The Herpetological Journal

pp.143-147

Authors: John Davenport , Nina De Verteuil And Shona H. Magill

Abstract: Young green turtles, Chelonia mydas responded to increasing current velocities by swimming upstream for a greater proportion of the time. At temperatures of 21-25°C currents equivalent to 1-2 body lengths s^·1 induced continuous upstream swimming. At low current velocity the turtles usually employed ' dog-paddle' (ipsilateral synchronized) swimming. At swimming speeds of 0.8-1.4 body lengths s^·1 they switched to synchronized forelimb flapping, with stationary rear limbs. Maximum dog-paddle speed was about 40% of maximum speed using synchronized foretlippers: the latter mechanism is clearly capable of generating far more propulsive power. Maximum sustained swimming speeds at 25°C, 21°C and 15°C were 3.3 1, 2. 96 and 2.09 body lengths s^·1 respectively; the speed at 15°C was significantly lower than at the other two temperatures, and could not be sustained for more than 2-4 min before instability in pitch, roll and yaw prevented the animal from swimming upstream. A detailed analysis of the swimming mechanism at different temperatures is presented. This demonstrated a significant degradation of co-ordination of swimming at 15°C, even though the lethal temperature of green turtles is well below 10°C. The significance of this finding is discussed in terms of vulnerability of the species to cold.