Photograph: Arco Images GmbH/Alamy Stock Photo/Alamy Stock Photo
The sweet singing charms of an old male appear to be irresistible to a younger female – if you are a field cricket in a Spanish meadow.
Researchers studying wild crickets have found older males are better than younger, more immature rivals at attracting females back to their burrows with their song.
Once there, however, the females were less impressed: scientists discovered they mated less with older males than their younger counterparts.
University of Exeter scientists studied thousands of Gryllus campestris field crickets in a meadow in northern Spain over 12 summers to see if a male’s age affected how attractive females found them.
Infrared cameras were fixed outside burrow entrances to record pairings and matings, activities the narrow burrows are too small to accommodate.
Previous studies have revealed male crickets to be chivalrous, letting females enter a burrow first when threatened by predators.
Field crickets only live as adults for a few weeks but the scientists have also shown that males decline with age – singing less often, and even becoming set in their ways.
They also have less sex: in findings published in Animal Behaviour, the scientists discovered polyandrous females mated less often with older males and more frequently with younger mates.
Crickets were trapped and DNA sampled, with miniature PVC tags fixed to the insects’ thoraxes to enable video identification.
“It seems that the age of a male is a poor guide to his suitability as a mate,” said Prof Tom Tregenza, one of the authors of the study. “This was reflected in the opposing effects it had on their success in pairing up and mating with females.”
Female crickets seek mates to obtain the best genes for their offspring and, according to Dr Rolando Rodríguez-Muñoz, of the Centre for Ecology and Conservation at the University of Exeter, they may be attracted to older males because they have shown they can live for a long time. The benefits of a younger male may include sperm not accumulating harmful mutations that could be passed on to offspring.
Both male and female crickets mate with multiple partners during their short lives but the scientists found that pairs that mated more frequently tended to stay together for longer.
Tregenza added: “Scientists have done lots of studies with large animals like birds and red deer but insects remain really mysterious to us. We know almost nothing about the natural lives of the trillions of insects in the world.”
