From there, Catania repeated the observation in more controlled environments -- boxes filled with dirt and a known number of worms, into which he put a mole and recorded the worms' behavior. In trials in an outdoor enclosure containing 300 worms and one mole, one third of the worms came to the surface within an hour. In contrast, Catania measured the worms' response to a rainstorm. Only six earthworms came to the surface over three trials, even though water was standing on the soil surface by the end of the trial. Afterward, the worms appeared healthy; they had not drowned. Catania also made recordings of both grunting and mole sounds and showed that the sound spectra overlapped. All of this points to moles, not rain, as the trigger to flee. (But why, then, do worms come to the surface during rainstorms, if they don't drown? Catania suggests that some species of worm may be more sensitive to oxygen, and therefore to rain, than others.) He published his results this week in the open-access journal PLoS ONE. In another paper published this week in Biology Letters, a team including Mac Callaham at the U.S. Geological Survey in Athens, Ga., showed that recordings of the worm grunting vibrations will bring worms to the surface, and that more worms surface nearer to the source of the vibrations, where they are stronger. "It seems remarkable that they would give up their safe haven and expose themselves to dry air and other predators," Bill Kristan, a neurobiologist at the University of California, San Diego told Discovery News. "It must be a really strong motivator. It's a very strong response. You don't have to do a video and look at subtle little movements. These guys are running out of their holes." "I think it's a wonderful combination of folk science and historical science and up-to-date science," Kristan said. "Darwin had it right 150 years ago." "I'm jealous as hell that somebody could have that much fun and make a really interesting insight," he added. "I think it's one of the most enjoyable papers I've ever read." Related Links: Treehugger: University Administrator Falls in Love With Worms |
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