On the Orbit Orientation and Visual Resolution of Mammalian Gliders

Abstract

In this study, I analyze the comparative visual system of gliders through orbit and skull dimensions and geometry between gliding rodents, marsupials, and colugos with their non‐gliding relatives. Gliders need: (1) the depth, distance, size, and orientation of target landing substrates prior to takeoff; (2) heading and acceleration data on movement in order to adjust while in air; and (3) to re‐position for landing based on visual approach to the landing substrate. Previous work has suggested that gliding mammals have higher orbit convergence to expand their visual fields or that these animals have larger interorbital distances to increase binocular parallax; both suggestions rely on greater depth perception as underlying functional causes. Additionally, I model the limitations imposed by visual resolution, sensitivity, and visual field sizes on distance and heading perceptions in gliders. Morphometric results do not support the suggestion that orbit dimensions and geometry vary with locomotor type; gliders do not have more convergent or widely spaced orbits. Perhaps more importantly, modeling of visual resolution of substrates at the distances commonly traversed by gliders suggests that these animals cannot rely solely on visual data for locomotor judgments.