Although they have few natural enemies, bats (with more than 1,200 species worldwide) are a favorite prey of spiders everywhere, except Antarctica. In fact, researchers Martin Nyffeler and Mirjam Knörnschild revealed that there are “52 cases of bat-catching spiders on earth, with approximately 90% of known species found to live in the warmer regions, particularly surrounding the equator.” About 40% live in the whole of South America, and the tropical regions of North America, while nearly a third live in Asia and more than a sixth live in Australia and Papua New Guinea.
According to their study (which examined 100 years of evidence), Nyffeler and Knörnschild found that web-building spiders accounted for 80% of the reported cases of bat catches made by giant tropical orb-weaving spiders (having a leg-span of 4 to 6 inches) seen catching bats in huge, strong orb-webs up to 5 feet wide in Panama and Costa Rica. These spiders had built their webs near buildings inhabited by bat colonies. Bat-catching via spiderwebs was also witnessed particularly often in the parks and forests of the greater Hong Kong area.*
Another 12% of bat kills were made by spiders that hunt without webs, including tarantulas, which were seen eating small bats in tropical rainforests in Peru and eastern Ecuador and on the forest floor in northeastern Brazil. A reddish parachute tarantula (Poecilotheria rufilata) was also seen predating on a small bat in Kerala, India, while a huntsman spider (Heteropoda venatoria) was observed capturing and killing a small bat in a shed near Kolkata, India. An attempt by a large fishing spider (Dolomedes triton) to kill a bat pup was also witnessed below a bridge in Indiana.
*Future research may investigate whether the huge webs that sometimes block the entrances of tropical bat caves in east and southeast Asia and South America may occasionally snag any members of the giant swarms of bats that emerge from the caves at night.
More details of the above study can be found in the March 13th online edition of the Journal PLOS One.