Have your cake and eat it too: Male sand gobies show more parental care in the presence of female partners

Traditionally, male parental effort and mate attraction effort are expected to be in conflict as they compete for the same resource budget. However, the quality of care provided by the male may be of a direct benefit to females and may provide an important mate choice cue. In a laboratory experiment, we examined how males modified their parental behavior with respect to mating opportunity by allowing male sand gobies to mate with a single female either in a big or small nest (a constraint on future mating potential). We then exposed half of these males to the visual stimulus from additional females and recorded male egg fanning and nest building (two components of care), courtship behavior, and reproductive success through out the brood cycle. We found that males fanned longer and more frequently and did more nest construction in the presence of females and in big nests. Males guarding large nests courted females more than did males guarding small nests. All males consumed eggs during the brood cycle, but complete clutch cannibalism was most frequent when males were guarding small nests in the absence of females. The pattern of filial cannibalism that we observed suggests that males prematurely terminated care when their reproductive potential was low, that is, when there was little nest space for additional mating and no mates present. We found no support for a trade-off between mate attraction and parental care. Indeed, taken together our results suggest that males may use parental care as a courtship strategy and that males who invest in mate attraction also have higher parental effort.