Slo-Mo Cricket Chirps Reveal Secret Serenades

Enlarge Gerardine Vargas

A snowy tree cricket feeds on a leaf from a mountain dalea plant.

Gerardine Vargas

A snowy tree cricket feeds on a leaf from a mountain dalea plant.

Want to know how crickets choose mates? Well, listen closely next time you're outside on a night when they're singing. Very closely.

It's the males that are doing that chirping; they're trying to attract females.

But it took biologist Laurel Symes of Dartmouth College years of listening — and recording — to figure out that different species of cricket have different calls. She slowed down the recordings and discovered that what sounds like a continuous call to us actually has pulses — or rhythm.

Enlarge Nancy Collins

The movement from the wings of the Oecanthus fultoni are what create the familiar chirping sound.

Nancy Collins

The movement from the wings of the Oecanthus fultoni are what create the familiar chirping sound.

Take the snowy cricket, Oecanthus fultoni, also called the thermometer cricket because you can count the number of chirps in 13 seconds, add 40 and get the temperature in Fahrenheit.

"Within each chirp, there are eight separate pulses," says Symes. The pulses are arranged in a rhythm of two beats, followed by three beats, and then another three beats. "Dun-dun, dun-dun-dun, dun-dun-dun," as Symes does it.

Another kind of cricket, called Riley's tree cricket, divides its chirps into 11 beats. Presumably, a female can distinguish the calls of the males of her species from others.

Symes throws herself into her work — she collects crickets while she's on the road, keeping them in boxes in her car. "Motels have been ... well, usually they don't know. Sometimes you bring them in the back door, you ask for an exterior room. Campgrounds are good."

Why do this? "What I'm really doing is asking a female cricket, you know, what she likes, how the female choice acts on the male traits, and also what does and doesn't matter about the males' calls," she says.

Symes' recordings will be part of the collection of the Cornell Laboratory of Ornithology in Ithaca, N.Y.