Male Medaka, Oryzias latipes, Determine Their Reproductive Tactics Based on Dominance Relationships With Rival Males and Courtship Aggressiveness Toward Females

), in which males flexibly change their reproductive tactics, not only the dominance relationships between males but also the courtship aggressiveness of individual males toward females may influence the selection of reproductive tactics such as pair-spawning, sneaking, and non-participation in reproduction. However, no previous studies have examined the relationship between the dominance relationship between two males and their reproductive tactics, nor the relationship between courtship behavior toward females and their reproductive tactics. In this study, two males were allowed to compete, and an ovulated female was introduced into a tank. Fighting behavior between males when only males were present, fighting behavior between males after the female was introduced, and the courtship behavior of each male toward the female were quantified, and the behavioral patterns were analyzed. The results showed that many subordinate males in male-male competition did not participate in reproduction, and that sneaker males could be classified into two different behavioral patterns: those that were subordinate to rival males and those that were dominant. These results suggest that sneaking is not a fixed tactic but rather that various behavioral patterns can be adopted depending on the aggressiveness of rival males and their courtship positivity toward females, providing important insights into the flexibility of male reproductive tactics.