The Squid's Stratagem

Squids, say the natural history books, use their ink to form clouds that blind pursuers. Not so, says D.N.F. Hall of the Singapore Regional Fisheries Research Station, writing in Nature. Squids are more subtle than that.

Hall began to doubt the cloud theory when he watched squids discharging their ink. It does not form a cloud for a considerable time, but hangs together as a dark, viscous mass. To learn more, Hall experimented with a small captive squid in a light-colored wooden tub. When his hand approached it, the squid changed color rapidly, as squids do. Just before Hall grabbed for it, it turned dark--and Hall found himself squidless. He had grabbed a blob of ink-darkened water. The real squid, now light-colored, was safe at the far side of the tub.

After many similar experiments, Hall decided that the squid's standard operating procedure is to turn as dark-colored as possible just before a pursuing enemy catches up with it. Then it ejects as a decoy a blob of inky water about as big as itself. Simultaneously, it turns light-colored and takes evasive action, pretending to be something else. This system fooled Hall, and he believes that it ought to fool the squid's natural enemies.

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