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Courtesy of Andreas Nieder

How Do Crows Count?

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Courtesy of Andreas Nieder

Crows are smart cookies. They can grasp analogies, use tools, and have bested human children in intelligence tests. They’re also decent at counting. 

Birds show an ability to keep track of numbers even without the parts of the brain that primates use to count. So how do they do it? A new study in the journal PNAS finds that even though birds and primates evolved with different brain structures, they developed similar neural processes to deal with quantification. 

Mammal brains feature a six-layered neocortex, a thin structure surrounding the brain which scientists think is involved in higher-level cognition. Birds and reptiles, by contrast, don’t have a neocortex. But, even though crows don’t have the brain structure that mammals like chimps and humans use to keep track of numbers, they somehow accomplish similar tasks. They do this using the nidopallium caudolaterale, a front part of the bird brain that’s comparable to (but not exactly like) a human’s prefrontal cortex.

Researchers from the Institute of Neurobiology in Tübingen, Germany, trained two crows to count, having them identify images with the same number of dots on a screen. They then recorded the crows’ brain activity during the task, checking in on 499 random neurons. About 20 percent of them fired during the tests. 

Certain neurons in the nidopallium caudolaterale needed to fire for the crows to count correctly. The researchers write that “if the neurons did not properly encode their preferred numerosity, the crow was prone to make mistakes.” These neurons contributed to “high-level, abstract visual representations” of numbers that allowed the crows to count properly. Essentially, the chemical codes that allow the brain to count looked similar to those seen in primates—but the structures were different. 

Determining how the brains of birds work helps scientists understand evolution. Similarities between the functions of mammal and bird brains could indicate that certain abilities evolved in a common ancestor, or that particular ways of coding information came about independently in different species. 

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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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