As the seasons heat up annually, males and females start looking for mates, and two summers' worth of steamy drama outside of a small European town have now been caught on tape.
A big, strong male comes by to strut his stuff for a female, but she also seems interested in a smaller potential mate who has a particularly enchanting song. Nearby, an especially promiscuous female seems to keep reproducing as fast as she can find new mates. Couples copulate dozens of times before splitting, and some females stray from their mates for quickies with other available males nearby.
This drama was captured by 24-hour surveillance collected by 64 different video cameras in northern Spain. Part Jersey Shore, part telenovela, this project, however, doesn't focus on human drama, but rather the social—and sexual—struggles of crickets.
These common insects are familiar to gardeners and researchers alike, but surprisingly little has been documented about how the orthopterans actually behave in the field. And it turns out that it can get pretty wild.
"We're seeing a lot of wild behavior that has never been seen on TV before," Tom Tregenza, a biologist from the University of Exeter at Cornwall and coauthor of a new paper on the research, said in a prepared statement. The same types of randy behavior also hadn't been seen before in the lab, where cricket mating practices have been studied extensively. "The discrepancy is a cause for concern," the researchers noted in their study, published online June 3 in Science and led by Rolando Rodríguez-Muñoz, a postdoctoral researcher at the University of Exeter.
To track the 152 field crickets (Gryllus campestris) being recorded, researchers glued small numerical tags onto the insects' backs and labeled their burrows. Special infrared cameras were trained on each burrow opening. During the mating season, the crickets would visit other burrows in search of partners. When crickets mate, the males deposit a packet of sperm on the females, which reaches her eggs over time (before she buries a clutch in the ground).
Despite the summer-of-love frenzy ("Females visit or receive visits from neighboring males and frequently remain with a male for hours or days, sharing his burrow and mating repeatedly," the authors described) and the hundreds of eggs most females deposited in the ground, many females end up with few surviving offspring—and males are even less likely to have their genes passed on to subsequent generations. (DNA sampling of each cricket allowed researchers to track which surviving offspring the next summer belonged to whom.) As documented on the tape, life as a field cricket is full of hazards—even individuals that make it through larval and maturation phases must face constant threats from other bugs, birds and even each other.
The researchers found that the best strategy for males and females was licentiousness. "Both sexes benefit from multiple mates," the authors noted. This might increase a female's selection of sperm from non-related males, upping fitness for the next generation. The number of times an individual cricket mated did not seem to predict how many surviving offspring they would have, however. And dominant males, in fact, did not mate with as many females as smaller, more subordinate males (who seemed to rely msoapore often on their song to woo).
"The cricket soap opera is a model of the life struggles of so many species," Tregenza said. "It tells us about how natural selection happens in the wild."
But the 250,000-plus hours of video was created for more than just entomologist voyeurs. "We urgently need to know how ecosystems like this meadow will respond to a changing climate," Tregenza said. "Will evolution allow existing populations to simply adapt? Or will they be replaced by completely new assemblages? These are tough questions and we need to directly observe how behavior affects reproductive success."
Image of male (left) and female field crickets courtesy of Tom Tregenza/Rolando Rodríguez-Muñoz
Videos courtesy of Tom Tregenza/Rolando Rodríguez-Muñoz/Science/AAAS