Thermal stress and availability of potential mates drive decisions related to thermoregulatory burrow retreat and emergence in fiddler crabs

Behavioral tradeoffs are common, as many behaviors are incompatible. In ectotherms, these tradeoffs often result from incompatibility between thermoregulatory behaviors and other critical behaviors. These trade-offs are resolved by choice, with decisions expected to be based on the costs and benefits of each behavior to optimize fitness outcomes. We examined the social and abiotic factors driving resolution of the trade-off between thermoregulatory behavior and courtship behavior in the fiddler crab Austruca mjoebergi. Male fiddler crabs perform a courtship display on the high intertidal sediment surface, where they face extreme thermal stress; retreat into the burrow is an effective thermoregulatory strategy but requires a cessation of courtship behavior. Surface duration decreased as environmental temperatures increased, indicating that time available for courtship is limited by high temperature. Yet when exposed to a stimulus female, males remained on the surface longer, spent less time in the burrow following a thermoregulatory retreat to the burrow, and spent an overall greater proportion of time on the sediment surface. Results demonstrate that behavioral decisions related to both burrow retreat and subsequent emergence are influenced by the abiotic and social context that determine the relative costs and benefits of the behavioral choices available to the individual.