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PiccoloNamek, Wikimedia Commons // CC BY-SA 3.0

How Just One Nasty Winter Forced This Lizard to Evolve

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PiccoloNamek, Wikimedia Commons // CC BY-SA 3.0

Scientists say a single unusually cold season altered the course of history for one American reptile. The green anoles who survived the winter of 2014 were those who could stand the cold—a trait they passed on to their offspring. The researchers published their findings in the journal Science.

The green anole, Anolis carolensis, also known erroneously as the American chameleon, is a vibrant little lizard that makes its home in the southeastern U.S. and Caribbean. Its range extends from Texas as far north as Oklahoma. This is unusual for reptiles, whose cold-blooded bodies typically restrict them to balmier climates.

Map of the geographic range of the green anole.
Graphic by Julie McMahon

To find out how the anoles were managing it, Shane Campbell-Staton, now of the University of Illinois, paid visits to five scattered populations in 2013. He collected samples and a few live lizards from each group to test their DNA, gene expression, and tolerance for low temperatures.

He found a fair amount of variation between lizard communities. Those in Oklahoma had clearly evolved to handle the weather there, while specimens from further south couldn't take the cold.

Satisfied with his data and findings, Campbell-Staton prepared to wrap up the project.

Then winter came. You may remember the winter of 2014, when a polar vortex created record-breaking low temperatures and wrought terrible storms across the U.S., including in anole territory. Campbell-Staton couldn't help but wonder how—or if—the cold-intolerant lizards had survived.

The next spring and summer, he and his colleagues made another circuit through anole country and collected more samples. The Oklahoma families hadn't fared too poorly. But down south, things had clearly changed. The genetic code of Texan lizards looked more like their northern cousins, and individuals were far better at handling a chill. 

The research team realized that the brutal winter had killed off most of the cold-intolerant lizards, leaving behind only those who happened to have genes more like their northern cousins'. Those lizards reproduced, creating new generations of cold-ready individuals.

But that's not necessarily a good thing.

"One might think, 'Oh, they responded! They're better now,'" Campbell-Staton said in a statement. "But selection always comes at a cost, which is death, basically. It may be that the animals that did not survive this storm had the genetic variants to survive a heat wave, or a drought, or some other extreme event. And now those lineages are essentially gone." 

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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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