Interspecific odour discrimination by a lizard (Eumeces laticeps)

When presented with odours on cotton swabs, adult borad-headed skinks (Eumeces laticeps) of both sexes flicked their tongues at much higher rates to conspecific odour stimuli than to those of their most closely related congeners, E. fasciatus and E. inexpectatus, during 60-s exposures to cloacal odours from lizards of the opposite sex. A successive discrimination design was used in which each lizard responded to five different odour treatments in a random sequence. In addition to the three lizard odours, water was used as a measure of baseline tongue protrusion rates and a cologne was used as a pungency control. There were no significant differences among the four non-conspecific odour treatments in numbers of tongue flicks elicited, but the skinks emitted significantly greater numbers of tongue flicks to conspecific cloacal odours than to any of the other stimuli. It is hypothesized that E. laticeps produces a pheromone which may function for species identification. Although it is tempting to speculate that the pheromone may serve as a pre-mating mechanism for maintaining reproductive isolation from syntopic congeners, insufficient information is avialable to draw firm conclusions regarding such a function.