Short-Term Forest Management Effects on a Long-Lived Ectotherm

Abstract

Timber harvesting has been shown to have both positive and negative effects on forest dwelling species. We examined the immediate effects of timber harvests (clearcuts and group selection openings) on ectotherm behavior, using the eastern box turtle as a model. We monitored the movement and thermal ecology of 50 adult box turtles using radiotelemetry from May–October for two years prior to, and two years following scheduled timber harvests in the Central Hardwoods Region of the U.S. Annual home ranges (7.45 ha, 100% MCP) did not differ in any year or in response to timber harvests, but were 33% larger than previous estimates (range 0.47–187.67 ha). Distance of daily movements decreased post-harvest (from 22 m±1.2 m to 15 m±0.9 m) whereas thermal optima increased (from 23±1°C to 25±1°C). Microclimatic conditions varied by habitat type, but monthly average temperatures were warmer in harvested areas by as much as 13°C. Animals that used harvest openings were exposed to extreme monthly average temperatures (∼40°C). As a result, the animals made shorter and more frequent movements in and out of the harvest areas while maintaining 9% higher body temperatures. This experimental design coupled with radiotelemetry and behavioral observation of a wild ectotherm population prior to and in response to anthropogenic habitat alteration is the first of its kind. Our results indicate that even in a relatively contiguous forested landscape with small-scale timber harvests, there are local effects on the thermal ecology of ectotherms. Ultimately, the results of this research can benefit the conservation and management of temperature-dependent species by informing effects of timber management across landscapes amid changing climates.

Seasonal variations in plasma vitellogenin and sex steroids in male and female Eastern Box Turtles, Terrapene carolina carolina

“…Throughout the animal kingdom, males with high testosterone are generally larger, more aggressive and usually associated with large home ranges, gaining them access to additional mates [40,41,71,72]. However, when comparing the concentration of sex hormones to the reported home range sizes of a subset of these animals [10], we found that males which maintained larger home ranges had significantly less TT than those with smaller home ranges. Males that maintain larger home ranges may be more stressed by the movements and therefore have lower TT.…”

“…There were no significant associations detected between E2 and behaviors in females (F 4,41 = 0.65, P = 0.6318), however some of the highest levels were associated with observed sexual behaviors ( Table 2). When investigating reported home range sizes [10] in relation to the concentration of sex hormones, we found there to be a significant negative correla- tion between median TT levels and maintained home range sizes in males (R 2 = 0.27, n = 22, P = 0.0134; Fig. 5).…”

“…As part of a concurrent radiotelemetry study [10] a subset of tracked individuals were sampled repeatedly over the active seasons. We used the reported home ranges of those tracked individuals to assess any effects of hormone concentrations on observed behavior.…”

“…We benefited from a broad, longer-term radiotelemetry study of a wild, free-ranging population of Eastern Box Turtles [10] to collect and determine the levels of reproductive markers linked to reproductive state. Over a two-year period, we measured the plasma levels of Vtg, TT, and E2 to address the following questions:…”

“…Mean transformed home range sizes (see[10]) regressed by median plasma total testosterone (TT) values in adult male Terrapene c. carolina from South-Central Indiana, USA. The fit line is significant (R 2 = 0.27, P = 0.0134), indicating that home range size is negatively correlated with TT.…”