Meeting Abstract
The costs of steady swimming can represent most of the daily energy budget of aquatic animals. Maintaining stability while swimming is thought to provide energetic advantages that can limit such costs, as well as sensory advantages. However, environmental fluctuations can dramatically influence animal behavior and performance. In water, one of the most common types of environmental fluctuation is changes in water flow conditions. How well can stability be maintained under changing flow conditions? We measured the stability of two different species of turtle, the pink bellied side-necked turtle (Emydura subglobosa) and the painted turtle (Chrysemys picta) as they swam in still water, as well as water flowing at 1 and 2 body lengths/sec. We found that both species increased their velocity at faster flow speeds. They achieved these higher speeds by increasing stride length rather than stride frequency, but the two species did so in different ways. E. subglobosa increased stride length through greater retraction of its arms and protraction of its legs, whereas C. picta increased stride length through greater protraction of its arms and greater retraction of its legs. E. subglobosa was more stable in still water than C. picta but, as flow speeds increased, C. picta became more stable than E. subglobosa. Our results show that animals may respond to changing conditions in an overall similar manner by increasing stride length, but that the mechanism behind increased stride length may differ, and these differences may result in differences in performance in across varying environments.
