Meeting Abstract
During swimming, animals can experience a variety of destabilizing forces, which can result in decreased energetic efficiency and locomotor performance. Many aquatic species exhibit external structural projections that, like the keels of boats, may increase their hydrodynamic stability. For example, juveniles of many aquatic turtle species possess small keels on the top of their shell (carapace), with some maintaining the keels into adulthood. To test if keels could provide similar stabilizing forces for turtles as they do for boats, we designed and affixed 3-D printed keels of various profiles to the carapace of a non-keeled turtle species, the painted turtle (Chrysemys picta). We used high-speed video to record turtles as they swam in a straight line following a prey stimulus. We then compared the performance between non-keeled swimming and swimming with keels of four size-shape configurations that span the range of those observed in nature. Our results did not indicate a substantial change in stability following the addition of any keel, though effects on maneuverability may be present. If keels do not provide locomotor benefits to swimming turtles, their presence and design may relate more strongly to other functional roles, such as inhibiting gape-limited predators and facilitating intraspecific or interindividual recognition.
