Responses of a forest-dwelling terrestrial turtle, Terrapene Carolina, to prescribed fire in a Longleaf Pine ecosystem

Ecological and Fitness Correlates of Personality in a Long-lived Terrestrial Turtle

An individual's behavioral tendencies (i.e., personality or temperament) can influence its interactions with the environment and thus have important ecological and evolutionary consequences for animal populations. Boldness, defined as an individual's tendency to engage in risk-taking activities, is a phenotypically variable trait linked with numerous behavioral and fitness outcomes in free-ranging animals. We examined variation and repeatability of boldness and other behavioral characteristics in two wild Eastern Box Turtle (Terrapene carolina carolina) populations using radiotelemetry, and assessed fitness correlates of boldness over multiple years. We observed large amounts of among-individual variation and within-individual consistency (i.e., repeatability) of boldness as measured by their head emergence latency following a standardized confinement assay. Individuals were also consistent in several in-field behaviors including movement rate, home range size, and date of emergence from overwintering refuges. Individuals with shorter head emergence latencies (i.e., bolder turtles) had larger home ranges, emerged earlier from overwintering dormancy, and experienced moderately lower survival compared with shy individuals. Boldness did not affect time spent within the thermal preference range, somatic growth rates, or the frequency of mating or same-sex aggressive encounters. Boldness and its effects on in-field behaviors differed between sexes and populations, and the relationship between boldness and survival was temporally variable. Our results suggest possible intrinsic behavioral types in T. c. carolina and highlight the importance of long-term and multipopulation studies when examining ecological and evolutionary processes that shape personality phenotypes in turtles.

Fire management alters the thermal landscape and provides multi-scale thermal options for a terrestrial turtle facing a changing climate

As effects of climate change intensify, there is a growing need to understand the thermal properties of landscapes and their influence on wildlife. A key thermal property of landscapes is vegetation structure and composition. Management approaches can alter vegetation and consequently the thermal landscape, potentially resulting in underappreciated consequences for wildlife thermoregulation. Consideration of spatial scale can clarify how management overlaid onto existing vegetation patterns affects thermal properties of landscapes relevant to wildlife. We examined effects of temperature, fire management, and vegetation structure on multi-scale habitat selection of an ectothermic vertebrate (the turtle Terrapene carolina triunguis) in the Great Plains of the central United States by linking time-since-fire data from 18 experimental burn plots to turtle telemetry locations and thermal and vegetation height data. Within three 60-ha experimental landscapes, each containing six 10-ha sub-blocks that are periodically burned, we found that turtles select time-since-fire gradients differently depending on maximum daily ambient temperature. At moderate temperatures, turtles selected sub-blocks with recent (<1 year) time-since-fire, but during relatively hot and cool conditions, they selected sub-blocks with later (2-3 year) time-since-fire that provided thermal buffering compared with recently burned sub-blocks. Within 10-ha sub-blocks, turtles selected locations with taller vegetation during warmer conditions that provided thermal buffering. Thermal performance curves revealed that turtle activity declined as temperatures exceeded ~24-29°C, and on "heat days" (≥29°C) 73% of turtles were inactive compared with 37% on non-heat days, emphasizing that thermal extremes may lead to opportunity costs (i.e., foregone benefits turtles could otherwise accrue if active). Our results indicate that management approaches that promote a mosaic of vegetation heights, like spatiotemporally dynamic fire, can provide thermal refuges at multiple spatial scales and thus be an actionable way to provide wildlife with multiple thermal options in the context of ongoing and future climate change.

Overwintering behavior reduces mortality for a terrestrial turtle in forests managed with prescribed fire

Prescribed fire is an essential management practice in pyrogenic ecosystems, but fire can also be a significant disturbance and source of mortality for both target and non-target species. Seasonal periods of animal inactivity may provide opportunities to design burn plans that minimize negative impacts to species of conservation concern, but few studies have rigorously examined this possibility. Using radiotelemetry, we studied overwintering behavior and interactions with fire in a forest-dwelling terrestrial turtle, the Eastern Box Turtle (Terrapene carolina carolina), over an eight-year period at two sites that use prescribed fire in forest management. Turtles at both sites selected predominantly hardwood forests and mesic habitats and avoided upland pine forests. Turtles buried deepest (2.9 - 3.2 cm) below the soil-litter interface in late February and then moved gradually shallower until emergence in early April. Emergence timing varied over a 58-day period, but was consistent within individuals from year to year. Turtles also maintained fidelity to refuge locations, but those overwintering in burned areas selected sites over twice as far from refuges used in previous years compared to those in unburned areas. The areas and habitats selected by turtles during winter served as refugia from fire, and those whose refuges did burn remained buffered from lethal temperatures even at shallow burial depths. The only fire-related injury or mortality occurred during seasons of surface activity. Timing burning and other forest management practices during periods of winter dormancy may thus minimize threats to turtle populations, but modifications to prescribed fire regimes must also be balanced with other management objectives.

Variation and repeatability of home range in a forest-dwelling terrestrial turtle: implications for prescribed fire in forest management

Animal movements and use of space are in part determined by interactions between individual attributes such as sex and body size and extrinsic environmental factors such as the seasonal availability, quality and spatial configuration of resource patches in the landscape. Fire is a common and widespread disturbance process that has the potential to affect animal movements through modifications to the environment. Using radiotelemetry, we examined the contribution of these factors to variation in movements and home range over a 5-year period in a forest-dwelling terrestrial turtle, Terrapene carolina, at fire-maintained and unburned habitats in the southeastern United States. Female turtles had annual home-range sizes twice as large as males and moved longer distances per day during the nesting season (June and July), but males exhibited greater spatial fidelity from year to year. Turtles at the unburned site had home-range sizes twice as large as those at the fire-maintained site, and home-range size also decreased with increasing frequency and extent of fire, but this latter effect was strongest in females. Home-range behavior was highly repeatable within individuals of both sexes over time. This is the first evidence that fire influences the spatial ecology and movements of turtles, most likely through fire's impact on the spatial configuration, availability and quality of critical resources. That individuals behaved consistently through time, but differently from one another according to both intrinsic individual attributes and extrinsic environmental factors provides strong evidence of consistent inter- and intra-population variation in space use and movement behaviors in T. carolina. Such intra-specific behavioral variation suggests applying caution when extrapolating results to other sites across the geographic range of a species for use in conservation and management.

Inter- and Intra-population Variation in Habitat Selection for a Forest-dwelling Terrestrial Turtle, Terrapene carolina carolina

Habitat selection, where observed use of a resource is disproportionate to availability, is an important behavior allowing individuals to position themselves spatially relative to critical resources in heterogeneous environments. For species that experience variable environments across broad geographic ranges, we expect resource selection templates to vary among populations accordingly. Using radiotelemetry, we examined habitat selection for populations of Eastern Box Turtles, Terrapene carolina, in fire-maintained forests of the sandhills compared to nearby unburned coastal plain forests in south-central North Carolina. Turtles at the fire-maintained sandhills site preferred bottomland habitats and areas near steams, whereas turtles in the unburned coastal plain environment preferred uplands and used streams randomly. In addition, turtles in the fire-maintained sandhills avoided Longleaf Pine and more strongly preferred hardwood and non-Longleaf Pine forests compared to turtles at the unburned coastal plain site. Body size, but not sex, was also an important source of variation in habitat selection within populations, with smaller turtles more strongly preferring areas near water. Selection of habitat structural components in the immediate area of locations did not differ between sites, sexes, or body sizes. These results highlight the variety of resource selection templates in T. carolina, underscoring a potential need for population- or region-specific conservation and management strategies.