The outcome of male-male encounters affects subsequent sound production during courtship in the cichlid fish Oreochromis mossambicus

摘要

Social status in lek-breeding species is highly correlated with mating success. Reproductive failure of subordinates may be caused either by direct aggression by dominant males or by induced physiological changes. We hypothesized that recent social status (winning or losing an encounter with another male) affects the production of courtship sounds in male Mozambique tilapia, Oreochromis mossambicus, in the absence of dominant males. We staged dyadic encounters between males and subsequently allowed full access to a female to either the winner or the loser (one fish per dyad). We minimized possible effects of social experience by isolating the subject males before the experiments. All males courted the females but winners produced more courtship sounds than losers and showed significantly shorter courtship latencies and longer courtship durations. The sounds of winners had longer pulse durations and lower peak frequencies. Male size and condition factor, fighting latency and duration, and number of escalated agonistic acts were not correlated with number of sounds or any of the courtship parameters measured. Differences between winners and losers in courtship were probably related to transient physiological changes induced by the encounter outcome, such as changes in levels of circulating monoamines, cortisol and androgens, which can modulate courtship behaviour including sound production. We suggest that in nature the outcome of recent social interactions between males may affect the production of courtship sounds and courtship behaviour in general from the early stages of hierarchy formation.