Poop-Eating Naked Mole Rats Get Suckered Into Babysitting

The animal kingdom is filled with deadbeat dads. Raising kids takes energy, and nature often rewards the father who walks (or hops or swims or flies) away. Fewer and farther between are the animal moms who just can’t be bothered. Most of them leave their young to fend for themselves, but there are some who get other animals to do the child-rearing for them.

Naked mole rat mothers definitely fall into that category. Dominant rats bear pups, then leave the rest to their subordinates. Why would the subordinates agree to this plan? Two Japanese researchers have a theory: Pregnancy hormones in the mother’s poop trick the other rats into feeling maternal.

Like ants and bees, naked mole rats follow a eusocial colony structure. That means that there’s one queen rat, a few virile males, and a whole bunch of female workers. The queen’s job is to make babies; the male rats help make babies; and the worker rats do absolutely everything else. This includes digging tunnels, keeping the chambers clean, and defending the colony. It also means raising a whole lot of rat babies. 

There’s something else you should know about naked mole rats: they eat poop. The rats’ favorite foods are roots and plant bulbs, which can be pretty hard to digest—so the rats chow down twice. They eat, pass their meal, then eat it again. But they don’t just eat their own poop. The rats use specialized bathroom chambers, which means that their recycled food could have come from anyone—including the queen.

Worker rats don’t have mature sex organs of their own, which means they don’t make sex hormones. But when the queen is knocked up, her poop is positively packed with estrogen. As reported this week in Nature News, researchers from Japan's Azabu University recently presented research findings at the Society for Neuroscience meeting in Chicago that suggest the queen’s hormones inspire maternal impulses in her subordinates. 

First, the scientists played a recording of crying rat pups for a group of subordinate female rats. The worker rats whose queen had just given birth were very interested in the pups’ cries. The other workers were not.

The next step was finding out how the queen rat’s poop affected her workers. The researchers gave subordinate rats hormones from their pregnant queen’s feces. Sure enough, the worker rats’ estrogen levels increased, as did their interest in the sound of crying rat babies. 

NOTE: Naked mole rats are not moles, or rats, or even naked, but that’s a story for another day.

There May Be an Ancient Reason Why Your Dog Eats Poop

Dogs aren't known for their picky taste in food, but some pups go beyond the normal trash hunting and start rooting around in poop, whether it be their own or a friend's. Just why dogs exhibit this behavior is a scientific mystery. Only some dogs do it, and researchers aren't quite sure where the impulse comes from. But if your dog is a poop eater, it's nearly impossible to steer them away from their favorite feces.

A new study in the journal Veterinary Medicine and Science, spotted by The Washington Post, presents a new theory for what scientists call "canine conspecific coprophagy," or dogs eating dog poop.

In online surveys about domestic dogs' poop-eating habits completed by thousands of pet owners, the researchers found no link between eating poop and a dog's sex, house training, compulsive behavior, or the style of mothering they received as puppies. However, they did find one common link between the poop eaters. Most tended to eat only poop that was less than two days old. According to their data, 85 percent of poop-eaters only go for the fresh stuff.

That timeline is important because it tracks with the lifespan of parasites. And this led the researchers to the following hypothesis: that eating poop is a holdover behavior from domestic dogs' ancestors, who may have had a decent reason to tuck into their friends' poop.

Since their poop has a high chance of containing intestinal parasites, wolves poop far from their dens. But if a sick wolf doesn't quite make it out of the den in time, they might do their business too close to home. A healthier wolf might eat this poop, but the parasite eggs wouldn't have hatched within the first day or two of the feces being dropped. Thus, the healthy wolf would carry the risk of infection away from the den, depositing the eggs they had consumed away in their own, subsequent bowel movements at an appropriate distance before the eggs had the chance to hatch into larvae and transmit the parasite to the pack.

Domestic dogs may just be enacting this behavior instinctively—only for them, there isn't as much danger of them picking up a parasite at home. However, the theory isn't foolproof. The surveys also found that so-called "greedy eaters" were more likely to eat feces than dogs who aren't quite so intense about food. So yes, it could still be about a poop-loving palate.

But really, it's much more pleasant to think about the behavior as a parasite-protection measure than our best pals foraging for a delicious fecal snack. 

[h/t The Washington Post]

Big Questions
What Makes a Cat's Tail Puff Up When It's Scared?

Cats wear their emotions on their tails, not their sleeves. They tap their fluffy rear appendages during relaxing naps, thrash them while tense, and hold them stiff and aloft when they’re feeling aggressive, among other behaviors. And in some scary situations (like, say, being surprised by a cucumber), a cat’s tail will actually expand, puffing up to nearly twice its volume as its owner hisses, arches its back, and flattens its ears. What does a super-sized tail signify, and how does it occur naturally without help from hairspray?

Cats with puffed tails are “basically trying to make themselves look as big as possible, and that’s because they detect a threat in the environment," Dr. Mikel Delgado, a certified cat behavior consultant who studied animal behavior and human-pet relationships as a PhD student at the University of California, Berkeley, tells Mental Floss. The “threat” in question can be as major as an approaching dog or as minor as an unexpected noise. Even if a cat isn't technically in any real danger, it's still biologically wired to spring to the offensive at a moment’s notice, as it's "not quite at the top of the food chain,” Delgado says. And a big tail is reflexive feline body language for “I’m big and scary, and you wouldn't want to mess with me,” she adds.

A cat’s tail puffs when muscles in its skin (where the hair base is) contract in response to hormone signals from the stress/fight or flight system, or sympathetic nervous system. Occasionally, the hairs on a cat’s back will also puff up along with the tail. That said, not all cats swell up when a startling situation strikes. “I’ve seen some cats that seem unflappable, and they never get poofed up,” Delgado says. “My cats get puffed up pretty easily.”

In addition to cats, other animals also experience piloerection, as this phenomenon is technically called. For example, “some birds puff up when they're encountering an enemy or a threat,” Delgado says. “I think it is a universal response among animals to try to get themselves out of a [potentially dangerous] situation. Really, the idea is that you don't have to fight because if you fight, you might lose an ear or you might get an injury that could be fatal. For most animals, they’re trying to figure out how to scare another animal off without actually going fisticuffs.” In other words, hiss softly, but carry a big tail.


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