Kevin Judge confirms what an ancient Chinese text stated 800 years ago about male cricket fighting—the bigger the head, the better the fighter.
Judge, a post-doctoral researcher at the University of Toronto Mississauga, along with co-author Vanessa Bonanno, conducted experiments on male field crickets Gryllus pennsylvanicus, test their hypothesis about sexually-selected male weaponry. They reported sexual dimorphism in head and mouthpart size and showed that males with larger heads, maxillae, and mandibles indeed win more fights against their male rival in aggressive physical contests. Their study was published in the December 2008 issue of PLoS One, a journal by the Public Library of Science.
Male crickets fight each other for territorial control, which leads to greater access to potential mates. The techniques in male aggressive combat include head-butting and grappling with their mouth-parts. Cricket fights have been a form of entertainment in China since the Sung dynasty (A.D. 960-1278). Judge and Bonanno’s findings are not only a contribution to the scientific community, but also highlight the Chinese cultural tradition of male cricket fighting.
In nature, male field crickets defend their territories, from which they sing to attract females. Responding to their song, females visit that territory to mate. “The more space you control as a male, the more likely you are to attract a female,” explains Judge. As a result, males always encounter each other as enemies and engage in physical combat.
Through a series of experiments, Judge and Bonanno were able to prove which traits make a male cricket a winner. In the first experiment, males were paired based on body size, and in the second, by body mass. They set up the cricket fights in a tiny arena and watched each battle unfold. “It’s a delicate dance between the meeting and the actual outcome,” says Bonanno, a recent MSc graduate, in a phone interview. She described what went on in the arenas, saying “they start checking each other out…meet antennae. Then it’s a series of escalations. They gyrate, kind of bop up and down, lock mandibles, and with that they try to knock each other over.” Through these experiments Judge and Bonnano showed that between males increasing differences in the size of weaponry heightened the fighting success of the male with larger weaponry.
Judge made the link between his findings and Chinese cricket fighting unintentionally. Taking his advisor’s advice to research the earliest scientific sources associated with cricket fighting, Judge found his hypothesis “wasn’t terribly novel.” He elaborates saying, “The Chinese knew about this head-size relationship with fighting ability a thousand years ago.” The earliest source he found was a work on cricket fighting by Shia Szu-Tao in the thirteenth century, stating that the best fighters have large heads. Judge explains how he found himself in the University of Toronto’s Asian Studies Library with an ancient Mandarin translator studying Szu-Tao’s text, as reading it made his research into male cricket fighting “more exciting.” He adds, “I also wanted the chance to cite an 800 year-old book.” Bonanno recalls her reaction to Judge’s discovery of the ancient Chinese sources, asking herself,“Can we prove that this information, used for hundreds of years, actually has a scientific basis to it?”
Making parallels between science and culture when discussing the ancient Chinese cricket fighters was natural to Judge. “When culture approaches [something] with scientific methodology, it can arrive at sound conclusions,” he says. The Chinese discovered what made the best male cricket fighters because “they were being scientific by…controlling for body size. The one thing they weren’t doing was analyzing the results statistically. They were analyzing it more for anecdotes.”
Judge and Bonanno’s statistical analysis of cricket fighting paid off. Their results are the first evidence that the head and mouthpart size of field crickets are under positive selection by male-male competition. Cricket fighting remains a cultural tradition and popular pastime in China. Despite how ancient Judge’s cricket fighting findings are, he says he is still motivated as a scientist by the “thrill of discovery.”
