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1 April 2005 Thermal Environment of Overwintering Ornate Box Turtles, Terrapene ornata ornata, in Iowa
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The carapace temperatures of ornate box turtles (Terrapene ornata ornata) were monitored by affixing temperature dataloggers during two winters, 2001–2002 and 2003–2004. The dataloggers recorded temperature every 3 h to the nearest 0.5 C. Date of burrowing in the fall, emergence time in the spring and temperatures 48 h prior to emergence were analyzed along with the entire temperature profile of the turtles during the winter. In 2003–2004 soil temperatures from the surface to 0.75 m depth were also monitored.

Most turtles did not experience freezing temperatures during either winter, but two turtles were below freezing for up to 54 consecutive days during winter 2001–2002.

During 2001–2002, eight of nine turtles began burrowing within 7 d of each other in the fall, and all nine emerged within 7 d of each other in the spring. During 2003–2004, fall burrowing for 16 turtles occurred within 14–21 d, and emergence happened within 15 d. Overwintering periods varied between 172–201 d, which was intermediate between dates noted in studies to the north, south and west for this species. During 2003–2004, it was inferred that turtles burrowed to a minimum of 0.5–0.75 m by comparing turtle temperatures to those recorded at different depths in the soil, although we recorded a previous depth of up to 1.67 m.

Emergence onto the surface in the spring did not relate to soil temperature, and there was no support for emergence triggered by 48 h of soil temperatures above 7 C (Grobman, 1990). It is suggested that spring emergence may be correlated with a more complex set of factors and that Terrapene ornata ornata can withstand prolonged freezing temperatures.

NEIL P. BERNSTEIN and ROBERT W. BLACK "Thermal Environment of Overwintering Ornate Box Turtles, Terrapene ornata ornata, in Iowa," The American Midland Naturalist 153(2), 370-377, (1 April 2005).[0370:TEOOOB]2.0.CO;2
Accepted: 1 September 2004; Published: 1 April 2005

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