Brian J. MacGowan

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

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.

A Survival Estimate of Midwestern Adult Eastern Box Turtles Using Radiotelemetry

Abstract Eastern box turtles (Terrapene carolina carolina) are widespread in U.S. eastern deciduous forests, yet many populations are experiencing dramatic declines. Herein, we present an assessment of annual survival for adult eastern box turtles that were radio-tracked over a period of 2 y. Using a known fates Kaplan-Meier estimator, the baseline annual survival estimate for adult eastern box turtles in Indianas south-central region is 96.2%. Annual survival rates varied slightly between the hibernal period (95.6%) and the active period (96.7%). These initial data provide wildlife managers with a baseline from which a recovery period can be calculated. In areas where road mortality and human interface are high, this estimate should be adjusted to ensure the time for recovery is adequate. Further research is recommended over generations and age-classes to better inform management of this protected species.

Survival of Timber Rattlesnakes (Crotalus horridus): Investigating Individual, Environmental, and Ecological Effects

Abstract:  A major effort in species conservation is the construction of life-history models to better predict, identify, and respond to population changes. Yet demographic studies linking individual, environmental, and ecological factors to survival are rare. We used radio telemetry to monitor 47 adult Timber Rattlesnakes (Crotalus horridus) during five active seasons and four overwinter periods from April 2007–November 2011 in south-central Indiana, USA. The study period serendipitously encompassed an oak (Quercus spp.) mast failure and subsequent 50% decline in prey abundance, allowing us to test hypotheses about ecological effects on survival. We detected 10 mortalities. The causes of mortality during active seasons included predation (n  =  5), human persecution (n  =  2), and vehicle strike (n  =  1). Variation in active season survival was explained best by the interaction of sex and prey availability along with an effect of marking cohort. Seasonal survival estimates ranged from 0.720–0.983 with female survival decreasing by at least 15% the year after prey availability declined. Overwinter survival was high in general (n  =  2 mortalities), with estimates weakly affected by sex (male  =  0.966; female  =  0.990) and decreasing slightly with colder monthly temperatures. Although ecological effects were most powerful in our study, 30% of mortalities were associated with human activities. Focused education and outreach efforts may be useful for improving survival of Timber Rattlesnakes.

Radio Transmitter Implantation and Movement in the Wild Timber Rattlesnake (Crotalus horridus)

Abstract Radiotelemetry transmitters have become critical to studies of wildlife ecology. However, little is known about how transmitter implantation surgery affects the mobility of some species, including the timber rattlesnake, Crotalus horridus. Tracking snake movement can provide insights into the effects of transmitter implantation. During 2007–11, 71 radio transmitters were surgically implanted intracoelomically in 47 timber rattlesnakes. Over 20 of these snakes underwent surgery at least twice in 5 yr to replace old transmitters. Surgeries were performed under general anesthesia with a local nerve block at the site of implantation, 20 cm cranial to the cloaca. Snakes were also administered postsurgical meloxicam and enrofloxacin every 24 h for three doses. Two to five days after surgery, snakes were released at their original locations and radiotracked regularly during the active seasons (April–October 2007–11). Average daily movement data (distance traveled) were compiled for each snake. Snakes undergoing transmitter surgery in a given year did not differ significantly in distance traveled compared to snakes that had transmitters but did not have surgery in that year. Distance traveled for each snake did not differ before or after surgery or between weeks 1 and 2 postsurgery, indicating that the transmitter implantation did not alter snake movement.

Seasonal Variation in Hematology and Blood Plasma Chemistry Values of the Timber Rattlesnake (Crotalus horridus)

Abstract Hematology, biochemical analyses, and body condition indices are useful tools for describing animal health, especially when making management decisions for species of conservation concern. We report hematologic, biochemical, and body condition index data for 13 free-ranging timber rattlesnakes (Crotalus horridus) sampled repeatedly over an active season in Indiana, USA.