KOJESZEWSKI, T. B. *; FISH, F. E.; West Chester University; West Chester University: Swimming of the Florida manatee: Mechanics and efficiency of an aquatic grazer

Swimming performance is associated with the foraging ecology of aquatic animals. Marine mammal predators may be characterized based on prey capture techniques that affects how efficient the animal needs to swim in order to forage successfully. Dolphins, which feed on elusive prey, are efficient swimmers that perform precise maneuvers at high speeds. Florida manatees (Trichechus manatus latirostris), the only herbivorous marine mammal, forage upon sedentary plants. The submerged swimming of captive Florida manatees was studied by videotaping individuals as they rectilinearly swam in large pools with underwater viewing. The kinematics of swimming were analyzed using a computerized video analysis system (Peak Motus). Manatees swam at velocities of 0.06-1.14 ms^-1. Locomotion was accomplished by undulation of the body and caudal appendage. The frequency of the propulsive cycle increased linearly with increasing swimming velocity. Amplitude at the tip of the caudal fluke was 22% of body length and remained constant with respect to velocity. Propulsive efficiency was 0.74 as calculated using a hydromechanical model. The thrust power increased curvilinearly with velocity. We conclude that despite the use of a primitive undulatory swimming mode and paddle-like fluke for propulsion, the manatee is capable of generating large amounts of propulsive power at efficiencies that are at the lower limits produced by the oscillatory movements of the high-aspect ratio flukes of cetaceans. The swimming performance of the manatee is in accordance with its habits as an aquatic grazer that seasonally migrates over extended distances.