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Galápagos lava lizards (Microlophus bivittatus) respond dynamically to displays from interactive conspecific robots

Abstract:

Abstract: In many species, outcomes of male duels determine access to females and, ultimately, male reproductive success. Ritualization of behavior in male contests can reduce the probability of injury, which benefits both contestants. Components of ritualized combat often include postures and displays that showcase a male’s quality in a sequential assessment of fighting ability. Among the most common contest acts in iguanine lizards are bobbing displays. Investigations of bobbing display dynamics often include experimental “playbacks,” in which video or robotic representations of conspecifics are presented to subjects. In most “playback” research, pre-programmed stimuli exhibit behavior that is independent of subjects’ responses, despite the fact that actual animal contests are highly interactive. In the present study, we utilized a robotic Galápagos lava lizard (Microlophus bivittatus) to investigate the importance of interaction in simulated contests under field conditions. Using a matched pairs design where each subject experienced two behavioral variants of the robotic stimulus, we tested the effect of a robot that displayed immediately following a subject’s display versus when the same robot display was postponed 30 s. Results showed that immediate response from the robot stimulated subjects to display significantly more often than when the stimulus was delayed. We speculate that subjects perceived a rapid response from their robotic contestant as being more aggressive than a delayed response. We discuss our results in light of relevant previous work, and we suggest possibilities for future research using interactive lizard robots. Significance statement: Some of the most impressive examples of ritualized animal behavior can be observed in male contests for access to reproductive females. The use of stereotyped displays in such duels allows males to assess one another’s quality while avoiding dangerous fighting that can lead to injury. For example, males in many lizard species perform bobbing displays where contestants respond to each other in reciprocal fashion. In this study, we used a realistic lizard robot as a stand-in for a contestant in simulated contests. We found that an immediate display response by the robot to a subject’s bobbing display stimulated subjects to display significantly more often than when the robot’s response was delayed by 30 s. To our knowledge, this is the first interactive robot “playback” experiment with lizards. Future research will further explore the “rules” underlying display behavior in lizard contests.