Why Pooping Can Be a Life-Threatening Experience for a Sloth

iStock/Damocean
iStock/Damocean

Being a sloth isn’t all lazing around in trees and munching on leaves. Occasionally, the slow-moving animals have to make their way to the forest floor to do the one task no animal can escape: pooping. It’s a much more intense process than heading to the bathroom is for humans. And for a startling number of sloths, it turns deadly.

The sloth metabolism, like everything else about these odd rainforest animals, works very slowly. It can take them up to a month to digest a meal. Their extra-slow digestion means they might only take a dump once a week, if not once a month. The poor creatures are always incredibly constipated.

So when they do poop, the result is enormous. A single bowel movement could be up to a third of the sloth’s body weight—a measurement that’s 282 percent of what scientists would expect to see in an animal of that size, according to one sloth-poop analysis from 1995.

The particular bathroom routine depends on the type of sloth, though. Two-toed sloths are often fine with letting it rip from the forest canopy (woe to any animals that might be hanging out below), while three-toed sloths determinedly make their way to the ground to do their business. Once they get down to the forest floor, they dig a hole, take a poop, then cover it up with leaves and make their way back up to the canopy.

That’s where the danger comes in. Pooping on the ground is one of the most risky things a sloth can do in life. By one estimate, up to half of sloth deaths can be linked to these rare bathroom trips. Sloths can barely walk, thanks to their long claws and limbs that are designed to hang from trees; they don't support their weight on the ground very well. (They have significantly less muscle mass than other mammals.) Instead, they crawl, dragging themselves forward with their forelimbs. That makes them laughably easy targets for predators.

Scientists aren’t entirely sure why three-toed sloths take this huge risk to poop. One study has suggested it could be related to the symbiotic relationship the animals have with the critters that live in their hair, which include a specific type of potentially nutritious algae that may benefit from the journey to the ground. That hypothesis is fairly controversial among sloth experts, though, because it’s not clear that the sloths actually eat this algae, or that it makes any kind of real impact on their diet.

For now, sloths’ dangerous bathroom habits remain mostly a mystery.

Do Dogs Understand What You’re Telling Them? Scientists Are Scanning Their Brains to Find Out

iStock/kozorog
iStock/kozorog

We all know that dogs can learn to respond to human words, but it’s not always clear what’s happening in a dog’s brain when they hear and recognize words like “cookie” and “fetch.” Do they have to rely on other clues, like gestures, to figure out what we mean by that word? Do they picture a dog biscuit when you say “cookie,” or just the sensation of eating? In a new study, scientists from Emory University and the New College of Florida tried to get to the bottom of this question by training dogs to associate certain objects with words like “blue” and “duck,” then using fMRI brain scanners to see what was happening in the dogs’ heads when they heard that word.

The study, published in Frontiers in Neuroscience, examined the brains of 12 different dogs of various breeds (you can see them below) that had been trained to associate two different objects with random words like “duck,” “blue,” and “beach ball.” Those two objects, which were different for each dog, were brought by the dogs’ owners from home or chosen from a selection of dog toys the researchers compiled. One object had to be soft, like a stuffed animal, and the other one had to be something hard, like a rubber toy or squeaky toy, to make sure the dogs could clearly distinguish between the two. The dogs were trained for several months to associate these objects with their specific assigned words and to fetch them on command.

Then, they went into the fMRI machine, where they had been trained to sit quietly during scanning. The researchers had the dogs lie in the machine while their owners stood in front of them, saying the designated name for the toys and showing them the objects. To see how the dogs responded to unknown words, they also held up new objects, like a hat, and referred to them by gibberish words.

Dogs in a science lab with toys
Prichard et al., Frontiers in Neuroscience (2018]

The results suggest that dogs can, in fact, discriminate between words they know and novel words. While not all the dogs showed the same neural response, they showed activation in different regions of their brains when hearing the familiar word versus the novel one.

Some of the dogs showed evidence of a greater neural response in the parietotemporal cortex, an area of the dog brain believed to be similar to the human angular gyrus, the region of the brain that allows us to process the words we hear and read. Others showed more neural activity in other regions of the brain. These differences might be due to the fact that the study used dogs of different sizes and breeds, which could mean differences in their abilities.

The dogs did show a surprising trend in their brains’ response to new words. “We expected to see that dogs neurally discriminate between words that they know and words that they don’t,” lead author Ashley Prichard of Emory University said in a press release. “What's surprising is that the result is opposite to that of research on humans—people typically show greater neural activation for known words than novel words." This could be because the dogs were trying extra hard to understand what their owners were saying.

The results don’t prove that talking to your dog is the best way to get its attention, though—it just means that they may really know what's coming when you say, "Want a cookie?"

Scientists Find Fossil of 150-Million-Year-Old Flesh-Eating Fish—Plus a Few of Its Prey

M. Ebert and T. Nohl
M. Ebert and T. Nohl

A fossil of an unusual piranha-like fish from the Late Jurassic period has been unearthed by scientists in southern Germany, Australian news outlet the ABC reports. Even more remarkable than the fossil’s age—150 million years old—is the fact that the limestone deposit also contains some of the fish’s victims.

Fish with chunks missing from their fins were found near the predator fish, which has been named Piranhamesodon pinnatomus. Aside from the predator’s razor-sharp teeth, though, it doesn’t look like your usual flesh-eating fish. It belonged to an extinct order of bony fish that lived at the time of the dinosaurs, and until now, scientists didn’t realize there was a species of bony fish that tore into its prey in such a way. This makes it the first flesh-eating bony fish on record, long predating the piranha. 

“Fish as we know them, bony fishes, just did not bite flesh of other fishes at that time,” Dr. Martina Kölbl-Ebert, the paleontologist who found the fish with her husband, Martin Ebert, said in a statement. “Sharks have been able to bite out chunks of flesh, but throughout history bony fishes have either fed on invertebrates or largely swallowed their prey whole. Biting chunks of flesh or fins was something that came much later."

Kölbl-Ebert, the director of the Jura Museum in Eichstätt, Germany, says she was stunned to see the bony fish’s sharp teeth, comparing it to “finding a sheep with a snarl like a wolf.” This cunning disguise made the fish a fearful predator, and scientists believe the fish may have “exploited aggressive mimicry” to ambush unsuspecting fish.

The fossil was discovered in 2016 in southern Germany, but the find has only recently been described in the journal Current Biology. It was found at a quarry where other fossils, like those of the Archaeopteryx dinosaur, have been unearthed in the past.

[h/t the ABC]

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