The tricky thing, though, is detecting a behavioral response to those higher sounds. In fact, those higher frequencies fall in the same range of sounds that predators, including birds, make as they move around or call, so it makes sense for spiders to listen for those frequencies, says Damian Elias, a biologist at the University of California, Berkeley who wasn’t involved in the study. Spiders may be using their sense of hearing for a range of things, including eavesdropping on predators, she says. Still, the fact that the spiders can detect higher frequencies means that these sounds are probably important to them, says Jayne Yack, a neuroethologist at Carleton University in Ottawa who wasn’t involved in the research. When it hears prey fly behind its back, the spider swings backward and, like a fisher throwing a net, it flicks a rectangular web at its would-be meal. (Humans generally hear between 20 Hz and 20,000 Hz.)Īn ogre-faced spider dangles from its web as it waits for prey in the dark. Spikes of activity revealed that the spiders can sense airborne sounds between 100 and 10,000 hertz, though not at every frequency, the team found. Stafstrom and colleagues inserted microelectrodes into the brains of 13 ogre-faced spiders, and then played tones of varying frequencies from a speaker while monitoring the spiders’ auditory nerve cell activity. Surprisingly, ogre-faced spiders can also hear fairly high frequencies, Stafstrom says. That includes jumping spiders, which respond to low frequencies ( SN: 10/15/16). But now, he and his colleagues have looked at several spider species, and most can hear using specialized organs on their legs, he says. “A couple years ago, we didn’t really have a great idea that spiders could hear,” says Jay Stafstrom, a sensory ecologist at Cornell University. This behind-the-back hunting technique is one clue that the spiders can hear an unexpectedly wide range of sounds, researchers report online October 29 in Current Biology. When an insect flies behind the dangling arachnid, the spider swings backward, casting the web toward the prey. Hanging upside down, the spider weaves a rectangular web between its legs. But the ogre-faced spider ( Deinopis spinosa) uses its sense of hearing to take its web to the prey. Some spiders wait for prey to come and tickle their web.
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