Everett, Wash.
Published: Saturday, March 22, 2008

Concert of ribbets means frogs have joined in a chorus

By Sharon Wootton
Herald Columnist

 Once, some people believed that if you made a wish after seeing the first frog in the spring, the wish would come true. There also was the belief that frogs were possessed by the souls of dead children, so killing a frog could bring bad luck.

We've passed that stage (at least when it comes to frogs), opting for smiles rather than superstitions when we hear the frog chorus.

Traditionally called Pacific tree frogs (although they aren't true tree frogs), they're more accurately called Pacific chorus frogs, having been reclassified from the genus hyla (true tree frogs) to pseudacris.

The Washington state native is not the spring peeper, a different species that's found in the eastern United States.

Very small (up to 2 inches), often green (can wear other earth tones); they sport black stripes running in front of and around the eyes, then down to the shoulders.

Males are heard croaking in nearby water-filled depressions, ditches and small freshwater ponds (preferably without fish or bullfrogs), sending out their come-hither messages. Males may even butt heads and kick each other with their feet to chase rivals.

After mating, the frogs can be found far from water. I've seen them crawling up the side of a house and hanging around in a metal bin; I've also lifted the hot tub lid and found one on the edge, attracted by the moisture.

They can stay away from water because they have skin glands that secret a waxy coating.

Pacific chorus frogs also provide sound tracks for scores of movies, cartoons and TV ads -- the familiar "ribbet, ribbet, ribbet!" That call has been heard in films set in Africa and alien planets, even though these frogs are only found along the western side of North America.

While the "ribbets" are used in January, February and March, a one-syllable call is used the rest of the year. They make sounds basically the same way we do, except they keep their nostrils and mouth closed so the air flows over vocal chords and into the vocal sac, puffing it up like a balloon.

The sac amplifies a certain frequency and broadcasts the sound, said Elliot Brenowitz, a professor of zoology and psychology at the University of Washington, who studies acoustic communication in frogs and birds.

Led by a chorus master, the vocal marathoners expend massive amounts of energy singing hour after hour, night after night. Just ask a resident who lives near a chorus. People have been known to fill in a pond to get rid of them.

It's possible to hear them a mile away on a quiet night. If, theoretically, you could put your ear next to one, "ribbet" would sound as loud as a jackhammer.

Female frogs orient better to a chorus than to the call of one frog, Brenowitz said. "It may sound like thousands, but start counting, there's never that many. If you find 100 frogs, that's a big chorus."

The males make shopping easier by gathering around twilight. It's the concept of a selfish herd. A frog in a chorus has a lower chance of being picked off by a predator.

Females apparently prefer choruses of males over single males, even walking right by a single male to reach a wider choice. Males can call a few thousand times a night while females sample the calls.

Loudness reflects the male's size, attractive to a female. She swims up to her choice, nudging him if he's caught up in croaking. They engage in a several-hour mating process that includes laying jellylike egg clusters, usually on plants, eventually laying 500 to 750 eggs.

A few weeks later, depending on water temperature, tadpoles emerge. Two months later, metamorphosis produces frogs, which will join the chorus next year.

Columnist Sharon Wootton can be reached at 360-468-3964 or www.songandword.com.
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