Animal Behavior Society Fellow Ann Hedrick Explains Irresistible Cricket Songs

Ann Hedrick holds up a cricket statue in her office. David Slipher/UC Davis
Ann Hedrick researches the mating behaviors of the field cricket Gryllus integer, trying to determine which heritable traits attract a mate. David Slipher/UC Davis

Come night—when the UC Davis campus is dark and still—Ann Hedrick seeks the light. That’s not a metaphorical statement. Sites like the campus tennis courts, illuminated by arena lights, are ideal for finding crickets, Hedrick’s research subjects.

“It’s really difficult to find crickets when you’re out in a field, which is a more natural habitat, but they’re attracted to bright lights,” said Hedrick, an adjunct professor of neurobiology, physiology and behavior. “They fly in and then drop down on the pavement and we can pick them up.”

For more than 30 years, Hedrick has researched the mating behaviors of the field cricket Gryllus integer, trying to determine which heritable traits attract a mate. For her research, Hedrick was recently elected as a fellow of the Animal Behavior Society. The announcement will be formally made in August at the 55th Annual Conference of the Animal Behavior Society in Milwaukee, Wis.

“I was very excited,” Hedrick said of receiving the fellow designation. “You do the work because you love it and you do it regardless, but it’s very nice to be recognized.”

Aerial view of the UC Davis tennis courts. Jim Con Rummelhoff
Hedrick finds her chirpy study subjects in areas like the campus tennis courts. Jim Von Rummelhoff

Why crickets chirp

Hedrick began studying crickets at UC Davis while obtaining a Ph.D. in zoology. At the time, all she had was a general hypothesis about animal behavior: that females select mates based on heritable traits. To test the hypothesis, she needed a subject with a discernible trait that also had a short generation time. Crickets fit the bill.

“Males rub their wings together to produce a song that attracts females, and it was conceivable that females liked something about particular male songs,” said Hedrick. “These crickets are local crickets from Davis and they make kind of a long trill.”

Hedrick recorded cricket songs and decided to test if the length of a male cricket’s trill influenced female selection. She’d play the trill uninterrupted against the same trill but with pauses interspersed through the recording. “I did that with a whole series of males and females and sure enough, females liked these long songs,” said Hedrick.

Cricket. Courtesy photo
Hedrick found that the same female—when played both long and short trills preferred whichever male was protected by cover. Courtesy photo

Aided by quantitative genetics techniques, she found that male offspring of male crickets with long trills similarly had long trills. Hedrick then wondered, if females prefer long songs, why do some males still sing short songs?

It turns out that though female crickets prefer males with long trills, male crickets with short trills benefit under certain conditions.

“Females have complicated decisions to make. They might like something, but they also have to worry about predation risk,” Hedrick said. “If a male is singing with short trills and he’s in a safer place, a female will go to him as opposed to the cricket with long trills.”

In the lab, Hedrick found that the same female—when played both long and short trills—preferred whichever male was protected by cover. Regardless of song length, safety was priority.  

Are campus crickets disappearing?

Hedrick’s current research continues her initial line of inquiry as a graduate student, but now she’s delving into the world of animal personalities.

“These are suites of correlated behavioral traits,” Hedrick explained. “For example, in crickets, we see that males who are more aggressive with one another are also bolder about predation risk.”

In one research project, Hedrick is trying to determine whether mate selection by females correlates with female boldness. She’s also working on an NSF-funded project with a colleague from North Dakota on the genetic architecture of these suites of correlated behaviors.

“So the question is, are there these clusters of traits because it’s adaptive for them to be clustered together or because of genetic constraints?” said Hedrick.

Aside from these projects, Hedrick voiced concern about campus cricket populations. For the past three years, she’s noticed a decline in their numbers, which she suspects is related to aerial and ground spraying meant to combat mosquitos carrying West Nile virus.

“It’s been very bad,” she said. “We’ve had to go far afield to get crickets.”   

Hedrick noted that the disappearance of crickets could affect other campus species that rely on crickets as a food source, such as birds.

“It’s good to take care of the mosquitos,” she said, “but it means a lot of other insects are getting hit.”

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