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Vampire Bats Regurgitate Meals for Their Friends

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Vampire bats are generous friends. When resources are scarce, they keep each other fed—literally vomiting up meals of blood for their compatriots. But they’re not equal-opportunity sharers, according to a new study in Proceedings of the Royal Society B. They keep careful track of how other vampire bats have treated them in the past.

Vampire bats feed exclusively on blood, and females often live in social groups of up to a dozen individuals. These female roost-mates help each other out, even those who aren’t related, as previous studies have shown. In this current study, two researchers from the University of Maryland and the Smithsonian Tropical Research Institute find that this sharing of food is not a random exchange, it's reciprocal.

To test how bats determine who they will share with, the researchers examined how a group of captive bats behaved when some were forced to fast, and when previous donors (including kin) were removed from the group. They found that bats that had previously shared more food with non-kin bats were more likely to get fed by others during their fasting period, and received more food. The bats also had go-to food donors—a mother and her adult daughter might be each other’s primary food donor, for instance, and would go to each other first if they failed in foraging. Deprived of those main donors, hungry bats sought out other food-sharing partners, and were most likely to be successful if they had shown generosity in the past. 

However, the bats also showed a degree of relationship repair. That is, some bats who had previously been stingy during their fast periods—because they had no food to share—seemed to try to get back into the good graces of a more generous partner by sharing significantly more food than they had before. 

The research suggests that bats have complex social lives that include keeping careful track (for weeks at a time) of who has shared with them—and who they are willing to help out in a time of need. 

[h/t: National Geographic]

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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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