Meeting Abstract
A wide range of circumstances can result in animals being turned over into an upside-down position, including falls, encounters with predators, and intraspecific combat. Self-righting from an upside-down position is a critical ability for rigid-bodied animals in particular, which are at risk of stranding, predation, starvation, and desiccation if they are unable to return to a right-side-up orientation. Among vertebrates, turtles are unique in their possession of a bony shell, which might present a significant barrier to self-righting. When upside-down, many turtles use their head and neck as a lever during efforts to flip back over. However, the mechanics of such head use has received little study, and the aspects of performance that correlate with successful versus unsuccessful righting are not clear. To evaluate how turtles use the head to right themselves, we synchronized high-speed video with force platform recordings to measure righting performance in the semi-aquatic pleurodire turtle Emydura subglobosa, a species that uses mainly the head, rather than limbs, to execute flips. Turtles were filmed from anterior and dorsal views after being placed on their backs with their head contacting a force plate. Our results indicate that successful flips were faster than failed attempts, and that in successful flips the head incurred greater ground reaction forces and turning moments. These data suggest that self-righting is highly dependent on both the position of the head during the self-righting attempt and the magnitude of force generated, and that a combination of factors must reach a critical threshold for a righting attempt to succeed.
