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Desert Ants’ Shiny Silver Hair Keeps Them Cool

Silver hair is very cool right now, perhaps nowhere more so than in the desert habitats of silver ants. Researchers say the ants actually deflect heat with the super shiny silver hairs that cover their bodies. The report was published this week in the journal PLOS ONE. 

Your average ant is pretty shiny to begin with, but the rear ends of silver ants (Cataglyphis bombycina) gleam like polished chrome. But they’re more famous for another reason: their ability to withstand ludicrous levels of heat. The ants make their homes in the Sahara and Sinai deserts, where daytime temperatures can reach 122°F. Other desert animals will retreat to cool caves or burrows to wait out the worst of the midday heat, but not the silver ants. As everyone else is bunkering down, workers emerge from the nest and set out to scavenge the bodies of animals that couldn’t stand the heat. 

It’s a pretty terrific strategy, the researchers note in their paper: “By restricting foraging activity to the hottest period of the day, the ants minimize the chances of encountering their most frequent predator—a lizard that ceases all activities when the temperature becomes unbearable.” For a little while every day, the desert becomes an all-you-can-eat carrion buffet. 

Scientists suspected that the ants’ impressive lacquer and their heat resistance were related. A study published last year showed that tiny, triangular hairs all over the ants’ bodies were responsible for the shine, and that those hairs prevented sunlight and heat from ever reaching the insects’ insides. Exactly how the hairs were doing it remained unclear. 

So a new team of researchers took a closer look. They traveled to an ant colony in the sand dunes of Morocco and scooped up workers, then brought them back to the lab. The scientists left half of the ants shiny and hairy, but the other half were given a shave with teeny tiny razors. We are not making this up. 

All of the ants were euthanized and their parts examined under three different kinds of microscopes (scanning electron, transmission electron, and optical). Some of the ants’ bodies were implanted with little rectal thermometers and subjected to high heat from a sunlight simulator. 

SEM and TEM images of ant hair. Image credit: Willot et al.

The researchers found that the triangular shape of the ants’ hair actually created a prism effect, bouncing the light inside each hair in a process called total internal reflection (TIR). The surface of the hair was jagged, which increased the reflection even further. At certain angles, a single hair was able to reflect almost 100 percent of the light aimed at it, making it essentially a long, thin silver mirror. The bodies of hairy ants reflected as much as 10 times more light than those of the ants who had been shaved. Consequently, hairy ants’ bodies were incredibly resistant to heat. In sunlight, they stayed up to 35°F cooler than their bald counterparts. 

Amount of reflectance by hairy and shaved ants. Image Credit: Willot et al.

The silver ants are not the first organisms to use TIR, but they are the first in the desert.

“The ability to reflect solar radiation by mean of total internal reflection is a novel adaptive mechanism in desert animals,” co-author Serge Aron said in a press statement, “which gives an efficient thermal protection against the intense solar radiation. To the best of our knowledge, this is also the first time that total internal reflection is shown to determine the color of an organism."

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Big Questions
Why Do Cats Freak Out After Pooping?
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Cats often exhibit some very peculiar behavior, from getting into deadly combat situations with their own tail to pouncing on unsuspecting humans. Among their most curious habits: running from their litter box like a greyhound after moving their bowels. Are they running from their own fecal matter? Has waste elimination prompted a sense of euphoria?

Experts—if anyone is said to qualify as an expert in post-poop moods—aren’t exactly sure, but they’ve presented a number of entertaining theories. From a biological standpoint, some animal behaviorists suspect that a cat bolting after a deposit might stem from fears that a predator could track them based on the smell of their waste. But researchers are quick to note that they haven’t observed cats run from their BMs in the wild.

Biology also has a little bit to do with another theory, which postulates that cats used to getting their rear ends licked by their mother after defecating as kittens are showing off their independence by sprinting away, their butts having taken on self-cleaning properties in adulthood.

Not convinced? You might find another idea more plausible: Both humans and cats have a vagus nerve running from their brain stem. In both species, the nerve can be stimulated by defecation, leading to a pleasurable sensation and what some have labeled “poo-phoria,” or post-poop elation. In running, the cat may simply be working off excess energy brought on by stimulation of the nerve.

Less interesting is the notion that notoriously hygienic cats may simply want to shake off excess litter or fecal matter by running a 100-meter dash, or that a digestive problem has led to some discomfort they’re attempting to flee from. The fact is, so little research has been done in the field of pooping cat mania that there’s no universally accepted answer. Like so much of what makes cats tick, a definitive motivation will have to remain a mystery.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Listen to the Impossibly Adorable Sounds of a Baby Sloth
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RODRIGO ARANGUA/AFP/GettyImages

Sometimes baby sloths seem almost too adorable to be real. But the little muppet-faced treasures don't just look cute—turns out they sound cute, too. We know what you're thinking: How could you have gone your whole life without knowing what these precious creatures sound like? Well, fear not: Just in time for International Sloth Day (today), we have some footage of how the tiny mammals express themselves—and it's a lot of squeaking. (Or maybe that's you squealing?)

The sloths featured in the heart-obliterating video below come from the Sloth Sanctuary of Costa Rica. The institution rescues orphaned sloths, rehabilitates them, and gets them ready to be released back into the wild.

[h/t The Kid Should See This]

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