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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
Slow Motion Is the Only Way to Appreciate a Chameleon’s Lightning-Fast Tongue
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From the unusual way they walk, to their ability to change color, the evolutionary adaptations of chameleons are pretty bizarre, and some of them remain mysterious even to scientists. Their super-powered tongues, for instance, can dart out so quickly that the movement can barely be seen with the naked eye. But modern high-speed cameras have enabled researchers at the University of South Dakota to observe this appendage at work like never before. The video below, shared over at The Kid Should See This, includes some of that groundbreaking footage, and it's pretty amazing to watch.

Shooting at 3000 frames per second, the camera was able to capture every split-second aspect of the chameleon's tongue strike. Slowed down, the video allows you to see how every component of the process works in harmony: First, muscles in the lizard’s tongue contract like the string of a bow. Then, when that tension is released, the bony base of the tongue shoots forward, pushing the sticky, elastic part toward the chameleon’s prey.

According to Christopher Anderson, one of the scientists who conducted the high-speed camera research, larger chameleons can catapult their tongues forward at distances of one to two times their body length. For smaller chameleons, this distance can reach up to two and a half times their body length. “Small chameleons need to be able to eat more food for their body size than large chameleons,” he tells bioGraphic in the video, “and so by being able to project their tongues proportionately further than these large species, they basically are opening up additional feeding opportunities to themselves that they wouldn’t have if they had a shorter tongue.”

To see one of nature’s greatest hunting tools in action, check out the full video below.

[h/t The Kid Should See This]

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There May Be an Ancient Reason Why Your Dog Eats Poop
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Dogs aren't known for their picky taste in food, but some pups go beyond the normal trash hunting and start rooting around in poop, whether it be their own or a friend's. Just why dogs exhibit this behavior is a scientific mystery. Only some dogs do it, and researchers aren't quite sure where the impulse comes from. But if your dog is a poop eater, it's nearly impossible to steer them away from their favorite feces.

A new study in the journal Veterinary Medicine and Science, spotted by The Washington Post, presents a new theory for what scientists call "canine conspecific coprophagy," or dogs eating dog poop.

In online surveys about domestic dogs' poop-eating habits completed by thousands of pet owners, the researchers found no link between eating poop and a dog's sex, house training, compulsive behavior, or the style of mothering they received as puppies. However, they did find one common link between the poop eaters. Most tended to eat only poop that was less than two days old. According to their data, 85 percent of poop-eaters only go for the fresh stuff.

That timeline is important because it tracks with the lifespan of parasites. And this led the researchers to the following hypothesis: that eating poop is a holdover behavior from domestic dogs' ancestors, who may have had a decent reason to tuck into their friends' poop.

Since their poop has a high chance of containing intestinal parasites, wolves poop far from their dens. But if a sick wolf doesn't quite make it out of the den in time, they might do their business too close to home. A healthier wolf might eat this poop, but the parasite eggs wouldn't have hatched within the first day or two of the feces being dropped. Thus, the healthy wolf would carry the risk of infection away from the den, depositing the eggs they had consumed away in their own, subsequent bowel movements at an appropriate distance before the eggs had the chance to hatch into larvae and transmit the parasite to the pack.

Domestic dogs may just be enacting this behavior instinctively—only for them, there isn't as much danger of them picking up a parasite at home. However, the theory isn't foolproof. The surveys also found that so-called "greedy eaters" were more likely to eat feces than dogs who aren't quite so intense about food. So yes, it could still be about a poop-loving palate.

But really, it's much more pleasant to think about the behavior as a parasite-protection measure than our best pals foraging for a delicious fecal snack. 

[h/t The Washington Post]

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