Repeatability, locomotor performance and trade-offs between performance traits in two lizard species, Oligosoma alani and O. smithi

Locomotor performance has often been used as a proxy for fitness and is likely to be highly repeatable. Trade-offs between locomotor performance traits can occur when selection acts in opposing directions on traits that rely on common morphological structures. We assessed the repeatability of sprint speed and dive duration in robust (Oligosoma alani) and shore skinks (O. smithi), compared locomotor performance among intraspecific groups and investigated whether a trade-off between sprint speed and diving behaviour exists. Sprint speed and dive duration were measured in the field and analysed for average maximum and absolute maximum performance using Bayesian hierarchical models. In robust skinks, sprint speed was repeatable, but sprint speed and dive duration in shore skinks had moderately low repeatability. Juvenile female robust skinks displayed faster average maximum speeds than adult males, while the absolute maximum speeds of adult males were slower than other groups. Sprint speed and dive duration in shore skinks were similar between sexes. Intraspecific differences in locomotor performance probably reflect variation in the proportion of maximum capacity used, or divergent foraging and behavioural ecologies. Research into the biology and ecology of the two species is required to reveal the proximal causes for the observed relationships.