Letters from the December 23 & 30, 2006, issue of Science News

Playing dead is a lively topic

I am amazed that “Why Play Dead?” (SN: 10/28/06, p. 280) concluded that “Scientists have a long way to go to explain why” prey animals play dead. As a veterinarian, I have learned that there are separate centers in the brain dealing with predatory behavior and with hunger. The effect seems to be that predatory behavior, by itself, is satisfying, even fun. It’s solidly established that a moving-away object (ball, rabbit, child) can prompt predatory behavior (dog chases). Freeze behavior is well established as a last-resort, genetic strategy in all kinds of prey animals. If the predator is just out for fun, it is at least more likely to look elsewhere for kicks if the prey is “frozen.”

D.B. Cameron
Nevada City, Ca.

I have noticed that chipmunks wiggle and hop after being swatted by our cat. One managed to hop near our woodpile, and suddenly it darted to safety inside. I guess this is protective behavior, but why the cats lose interest after the very active behavior begins, I don’t know.

Doug Stone
Hartford, Conn.

You’ve probably received a number of references to the motto of the Possum Lodge on the Canadian Broadcasting Corporation’s Red Green Show: “Quando omni flunkus moritati.” (When all else fails, play dead.)

Marshall Butler
Seattle, Wash.

Safer than we think

The article on organohalogens in 1920s whale oil (“A Whale’s Tale: Puzzling marine compounds are natural,” SN: 10/28/06, p. 278) indicates both the stability of such natural products and their bioaccumulation in organisms at the top of the food chain. It is no doubt prudent that human activity—i.e., chemical manufacturing—should not increase the quantity of these chemicals in the oceans. But it should be recalled that banning of PCBs and similar substances was based solely on the fears aroused by their stability. Their human toxicity is relatively low. Continued information of the kind reported is valuable in that it indicates we live in a chemical world.

Anthony Trewavas
Edinburgh, Scotland