Andrea F. Currylow

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.

Evidence of Ranavirus Infections among Sympatric Larval Amphibians and Box Turtles

Abstract Ranaviruses are emerging as serious pathogens across ectothermic taxa, recently causing mass die-offs including entire chelonian populations. Amphibians may serve as reservoirs for chelonian infections. To assess this idea and determine whether chelonians in the Midwest are infected with (or at risk for) ranavirus infections, we tested for presence of ranavirus infections among sympatric larval amphibians (N = 135) and Eastern Box Turtles (Terrapene carolina carolina, N = 132) earlier and later in the Box Turtle active season (between May and October 2009) in south-central Indiana. Three larval amphibians (2.2%; one Ambystoma sp. and two unidentifiable anuran larvae) and four Box Turtles (3.0%) tested positive for a ranavirus. Ranavirus infections were found in both early-season pond breeders (anurans) and then later-season pond breeders (salamanders), spanning the Box Turtle active period, but we did not detect mass die-offs. The majority (75%) of our ranavirus-positive Box Turtles were found later in the season. This represents the first documented case of ranavirus infection among a Box Turtle population in the Midwest and one of the few studies reporting ranaviruses across wild sympatric taxa. Our results suggest that ranaviruses persist sublethally in both larval amphibians and individual Box Turtles, allowing them to serve as reservoirs for this disease. Future studies should include sampling of all sympatric herpetofauna and investigate prevalence and persistence of the viruses to understand better the risks of cross-contamination.

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.

Stress response to handling is short lived but may reflect personalities in a wild, Critically Endangered tortoise species

Abstract We detected a short-term stress response to our handling procedures in only half of wild, critically endangered radiated tortoises. After collecting nearly 2 years of monitoring data, we found that those initial stress responses were also reflective of differences in traits, i.e. body sizes, behaviours, home ranges and movements.

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.

Characterization of seasonal reproductive and stress steroid hormones in wild Radiated Tortoises, Astrochelys radiata

The critically endangered Radiated Tortoise (Astrochelys radiata) is endemic to the southern coastlines of Madagascar. Once common, wild populations of this tortoise have undergone dramatic declines in recent years. Although there have been studies documenting reproductive activities, reproductive physiological parameters are unknown yet may be crucial in the recovery of the species. Over four research seasons in remote field locations native to A. radiata, we surveyed for, radio-tracked, and sampled wild, free ranging tortoises. We sampled and measured stress and reproductive parameters (corticosterone [CORT], testosterone [T], estradiol-17β [E2], and progesterone [P]) in 311 plasma samples from 203 wild A. radiata, capturing their active period. Generally, hormone concentrations were associated with body condition, temperature, and humidity. There was wide variation in CORT that varied monthly and by group. Juvenile tortoises maintained more than twice the mean basal CORT concentrations than either adult sex, with the most dramatic distinctions in the middle of the wet season. For adult sex hormones, the last months of the dry season and into the wet season when ground humidities are low and just begin to rise prior to temperature declines, male T concentrations gradually increased to a peak before returning to near undetectable values into the dry season. We had limited data for T concentrations in females, but found average T concentrations were much lower than in males and positively correlated with larger female home range sizes. For female hormone cycles, E2 also peaked in the early 1/3 of the wet season along with male T, and was followed by an uptick in P which correlates to the putative ovulatory cycle. Females tracked over four years showed variation in patterns of P, indicating that number and frequency of clutches vary. Our results suggest that 1) there is high species plasticity in response to stress; 2) A. radiata reproductive cycling is somewhat dissociated with courtship timing and is instead triggered by environmental cues; and 3) individual female reproductive output is irregular. This study is oone of the first to document and describe multi-year seasonal stress and reproductive hormones in a free-ranging Malagasy chelonian. These data may be used to identify key high-production habitats for conservation, and aide in captive management and reproduction in assurance colonies for species health and survival.