The ability of juvenile black iguanas, Ctenosaura similis, to discriminate
between the chemical cue of an unfamiliar and a familiar conspecific was te
sted. Lizards directed significantly more tongue extrusions toward the chem
ical cue of a size-matched conspecific with whom they had never interacted
than the chemical cue of a size-matched conspecific with whom they had inte
racted for 3 d. We consider the possibility that the social relationship be
tween familiar associates may explain variation in the direction and degree
of response to unfamiliar vs. familiar chemical cues.