Abstract
Loggerhead turtle hatchlings in laboratory tanks had a sustained swimming speed of approximately 20 cm/s at temperatures between 25.6.degree. and 28.9.degree. C. Test temperatures of 30.0.degree. and 33.0.degree. C significantly reduced this speed. The swimming speed of hatchlings exposed to fluctuating temperatures varied with the temperature. A temperature of 33.0.degree. C eliminated phototactic orientation.