Phenology and ecology of hibernation in spotted turtles (Clemmys guttata) near the northern limit of their range

Using mark-recapture techniques, temperature-sensitive radio transmitters, and miniature temperature data loggers we investigated the hibernation ecol ogy of northern temperate zone spotted turtles (Clemmys guttata) in Georgia n Bay, Ontario, over 4 winters (1993-1997). We observed 18 hibernacula that were occupied by 34 turtles; 11 hibernacula were apparently occupied by si ngle turtles, and 7 were used communally by up to 9 individuals. Hibernacul a were located in swamps and were of 2 types: sphagnum moss hummock (n = 15 ) and rock cavern (n = 3). Almost half of the individuals (16 of 34) used t he same hibernaculum in at least 2 winters. Turtles entered hibernacula bet ween mid-September and October, when their body temperature was between 12 and 16 C, and exited them in mid to late April, when ambient temperatures r anged between 1 and 5 C. A waterproof temperature data logger attached to a turtle indicated that this turtle was protected from freezing in a thermal ly stable hibernaculum (body temperature range 0.3-3.9 C) despite highly va riable (a 37 C change over 5 days) and low air temperatures (minimum -35 C) . Loss of body mass (2%) during hibernation was not significant. We observe d no mortality within hibernacula over the 4 winters; however, 3 turtles we re destroyed by predators near the hibernacula. These data provide insight into the role of climate in limiting the northern distribution of this spec ies.