IN REPTILES, ARGININE VASOTOCIN (AVT) IMPACTS THE PERFORMANCE OF AND RESPONSE TO VISUAL SOCIAL SIGNALS, BUT WHETHER AVT ALSO OPERATES WITHIN THE CHEMOSENSORY SYSTEM AS ARGININE VASOPRESSIN (AVP) DOES IN MAMMALS IS UNKNOWN, DESPITE SOCIAL ODORS BEING POTENT MODIFIERS OF COMPETITIVE AND APPETITIVE BEHAVIOR IN REPTILES. HERE, WE ASK WHETHER ELEVATED LEVELS OF EXOGENOUS AVT IMPACT RATES OF CHEMICAL DISPLAY BEHAVIOR (E.G. TONGUE FLICKS) IN ADULT MALES, AND WHETHER CONSPECIFIC MALES OR FEMALES CAN CHEMICALLY DISCRIMINATE BETWEEN COMPETITOR MALES BASED ON DIFFERING LEVELS OF EXOGENOUS AVT IN GREEN ANOLES (ANOLIS CAROLINENSIS). WE INJECTED WILD-CAUGHT GREEN ANOLE MALES WITH EITHER AVT (AVT-MALES) OR A VEHICLE CONTROL (CON-MALES) SOLUTION, THEN PRESENTED TREATED MALES WITH A CONSPECIFIC STIMULUS (INTRUDER-MALE OR INTRUDER-FEMALE) AND FILMED 30-MINUTE INTERACTIONS. WE FOUND THAT AVT-MALES WERE FASTER THAN CON-MALES TO PERFORM A TONGUE FLICK TO CONSPECIFICS, AND FASTER TO CHEMICALLY DISPLAY TOWARD INTRUDER-FEMALES, SUGGESTING AVT INCREASED MALE INTEREST IN AVAILABLE CHEMICAL INFORMATION DURING SOCIAL ENCOUNTERS. INTRUDERS PERFORMED MORE LIP SMACK BEHAVIOR WHEN INTERACTING WITH AVT-MALES THAN WITH CON-MALES, AND INTRUDER-MALES PERFORMED MORE TONGUE FLICK BEHAVIOR WHEN INTERACTING WITH AVT-MALES THAN WITH CON-MALES, SUGGESTING ANOLES CAN DISCRIMINATE BETWEEN CONSPECIFICS BASED ON EXOGENOUS AVT LEVELS. WE ALSO FOUND A REDUCTION IN INTRUDER MOVEMENT BEHAVIOR WHEN INTRUDERS WERE PAIRED WITH AVT-MALES. THIS STUDY PROVIDES EMPIRICAL SUPPORT FOR AVT-MEDIATED CHEMOSENSORY BEHAVIOR IN REPTILIAN SOCIAL INTERACTIONS, IN A MICROSMATIC LIZARD SPECIES, SUGGESTING THE MECHANISM BY WHICH MAMMALIAN AVP AND NON-MAMMALIAN AVT MEDIATE CHEMOSENSORY BEHAVIOR DURING SOCIAL INTERACTIONS MAY BE EVOLUTIONARILY CONSERVED.

SOCIAL INTERACTIONS IN NONMAMMALIAN VERTEBRATES ARE MODULATED BY ARGININE VASOTOCIN (AVT), WHICH FUNCTIONS SIMILARLY TO ITS MAMMALIAN HOMOLOGUE, VASOPRESSIN. AVT IMPACTS THE PERFORMANCE OF AND RESPONSE TO VISUAL SIGNALS IN REPTILES, BUT WHETHER AVT ALSO OPERATES WITHIN THE CHEMOSENSORY SYSTEM AS IT DOES IN MAMMALS IS UNKNOWN, DESPITE SOCIAL ODORS BEING POTENT MODIFIERS OF AGGRESSIVE AND REPRODUCTIVE BEHAVIOR. PREVIOUS STUDIES IN GREEN ANOLES (ANOLIS CAROLINENSIS) LINKED ELEVATED LEVELS OF EXOGENOUS AVT IN MALES (AVT-MALES) TO LOWER RATES OF AGGRESSIVE VISUAL DISPLAYS, WHEREAS UNTREATED FEMALES VISUALLY DISPLAYED TO AVT-MALES MORE THAN TO SALINE-TREATED CONTROL-MALES. HERE, WE TEST WHETHER EXOGENOUS AVT IN RESIDENT-MALES IMPACTS THE CHEMOSENSORY OR LOCOMOTOR BEHAVIOR OF CONSPECIFICS (INTRUDERS). WE INJECTED RESIDENT-MALES WITH EITHER AVT OR A CONTROL SOLUTION, AND AFTER 10 MINS ALONE IN THEIR HOME TANKS, WE PRESENTED RESIDENT-MALES WITH AN UNTREATED INTRUDER (MALE OR FEMALE) FOR 30 MINS. WE FOUND THAT INTRUDER-MALES PERFORMED MORE CHEMICAL BEHAVIOR TOWARDS AVT-MALES THAN TO CONTROL-MALES, WHEREAS AVT-MALES RESPONDED WITH A CHEMICAL DISPLAY TO INTRUDER-FEMALES FASTER THAN DID CONTROL-MALES. IN CONTRAST, VISUAL BEHAVIOR DID NOT DIFFER BETWEEN TREATMENT GROUPS FOR EITHER RESIDENT-MALES OR INTRUDERS IN THIS EXPERIMENT. OUR RESULTS DEMONSTRATE FOR THE FIRST TIME THAT AVT MODULATES CHEMOSENSORY BEHAVIOR IN REPTILES, HAVING IMPORTANT EVOLUTIONARY IMPLICATIONS REGARDING MULTIMODAL COMMUNICATION AND THE MECHANISMS USED BY AVT TO MODULATE ANIMAL INTERACTIONS.