Short-term water deprivation has widespread effects on mating behaviour in a harvestman

Abstract

Individual variation in resource acquisition prior to mating can influence the expression of sexually selected traits and mating dynamics. One important resource that has the potential to affect mating is water; however, little is known about whether variation in individual hydration status impacts mating behaviour. Here, we investigate the effects of short-term water deprivation on mating behaviour in the harvestman Leiobunum vittatum, commonly known as daddy longlegs. These harvestmen follow stereotyped stages of mating during which males attempt to clasp females in a ‘mating embrace’, then attempt to copulate, and may guard females after copulation; females are able to resist male attempts at each stage to end the interaction. During these interactions, males pass fluid nuptial gifts to females for their consumption. We tested how short-term water deprivation affects mating dynamics in harvestmen using a fully factorial, single-choice mating trials between males and females that were deprived or not deprived of water for 4 h. Water deprivation affected behaviour at multiple stages of mating. Females deprived of water were less likely to resist male advances but also less likely to be embraced by males. Most dramatically, the duration of intromission was greatly reduced in trials where both sexes were water-deprived. Together, these results suggest that even short periods of water deprivation impact mating-related behaviour of both sexes and may be an important but neglected factor in sexual selection.