The Chemical Detection of Conspecifics by Juvenile Yarrow's Spiny Lizard, Sceloporus jarrovi

Abstract

The role of tongue extrusions in the chemical detection of conspecifics was examined in juvenile Yarrow's spiny lizard (Sceloporus jarrovi). A comparison was made between the number of tongue-touches performed under three different experimental conditions: home cage, unfamiliar clean cage and an unfamiliar cage previously occupied by conspecifics of the same sex. Both males and females exhibited the same number of tongue-touches in each condition. As a result data were combined before analysis of the differences between the three experimental conditions. The rate of tongue-touching in the home cage was significantly less than the rate in the clean unfamiliar cage, which in turn was less than the rate in the unfamiliar marked cage. This indicates that juvenile S. jarrovi deposit chemicals that are detected by conspecifics. DeFazio et al. (1977) determined that adult Yarrow's spiny lizards, Sceloporus jarrovi, exhibit an increase in substrate tongue-touches (touching the tongue to the substrate) when placed in an unfamiliar cage as compared to the home cage, and an even greater increase when placed in a cage where another lizard had been kept. The authors suggest that the tongue is used to explore new situations, that pheromones may be deposited and detected by the lizards and that the tongue-Jacobson's organ system plays a role in chemical detection, as it does in snakes. Bissinger and Simon (1979) further explored these three possibilities for a variety of lizard species. Field experiments also indicate that chemicals deposited by adult S. jarrovi during the breeding season are detected by conspecifics (Gravelle and Simon, submitted). Both sexes spent less time in the section of the enclosure containing chemical cues left by lizards of the same sex, while males remained in the female's area, after she was removed, for longer periods of time. Additionally, tongue-touches performed by both males and females decreased in areas previously inhabited by a same-sex adult, while males responded to the absent female's home area with an increase in tongue-touches. Males also showed a significant increase in marking behavior (defecations and pelvic rubs) in the female's home area. Recently, Duvall (1979) observed that male western fence lizards, S. occidentalis, can discriminate between unmarked surfaces and those labelled by conspecifics of the same sex.