Locomotor performance in a running toad: roles of morphology, sex and agrosystem versus natural habitat

Abstract

Locomotor performance is often key in animal fitness, and may be affected by habitat anthropization. This study compares locomotor performance of natterjack toads (Epidalea calamita), which move by intermittent runs, from a natural pine grove and surrounding agrosystems. The effects of sex, morphology and habitat on sprint speed and run rate (number of runs per metre) were assessed. Males were faster than females, and had longer limbs, but the latter trait only partially explained sex differences in sprint speed. Sprint speed was directly related to hindlimb length, but not to any of the other morphological traits measured. Thus, other factors, such as amplexus ability, seemingly shape longer forelimbs in males. Habitat did not affect sprint speed, but toads from the agrosystem habitat had a higher run rate, which could help increase vigilance or confound predators, probably related to habitat openness and/ or human presence. For a given speed, males used greater run rates than females, probably because males encounter predators more often and face higher predator pressure. Finally, a negative relationship between sprint speed and run rate suggests that slower toads tend to use short runs, which may improve vigilance or help to confuse predators, while faster toads tend to use long runs, probably for fast escape from predators.