Running of the feathertail glider (Acrobates pygmaeus) on level ground: Gaits.

Gliding is a crucial adaptation to arboreal habitats in several groups of mammals. Along with certain advantages it imposes limitations on the quadrupedal running since it affects the locomotor apparatus. To estimate the impact on quadrupedal running in gliders, the feathertail glider (Acrobates pygmaeus) was chosen considering that the small size allows minor morphological modifications for aerial locomotion. The gaits were studied on horizontal flat substrate which made it possible to compare running technique of the glider with that of terrestrial mammals. In all analyzed plots the footfall sequence was found to be asymmetrical; in most cases the bound was used, in contrast, the gallop occurred only occasionally. The half-bound with the fore lead, the most usual asymmetrical gait in quadrupedal marsupials, was much less common in A. pygmaeus than the bound; the rare among mammals half-bound with the hind lead was also found. The bound was not only the most common gait but also the steadiest one; therefore we can conclude that A. pygmaeus uses all other asymmetrical gaits as transitional forms associated with changes in speed, direction, etc. The bound with extended suspension is probably preferred by A. pygmaeus because it most closely resembles gliding by posture.