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Some Spiders Can Eat Bats

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Wikimedia Commons

One night in 1941, G.C. Bhattacharya walked in to a cowshed in Calcutta, India and saw a small figure struggling and twisting against one of the walls. It was a small bat fighting its way out from in between two of the bamboo strips that the shed's walls were made of.

As he got closer, Bhattacharya saw that the crevice was not the only thing the bat was struggling with. A large spider was holding the bat by the neck with its mandibles and biting it. The bat gasped and screamed and struggled against its attacker, but the spider would not let go. When Bhattacharya lit a torch to help him see better, the bat shrieked and flapped its wings, freeing itself from the crevice, but not from the spider.

After managing to crawl along the wall a little bit, the bat exhausted itself and stopped moving for around 20 minutes before flapping one wing a few last times and stretching it out, as if reaching out to Bhattacharya for help.

The battle's victor clearly decided, Bhattacharya captured both the bat and the spider in a glass jar and brought them home for closer observation. The next morning, he found the spider resting upside down at the top of the jar, and the bat lying stiff on the bottom with visible injuries to its neck. It had not survived the night.

Bats’ most prominent predators are owls, hawks, and snakes, but a study published earlier this year reveals that spiders are also a formidable enemy, and that plenty of other people have witnessed incidents of chiropterophagy like the one Bhattacharya did.

To see just how common spider predation on bats was, Martin Nyffeler from the University of Basel (Switzerland) and Mirjam Knörnschild from the University of Ulm (Germany), combed through published research, blog posts and Flickr photographs and interviewed scientists who studied spiders and bats and veterinarians who worked at bat hospitals.

Altogether, they were able to gather 52 reports of bats being caught by spiders (whether in webs, or being actively hunted by non-web-building spiders), 29 of which had never been published before. Reports came in from every continent except Antarctica, but more than three-quarters of the cases happened in tropical areas around the Equator, most often in Latin America and Southeast Asia.

In most of these incidents, the spiders were large (10–15 cm legspan, ~1–7 g weight) web builders, mainly from the genus Nephila. These spiders are nocturnal hunters that spin webs up to 1.5 m across, and occasionally get together to build several webs connected to each other. The victims, meanwhile, were overwhelmingly small (10–24 cm wingspan, 3–8 g weight) insect-eaters, mostly from the family Vespertilionidae.

It doesn’t seem like the spiders intended to catch a bat every time. In some of these incidents, the spider completely ignored the bat caught in its web. Other times, the bat was known to be dead already before a spider found and began eating it. In these cases, it appears that bats simply sometimes get stuck in spiderwebs and die of exposure or starvation without being preyed upon, and sometimes spiders simply scavenge the body of dead bats without having killed them. In many cases, though, it was clear that spiders were intentionally killing and eating bats, immobilizing ones that got caught in their webs with a silk wrap, biting them and later consuming them.

Fifty-two spider-on-bat battles doesn’t not seem like a whole lot, especially when you consider that these reports cover a timespan of 100+ years. Indeed, Nyffeler and Knörnschild were actually surprised that that was all they found, given the sheer number of spiderwebs that must stand in the way of bats’ flight paths throughout the tropical parts of the world. They suggest that bats may be very good at avoiding spiderwebs with the help of echolocation. While the silk threads that make up the web are likely too thin to echolocate, the denser decorations and barriers that spiders place on them—plus the spider itself sitting in the center of web—should be large enough for the bats to detect in flight.

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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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