Mate guarding enables males to bias fertilization, increase their share of paternity, and thereby enhance reproductive success. If the risk of sperm competition is high, males may benefit by investing more in guarding behaviors. While some species physically restrain females during guarding, others utilize more passive tactics. Male Pacific field crickets (Teleogryllus oceanicus) sing after mating to entice females to stay, even though they cannot immediately mate again. Post-copulatory song effectively keeps females in proximity, prolongs spermatophore attachment, and ultimately enhances male reproductive success. We investigated whether cues about the risk of sperm competition determine male investment in post-copulatory song. Additionally, we studied whether hearing cricket calls modified the listeners' behavior, either during rearing or immediately before mating. Males exposed to cues of sperm competition during rearing or immediately before mating were not more likely to sing post-copulatory songs. Males exposed to acoustic cues of male competitors had greater latency to begin singing and overall spent less time singing post-copulation than males exposed to silence. Rearing environment mattered more than the immediate environment, and although post-copulatory song presence was not affected by sperm competition exposure, males reared under low sperm competition invested more in post-copulatory song when they did sing.
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