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Dmitry Bogdanov via Wikimedia Commons // CC BY-SA 3.0

To Save Their Species, These Prehistoric Animals Mated Early and Died Young

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Dmitry Bogdanov via Wikimedia Commons // CC BY-SA 3.0

For better or worse, every organism is affected by the world around it. Changes in climate or available resources can inspire animal species to relocate, grow bigger or smaller, quit migrating, and even fall down more. Now a group of scientists say a mass extinction event inspired a prehistoric mammal ancestor to condense its lifespan. Their paper was published today in the journal Scientific Reports.

The Lystrosaurus was a charmingly dumpy creature: As you can see in the depiction above it's a bit like a cross between a corgi, a naked mole rat, and an iguana. Therapsids like Lystrosaurus and their cousins the cynodonts roamed the planet 250 million years ago—which was, unfortunately, not a great time to be alive. A series of volcanic eruptions filled the atmosphere with carbon, thereby seriously disrupting the planet’s climate and leading to a mass extinction event. Up to 96 percent of aquatic species were lost, as were around 70 percent of land species. Somehow, through all this, sturdy Lystrosaurus managed to hang on.

Scientists have developed a number of theories on the therapsids' success, including their fondness for underground living, their willingness to travel, and sheer dumb luck. The latest report proposes a new strategy: living fast and dying young.

A team of paleontologists from the U.S. and South Africa examined the tissue microstructure of bones from 103 therapsid specimens. (Bones, like tree rings, are a great way of studying how an individual has aged, and how much.) The specimens represented around 20 million years of evolution, including the periods before, during, and after the mass extinction event.

Image Credit: The Field Museum

The researchers found that, while the therapsids had survived, they’d undergone some major changes. After the event, Lystrosaurus and some of its cousins were quicker to reach maturity, and their lives were much shorter.

“Before the Permo-Triassic extinction, the therapsid Lystrosaurus had a life span of about 13 or 14 years based on the record of growth preserved in their bones,” co-author Ken Angielczyk, of The Field Museum, said in a press statement. “Yet, nearly all of the Lystrosaurus specimens we find from after the extinction are only 2–3 years old. This implies that they must have been breeding when they were still juveniles themselves.”

Post-extinction therapsids had also shrunk. Before the volcanoes, Lystrosaurus was about the size of a little hippopotamus. After, a full-grown animal was closer in size to a large dog—partly because it was so much younger than its ancestors.

How could this have helped? The research team ran computer simulations to model the therapsids’ environment. The simulations revealed that maturing fast and mating young could have increased therapsid species’ chances of survival by as much as 40 percent. The individuals died, but their family lived on.

“With the world currently facing its sixth mass extinction, paleontological research helps us understand the world around us today,” Angielczyk said. “By studying how animals like Lystrosaurus adapted in the face of disaster, we can better predict how looming environmental changes may affect modern species.”

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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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