TYPE OF SOIL AFFECTS SURVIVAL BY OVERWINTERING HATCHLINGS OF THE PAINTED TURTLE

1. We placed hatchlings of the North American painted turtle (Chrysemy s picta) on a dry surface and exposed them for 30 days to temperatures near - 5 degrees C to determine the risk to overwintering animals of freezing spontaneously by heterogeneous nucleation. We then placed ani mals in a second experiment into artificial hibernacula in damp clay o r damp, loamy sand, and exposed them to subzero temperatures near -4 d egrees C or -7 degrees C to assess the influence of different sails on survival by overwintering animals. 2. Hatchlings on a dry surface (an d making no contact with crystals of ice) remained unfrozen for 30 day s at temperatures near -5 degrees C, and all animals survived the expo sure. Thus, neonates are not at appreciable risk of freezing spontaneo usly by heterogeneous nucleation. 3. Turtles in artificial hibernacula in loamy sand survived as well as turtles in clay at temperatures nea r -4 degrees C, but animals in sand sustained higher mortality than th ose in clay at temperatures near -7 degrees C. 4. Some turtles in arti ficial hibernacula were inoculated by ice in the frozen soil, and none of these animals survived the tests of tolerance. Animals that surviv ed the tests remained unfrozen and supercooled. Thus, the key to survi val by hatchlings overwintering in the field apparently is to remain u nfrozen and supercooled regardless of the type of soil in which hibern acula are located. (C) 1997 Published by Elsevier Science Ltd.