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No. 98: Mar-Apr 1995

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Some Shaky Observations

Back in SF#65, we offered an item on how wood turtles stomp the ground to force earthworms out of their burrows. (When humans do this -- and they do -- it is called "grunting for worms!) Other animals also use vibrations for communication and, rather surprisingly, for cutting leaves.

Malaysian tree frogs. Zoologists already knew that Puerto Rican white-lipped frogs use vibrations to communicate amongst themselves. The Malaysian tree frog can now be added to the list of substrate vibrators. The female will sit on a reed or small sapling and tap out a "come-hither" message with her toes. The message goes forth in minute seismic waves. The males detect these vibrations and proceed, sometimes in great numbers, to the source of the vibrations, and the species is thereby perpetuated.

(Mestel, Rosie; "Courting Tree Frogs Make the Earth Move," New Scientist, p. 8, December 10, 1994.)

Leaf-cutting ants. Leaf-cutting ants neatly excise penny-size pieces of leaves and tote them back to their fungus gardens. J. Tautz and colleagues, University of Wurtzburg, noted that the ants chirped as they sliced at the leaves with their jaws. With a little instrumentation, they discovered that during each chirp both ant and leaf vibrated at about 1,000 hertz. The vibration apparently rigidizes soft leaf tissues and makes them easier to cut. The same principle is used by biologists when they slice soft material for microscope examination. The leaf-cutting ants apparently invented the Vibratome millions of years ago.

(Tautz, Jurgen, et al; "Use of a Sound-Based Vibratome by Leaf-Cutting Ants," Science, 267:84, 1995.)

Comment. It is rather amazing that ants, viewed by most animal behaviorists as mere automatons, could parlay small random mutations into such a technically sophisticated technique.

From Science Frontiers #98, MAR-APR 1995. � 1995-2000 William R. Corliss