Fighting fish love robots: mate discrimination in males of a highly territorial fish by using female-mimicking robotic cues

Among territorial animals, several species are characterized by males showing the same initial behaviours towards both sexes, leading to significant chances of injuries against conspecifics. In this study, we investigated how visual stimuli exhibited by a female-mimicking robotic replica can be exploited by highly territorial Betta splendens males to discriminate males from females. In addition, we tested the effect of light stimuli, mimicking the colour pattern of a reproductive female, on the consistence of courtship displays in B. splendens males. The intensity of male behaviours used in both courtship and not-physical agonistic interactions (e.g. fin spreading and gill flaring) was not importantly modulated by different stimuli. Conversely, behavioural displays used specifically in male–female interactions significantly increased when the robotic replica colour pattern mimicked a reproductive female. Furthermore, male courtship behaviours obtained in response to the robotic replica exhibiting light stimuli were comparable with responses towards authentic conspecific females. Our biomimetic approach to establish animal–robot individual interaction can represent an advanced strategy for trait-based ecology investigation, a rapidly developing research field.