Big males outperform smaller ones in head-to-head mating contests butdiminutive males make ten times better lovers because they're quickerto mature and faster on their feet, a new study of redback spidersreveals.
Published in the current online issue of Journal of EvolutionaryBiology, the study shows the importance of maturation in definingmating and paternity success. In field enclosures, researcherssimulated two competitive contexts favouring the development ofdifferently sized male redbacks (Latrodectus hasselti). The largermales were more successful at mating with and impregnating femaleswhen they competed directly with smaller males. However, when fastermaturing smaller males were given a one-day head start, reflectingtheir earlier maturation in nature, they had a ten-times higherpaternity rate than larger males.
Courtship between redbacks lasts an average of 50 minutes when malesare competing and 4.5 hours for single, non-competing males.Copulation lasts from 6 to 31 minutes, and males are usually injuredor killed during the process.
"The results reveal that big males don't get it all their own way,"says lead author, UNSW postdoctoral fellow, Dr Michael Kasumovic, whoco-authored the paper with Maydianne Andrade of the University ofToronto. "Nature favours larger and smaller males under differentcircumstances. Larger males experienced a longer maturation process sothey are unable to search for and mate with females and produceoffspring at the same rate as smaller redback spiders.
"Large size and weaponry are strong predictors of a male's competitivestrengths because those traits help them dominate smaller males whenthey compete for food and mating rights. However, evidence fromstudies of midges, dung flies and seed beetles reveals that smallermales develop sooner than larger males and often mate before largercompeting males arrive on the scene. Size isn't the only ruler bywhich we can measure a male's quality. Many other factors, includingmaturation time, are critical in that definition."
Source: University of New South Wales