Lightweight and long-legged males go the distance for sex

Sep 05, 2008
A pair of giant weta in which the male is carrying a radio-tag on his back. 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, published in the September issue of The American Naturalist, 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.

Citation: Clint D. Kelly, Luc F. Bussière, and Darryl T. Gwynne, "Sexual Selection for Male Mobility in a Giant Insect with Female-Biased Size Dimorphism." American Naturalist (2008) 172:417-423.

Source: University of Chicago

Explore further: Cell division, minus the cells

add to favorites email to friend print save as pdf

Related Stories

Researchers study the biomechanics of locomotion

Oct 03, 2014

Rodger Kram, a faculty member in the integrative physiology department and an expert on human locomotion, has a fond place in his heart for kangaroos. A few decades ago he and colleagues measured the gait ...

California's sea otter numbers holding steady

Sep 23, 2014

When a sea otter wants to rest, it wraps a piece of kelp around its body to hold itself steady among the rolling waves. Likewise, California's sea otter numbers are holding steady despite many forces pushing ...

Recommended for you

Himalayan Viagra fuels caterpillar fungus gold rush

9 hours ago

Overwhelmed by speculators trying to cash-in on a prized medicinal fungus known as Himalayan Viagra, two isolated Tibetan communities have managed to do at the local level what world leaders often fail to ...

Science casts light on sex in the orchard

12 hours ago

Persimmons are among the small club of plants with separate sexes—individual trees are either male or female. Now scientists at the University of California, Davis, and Kyoto University in Japan have discovered ...

Researchers capture picture of microRNA in action

12 hours ago

Biologists at The Scripps Research Institute (TSRI) have described the atomic-level workings of "microRNA" molecules, which control the expression of genes in all animals and plants.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.