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Wikimedia Commons
Wikimedia Commons

Some Spiders Can Eat Bats

Wikimedia Commons
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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Animals
Pigeons Are Secretly Brilliant Birds That Understand Space and Time, Study Finds
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Of all the birds in the world, the pigeon draws the most ire. Despite their reputation as brainless “rats with wings,” though, they’re actually pretty brilliant (and beautiful) animals. A new study adds more evidence that the family of birds known as pigeons are some of the smartest birds around, as Quartz alerts us.

In addition to being able to distinguish English vocabulary from nonsense words, spot cancer, and tell a Monet from a Picasso, pigeons can understand abstract concepts like space and time, according to the new study published in Current Biology. Their brains just do it in a slightly different way than humans’ do.

Researchers at the University of Iowa set up an experiment where they showed pigeons a computer screen featuring a static horizontal line. The birds were supposed to evaluate the length of the line (either 6 centimeters or 24 centimeters) or the amount of time they saw it (either 2 or 8 seconds). The birds perceived "the longer lines to have longer duration, and lines longer in duration to also be longer in length," according to a press release. This suggests that the concepts are processed in the same region of the brain—as they are in the brains of humans and other primates.

But that abstract thinking doesn’t occur in the same way in bird brains as it does in ours. In humans, perceiving space and time is linked to a region of the brain called the parietal cortex, which the pigeon brains lack entirely. So their brains have to have some other way of processing the concepts.

The study didn’t determine how, exactly, pigeons achieve this cognitive feat, but it’s clear that some other aspect of the central nervous system must be controlling it. That also opens up the possibility that other non-mammal animals can perceive space and time, too, expanding how we think of other animals’ cognitive capabilities.

[h/t Quartz]

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The Queen's Racing Pigeons Are in Danger, Due to an Increase in Peregrine Falcons
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Queen Elizabeth is famous for her love of corgis and horses, but her pet pigeons don't get as much press. The monarch owns nearly 200 racing pigeons, which she houses in a luxury loft at her country estate, Sandringham House, in Norfolk, England. But thanks to a recent boom in the region’s peregrine falcon population, the Queen’s swift birds may no longer be able to safely soar around the countryside, according to The Telegraph.

Once endangered, recent conservation efforts have boosted the peregrine falcon’s numbers. In certain parts of England, like Norfolk and the city of Salisbury in Wiltshire, the creatures can even find shelter inside boxes installed at local churches and cathedrals, which are designed to protect potential eggs.

There’s just one problem: Peregrine falcons are birds of prey, and local pigeon racers claim these nesting nooks are located along racing routes. Due to this unfortunate coincidence, some pigeons are failing to return to their owners.

Pigeon racing enthusiasts are upset, but Richard Salt of Salisbury Cathedral says it's simply a case of nature taking its course. "It's all just part of the natural process,” Salt told The Telegraph. "The peregrines came here on their own account—we didn't put a sign out saying 'room for peregrines to let.' Obviously we feel quite sorry for the pigeons, but the peregrines would be there anyway."

In the meantime, the Queen might want to keep a close eye on her birds (or hire someone who will), or consider taking advantage of Sandringham House's vast open spaces for a little indoor fly-time.

[h/t The Telegraph]

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