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Watch Giant Spider Crabs Form a Thick, Living Carpet

The ocean is a weird place. Today’s proof? The video above, in which hundreds of thousands of crabs weave themselves into a vast living carpet.

The stacking of the crabs is an annual event in Melbourne’s Port Phillip Bay. The gargantuan crabs can reach nearly 30 inches across from claw to claw. With huge claws and thick carapaces, you’d think they’d be all set for self-defense. But once a year, during molting season, the giant spider crabs become very vulnerable.

Like lobsters, crabs continually grow inside their shells, but at a certain point, their shells stop growing. To keep from being crushed inside their own exoskeletons, crabs have to shuck their hard shells and grow new ones. But the moment they climb out of their old armor into the water, the newly de-shelled crabs lose all their defense mechanisms while, unfortunately for them, retaining their deliciousness.

Here’s where the carpet comes in. Relying on the principle of safety in numbers, the crabs converge to form a dense, clacking mat of bodies. The crabs have no concern for personal space, and will stack themselves up to 10 crabs high in a mass that stretches hundreds of meters across the sand. In the hour it takes them to molt and the period of tenderness that comes after that, the crabs can rest assured that no predators will eat them all.

This may seem uncomfortable and kind of creepy to us, but the alternative, as you can see below, is much worse.

Images from YouTube // The Nature of Science

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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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