Species recognition of color and motion signals in Anolis grahami: evidence from responses to lizard robots

Male Anolis lizards exhibit an impressive diversity of dewlap color patterns and motion displays. These traits are thought to mediate species recognition, but direct experimental support is limited. It is also unclear if and how color and display behavior each may contribute to the signaling of species identity. We used a programmable robotic lizard to manipulate these signal components independently in Anolis grahami. Four robot variants were used: a control treatment that displayed the conspecific (orange) dewlap color and headbobbing sequence, 2 treatments that differed from the control only in dewlap coloration (light or dark blue), and a fourth treatment that differed from the control only in headbob display pattern (reversed headbob display structure). Artificial dewlaps were calibrated in color and brightness to the A. grahami visual system using a computational model. We presented robots to 102 adult male subjects and quantified their responses for durations of dewlap pulsing and headbob displays. Subjects spent significantly more time pulsing their dewlaps in response to control (conspecific) robot displays than to treatments that deviated from the control either in dewlap color or in headbob display structure. Our findings implicate both morphology and behavior as functional components of social signaling in A. grahami, thus underscoring the complex, multicomponent nature of anoline displays.