Animals frequently traverse a range of deformable substrates, leaving tracks. Track morphology is controlled by anatomy and motions of the foot, and substrate consistency, resulting in complex, three-dimensional structures that record dynamic foot-substrate interactions. Understanding such interactions can provide valuable biological and environmental insights, but visualising them remains challenging. Prior physical experiments explored track formation using various indenters impressed into a range of substrate types and consistencies. However, to visualise the deformation below the surface, destructive methods such as physical sectioning are often used, typically resulting in the sample being destroyed. Here, we present the methodology and challenges involved in experimentally generating tracks and introduce micro-CT scanning as a non-destructive approach to visualising sub-surface sediment movement during track formation. Two separate track volumes were produced using different substrate consistencies (‘soft’ and ‘very soft’) whereby sand and clay were alternately layered and then scanned during indentation by a cadaveric pheasant (Phasianus colchicus) foot. Across the two substrate consistencies, the CT reconstructions revealed differences in sub-surface sediment displacement, and in complex sub-surface features. Although there are challenges attributed to experimentally producing and visualising tracks, micro-CT offers a novel approach to viewing sub-surface sediment movement during experimental track formation in the lab.
Prescott et al. (Mon,) studied this question.