TRADE-OFFS BETWEEN SPRINTING AND CLINGING ABILITY IN KENYAN CHAMELEONS

1. We measured the force required to pull chameleons from perches of varying diameters and the sprint speed of chameleons on flat surfaces and on perches of varying diameters. The two species examined differ in their degree of terrestriality: Chamaeleo jacksonii is almost completely arboreal, whereas C. dilepis is semi-arboreal and is often observed on the ground. 2. We tested the following hypotheses: (a) each species has relatively greater sprinting and clinging abilities on surfaces corresponding to those it uses most frequently; or (b) a trade-off exists between maximizing clinging and sprinting abilities. 3. The results support the second hypothesis: C. dilepis runs faster than C. jacksonii on almost all diameters, but has poorer clinging ability on all diameters. 4. Differences in muscle architecture and composition may underlie this trade-off. Comparison with trade-offs in arboreal locomotor performance exhibited by less-specialized lizards indicates that the extreme adaptations of chameleons have allowed them to enter and diversify in a novel adaptive zone, but also may constrain the direction of subsequent adaptive change.