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Illustrator unknown via Wikimedia Commons // Public Domain
Illustrator unknown via Wikimedia Commons // Public Domain

These Fish Can Recognize Human Faces

Illustrator unknown via Wikimedia Commons // Public Domain
Illustrator unknown via Wikimedia Commons // Public Domain

We really need to stop underestimating our fellow creatures. A new study adds a talented tropical fish to the swelling ranks of non-human animals that can tell humans apart. The research was published in the journal Scientific Reports. 

Facial recognition is a vital but complex task—so complex that humans have an entire region in our brains dedicated to it. And because it’s such a sophisticated process, scientists used to assume that we were the only animals that could do it. Then that circle widened a little bit to include other primates. But that circle just keeps growing, and currently includes octopuses, bees, and at least four types of birds. This is, admittedly, kind of strange; with the possible exception of birds, none of these animals have any natural need to tell people apart. 

Nor do fish. And like the cognitive abilities of birds, bees, and cephalopods, fishes’ mental skills have been more or less written off until quite recently. With this fact in mind, a team of researchers from the UK and Australia decided to find out if fish were up to the task. 

One species, the archerfish (Toxotes chatareus), seemed especially well-suited for the experiment. Archerfish are amazing creatures with a super-cool hunting strategy: They wait near the water’s surface for an insect to land on a nearby leaf, then shoot a jet of water at the bug, knocking it into the water. 

Illustration: Pearson Scott Foresman via Wikimedia Commons // Public Domain

Their aim is superb, and their vision acute, which suggests fairly sophisticated mental function. It also makes them great experimental subjects, since they can be trained to choose an object or image by spitting at it. 

The new study consisted of training and two experiments. First, researchers set up a screen above a tank holding a single fish. To see if the fish could tell the difference between two faces, the scientists displayed two faces on the screen, then attempted to train the fish to spit water at only one of them whenever it appeared. The training worked, and quickly, too; within just a few sessions, all the fish had learned to spit at the right face.

Image Credit: Newport et al. 2016.Nature Communications

Then the researchers brought back the same fish and exposed them to lots and lots of faces—44, to be precise. The goal was to see if the fish could still pick out the face they learned in the first round of training. To make it even harder, the researchers then cut all the face images into oval shapes and displayed them in grayscale so the fish couldn’t rely on more obvious cues like face shape or color. 

But the fish didn’t need color or shape. As in their hunting, the archerfish were incredibly accurate when it came to spotting faces. In the first round of 44 faces, the fish subjects averaged 81 percent accuracy. Once the obvious cues were removed they did even better, selecting the right face 86 percent of the time.   

“Fish have a simpler brain than humans and entirely lack the section of the brain that humans use for recognizing faces,” said lead author and Oxford University zoologist Cait Newport in a press statement. “The fact that archerfish can learn this task suggests that complicated brains are not necessarily needed to recognize human faces.”

 

 

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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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