Behavioral responses of hatchling painted turtles (Chrysemys picta) and snapping turtles (Chelydra serpentina) at subzero temperatures

We monitored behavioral responses of cold-acclimated hatchling painted turt les (Chrysemys picta) indigenous to Nebraska and hatchling snapping turtles (Chelydra serpentina) indigenous to Nebraska and Arkansas during cooling ( 0.1 degrees C/min) to temperatures as low as -19 degrees C. All turtles mad e exploratory movements during cooling and locomotion occurred at temperatu res as low as -2 to -4 degrees C. but C. picta maintained relatively higher levels of locomotor activity than C. serpentina, and no differences in mot ility occurred between northern and southern groups of C. serpentina. Slow movements of the head and limbs were observed in supercooled hatchling C. p icta at temperatures as low as -10 degrees C. whereas at about -5 degrees C , C. serpentina exhibited an increase in spontaneous motor activity followe d by muscle contracture, immobility, and spontaneous freezing. C. picta spo ntaneously froze at about -16 degrees C without exhibiting cold contracture , suggesting that they are better adapted to survive exposure to extreme co ld. (C) 1999 Elsevier Science Ltd. All rights reserved.