Agonistic and sensory behaviour of the salamander Ensatina eschscholtziiduring asymmetrical contests

Abstract

The outcome of interactions between individuals depends on the sex of the interacting individuals as well as asymmetries in residency or body size. This study tested the effects of these asymmetries on the agonistic and sensory behaviour of the western plethodontid salamander Ensatina eschscholtzii. Behaviour was observed during the non-courtship season for same-sex, same-population pairs. Asymmetries due to resident status had strong effects on agonistic and sensory behaviour. Residents were more aggressive than intruders, and intruders nose-tapped more frequently than residents. Asymmetries in body size had weaker effects. These results suggest that residents are capable of marking, recognizing and defending home areas, and that intruders are capable of assessing their role as interlopers in other salamanders& home areas. The defence of home areas further suggests that Ensatinamay be territorial. The effects of asymmetries of residency on behaviour also differed between the sexes. Males performed more aggressive behaviour than females, and females performed more sensory behaviour than males. Males may be more aggressive than females because they are more territorial and/or because intra-sexual competition (mate competition) is stronger between males than between females. Sex differences in sensory behaviour suggest that females may rely more heavily than males on olfactory reception to assess territories and/or competitors and potentially to assess mates.