Science

Bat-Eating Spiders Are Everywhere

By Sean Kane , Mar 18, 2013 06:11 PM EDT
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Spiders capable of eating bats live everywhere that we do.

New research reveals that bat-catching spiders live on every continent except for Antarctica.

Population-wise, bats are some of the most successful mammals on the planet. So successful that the 1,200 bat species around the world account for about one-fifth of all mammals. Much of this has to do with the flying rodents lacking many natural predators, other than owls, hawks and snakes. But bats are also preyed upon by some invertebrates. Giant centipedes have been seen killing and eating bats in a cave in Venezuela, whip spiders in Caribbean caves were seen eating dead bats from cave floors and even cockroaches have been observed feeding on bat pups that fall to cave floors.

And new research shows that spiders hunting and feeding on vertebrates, especially bats, is much more common than previously thought. A recent study published online last week in the journal PLOS One, came to this conclusion while studying the web-building Argiope savignyi species and the Tarantula species Poecilotheria rufilata, reported Live Science.

If you live far from the equator, you’re in luck. About 90 percent of bat-catching spiders (that we know of) live in the third of the Earth around the equator. And 40 percent live in the neotropics, the area that includes the entire South American continent, and the small tropical area of North America (coastal Mexico, southern Latin America, the Caribbean and southern Florida).

Almost all (88 percent) of the bat-hunting arachnids are web-building spiders. The invertebrates are small, with leg-spans of four to six inches, but build orb-webs as large as five feet wide. In Panama and Costa Rica, these spiders built their giant orb-webs near buildings where bat colonies roost. In the greater Hong Kong area, their webs were found in parks and forests.

And 12 percent of the bat-killing spiders observed hunted without webs. Tarantulas were observed killing small bats in the Peruvian and Ecuadorian rainforests, and on forest floors in northeastern Brazil.

The bats trapped in the spider webs were often not much bigger than their predators. The bats typically found in spider webs had wingspans of about four to 9.5 inches. The spiders were observed attacking and killing their trapped prey, but some of the bats also succumbed to overheating, dehydration, starvation and exhaustion. Catching bats was well worth the effort that spiders put into the hunt; if web-building Nephila pilipes managed to catch a bat that weighed just two grams, the flying rodent would provide the spider with 10 times the mass of a normal day’s insect prey.

So while a Batman versus Spiderman battle might take up a few comic book issues, in the nature world, Peter Parker is the clear winner.

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