Glyptemys Insculpta Research Articles

Development and validation of rapid environmental DNA (eDNA) detection methods for bog turtle (Glyptemys muhlenbergii).

Bog turtles (Glyptemys muhlenbergii) are listed as Species of Greatest Conservation Need (SGCN) for wildlife action plans in every state it occurs and multi-state efforts are underway to better characterize extant populations and prioritize restoration efforts. However, traditional sampling methods can be ineffective due to the turtle’s wetland habitat, small size, and burrowing nature. Molecular methods, such as qPCR, provide the ability to overcome this challenge by effectively quantifying minute amounts of turtle DNA left behind in its environment (eDNA). Developing such methods for bog turtles has proved difficult partly because of the high sequence similarity between bog turtles and closely-related, cohabitating species, most often wood turtles (Glyptemys insculpta). Additionally, substrates containing bog turtle eDNA are often rich in organics or other substances that frequently inhibit both DNA extraction and qPCR amplification. Here, we describe the development and validation of a qPCR assay, BT3, targeting the mitochondrial cytochrome oxidase I gene that correctly identifies bog turtles with 100% specificity and sensitivity when tested on 201 blood samples collected from six species over a wide geographic range. We also developed a full-process internal control employing a genetically modified strain of Caenorhabditis elegans to improve DNA extraction methods, limit false negative results due to qPCR inhibition, and measure total DNA recovery from each sample. Using the internal control, we found that DNA recovery varied by over an order of magnitude between samples and likely explains the lack of bog turtle detection in some cases. Methods presented herein are highly-specific and may offer a more cost effective, non-invasive tool to supplement bog turtle population assessments in the Eastern United States. Poor or differential DNA recovery, which remains unmeasured in the vast majority of eDNA studies, significantly reduced the ability to detect bog turtle in their natural environment.

Exploring motivation crowding around farmer incentives for riparian management in Nova Scotia

AbstractIncentive programs to encourage landowners to protect habitat should be carefully designed to avoid motivation crowding: basically, replacing intrinsic reasons such as a land ethic with extrinsic ones like payments. Little research on motivation crowding tests real programs, and no such work has been done in Canada. We surveyed farmers in Nova Scotia in 2017 to explore whether participation in a new incentive program called Wood Turtle Strides, or knowledge about a similar incentive program potentially available in the future, would alter reported motivations to use riparian setbacks and buffers. Motivations to use setbacks or buffers were heavily intrinsic across all four survey cohorts: wildlife stewardship and sacrifice motivated actions more than social pressures. We were not able to statistically test for motivational crowding due to low program uptake and thus post‐program survey responses, but there was no evidence of second‐hand crowding: farmers being motivated by hearing about a program in an adjacent jurisdiction. Findings point to the significance of wildlife stewardship for many farmers, and persistent resistance to conservation among others, as well as a risk of low additionality. More post‐program research is necessary to fully understand the program's net impact on motivations and conservation.

Impact of natural resource extraction on thermal properties of wood turtle (Glyptemys insculpta) habitat.

One of the main threats to freshwater turtle populations is habitat destruction, which occurs as a result of human activities such as infrastructure development, forestry, aggregate extraction, and agriculture. However, the impacts of these activities on thermoregulatory opportunities for turtles are not well understood. We examined the impacts of forestry and aggregate extraction on thermal characteristics of wood turtle (Glyptemys insculpta) habitat in the Sudbury District, Ontario, by measuring the differences in absolute temperature, thermal landscape structure, and habitat thermal quality among relatively undisturbed sites (N = 2), harvested forestry sites (N = 2), and aggregate pits (N = 2) in 2015. We also tested the potential use of the thermal landscape concept as a predictor of habitat thermal quality. Undisturbed habitats were of higher thermal quality than impacted sites in terms of temperatures experienced in situ by wild wood turtles in their natural home ranges, and never reached temperatures that would be injurious to turtles (i.e., below CTMIN or above CTMAX). The undisturbed sites were of lower quality in terms of optimal temperatures (i.e., Tset), and were generally cooler and their temperatures less variable than those in impacted habitats. The thermal landscape concept provided a useful predictor of habitat thermal quality when the influence of time of day was factored into the predictive model. Our data are important to the conservation and management of wood turtles because they provide a preliminary quantification of the thermal impacts of natural resource extraction on the habitat of an endangered species, and can guide the development of mitigation and rehabilitation plans by providing measures of, and targets for, thermal habitat quality.

Concurrent visual encounter sampling validates eDNA selectivity and sensitivity for the endangered wood turtle (Glyptemys insculpta).

Environmental DNA (eDNA) has been used to record the presence of many different organisms in several different aquatic and terrestrial environments. Although eDNA has been demonstrated as a useful tool for the detection of invasive and/or cryptic and declining species, this approach is subject to the same considerations that limit the interpretation of results from traditional survey techniques (e.g. imperfect detection). The wood turtle is a cryptic semi-aquatic species that is declining across its range and, like so many chelonian species, is in-need of a rapid and effective method for monitoring distribution and abundance. To meet this need, we used an eDNA approach to sample for wood turtle presence in northern Virginia streams. At the same time, we used repeat visual encounter surveys in an occupancy-modelling framework to validate our eDNA results and reveal the relationship of detection and occupancy for both methods. We sampled 37 stream reaches of varying size within and beyond the known distribution of the wood turtle across northern Virginia. Wood turtle occupancy probability was 0.54 (0.31, 0.76) and while detection probability for wood turtle occupancy was high (0.88; 0.58, 0.98), our detection of turtle abundance was markedly lower (0.28; 0.21, 0.37). We detected eDNA at 76% of sites confirmed occupied by VES and at an additional three sites where turtles were not detected but were known to occur. Environmental DNA occupancy probability was 0.55 (0.29, 0.78); directly comparable to the VES occupancy estimate. Higher probabilities of detecting wood turtle eDNA were associated with higher turtle densities, an increasing number of days since the last rainfall, lower water temperatures, and lower relative discharges. Our results suggest that eDNA technology holds promise for sampling aquatic chelonians in some systems, even when discharge is high and biomass is relatively low, when the approach is validated and sampling error is quantified.

Watersheds influence the wood turtle’s (Glyptemys insculpta) genetic structure

The wood turtle (Glyptemys insculpta) is a freshwater species endemic to eastern North America and is currently listed as endangered by the International Union for Conservation of Nature. Wood turtle local populations are considered units for the species recovery, and are defined as discrete interbreeding populations in a distinct watershed; however, there are no studies to date supporting this definition. The main objective of this paper was to genetically characterize wood turtles from a northern portion of their range, and test an isolation-by-watershed hypothesis, the first of its kind at such a large geographical scale. Turtles were sampled in 24 watercourses from 12 different watersheds for a total of 331 individuals, each genotyped for nine microsatellite loci. Within each watershed, genetic diversity was similar between sites, and observed heterozygosity ranged from 0.677 to 0.754. Partial redundancy analyses then confirmed that watershed isolation contributed to 18% of the total observed genetic variation, while spatial autocorrelation and the post-glacial Expansion Model did not significantly explain any variation. Clustering methods revealed substantial spatial genetic structure, with sampled groups falling into ten nested hierarchical clusters. We recommend further consideration of these ten clusters to determine if they meet the evolutionary significance criterion to become designatable units, whose genetic structures were influenced by watershed structure.

GPS Technology for Semi-Aquatic Turtle Research

Global positioning system (GPS) telemetry units are now small enough to be deployed on terrestrial and semi-aquatic turtles. Many of these GPS units use snapshot technology which collects raw satellite and timestamp data during brief periods of data recording to minimize size. We evaluated locations from snapshot GPS units in stationary tests and on wood turtles (Glyptemys insculpta) in northeastern Minnesota. Stationary GPS units were placed in wood turtle habitat to evaluate location accuracy, fix success rate, and directional bias. The GPS fix success rate and accuracy were reduced in closed canopy conditions and when the stationary GPS unit was placed under a log to simulate wood turtle hiding behavior. We removed GPS location outliers and used a moving average calculation to reduce mean location error in stationary tests from 27 m (SD = 38) to 10 m (SD = 8). We then deployed GPS units and temperature loggers on wood turtles and collected 122,657 GPS locations and 242,781 temperature readings from 26 turtles from May to September 2015 and 2016. Location outliers accounted for 12% of locations when the GPS receiver was on a turtle. We classified each wood turtle location based on the GPS location and by comparing temperature profiles from river, sun, and shaded locations to the temperature logger on the turtle. We estimated that wood turtles were on land 68% (SD = 12) of the time from May to September. The fix success rate for land locations was 38% (SD = 9), indicating that wood turtles often use habitats with obstructed views of the sky. Mean net daily movement was 55 m (SD = 192). Our results demonstrate that snapshot GPS units and temperature loggers provide fine-scale GPS data useful in describing spatial ecology and habitat use of semi-aquatic turtles.

Characterizing Wood Turtle (Glyptemys insculpta) Populations at the Northwestern Periphery of the Species' Range in Canada

We report morphometric and demographic characteristics of 2 distinct populations of Glyptemys insculpta (Wood Turtle), at the northwestern periphery of the range in Canada, where they are designated as a species at risk. Our surveys of the 2 study watersheds (2012–2015) were assisted by a trained canine unit which was demonstrably more efficient than human crews in detecting Wood Turtles. We observed that both populations were large—214 and 114 uniquely marked individuals documented over time. We found no significant differences (P ≥ 0.05) in age structure, sex ratios, sexual size-dimorphism, body condition, number of observed mating attempts, or frequency and type of injuries between populations. We observed female-biased sex ratios in both populations (1:1.47 and 1:1.84, respectively) that were not attributable to sampling bias. Our data generally support the postulate of an inverse relationship between Wood Turtle body size and number of frost-free days or latitude. The general health of the 2 study populations was evidenced by the numerous large and reproductively mature individuals of both sexes, relatively high percentage of juveniles observed (average = 26%), and size-class frequency distributions that indicated sustained juvenile recruitment over several years in both watersheds. Our data suggest that high-quality forested watershed habitats, even at the northwestern extreme of the species range in Canada, can and do support large, healthy populations of Wood Turtles.

Observations of Wood Turtle Activity, Diet, Movements, and Morphometrics in the Central Appalachians

Glyptemys insculpta (Wood Turtle) populations are declining as habitat is developed and individuals are collected for the pet trade. Information about the natural history and life history of the species can help inform conservation strategies, especially for populations about which little information is currently available. Because basic ecological information is lacking for populations in the Central Appalachians, we studied the natural history of Wood Turtles in West Virginia from 2009 to 2011. Wood Turtle males were larger than females in carapace length and width, bridge height, and mass. Turtles were primarily terrestrial in spring and summer and aquatic in autumn and winter. Aquatic mating was most prevalent in autumn. Nesting attempts, which were mostly in sandy substrates, were made in spring during early morning and evening. Slugs made up the majority (67%) of the turtles' diet, although other invertebrates, vertebrate remains, berries, and green leaves were also consumed. In autumn, turtles entered the river for brumation. This study adds to our understanding of the natural history of Wood Turtles near the southern extent of their range.

Fine- and coarse-scale movements and habitat use by Wood Turtles (Glyptemys insculpta) based on probabilistic modeling of radiotelemetry and GPS-telemetry data

Understanding animal movement and habitat use is critical for the delineation of habitat requiring protection for species at risk. Defining critical habitat requires studies with observations at a fine enough scale to reflect how animals use and move among habitats and include enough individuals to generalize findings to the population. We present results of a multiyear study on 48 adult Wood Turtles (Glyptemys insculpta (Le Conte, 1830)) from two different populations monitored with low-frequency radiotelemetry and high-frequency GPS telemetry. Results demonstrated the propensity for conventional radiotelemetry to underestimate cumulative distances moved and overestimate the amount of habitat used by Wood Turtles. Together the two data sets demonstrate the propensity for Wood Turtles to remain in close proximity to the river and that some differences in habitat use occur between the sexes; males tended to move parallel to the river, whereas females moved perpendicular to the river. The GPS-telemetry data provided a robust spatiotemporal data set that provided a better understanding of frequently used habitat types and features. Overall, study results suggest that currently delineated areas of protected habitat are likely to be effective in conserving these two populations and provides significantly improved, spatially explicit knowledge that can be used to inform further mitigation efforts if necessary.

Geographic Variation in Somatic Growth Rate of Wood Turtles (Glyptemys insculpta)

Life history traits, such as body size and age at maturity, display intraspecific variation across a species' geographic range. Previous studies that examined body size variation among conspecific populations of turtles found that body size generally increases with increasing latitude, with the exception of Wood Turtles (Glyptemys insculpta) and Spotted Turtles (Clemmys guttata), which follow a non-linear relationship with larger body sizes at the two range extremes. Similarly, growth rates are influenced by climatic variables and should display geographic patterns reflective of different environments. The objectives of our study were to a) quantify somatic growth in a northern population of Wood Turtles, and b) determine if the observed geographic variation in body size was the result of interpopulation variation in somatic growth rates. In the northern population, as turtles approached maturity, somatic growth increments varied between the sexes such that on average males grew to larger mean carapace le...

Habitat Use and Activity Patterns of a Terrestrial Turtle (Rhinoclemmys rubida perixantha) in a Seasonally Dry Tropical Forest

Abstract We report the results of a field study on Mexican Spotted Wood Turtles (Rhinoclemmys rubida perixantha) in a seasonally dry tropical forest of coastal Jalisco, Mexico. We used field surveys, trail spools, and radio telemetry to investigate activity patterns, estimate home range size with three different techniques, and develop a generalized linear model to identify features associated with habitats used by R. r. perixantha. We found that turtles were most frequently active at midday, with peak activity occurring from 0900 to 1500 h. During the dry season (January–mid-June), R. r. perixantha showed reduced activity (fewer movements and shorter travel distances) compared to the wet season (late June–September). Home range size did not differ among the three methods we compared, and all estimates revealed that R. r. perixantha have small home ranges, with males having larger home ranges than females. Sites used by turtles were positively associated with leaf litter and woody debris, herbaceous plant...

Hunting, use and Trade of Chelonians in the South of Sucre, Colombia

Objective: To evaluate the use and trade of Trachemys callirostris (Colombian slider), Rhinoclemmys melanosterna (Colombian wood turtle) and Kinosternon scorpioides (Scorpion mud turtle) during the months of January to May, 2015. Methods/statistical Analysis: This study was carried out in the south of the Department of Sucre, Colombia, taking sample in the municipalities of San Marcos and Caimito with traditional sites of extraction, stockpiling and distribution for these turtles. 110 surveys were given to collect information on the availability, use and trade of hunted chelonians. Findings: The most commonly used species in both municipalities was T. callirostris, which had 66% commercialized and 34% subsistence consumption. The hunting effort for T. callirostris resulted in, on average, 66 individuals/month/ hunter. The average sale price that the hunter obtained was $3,567 Colombian Pesos (COP) (US $1.20), for a monthly/ hunter income of $235,422 COP (US $78.5). As for R. melanosterna and K. scorpioides, their capture rate was incidental, and their consumption was a measure of occasional and opportunistic exploitation. Application: The hunting of turtles and their consumption are linked to the culture of the study area and, in many cases, are a subsistence strategy that, according to economic calculations, produces temporary, insignificant income that does not justify this practice from a market perspective. Keywords: Chelonians, Colombia, Commerce, Utilization, Sucre

Water exchange relationships predict overwintering behavior in hatchling turtles

Neonatal ectotherms face a wide range of environmental hazards because of the diverse habitats that they inhabit and their small body sizes; this is especially true among turtles that live in temperate zones and experience cold winter conditions after hatching. Such hatchlings must balance challenges involving desiccation, freezing, and predation, among other threats. Turtle hatchlings either overwinter in water, terrestrially in relatively shallow nests, terrestrially deep below nests, or terrestrially outside of the nest entirely, and these different microhabitats are associated with different desiccation and freezing risks. We measured desiccation tolerance of individuals of six turtle species, including two (Diamondback Terrapins, Malaclemys terrapin (Schoepff, 1793), and Eastern Box Turtles, Terrapene carolina (Linnaeus, 1758)) that use a strategy that has not previously been explored, along with Wood Turtles (Glyptemys insculpta (Le Conte, 1830)), whose overwintering microhabitat is uncertain. We found additional support for the hypothesis that desiccation resistance is associated with overwintering strategies in hatchling turtles. Further investigation into the overwintering strategies of M. terrapin and T. carolina would be productive.

An 18-Year Mark–Recapture Study of Wood Turtles (Glyptemys insculpta) in Michigan

Wood Turtles (Glyptemys insculpta) occupy forested streams at midlatitudes in eastern North America and are listed as endangered by the International Union for Conservation of Nature, but few populations have been rigorously studied. We studied a population of Wood Turtles in Michigan for 18 yr, individually marking 260 different turtles (146 females, 88 males, and 26 unsexed juveniles), including 118 turtles that we followed for one or more years using radiotelemetry. We analyzed our encounter data using a Cormack–Jolly–Seber model in Program MARK; and we estimated total population size using a Bayesian integrated population model that combined Horvitz–Thompson estimates of annual population size, mark–recapture estimates of annual survival, and derived estimates of annual recruitment. Annual adult survival was 0.970 ± 0.016 SD and annual recruitment to age 15 (mean age of first capture) was 0.058 ± 0.019 SD. Over the 18-yr study, estimated population size grew from 770 (95% CI 631–928) to 1,196 (95% CI 977–1,444) individuals.

Paternity Analysis of Wood Turtles (Glyptemys insculpta) Reveals Complex Mating Patterns

Mating system characteristics are of great importance as they may influence male and female reproductive success and reproductive isolation. The wood turtle (Glyptemys insculpta) is a terrestrial freshwater species listed as endangered by the International Union for Conservation of Nature. Considering its conservation status and the paucity of information currently available on parentage relationship for the species, we performed a microsatellite analysis to study the mating system of wood turtles in the Shawinigan River (Québec). We sampled 38 clutches over 2 years (14 in 2006 and 24 in 2007), for a total of 248 offspring genotyped with 7 microsatellite loci. The reconstructed genotypes of the fathers revealed that reproductive success in the sampled clutches varied greatly between males and are positively correlated with the number of mates and clutches sired. Frequency of multiple paternity was estimated at 37% through a consensus of 3 different estimation methods. Positive correlation was observed between the genetic diversity of clutches and the number of fathers. Repeat paternity, however, was observed in 88% of the clutches by the same female in successive years, which suggests either a frequent use of sperm storage, or remating with the same partner in successive years.

Survey and analysis design for wood turtle population monitoring

ABSTRACTPopulation monitoring is a fundamental component of wildlife management, and is necessary to track site‐ and regional‐level status and recovery of species of conservation concern. The wood turtle (Glyptemys insculpta) is a species of conservation concern for federal and state agencies because of population declines across the species’ range. We developed and tested a survey and analysis design to assist agencies in the Upper Midwest, USA, with establishment of long‐term monitoring programs for wood turtle populations. In spring of 2016, we conducted 8 replicate population surveys at 8 candidate long‐term monitoring sites in northeastern Minnesota, USA. Using field survey data and simulation models, we assessed the influence of distance from river surveyed, number of survey replications, and number of sites on abundance estimates; we also delineated important survey covariates and compared demographic estimates based on distance from river surveyed. We estimated site‐level abundances and compared survey designs using a multinomialN‐mixture model that included a removal sampling observation process. Mean abundance estimates were similar when surveying 2 transects (i.e., the river‐land interface to ∼25 m inland) or 4 transects (i.e., the river‐land interface to ∼55 m inland), but decreasing the survey distance from river reduced the precision of estimates. Mean abundance estimates were similar with ≥6 replications. Air temperature was an important predictor of survey‐specific detection probability, with maximum detectability at 19−23°C. Sex ratio and mean carapace length did not differ based on whether we surveyed 2 or 4 transects, and percentage of individuals by size class was nearly identical between the sampling designs. Simulations indicated that 75% of mean abundance estimates were within ±8% of true abundance when ≥15 sites were surveyed. The wood turtle survey and analysis design we developed and tested was effective for estimating abundance of wood turtle populations in northeastern Minnesota, and we encourage its use as a template for wood turtle monitoring programs in the Upper Midwest. © 2017 The Wildlife Society.

Development of sexing primers in Glyptemys insculpta and Apalone spinifera turtles uncovers an XX/XY sex-determining system in the critically-endangered bog turtle Glyptemys muhlenbergii

In species or developmental stages where the sex of an individual cannot be reliably identified through external morphology, molecular markers can provide a critical tool to study sex-specific traits that are elusive otherwise. Here we generated two sets of sex-diagnostic PCR primers for each of two focal turtle species with contrasting genotypic sex determination (GSD) systems: the wood turtle, Glyptemys insculpta (XX/XY), and the spiny softshell turtle, Apalone spinifera (ZZ/ZW). These markers identified males and females with 100% accuracy as validated with numerous individuals of known sex. Notably, one of the markers developed for G. insculpta permitted the successful diagnosis of individual sex in the critically-endangered bog turtle, Glyptemys muhlenbergii, also with 100% accuracy. This cross-species application provided the first evidence that G. muhlenbergii shares an XX/XY sex-determining mechanism with G. insculpta, a finding with important evolutionary and conservation implications. Similarly, the markers from A. spinifera were successful in identifying the sex of two individuals (one male and one female) of the Chinese softshell turtle, Pelodiscus sinensis (ZZ/ZW). These cross-species observations highlight the potential applicability of these types of markers on closely related taxa that share a sex-determining mechanism, which should be tested in a case-by-case basis.

Factors Affecting Predation on Wood Turtle (Glyptemys insculpta) Nests in the Upper Peninsula of Michigan

Abstract Depredation rates on turtle nests can be very high, resulting in low recruitment to populations. Understanding predator foraging habits and nesting ecology of turtles is essential for the long-term management of threatened turtle species. Cues used by predators to locate wood turtle (Glyptemys insculpta) nests were investigated by creating simulated nests with 1 of 4 treatments: soil disturbance, water with turtle scent, soil disturbance plus turtle scent, or distilled water. Nest predators primarily used soil disturbance cues for locating nests. Additionally, artificial nests with buried chicken eggs were created at varying distances from the river and monitored for predation. Nest predation decreased as nest distance from the river increased. These data can be used to develop strategies for more effective management of this threatened species.

Wood Turtle Home Range and Habitat Use in the Central Appalachians

Abstract Conservation of wood turtles (Glyptemys insculpta) requires improved ecological knowledge near the southern extent of their geographic range. Our objectives were to determine home range sizes and structural habitat characteristics of wood turtles near the southern border of their geographic range in eastern West Virginia. We captured 284 wood turtles (137 males, 88 females, and 59 juveniles) along a 13.7-km reach of river from spring 2009 to summer 2011. Home ranges (95% minimum convex polygons) varied from 0.62 to 36.97 ha; male home ranges tended to be elongated along the river, whereas female and juvenile home ranges encompassed a greater proportion of terrestrial habitat. Low bare ground and rock cover and high vegetative vertical density were structural characteristics associated with the turtles' habitat compared with random plots. Our study provides vital data about home range, movements, and habitat use of wood turtles along the southern border of their range. These data will assist in pl...

Research and Conservation Priorities for Tortoises and Freshwater Turtles of Colombia

The objective of our study was to review and quantify the level of knowledge of the biology of tortoise and freshwater turtle species of Colombia based on studies conducted in the country. We used the resulting rankings in knowledge, in combination with IUCN threat category, presence in protected areas, and endemism, to propose conservation priorities. This process also allowed us to evaluate which aspects of turtle biology have been least studied. Four species obtained total values of zero or one over the 21 knowledge criteria employed, so they were ranked as the highest priority for research based on the lack of knowledge of their biology: Black-lined Toad-headed Turtle ( Mesoclemmys raniceps), Amazon Toad-headed Turtle ( Mesoclemmys heliostemma), Gibba Toad-headed Turtle ( Mesoclemmys gibba), and Dunn’s Mud Turtle ( Kinosternon dunni). Moreover, species in the family Chelidae in general were found to have limited levels of knowledge, which makes this group a priority for investigation. Evaluation of the distinct criteria used in the knowledge assessment revealed that the best-known criteria were geographic distribution (modeled), presence or absence in protected areas, and clutch size. The most poorly known biological characteristics, which constitute research priorities, are the frequency of nesting, longevity and generation time, and population parameters. According to the criteria used, the priority species for conservation were the Magdalena River Turtle ( Podocnemis lewyana), Dahl’s Toad-headed Turtle ( Mesoclemmys dahli), K. dunni, and Maracaibo Wood Turtle ( Rhinoclemmys diademata), three of which are endemic or semiendemic ( R. diademata only occurs in Colombia and Venezuela), followed by two species of Mesoclemmys.