Freeze Avoidance and Freeze Tolerance: An Overview

The Physiology of Overwintering Turtle Hatchlings

   
Supercooling Reptiles, amphibians, mammals, and birds rely on the ability to raise their body temperatures. However, reptiles and amphibians are not able to raise their body temperatures themselves, as mammals and birds do (Pough, 1980). While birds and mammals generate energy to raise their body temperatures to appropriate levels (endothermy), reptiles and amphibians obtain the energy to do this from their external environments (ectothermy) through thermoregulatory behavior (Pough, 1980).
   
Freeze Avoidance in Overwintering Snapping Turtle (Chelydra serpentina) Hatchlings

Freeze Avoidance in Overwintering Blanding's Turtle (Emydoidea blandingii) Hatchlings  
 

Photo by Christian Oldham

   
Variation in Freeze Tolerance Between Species As a subset of ectothermic reptiles, various species of turtles are known to possess the ability to survive cold temperatures during winter months at different life stages. Such species employ different methods in overwintering strategies. Overwintering strategies within species may be dependent on morphological characteristics, behavior, or distribution (Packard et al., 1999).
   
Freeze Tolerance in Overwintering Slider (Trachemys scripta) Hatchlings  
   
Freeze Tolerance in Overwintering Northern Map Turtle (Graptemys geographica) Hatchlings  
   
Literature Cited  
   
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