Crabs
Media playback is unsupported on your device
Video

Male fiddlers wave down female

Researchers have used robotic crabs to show that female fiddler crabs prefer males who can "out-wave" their neighbours.

Male crabs advertise their quality as a potential mate to passing females by waving their large yellow claws.

Using robotic arms, researchers evaluated how the size and speed of the waving claw affected mating success.

On the Australian mudflats males signal with their claws to females up to half a meter away.

Here males are displaying to a female, who is well camouflaged in the middle of the group.

Males who lose their claws can grow replacements, although these are usually weaker than the original claw.