Male Grijalva mosquitofish (Heterophallus milleri Radda, 1987) increase individual mating preferences in front of an audience

Socially influenced mate choice behavior is currently a growing field in the study of sexual selection and evolution. Here, we provide the first description of male Grijalva mosquitofish (Heterophallus milleri) courtship behavior, and further report on an unparalleled “audience effect” in that species. Lab-reared male Grijalva mosquitofish significantly increased their preference for an initially preferred female in a full contact design in the presence of another male. This is somewhat unexpected as previous studies found males of other members of the family Poeciliidae to interact more evenly with stimulus females when faced with an audience, and thus decreasing their preference for the initially preferred female. As those “audience effects” are assumed to represent male tactics to prevent sperm competition risk arising through male mate choice copying, we argue that male mate choice copying might not play a major role in the reproductive biology of H. milleri.