Posted on 04/11/2006 6:44:25 PM PDT by Lessismore
Australian red-back spiders sniff out how much competition they have for females as they are growing up and tailor their adult size accordingly, Canadian researchers say.
Michael Kasumovic and Dr Maydianne Andrade of the University of Toronto report their findings in the latest issue of the journal Current Biology.
"Males are really tracking the selection pressures that they're facing in an environment. They're aware of male density and the amount of competition they're going to be facing," Mr Kasumovic said.
Like most spiders, male red-back spiders are much smaller than the females but they vary in size.
Mr Kasumovic and Dr Andrade have found that an individual spider's development is determined by a trade-off between traits that benefit a spider's sexual success versus their longer term survival.
"A trait that's good for sex is often not good for surviving and a trait that's very good for surviving may not be good for sex," Australian spider expert, Dr Marie Herberstein of Macquarie University in Sydney, said.
She says the classic example is the male peacock's tail, which is good for attracting females but weighs him down and affects his chances of survival when being pursued by a predator.
She says Mr Kasumovic and Dr Andrade have found that when it comes to the red-backs - maturing early is good for their sexual success, but maturing later is better for survival.
The study
Mr Kasumovic and Dr Andrade studied how immature male red-backs develop in the presence and absence of females.
They found that when females are not around, the males develop into sexually mature adults slowly, growing into relatively large adults with lots of energy stores.
The researchers say this gives the male spiders a higher chance of survival when they set out on their search for female mates.
When male spiders are surrounded by females, they focus their energy on maturing quickly, ending up both smaller and leaner because they have spent less time foraging.
Mr Kasumovic and Dr Andrade say growing up fast gives the spiders the best chance of being first to mate with the nearby females, something that is important considering the sex life of red-backs.
Male red-backs only have one or two chances to mate before they are killed by the female, and mating is most successful when the female is a virgin.
"Everybody always states that the small males are a by-product of them not being able to get enough resources, but we're showing that they're intentionally developing that way," Mr Kasumovic said.
Wow.. what an image that headline put in my head....
Thankfully this does not hold true for humans, I grew up in a rather small town.
LOL! For a moment I thought that it read: "Female redneck..."
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.