Abstract
Males often produce dynamic, repetitive courtship displays that can be demanding to perform and might advertise male quality to females. A key feature of demanding displays is that they can change in intensity: escalating as a male increases his signalling effort, but de-escalating as a signaller becomes fatigued. Here, we investigated whether female fiddler crabs, Uca mjoebergi, are sensitive to changes in male courtship wave rate. We performed playback experiments using robotic male crabs that had the same mean wave rate, but either escalated, de-escalated or remained constant. Females demonstrated a strong preference for escalating robots, but showed mixed responses to robots that de-escalated (‘fast’ to ‘slow’) compared to those that waved at a constant ‘medium’ rate. These findings demonstrate that females can discern changes in male display rate, and prefer males that escalate, but that females are also sensitive to past display rates indicative of prior vigour.
Highlights
Dynamic, repeated displays are often performed by males during courtship interactions and occur in several modalities [1]
Female fiddler crabs generally prefer males that wave at higher rates than their rivals [8]
A characteristic of dynamic, repeated displays is that the rate of display changes during the course of an interaction. This is especially true of energetically costly signals [1,2], because a signaller often initiates a display with a low intensity signal to avoid unnecessary production costs, but increases his signalling effort if the courted female needs more inducement to mate
Summary
Dynamic, repeated displays are often performed by males during courtship interactions and occur in several modalities [1]. Courtship can cause male field crickets (Gryllus bimaculatus) to undergo anaerobic respiration [3] and male fiddler crabs (Uca mjoebergi) demonstrate a prolonged reduction in sprint performance postcourtship, indicative of lactic acid build-up [4] and oxygen debt [5] This heavy investment in signal production is likely to allow females to select physically fit mates as these ‘signals of stamina’ will reflect a male’s ability to perform other demanding activities associated with survival [6], and reduce the risk of mating with weaker signallers that might be diseased or parasitized [7]. A characteristic of dynamic, repeated displays is that the rate of display changes during the course of an interaction This is especially true of energetically costly signals [1,2], because a signaller often initiates a display with a low intensity signal to avoid unnecessary production costs, but increases his signalling effort if the courted female needs more inducement to mate. We presented females with replica robot males that waved in the species-specific pattern (see [10]) at either a constant rate, or at a rate that escalated or de-escalated as the encounter progressed
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