Biomechanical factors influencing successful self-righting in the pleurodire turtle,Emydura subglobosa

Abstract

Self-righting performance is a key ability for most terrestrial animals, and has been used as a metric of fitness, exhaustion and thermal limits in a variety of taxa. However, there is little understanding of the underlying mechanisms that drive variation in self-righting performance. To evaluate the mechanical factors that contribute to success versus failure when animals attempt to self-right, we compared force production and kinematic behavior in the rigid-bodied, pleurodire turtle between successful and unsuccessful self-righting efforts. We found that the moment exerted during efforts to roll the body and the velocity of that roll are the primary drivers behind self-righting success. Specifically, turtles that self-righted successfully produced both larger moments and faster rolls than turtles that failed. In contrast, the angle at which the head was directed to lever the body and the extent of yaw that was incorporated in addition to roll had little impact on the likelihood of success. These results show that specific performance metrics can predict the ability of animals to self-right, providing a framework for biomimetic applications as well as future comparisons to test for differences in self-righting performance across animals from different environments, sexes, populations and species.

Turning turtle: scaling relationships and self-righting ability in Chelydra serpentina

“…Snapping turtles retain a high degree of carapace rotation as they walk [17] and the neck remains the primary driver in self-righting [18], throughout their lives. A Testudine's ability to self-right is dependent on body size, body shape, and flexibility of the limbs, neck, or tail [19][20][21]. There are two distinct mechanisms by which Testudines self-right: (i) rotating the limbs, to generate rocking movements to ultimately induce body rolling, or (ii) extending the neck, to directly push against the ground and flip the animal over [20,22].…”

“…Investigations of self-righting in Testudines are often limited to theoretical models of the impact of shell shape [20,23,24], the time to self-right (e.g., [25]), and biotic or abiotic influences (e.g., [11]). And, to our knowledge, just one study has looked at the biomechanics of self-righting [19].…”

“…The ability to self-right is dependent on body size, body shape and flexibility of the limbs, neck or tail [ 19 – 21 ]. There are two distinct mechanisms by which Testudines self-right: (i) rotating the limbs, to generate rocking movements to ultimately induce body rolling; or (ii) extending the neck, to directly push against the ground and flip the animal over [ 20 , 22 ].…”

“…[ 11 ]). To our knowledge, just one study has looked at the biomechanics of self-righting [ 19 ]. The challenge of self-righting is that the inverted animal is in a stable and low-gravitational potential-energy state.…”

The metabolic cost of turning right side up in the Mediterranean spur-thighed tortoise (Testudo graeca)

“…Aside from the impacts on how they breathe, being limited by their mobility, rigid-bodied and armoured terrestrial Testudines species are also susceptible to overturning through every-day occurrences such as competition, mating behaviour, predation attempts, or locomotion over uneven landscapes 14 , 15 . Failure to self-right once turned upside-down can lead to life-threatening consequences including predation, starvation, desiccation, loss of mating or foraging opportunities, and thermal stress 14 – 18 .…”