Courtship songs

Simmons has been studying the courtship songs of several Australian cricket species. The males advertise their presence at night with long-distance chirping that the female can detect at a distance of five to six metres. If the female is sufficiently interested to follow the song to its source, the male switches to a quieter courtship song with a different temporal structure.

“One indication of male quality is immunocompetence – the ability to mount an effective immune response to pathogens. It confers major fitness advantages on a female’s offspring, increasing their chances of developing to reproductive maturity.

“We’re trying to determine if immune function correlates with male singing and courtship behaviour, and what song parameters appeal most to females.

“There also appears to be a link between semen quality and male immunocompetence, but we don’t yet understand the mechanisms involved. Males from cricket families [experimental lineages] that have to invest heavily in antimicrobial immunity tend to have lower semen quality, so they make fairly poor mates.

“We’re looking for patterns of genetic variation that correlate with male quality, including sperm quality. But sperm quality is also very sensitive to environmental perturbation.

“We’re looking at the contribution of male genetic variation by taking a series of males and mating each of them to three or four different females, and looking how particular traits vary between half-sib and full-sib offspring, which gives us a quantitative measure of genetic variation.”

One of Simmons’ research students, Renee Firman, recently completed her PhD study, in which she established a link between semen quality and sperm competition in a mouse model.

“Her project extended our work to vertebrate models. She found that, after 12 generations, semen quality and competitiveness diverged in different mouse lineages.

“Because the mouse genome project has been completed, we have the potential to identify genes coding for fertility factors, which may have important implications for studies of mammalian fertility.”

People learning of Simmons’ unusual interest in the mating strategies of beetles and crickets inevitably ask him to join the dots between the affairs of beetles and humans, and are politely rebuffed. “The only way to make a statement about mating strategies in humans is to study them in their own right,” he says.

That said, Simmons’ studies of human semen quality are revealing some remarkable parallels. Men viewing images depicting situations that would promote sperm competition produce ejaculates with faster-swimming sperm.

Cuckoldry has a long and ignoble history in human affairs. In The Rise and Fall of the Third Chimpanzee, Jared Diamond reports that anonymous surveys indicate that around 30 per cent of human couplings occur outside long-established pair bonds – close to the maximum frequency predicted by models of human mating behaviour, before the system descends into chaos.

Cuckoldry is not only a sneaky, but potentially fatal strategy. If Simmons is right, even in death, the incautious cuckold has a better than even chance of keeping the genes for his sneaky behaviour alive and swimming just that little bit faster in the human gene pool.