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Frogs Eat with Their Eyes—Literally

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When someone says people eat with their eyes, they usually mean that we assess and appreciate food by sight well before it ever hits our tongues. (What’s more, the appearance of food and even the container it’s in can actually change our perception of its taste.) If they’re talking about frogs, though, they mean it in a much different, more literal way. 

Scientists and nature lovers have often pointed out that frogs’ and toads’ eyes shut tight and sometimes seem to sink into their heads when they swallow food. This is because, scientists proposed, the amphibians’ eyes play a role in moving the food along. Specifically, they push food down the throat like a trash compactor. As biologist Mary Dickerson put it in 1906, “Strange as it may seem, the large eyes of the the toad can be pressed down into the mouth as far below its roof as they rise above the head, and the movement aids effectually in swallowing.” 

That does seem strange, but also really cool. The catch is that no one really tested the idea until 2004, when a team of biologists at the University of Massachusetts set out to see just what a leopard frog’s eyes are up to when it eats.

X-ray videos of the animals taken during meal time revealed that the eyes did move into the mouth, “came in contact with the prey and appeared to force it toward the pharynx.” Recordings of the electrical activity in the eye retractor muscles, meanwhile, showed that the eye retractions were active and on purpose, and that the eyes weren’t just sinking due to low pressure in the mouth below them during swallowing. Finally, an experiment where the researchers cut the nerves to the retractor muscles showed that frogs that couldn't retract their eyes were still able to swallow, but had to swallow almost twice as many times as usual to get each piece of food down. 

All this suggests, the researchers say, that frogs' eyes do help them swallow by aiding the tongue in pushing food into the throat, and probably contribute more to the process when their meals are larger. 

[h/t Io9]

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Animals
7 Fun Facts for World Elephant Day
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Happy World Elephant Day! Celebrate the occasion with some facts about everyone's favorite gentle giant. 

1. ELEPHANTS CAN RECOGNIZE OTHER ELEPHANT CARCASSES.

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The University of Sussex's Karen McComb told National Geographic that elephants "become excited and agitated if they come across a dead elephant," and, in particular, will investigate skulls and tusks. McComb teamed up with researchers at the Amboseli Elephant Research Project in Kenya to study the behavior, showing wild elephants a range of objects that included skulls. They found that the elephants examined skulls—and tusks in particular—of their own kind twice as long as other skulls, and examined tusks six times as long as they did pieces of wood. They were even able to recognize elephant skulls with the tusks removed, but didn't show preference for certain elephant skulls over others, which suggests they didn't know which skulls belonged to their own relatives. "Animals that are intensely social in life may be most likely to display an interest in their dead," McComb told National Geographic. "But what goes on in their minds while they are doing this is a total mystery."

2. THEY'RE SCARED OF BEES.

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Forget about mice scaring off elephants: When farmers need to keep elephants away from their crops, they should use bees. Researchers in Kenya discovered that even the recorded sound of buzzing bees was enough to make elephants retreat—and cause them to emit low-frequency sound, inaudible to humans, that warns other elephants. "It's impossible to cover Africa in electric fences," Lucy King, author of the paper, told the Huffington Post. "The infrastructure doesn't exist in many places and it would restrict animals' movement." But something like a bee fence—hives strung on strong wires a certain distance apart that would move when elephants walked into them, disturbing the hives—"could be a better way to direct elephants away from farmers' crops," she said.

3. THEY MIGHT UNDERSTAND POINTING.

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Human adults and babies often use pointing as a way to nonverbally get a message across, but not many other animals grasp the concept. But according to a two-month study of 11 tame African elephants, these pachyderms might be able to: When presented with two identical buckets and pointed in the direction of the one containing food, elephants picked up on the cue fairly consistently: Elephants had a success rate of 67.5 percent (1-year-old humans have a success rate of 72.7 percent). But an earlier study of Asian elephants indicated that they don’t notice pointing gestures, which is a bit of a mystery.

4. ONE ELEPHANT CAN "TALK." 

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Koshik, an elephant in a South Korean zoo, developed the ability to imitate the sounds of five words he's heard from his trainer—annyeong (hello), anja (sit down), aniya (no), nuwo (lie down), and joa (good)—by sticking his trunk in his mouth. The scientists who first noticed Koshik’s ability speculate that he learned to “talk” because he was lonely.

5. THEY'RE DIGITIGRADES.

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It's Latin for "finger walking," and what it means is that elephants walk on their toes (there are five of them, as well a sixth false toe). According to the book Mammal Anatomy: An Illustrated Guidemost of the animals' weight "rests on a broad pad of elastic tissue behind the toes" which "acts as a shock absorber and prevents the skeleton from jolting too much when the animals walk. It also allows elephants to move surprisingly quietly despite their size."

6. AN ELEPHANT PREGNANCY LASTS ABOUT TWO YEARS.

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If you thought being pregnant for nine months was bad, be glad you're not an elephant, which can be pregnant for up to 680 days, according to the BBC. All that time in the oven has a benefit, though: Elephant calves are born with highly-developed brains, capable of learning their herds’ complex social structures and ready to put their trunks to use.

7. NINETY-SIX ELEPHANTS ARE KILLED IN AFRICA EVERY DAY.

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Unfortunately, elephant poaching remains a very big problem: An estimated 35,000 elephants are killed annually, their tusks sold illegally in the ivory market. Do the math, and that comes out to nearly 96 elephants every day. Find out what you can do to help elephants and stop poaching at 96Elephants.org.

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Animals
Audible Launches 'Audible for Dogs' to Help Pet Parents Calm Their Stressed Canines
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In addition to a mutual love of hamburgers and lazy sunny afternoons in the backyard, dog owners can now share their affinity for audiobooks with their furry friends. As Fast Company reports, Audible has launched Audible for Dogs, a new service designed to keep canines relaxed while their owners are away from home.

Some people play music for lonely dogs, but according to an Audible press release, a 2015 academic study revealed that audiobooks worked better than tunes to calm stressed-out pets. To investigate the phenomenon further, Audible teamed up with Cesar Millan, the dog behaviorist who’s better known as the "Dog Whisperer." Their own research—which they conducted with 100 dogs, in partnership with Millan’s Dog Psychology Center in Santa Clarita, California—found that 76 percent of participating dog owners noticed that audiobooks helped their pets chill out.

Dog owners can play Cesar Millan’s new Guide to Audiobooks for Dogs—which is both written and narrated by Millan—for initiation purposes, along with a curated rotating selection of dog-focused audiobook titles including Trevor Noah’s Born a Crime: Stories from a South African Childhood, performed by Trevor Noah; Jane Austen’s Pride and Prejudice, performed by Rosamund Pike; and W. Bruce Cameron’s A Dog’s Purpose, performed by William Dufris. Each title features a special video introduction by Millan, in which he explains why the book is suited for doggy ears. (Pro tip: According to Audible’s research, dogs prefer narrators of the same gender as their primary owners, and books played at normal volume on an in-home listening device.)

Don’t have an Audible subscription, but want to see if your dog succumbs to the purportedly calming magic of audiobooks? New listeners can listen to one free Audible for Dogs selection with a 30-day membership trial.

[h/t Fast Company]

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