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Lightweight And Long-legged Males Go The Distance For Sex

Date:
September 8, 2008
Source:
University of Chicago Press Journals
Summary:
A study of giant cricket-like insects suggests that sexual selection for smaller, more mobile males could be responsible for some of the impressive sexual difference in body size in this species and may explain other species where males are smaller than females.
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An adult female giant weta (Deinacrida rugosa) on the hand of Darryl Gwynne, one of the study's researchers.
Credit: Darryl T. Gwynne

Finding a mate can take considerable legwork as recently illustrated by the flightless and nocturnal Cook Strait giant weta Deinacrida rugosa. This cricket relative is found in New Zealand and is one of the world's heaviest insects with females weighing in at 20 g, averaging twice the size of males.

In a field study on Maud Island, New Zealand, evolutionary biologists from the University of Toronto at Mississauga discovered that male giant weta most successful at mating travel greater distances each night. Remarkably, it appears that being lightweight and having longer legs assist male wanderlust. Clint Kelly, Luc Bussière, and Darryl Gwynne found that males can walk more than 90 m each night in search of a mate – roughly equivalent to a 7000 m outing by a human male.

Kelly and colleagues gained unprecedented insight into mating habits of weta by radio-tracking them over several days. This allowed calculations of distance walked and identification of with whom each male and female "spent the day."

Because a male giant weta copulates repeatedly with his mate throughout the day, the biologists estimated how much sperm was transferred by counting the empty packets (spermatophores) piled beneath the pair. Not only do males travel more than twice as far as females but small, long-legged individuals walked further, acquired more mates, and transferred more spermatophores to females (no female traits predicted female mobility or mating success).

"Our findings are a rare example of sexual selection favoring a suite of traits that promote greater mobility in one sex only," stated Kelly, adding " this is exciting because it suggests that sexual selection for smaller, more mobile males could be responsible for some of the impressive sexual difference in body size in this species." Importantly, however, this phenomenon may also help to explain why males are smaller than females in some other animals.


Story Source:

The above story is based on materials provided by University of Chicago Press Journals. Note: Materials may be edited for content and length.


Journal Reference:

  1. Kelly et al. Sexual Selection for Male Mobility in a Giant Insect with Female‐Biased Size Dimorphism.. The American Naturalist, 2008; 172 (3): 417 DOI: 10.1086/589894

Cite This Page:

University of Chicago Press Journals. "Lightweight And Long-legged Males Go The Distance For Sex." ScienceDaily. ScienceDaily, 8 September 2008. <www.sciencedaily.com/releases/2008/09/080905153853.htm>.
University of Chicago Press Journals. (2008, September 8). Lightweight And Long-legged Males Go The Distance For Sex. ScienceDaily. Retrieved May 28, 2015 from www.sciencedaily.com/releases/2008/09/080905153853.htm
University of Chicago Press Journals. "Lightweight And Long-legged Males Go The Distance For Sex." ScienceDaily. www.sciencedaily.com/releases/2008/09/080905153853.htm (accessed May 28, 2015).

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