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

Abstract

Using mark-recapture techniques, temperature-sensitive radio transmitters, and miniature temperature data loggers we investigated the hibernation ecology of northern temperate zone spotted turtles (Clemmys guttata) in Georgian Bay, Ontario, over 4 winters (1993-1997). We observed 18 hibernacula that were occupied by 34 turtles; 11 hibernacula were apparently occupied by single turtles, and 7 were used communally by up to 9 individuals. Hibernacula 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 the same hibernaculum in at least 2 winters. Turtles entered hibernacula between 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 ranged between 1 and 5°C. A waterproof temperature data logger attached to a turtle indicated that this turtle was protected from freezing in a thermally stable hibernaculum (body temperature range 0.3-3.9°C) despite highly variable (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 observed no mortality within hibernacula over the 4 winters; however, 3 turtles were destroyed by predators near the hibernacula. These data provide insight into the role of climate in limiting the northern distribution of this species.