Pacific field crickets are found throughout the Hawaiian Islands. You might have heard them chirping in your backyard. Originally from Australia, they've spread throughout Oʻahu, Kauaʻi, Hawaiʻi Island and Molokaʻi.
A new study published in the journal Proceedings of the National Academy of Sciences peers into their private lives. University of Minnesota evolutionary biologist Marlene Zuk and postdoctoral researcher Jon Richardson spoke to HPR about their research.
They explored the idea that male crickets in poor condition have narrower "mating filters," and thus engage in less same-sex sexual behavior to save energy. The study stresses that the results should not be applied to humans.
"The idea kind of started with when and why do animals engage in same-sex sexual behavior," Richardson said. "What if some animals just are really kind of open and broad in what they consider a potential mating partner?"
Crickets have two songs, one for calling — which people often hear as chirps — and one for courtship, Zuk said.
"When two crickets encounter each other, or when a male encounters something that seems like it's a cricket-like object, the male switches to a different song that he then produces before mating," Zuk said. "It also means that he has to engage in something costly because both the calling song and the courtship song are energetically costly."
The male crickets in poor condition have to be more restrictive and narrow their mating filters, Richardson said.
"Potentially, what they're doing is kind of figuring out that it is a female before they sing. Whereas the males that are on the very good diet, they've got lots of energy," he said. "Presumably, for them, it just makes sense to just sing at whatever is in front of them that's vaguely cricket shaped."
Zuk and Richardson experimented to figure out what crickets considered cricket-like enough to sing their courtship song. They used male, female, juvenile and plastic crickets.
"We saw a lot fewer of the males would sing towards these plastic crickets, but it was still like some of them would still do it, and they would sing towards the juveniles, and they sing towards the males. So that told us that, in general, these crickets have quite a broad filter, as we describe it, or that they're quite open to what they consider a potential mating partner," Richardson.
Zuk stressed that humans are the ones identifying this as same-sex sexual behavior — the crickets aren't calling it anything.
"The crickets are just doing what they're doing, and they're responding to things in their environment, and enough of the time that results in them successfully mating and siring offspring that it's all good," she said.
She also researches the mating of the Kīlauea lava cricket. She said it was some of the hardest fieldwork she's ever done because of the difficulty of acquiring the crickets.
This interview aired on The Conversation on Sept. 25, 2024. The Conversation airs weekdays at 11 a.m. on HPR-1.
