Tuesday, December 6, 2011

Born to be Viral: Robo-crabs compete for female

Instead of wolf-whistling, groups of male fiddler crabs signal their interest in a female by waving a large, brightly-coloured claw. But is a male surrounded by smaller, weaker crabs more likely to get the girl than if he hangs out with males of a similar size?
To answer the question, Sophia Callander a PhD candidate at the Australia National University in Acton, Australia, set up robotic claws around a female crab in various configurations. Some groups were composed of identical robo-crabs waving at the same speed, whereas others were made up of small, slow crabs, as well as larger, faster ones.
Callander then released a female crab at a point equidistant to all the robots and observed its choice of suitor. She found that at distances greater than 50 cm, a robo-crab's neighbours had little impact on how likely he was to be chosen. But at shorter distances - around 20 cm - the simulated males were more likely to get the girl if they were surrounded by smaller claws.
The finding could explain why large male crabs often team up to protect smaller, weaker males from intruders: a mixed group makes them more attractive to females. Previous research has also shown that female fiddler crabs prefer males that build hooded burrows.
For more crab videos, check out this crab-eating snail, or watch as giant crabs invade the Antarctic sea floor.


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