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Sommer et al./Cell Reports 2016

Gut Bacteria May Keep Fat, Hibernating Bears Healthy

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Sommer et al./Cell Reports 2016

It’s a tale about nature that even small children know: at winter’s approach, a bear sets out to stuff itself with all the food it can find. After a prolonged feast, the bear, now significantly fatter, lays down for a long winter’s nap. But, as an adult, do you ever wonder how it is that bears can enjoy the benefits of obesity without incurring any of the drawbacks? Scientists do. A paper published today in the journal Cell Reports suggests that one secret to the bears’ success may lie in their gut bacteria. 

Lead author Fredrik Bäckhed has been studying the influence of gut bacteria on human health for more than a decade. He’s especially interested in the relationship between our microbiomes—the microbial ecosystems living in and on our bodies—and obesity. In one experiment, Bäckhed and his colleagues were able to show that our microbiome can affect the way we metabolize food. 

It was a natural next step for the scientist then to turn his attention to bears, whose metabolisms do a fantastic job managing the way their bodies use nutrients during the annual big sleep. 

A common way to look at someone’s gut bacteria is to collect a sample of his or her poop. This is an easy, if not pleasant, task with humans. With hibernating bears, however, it’s something altogether different, as hibernating bears don’t poop. Just before they lie down for the winter, bears clean their bodies and paws with their tongues, ingesting a lot of hair and foot pad skin in the process. But their stomachs can’t digest hair or pieces of foot pad, so these items travel unharmed through their gastrointestinal tract, along with whatever waste is left in there at the time. This becomes lodged and forms a solid plug in the bear’s butt. Nothing’s coming out of there until springtime.

Curious researchers have two options: wait until spring, when the bear passes the plug and starts pooping again, or go in there and get it. Bäckhed opted for the latter: “We took it from the rectum,” he explained in a very succinct email to mental_floss.

The researchers took both fecal and blood samples from hibernating bears in winter and active bears in the summer—and it’s hard to imagine which must have been more nerve-wracking. They then brought them (the samples, not the bears) back to the lab for a closer look.

The fecal samples taken from hibernating bears were less diverse than those of their counterparts. The makeup of the two groups was also different. The microbiota of sleeping bears was more heavily populated with Bacteroidetes bacteria, whereas the summer bears hosted more bacteria from the Firmicutes and Actinobacteria groups. The bears’ blood revealed differences as well: shifting levels of metabolic substances like triglycerides, cholesterol, and bile acids.

Next, the scientists inoculated lab mice with the bears’ bacteria. They found that mice treated with summer bacteria gained both more weight and more fat than the winter-bear mice. But despite their weight gain, the summer mice suffered no damage to their glucose metabolism. This suggests that, unlike obese humans, those mice (and the bears from which they got their bacteria) were not especially vulnerable to metabolic conditions like diabetes. 

Bäckhed hopes that further study of the microbiome may lead to a better understanding of and ways to manage obesity in humans. "I think it's too early [to say], as I consider this being very basic science," he said in a press statement. "However, if we learn more about which bacteria and the functions that promote and/or protect against obesity [in hibernating bears], we may identify new potential therapeutic targets." 

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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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