Behaviour 2019
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How Do Audience Effects Manifest in a Polymorphic Species? Exploring a Puzzling Display
Samantha M. West, Hunter A. Wortmann, William A. Johnson, Gita R. Kolluru. California Polytechnic State University, San Luis Obispo, CA, United States

Animal behavior occurs within a network of witnesses; an audience effect occurs when the presence of a witness alters an individual’s behavior. Girardinus metallicus is a polymorphic, livebearing fish: black morph males display during mating whereas plain morph males sneak copulations. The functional significance of the display is debated because neither black morphs nor their display traits are preferred by females. Understanding how black morph males respond to an audience of each morph may illuminate the role of the display and allow us to explore audience effects in polymorphic species. We asked whether display duration, proportion of successful copulations, and total number of copulations were adjusted based on audience (plain morph male, black morph male, female, none). Display duration increased with increasing body size of the focal male relative to the audience male, and increasing body size of the focal female relative to the audience female, indicating courtship and aggressive intermale functionality. Males also had higher proportions of successful copulations with a black morph over a plain morph audience, providing evidence for morph-specific audience effects.