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David M. Jensen via Wikimedia Commons // CC BY-SA 3.0
David M. Jensen via Wikimedia Commons // CC BY-SA 3.0

Capuchin Monkeys Can Be Spiteful Jerks, Study Finds

David M. Jensen via Wikimedia Commons // CC BY-SA 3.0
David M. Jensen via Wikimedia Commons // CC BY-SA 3.0

Humanity’s throne atop the animal kingdom is wobbling these days. Research has shown that non-human animals can make complex tools, give gifts to their friends, and even read complicated medical images. But it can’t all be good news. Some of humanity’s less desirable traits have parallels in our non-human relatives. In fact, a recent study published in Evolution and Human Behavior shows that capuchin monkeys share our capacity for acting spiteful.

We’ve all seen animals behaving in ways we could interpret as spiteful. But scientists have argued that there’s really no way to understand the motivations of, say, a dog that chews up your socks, because there are just too many variables at play.

So scientists designed an experiment that would allow them to test for spite and spite alone. “One hallmark of the human species is the fact that we’re willing to make a special effort to punish those who violate social norms,” senior author Laurie Santos said in a press statement. “We punish those who take resources unfairly and those who intend to do mean things to others. Many researchers have wondered whether this motivation is unique to our species.”

Capuchin monkeys (Cebus apella) are carefully attuned to one another’s behavior. Previous experiments with C. apella have shown that capuchins pay attention to how fairly or evenly resources are distributed—that is, if another monkey got more of something. When they have to complete a group task, capuchins tend to avoid teaming up with monkeys who have a track record of being uncooperative or selfish. 

To complete the research, the researchers first set up collapsible tables attached to long ropes. Then, they gave the monkeys some time to learn how the rope-table setup worked. When the scientists were sure the monkeys understood the consequences of pulling the rope, the capuchins were divided into two groups: subjects and stooges.

During each test, the researchers sat one stooge monkey at the table and gave control of the rope to a subject monkey. Then the food came out. It was good food, too—Fruity Pebbles cereal (which the researchers describe as “a highly valued food reward”) and marshmallow fluff. The stakes were high.

There was no mistaking the intentions of these monkeys. Time and time again, subject monkeys would yank the rope to collapse the stooges’ table and make the food disappear. This was true even when the stooges had done nothing to get the food; in other words, the subjects punished them for getting food even when they were innocent.

“Our study provides the first evidence of a non-human primate choosing to punish others simply because they have more,” first author Kristin Leimgruber, said in the press release. “This sort of ‘if I can't have it, no one can’ response is consistent with psychological spite, a behavior previously believed unique to humans.”

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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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