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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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Big Questions
Why Do Cats Freak Out After Pooping?
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Cats often exhibit some very peculiar behavior, from getting into deadly combat situations with their own tail to pouncing on unsuspecting humans. Among their most curious habits: running from their litter box like a greyhound after moving their bowels. Are they running from their own fecal matter? Has waste elimination prompted a sense of euphoria?

Experts—if anyone is said to qualify as an expert in post-poop moods—aren’t exactly sure, but they’ve presented a number of entertaining theories. From a biological standpoint, some animal behaviorists suspect that a cat bolting after a deposit might stem from fears that a predator could track them based on the smell of their waste. But researchers are quick to note that they haven’t observed cats run from their BMs in the wild.

Biology also has a little bit to do with another theory, which postulates that cats used to getting their rear ends licked by their mother after defecating as kittens are showing off their independence by sprinting away, their butts having taken on self-cleaning properties in adulthood.

Not convinced? You might find another idea more plausible: Both humans and cats have a vagus nerve running from their brain stem. In both species, the nerve can be stimulated by defecation, leading to a pleasurable sensation and what some have labeled “poo-phoria,” or post-poop elation. In running, the cat may simply be working off excess energy brought on by stimulation of the nerve.

Less interesting is the notion that notoriously hygienic cats may simply want to shake off excess litter or fecal matter by running a 100-meter dash, or that a digestive problem has led to some discomfort they’re attempting to flee from. The fact is, so little research has been done in the field of pooping cat mania that there’s no universally accepted answer. Like so much of what makes cats tick, a definitive motivation will have to remain a mystery.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Watch a School of Humpback Whales 'Fish' Using Nets Made of Bubbles 

Just like humans, humpback whales catch many fish at once by using nets—but instead of being woven from fibers, their nets are made of bubbles.

Unique to humpbacks, the behavior known as bubble-net feeding was recently captured in a dramatic drone video that was created by GoPro and spotted by Smithsonian. The footage features a school of whales swimming off Maskelyne Island in British Columbia, Canada, in pursuit of food. The whales dive down, and a large circle of bubbles forms on the water's surface. Then, the marine mammals burst into the air, like circus animals jumping through a ring, and appear to swallow their meal.

The video offers a phenomenal aerial view of the feeding whales, but it only captures part of the underwater ritual. It begins with the group's leader, who locates schools of fish and krill and homes in on them. Then, it spirals to the water's surface while expelling air from its blowhole. This action creates the bubble ring, which works like a net to contain the prey.

Another whale emits a loud "trumpeting feeding call," which may stun and frighten the fish into forming tighter schools. Then, the rest of the whales herd the fish upwards and burst forth from the water, their mouths open wide to receive the fruits of their labor.

Watch the intricate—and beautiful—feeding process below:

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