Published: 17 January 2018 at 09:48
Robotic crabs help researchers understand the importance of tempo during mating
Female fiddler crabs are sensitive to changes in the speed of a male’s courtship display, significantly preferring displays that accelerate to those that are performed at a constant speed or slow down.
The new research is published in the journal Biology Letters and was carried out by Dr Sophie Mowles of Anglia Ruskin University, alongside academics from the Australian National University in Canberra.
Male fiddler crabs (Uca mjoebergi) wave their larger claw during courtship displays, which is a demanding exercise that leads to fatigue. A previous study by Dr Mowles has shown that male crabs that perform more vigorous, energetically costly, waving displays have higher physical fitness, meaning this signal is worth paying attention to from the perspective of a female crab.
To study the importance of tempo in mating decisions, Dr Mowles and her colleagues constructed robotic male fiddler crab arms that could move at a constant speed, slow down or speed up as the encounter progressed.
Female fiddler crabs were then introduced to these robotic crabs, and the research showed that females demonstrated a strong preference for escalating robots.
Even at points when all three robotic crabs were waving at the same frequency, the female crabs preferred the male robot whose speed was increasing. This indicates that the females realise the male might be on a trajectory to increase their wave rate further, while also demonstrating that they can conserve energy until necessary.
Dr Mowles, Lecturer in Animal and Environmental Biology at Anglia Ruskin University, said: