In a warming climate, organisms may use thermal refuges. One type of refuge in the Temperate Zone is afforded by groundwater upwelling, which cools the microclimate in summer and warms it in winter. To investigate the role that groundwater exchange plays in turtle habitat use, relative to more commonly measured habitat variables, we draw on 9 yrs of detailed habitat and turtle trapping data from Blanding's turtle (Emydoidea blandingii) core habitats in 6 wetland pools in proximity. Three pools are in preexisting, seminatural, "reference" wetlands, and 3 are in "constructed" wetlands built to offset habitat loss for the threatened Blanding's turtle, at the site of a school facilities expansion. The site is on gravelly glacial outwash in the town of La Grange, Dutchess County, New York. Quantification of vegetation, benthic organic matter layer thickness, water depth, and groundwater exchange (measured with volumetric seepage meters) was completed in each wetland pool and compared to turtle trap catches in each pool. Rank correlations (q) indicated that maximum groundwater seepage rate was correlated with turtle catch-per-unit-effort as was organic matter thickness in the reference wetlands. We also conducted an organic sediment-removal experiment to investigate the relationship between groundwater exchange dynamics and organic matter thickness. Groundwater exchange rates were either higher or lower following organic matter removal. The organic layer modulates groundwater exchange, increasing spatial homogeneity. We provide preliminary evidence that upward groundwater exchange is related to habitat use by Blanding's turtle. We suggest that volumetric measurements of groundwater exchange should be more commonly considered in research and conservation of freshwater turtles and other aquatic fauna.
Early life is a period of high mortality for many turtle species, so understanding how turtles select nest sites may be important in our ability to manage declining populations and species. In gopher tortoises (Gopherus polyphemus), nest-site selection in relation to vegetation and soil characteristics is poorly understood. From mid-May to mid-July 2022 and 2023, we investigated aspects of gopher tortoise nest-site selection within longleaf pine habitat in southwestern Georgia. We conducted repeated searches at burrows to locate nests, and at each nest (n=132) we collected soil samples and measured canopy and understory cover. We collected the same data at an equal number of burrows without nests. Using multiple logistic regression, we created a suite of 6 biologically relevant candidate models (combinations of percent clay in soil and canopy and understory vegetation cover) and compared models with Akaike's Information Criterion corrected for small sample sizes. The top 3 models identified canopy cover and understory vegetation cover as meaningful predictors of nest presence at burrows, with tortoises in our sites nesting at burrows with lower understory and canopy cover than available burrows. Furthermore, there was an interaction between the effects of understory vegetation and canopy cover, where the effect of understory cover decreased as canopy cover increased. This result suggests that the vegetation effect may be primarily driven by an avoidance of shade, whereby nests laid in burrows with high canopy cover were so shaded that understory vegetation had a weaker influence on nest-site selection. We did not observe an effect of percent clay in soils on nest-site selection, as has been observed at other sites. This may indicate that nest-site selection differs across the species' range. Our results suggest that maintaining habitats with very open or patchy overstories may be most important for providing preferred nest sites for gopher tortoises in this part of their range.
This study provides the first comprehensive physiological health assessment of 2 endemic Caribbean freshwater turtles: the Dominican slider (Trachemys stejnegeri vicina) and Haitian slider (Trachemys decorata) in the Dominican Republic. We examined steroid hormone profiles, hematological parameters, parasitic infections, and morphometrics in 118 wild-caught turtles. Haitian sliders exhibited significantly elevated stress hormones in plasma compared to Dominican sliders, with corresponding differences in heterophil-to-lymphocyte ratios. Body condition negatively correlated with stress hormones only in Haitian sliders, suggesting energy allocation trade-offs under stress. No hemoparasites were detected in either species, contrary to typical findings in related slider populations. Dominican sliders showed higher incidence of physical injuries and elevated thrombocyte counts, indicating potential immune system activation. These sublethal physiological differences likely reflect species-specific responses to habitat pressures and may serve as early warning signs of population decline before demographic impacts become apparent. Our research establishes critical baseline data and a nonlethal framework for long-term monitoring to inform conservation of these endemic turtles. Because each species was sampled from a single site, some physiological differences may reflect local conditions rather than species traits, but the results still provide valuable initial evidence of interspecific variation and environmental sensitivity to guide future studies.
Turtle researchers and enthusiasts and, indeed, most people familiar with boating in freshwater lakes, rivers, or ponds have observed groups of turtles basking on logs and their tendency to dive or slide into the water as a boat approaches. Herein I used a serendipitous experiment to reveal, for the first time, that turtles can use conspecific cueing when escaping from basking structures. Groups of basking turtles that could not see a perceived threat copied a conspecific that saw the threat by escaping into the water; these observations give insights into the mechanisms of predator avoidance while turtles bask, but additional studies are needed, particularly how season, body size, and sex influence these behaviors.
Freshwater turtles in Mexico remain poorly studied, limiting effective conservation assessments for many species. The Baja California and Rio Fuerte sliders (Trachemys nebulosa nebulosa and T. n. hiltoni) are no exception, and despite their limited range no field studies have been conducted on their populations. In this study we evaluated abundance, population structure, morphology, and potential threats across 19 sites spanning Baja California Sur, Sonora, and Sinaloa. Using baited hoop nets, we conducted 234 trap nights and captured 75 individuals, including 43 unique T. n. hiltoni (23 recaptures) and 9 unique T. n. nebulosa. Capture rates were low across most sites (0-2.00 turtles/trap night), suggesting that this species exists in low densities across their range. Populations were dominated by large adults above 200 mm carapace length (CL, n = 45), and subadults below 200 mm CL were infrequent (n = 8) except for 1 ephemeral water body in Sonora where we trapped 8. Females were significantly larger than males in both subspecies, T. n. hiltoni female carapace length (CL): x = 277.9 +/- 48.2 (n = 18), males: x = 236.4 +/- 35.7 (n = 18), and T. n. nebulosa female CL: x = 299.3 +/- 11.6 (n = 6), and males: x = 265.3 +/- 19.1 (n = 3), consistent with female-biased sexual size dimorphism reported for this species. Interviews with local residents revealed that turtle consumption and gillnet use were the most widespread and severe threats, particularly in Sinaloa, alongside sewage runoff, invasive turtles, and habitat degradation from agricultural water diversion. Our findings provide the first range-wide ecological assessment of T. nebulosa and highlight declining detectability and multiple anthropogenic pressures. These results underscore the need for more surveys and an updated conservation status for both subspecies.
