Classical conditioning provides paternity advantage for territorial male blue gouramis (Trichogaster trichopterus)

An irony of territorial behavior is that successful territory defense requires males to be aggressive, but highly aggressive males often inadvertently repel females, potential mates that the territory was created to attract. The authors provide empirical evidence that learning to anticipate the arrival of a female not only can overcome this well-recognized cost of territorial behavior but also can provide a significant paternity advantage. Following a short training period in which male blue gourami fish (Trichogaster trichopterus) either received classically conditioned pairings of a signal and a receptive female or received unpaired presentations of the signal and a female, male subjects were given an opportunity to mate. Signaling of female accessibility not only enabled classically conditioned males to attenuate their initial aggressive response to arriving females but, more important, classically conditioned males were able to spawn with females sooner, clasp females more often, and produce more young than males that did not have the benefit of a signal. Results provide the first demonstration of direct reproductive benefits resulting from classical conditioning.