Moving in complex environments: a biomechanical analysis of locomotion on inclined and narrow substrates

Abstract

ABSTRACT Characterisation of an organism s performance in different habitats provides insight into the conditions that allow it to survive and reproduce. In recent years, the northern quoll (Dasyurus hallucatus) – a medium-sized semi-arboreal marsupial native to northern Australia – has undergone significant population declines within open forest, woodland and riparian habitats, but less so in rocky areas. To help understand this decline, we quantified the biomechanical performance of wild northern quolls as they ran up inclined narrow (13\u2005mm pole) and inclined wide (90\u2005mm platform) substrates. We predicted that quolls may possess biomechanical adaptations to increase stability on narrow surfaces, which are more common in rocky habitats. Our results showed that quolls have some biomechanical characteristics consistent with a stability advantage on narrow surfaces. This includes the coupled use of limb pairs, as indicated via a decrease in footfall time, and an ability to produce corrective torques to counteract the toppling moments commonly encountered during gait on narrow surfaces. However, speed was constrained on narrow surfaces, and quolls did not adopt diagonal sequence gaits, unlike true arboreal specialists such as primates. In comparison with key predators, such as cats and dogs, northern quolls appear inferior in terrestrial environments but have a stability advantage at higher speeds on narrow supports. This may partially explain the heterogeneous declines in northern quoll populations among various habitats on mainland Australia. Summary: An organism s performance provides insight to its survival. To understand significant population declines in the northern quoll, we quantified biomechanical performance as they ran up narrow and wide substrates.