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Vampire Bats Regurgitate Meals for Their Friends

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Vampire bats are generous friends. When resources are scarce, they keep each other fed—literally vomiting up meals of blood for their compatriots. But they’re not equal-opportunity sharers, according to a new study in Proceedings of the Royal Society B. They keep careful track of how other vampire bats have treated them in the past.

Vampire bats feed exclusively on blood, and females often live in social groups of up to a dozen individuals. These female roost-mates help each other out, even those who aren’t related, as previous studies have shown. In this current study, two researchers from the University of Maryland and the Smithsonian Tropical Research Institute find that this sharing of food is not a random exchange, it's reciprocal.

To test how bats determine who they will share with, the researchers examined how a group of captive bats behaved when some were forced to fast, and when previous donors (including kin) were removed from the group. They found that bats that had previously shared more food with non-kin bats were more likely to get fed by others during their fasting period, and received more food. The bats also had go-to food donors—a mother and her adult daughter might be each other’s primary food donor, for instance, and would go to each other first if they failed in foraging. Deprived of those main donors, hungry bats sought out other food-sharing partners, and were most likely to be successful if they had shown generosity in the past. 

However, the bats also showed a degree of relationship repair. That is, some bats who had previously been stingy during their fast periods—because they had no food to share—seemed to try to get back into the good graces of a more generous partner by sharing significantly more food than they had before. 

The research suggests that bats have complex social lives that include keeping careful track (for weeks at a time) of who has shared with them—and who they are willing to help out in a time of need. 

[h/t: National Geographic]

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Animals
Slow Motion Is the Only Way to Appreciate a Chameleon’s Lightning-Fast Tongue
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From the unusual way they walk, to their ability to change color, the evolutionary adaptations of chameleons are pretty bizarre, and some of them remain mysterious even to scientists. Their super-powered tongues, for instance, can dart out so quickly that the movement can barely be seen with the naked eye. But modern high-speed cameras have enabled researchers at the University of South Dakota to observe this appendage at work like never before. The video below, shared over at The Kid Should See This, includes some of that groundbreaking footage, and it's pretty amazing to watch.

Shooting at 3000 frames per second, the camera was able to capture every split-second aspect of the chameleon's tongue strike. Slowed down, the video allows you to see how every component of the process works in harmony: First, muscles in the lizard’s tongue contract like the string of a bow. Then, when that tension is released, the bony base of the tongue shoots forward, pushing the sticky, elastic part toward the chameleon’s prey.

According to Christopher Anderson, one of the scientists who conducted the high-speed camera research, larger chameleons can catapult their tongues forward at distances of one to two times their body length. For smaller chameleons, this distance can reach up to two and a half times their body length. “Small chameleons need to be able to eat more food for their body size than large chameleons,” he tells bioGraphic in the video, “and so by being able to project their tongues proportionately further than these large species, they basically are opening up additional feeding opportunities to themselves that they wouldn’t have if they had a shorter tongue.”

To see one of nature’s greatest hunting tools in action, check out the full video below.

[h/t The Kid Should See This]

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There May Be an Ancient Reason Why Your Dog Eats Poop
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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]

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