The rate of mate sampling is one of the critical components associated with the sampling costs in female mate choice. In ectotherms, environmental temperature generally constrains locomotion performance. In addition, females will adjust the mate sampling rate depending on their breeding schedule because of the risk of remaining unfertilized eggs or a loss of benefits related to mating, if they lost the opportunity to copulate. This study investigated how these effects influence the rate of female mate sampling in the temperate fiddler crab (Austruca lactea) in the field. The number of sampled males per searching duration formed a convex curve against environmental temperature. The optimal environmental temperature increased with the female body size. These results suggest that the mate sampling rate would be under a size-dependent temperature constraint, and sampling costs would be lower for larger females than smaller individuals under high-temperature conditions. Furthermore, when there were fewer remaining days, the mate sampling rate increased. Females would hasten the sampling rate to ensure a suitable burrow for breeding. Mate sampling rate in female A. lactea is therefore associated with environmental temperature, female body size, and remaining days until oviposition.

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