Scaly-tail organ enhances static stability during Pel's scaly-tailed flying squirrels' arboreal locomotion

Scaly-tailed squirrels (Anomaluridae) are one of the least studied mammalian families. Their name is due to a peculiar and unique scaly-tail organ extruding from the caudal vertebra that has been predicted to help reduce skidding. This study investigates the function of the scaly-tail organ found in Anomalurus pelii, investigating its potential role in enhancing arboreal locomotion. As these animals glide from tree to tree in a habitat abundant with smooth-bark trees, we hypothesize that the scaly-tail organ assists with friction enhancement in their native smooth-bark habitat. Through a combination of analyses using mathematical and physical models for experimental validation, we explore whether the scaly-tail organ could improve the sliding and pitching stability during perching. Our experimental results showed that the scaly-tail organ can act as a skid-reduction mechanism by enhancing substrate engagement on intermediate roughness substrates by 58%. Mathematical models showed the scaly-tail organ enhances static pitch stability by acting as an additional support point. Our model showed that the scaly-tailed squirrel can reach up to 82.5° inclination without claw force; however, without scales, it reduces to 79.6°. Overall, this research highlights the functional significance of scaly-tail organs in adaptations in scaly-tailed flying squirrels and contributes to our understanding of their locomotion strategies and environmental stresses. Our study also provides insights into innovative locomotion mechanisms for robots operating in arboreal environments.