Posted on February 15, 2011
Instead, female crickets prefer the higher-pitched and louder songs sung by younger males, he says.
Verburgt and colleagues recorded the mating songs of the same 25 male field crickets when they were young (10 to 12 days old) and older (48 to 50 days old).
He analysed the songs' traits, including the number of single sounds – or syllables – per song, the length of the syllables and the song's frequency.
Nearly all the traits changed with age. For instance, as crickets became older they sang lower, more staccato songs. The young male song was louder and on average 80 hertz higher than the older male songs.
Verburgt believes the muscles needed to produce songs become weaker with age, and so older crickets may not be able to sustain the force required to produce longer syllables.
To see if females preferred the older or younger songs, Verburgt used software to mix recordings and create "average" old and young songs.
He placed two speakers on opposite sides of a box and simultaneously played the average songs to 21 females four times, and recorded which way the females turned.
They found females chose the young male song a whopping 90 per cent of the time.
According to Verburgt, females probably prefer younger crickets because damage associated with ageing can mutate DNA and reduce sperm quality.
"Sperm ages rapidly and older testes are not as good as younger testes in producing lots of viable sperm," says Trish Fleming a behavioural biologist at Murdoch University in Australia. As a result, younger males are more likely to be capable of fertilising all a female cricket's eggs.
Original article: http://www.newscientist.com/article/dn19972-female-crickets-fall-for-serenades-of-younger-males.html
Journal reference: Animal Behaviour, DOI: 10.1016/j.anbehav.2010.09.010
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