it. White-coated animals reflect unpolarized light, so they get less attention.

That’s as far as they got at the time, but hey — it was a start. Now, the same team of researchers has answered their next question: Why do flies still only flock to dark-coated animals in the shade, when there are other equally dark patches (from vegetation or other objects) in sight? Wouldn’t those other dark patches reflect polarized light too?

The key is the shiny smoothness of animal hair. Smooth animal coats reflect polarized light strongly. Dark objects nearby, like bushes and shrubs, are less shiny and reflect light in a different, less direct, manner. This makes the animal stand out from its surroundings, at least in fly-vision; the animal coat is reflecting what little light there is more clearly than anything else.

“Previously, we discovered that horseflies see, and are attracted to, polarized light, but not how polarized light reflected from dark, smooth coats differs from other polarized light,” said Susanne Åkesson, study lead.

No word yet on whether the study authors will receive an award again. The 2017 Ig Nobel Prizes, awarded in September at the “27th First Annual Ig Nobel Prize Ceremony,” have already been given out. Winners include researchers showing that digeridoos cure snoring in sleeping sheep, a team that used fluid dynamics to determine if a cat could be both a solid and a liquid, and scientists who tested whether exposure to a live crocodile affected a person’s willingness to gamble.