Effects of forest management on the ecology and behavior of Eastern Box Turtles

Andrea F Currylow, Purdue University

Abstract

Declines in long-lived and geographically widespread forest animals, such as the case with Eastern Box Turtles (Terrapene carolina carolina ), warrants investigation. Despite declines, this species' ability to endure in a range of available habitat and its physiological ties to environmental flux make it ideal for study of habitat use and selection amid anthropogenic disturbances. For my thesis work, I focused on investigating the ecology and behavior of Eastern Box Turtles following timber harvests. As part of the Hardwood Ecosystem Experiment, I used nine experimental forest management sites to investigate the effects of clearcut harvest openings and group selection harvest openings on box turtles. I used standard homing radiotelemetry to collect GPS location, morphometric, temperature, and behavior data on 50 adult Eastern Box Turtles. I conducted the majority of this work during the active seasons (May–October) but during the winter of 2010 I investigated the hibernal thermal ecology within clearcut harvest openings. Combined with the radiotelemetry data previously collected on these turtles from 2007-08, I was able to measure the effects of the harvests by analyses of movement parameters and temperatures. I found that timber harvests had no effect on the typical measurement of home range size, 100% Minimum Convex Polygons (MCP), however the MCPs here are 33% larger than any other published report for this species. Additionally, I found that turtles decreased the daily distances they traveled by approximately 30%, but their thermal optima increased by 8% following the harvests. Microclimates inside the timber harvests were significantly warmer (29%) in the summer and colder (31%) in the winter than forested habitats, effectively excluding many animals from consistently using them. Instead of leaving the harvested areas, however, turtles continued to use them differently. During the active season, box turtles used the edges of harvest areas apparently for behavioral thermoregulation and possibly for foraging. Turtles that used the harvest areas maintained 9% higher body temperatures during the active season than those that did not. During the winter, turtles generally burrowed to 10 cm for overwintering, but depth varied by slope and gender. I found that the depth influenced the emergence timing, which was also correlated with a soil-surface temperature inversion. A single female turtle that hibernated in a group-selection harvest opening had an estimated burrowing depth of nearly 30 cm to maintain her hibernal body temperature. Moreover, I estimated the annual survival rate (96.2%) of box turtles in our population, the first for the Midwest. The investigation of ecological mechanisms underlying species declines has become paramount in conservation literature. Simply reporting the extirpation of populations without testing mechanistic causes does little to promote conservation management. Herein, I investigated temporal thermal habitat availability, habitat use, thermal behavior, survival, and intersexual differences among Eastern Box Turtles within the framework of a managed forest setting.

Degree

M.S.

Advisors

Williams, Purdue University.

Subject Area

Wildlife Conservation|Ecology|Zoology

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