SYNCHRONIZED WAVING

Courtship synchrony is an extremely rare phenomenon within the animal world, exhibited by only a small number of groups (Backwell, 2019). Male fiddler crabs have been observed to produce synchronized claw waving displays, especially clusters of neighbouring males while in the presence of a passing female crab during the mating season (Rorato, Araujo, Perez, & Pie, 2017). At the present time, five species of fiddler crab are known to incorporate synchrony in their claw waving behaviours (Rorato et al., 2017). Although the topic of synchrony has not been fully explored by scientific research, it is believed that the evolution of this behaviour is driven by sexual selection: namely, female crabs’ mating preference for a male who can wave his claw before his neighbours (Backwell, Jennions, Wada, Murai, & Christy, 2006).

This may seem counterintuitive, but the process by which synchrony has evolved can be referred to as a ‘precedence effect' (Backwell et al., 2006). Backwell et al. (2006) describe the general process beginning with the female crabs preferring, or selecting for, males who wave their claws faster than—and before—their neighbours. Presumably, this indicates to the female that a male is energetically fit, which is a high-quality trait that she likely wishes to pass onto her offspring. This selection and preference on the part of the female fiddler crab is an example of sexual selection, and will drive synchrony over time. As male crabs attempt to wave their major claw at a quicker intensity than their neighbours in order to ‘lead’ the group in their display, competition between the rest of the males is at play. In an attempt to catch up in waving rate to the leading males, other male crabs will adapt their own claw waving behaviours; ultimately, the resulting synchrony nullifies the efforts of any males in the group to stand out.