Jeffrey W. Tamplin

The Wood Turtle (Glyptemys insculpta) is an endangered species in the state of Iowa and a species of conservation concern across their entire range. The Iowa population is characterized by high levels of adult and egg predation, displays little or no annual recruitment, and harbors an extremely low number of juveniles (7.3%). Home range and habitat usage studies of hatchling and juvenile Wood Turtles are limited to a few studies, and only one study of juveniles exists from the state of Iowa. Over a 10 yr period, we conducted a radiotelemetry study in Iowa on seven juvenile wood turtles for 32–182 weeks, and a 6-week study on six head-started hatchlings to determine home range sizes and habitat usage patterns and to provide comparisons with similar studies on adult Wood Turtles. Mean home range sizes of hatchling Wood Turtles were significantly smaller than the mean home range of older juvenile turtles for 100%, 95%, and 50% minimum convex polygons (MCPs), for 95% and 50% kernel density estimators (KDEs), and for linear home range (LHR) and stream home range (SHR). Habitat usage patterns of hatchlings and juveniles also differed. During periods of terrestrial activity, older juveniles utilized grass and forb clearings significantly more frequently than did hatchlings, and hatchlings used riverbank habitat more frequently than did juvenile turtles. In addition, juveniles were, on average, located significantly farther from the stream than were hatchlings. Our study provides important data on the home range size and habitat usage patterns of two under-represented age classes of this endangered species. These data will inform conservation agencies regarding relevant habitat protection and age-class management strategies of riparian areas that are necessary for the continued survival and protection of this imperiled species.

The Wood Turtle (Glyptemys insculpta) is an endangered species in the state of Iowa and a species of conservation concern across their entire range. The Iowa population is characterized by high levels of adult and embryo predation, displays little or no annual recruitment, and harbors an extremely low number of juveniles (7.3%). Home range and habitat usage studies of hatchling and juvenile Wood Turtles are limited to a few studies, and none exist from the state of Iowa. We conducted a radiotelemetry study in Iowa on seven juvenile wood turtles for 32–182 weeks over a 10-yr period, and a 6-week study on six head-started hatchlings to determine home range sizes and habitat usage patterns and to provide comparisons with similar studies on adult Wood Turtles. Mean home range sizes of hatchling Wood Turtles were significantly smaller than the mean home range of older juvenile turtles for 100%, 95%, and 50% minimum convex polygons (MCPs), for 95% and 50% kernel density estimators (KDEs), and for Linear home range (LHR) and Stream home range (SHR). Habitat usage patterns of hatchlings and juveniles also differed. During periods of terrestrial activity, older juveniles utilized grass and forb clearings significantly more frequently than did hatchlings, and hatchlings used riverbank habitat more frequently than did juvenile turtles. In addition, juveniles were, on average, located significantly farther from the stream than were hatchlings. Our study provides important data on the home range size and habitat usage patterns of two under-represented age classes of this endangered species. These data will inform conservation agencies regarding relevant habitat protection and age-class management strategies of riparian areas that are necessary for the continued survival and protection of this imperiled species.

Habitat suitability models (HSMs) play an important role in conservation planning by identifying areas for habitat management and guiding surveys for population discovery and monitoring. The wood turtle Glyptemys insculpta is a riverine turtle that uses both riparian and upland environments. Habitat loss and degradation have resulted in range‐wide declines of this species throughout the United States. Previous HSMs have been developed for wood turtles; however, no published HSM we are aware of exists for their range in the midwestern United States (including parts of Iowa, Michigan, Minnesota, and Wisconsin), or has incorporated terrestrial, aquatic, and climatic variables. We developed a wood turtle HSM across their distribution in the midwestern United States using Random Forest. Modeling units consisted of 800–1,000‐m stream segments and a 300‐m buffer surrounding each segment. We obtained verified occurrence records from 2000–2024 from state agencies, concurrent research projects, and the community science platform iNaturalist, resulting in 1,833 segments with documented occurrence to serve as model training data. Assessment metrics indicated good model performance (area under the operator curve = 0.92, true skill statistic = 0.6704). Stream order, width, and gradient were the most influential aquatic variables, with lower stream order, lower widths, and lower gradient being associated with higher probability of occurrence. The most influential terrestrial variables were proportion of still water in the terrestrial environment, landscape condition index, and topographic ruggedness index, with lower proportion of still water in the terrestrial environment, moderate to high landscape condition, and lower topographic ruggedness being associated with higher occurrence probability. The majority of stream segments (68.4%) with ≥0.8 probability of occurrence currently lack documented wood turtle populations, allowing for prioritization of these streams for future surveys. These results can assist with guiding habitat management and restoration efforts in their midwestern United States range.

Long-term survival of a conservation-reliant species requires understanding the impact of threats on population growth rate and the management actions that can help mitigate these threats. We used a threat assessment with expert-elicited estimates to determine the relative effect of each stage-specific threat on the population growth rate of the wood turtle Glyptemys insculpta. In addition, we offered potential management actions that could mitigate these threats and examined the relative cost and benefit of each. The experts responded that predators had the largest effect on hatchling and juvenile survival and that road mortality had the largest effect on adult survival. The population growth rate of the simulated turtle population increased the most when predators were removed from the system, though the population trajectory remained negative. Finally, we found that predator control had the lowest cost:benefit ratio of the proposed management actions. The process used in this analysis of expert elicitation combined with modeling that accounts for uncertainty proved to be a useful technique that is less expensive and labor intensive than empirical studies and quicker to implement, although it relies on sufficient empirical studies to inform expert responses. This process could be replicated for other species to inform species status assessments.

Water depth may be a primary factor that influences aquatic habitat use by Glyptemys insculpta (Wood Turtle). We used radio telemetry to investigate the influence of sex and activity period on water depth used by Wood Turtles to reveal aquatic behavioral patterns with potential habitat-management implications for this imperiled species. We located 42 Wood Turtles (28 females, 14 males) from 3 sites in Iowa biweekly to bimonthly during 2017–2021. We measured water depth at 1784 individual turtle locations and compared turtle depth to the minimum and maximum depths within 10 m of the turtle, and stream depth at mid-channel, to determine if water depth differed between sexes and/ or 5 seasonal activity periods (brumation, pre-nesting, nesting, post-nesting, and pre-brumation). Activity period significantly affected water depth used, and both sexes chose deeper water locations during winter brumation (mean = 110.6 cm) than during the other 4 activity periods. However, sex, and the interaction between sex and activity period, were not significant factors. Both sexes utilized deep water (81–121 cm) most frequently (35.6% of observations) during brumation. Utilization of moderately deep, flowing-water areas during winter may be an adaptation in Wood Turtles that provides protection from thickening river ice and fluctuating water levels while they are largely inactive. Our results provide data that can be used by habitat managers to mitigate the effects of various bridge, roadway, and stream-based construction projects that may influence stream depth and water flow in Wood Turtle habitat.

Painted turtles are remarkable for their freeze tolerance and supercooling ability along with their associated resilience to hypoxia/anoxia and oxidative stress, rendering them an ideal biomedical model for hypoxia-induced injuries (including strokes), tissue cooling during surgeries, and organ cryopreservation. Yet, such research is hindered by their seasonal reproduction and slow maturation. Here we developed and characterized adult stem cell-derived turtle liver organoids (3D self-assembled in vitro structures) from painted, snapping, and spiny softshell turtles spanning ~175My of evolution, with a subset cryopreserved. This development is, to the best of our knowledge, a first for this vertebrate Order, and complements the only other non-avian reptile organoids from snake venom glands. Preliminary characterization, including morphological, transcriptomic, and proteomic analyses, revealed organoids enriched in cholangiocytes. Deriving organoids from distant turtles and life stages demonstrates that our techniques are broadly applicable to chelonians, permitting the development of functional genomic tools currently lacking in herpetological research. Such platform could potentially support studies including genome-to-phenome mapping, gene function, genome architecture, and adaptive responses to climate change, with implications for ecological, evolutionary, and biomedical research.

Painted turtles are remarkable for their well-developed freeze tolerance and associated resilience to hypoxia/anoxia, oxidative stress, and ability to supercool. They are, therefore, an ideal model for biomedical research on hypoxia-induced injuries (including strokes), tissue cooling during extensive surgeries, and organ cryopreservation. Yet, the seasonal reproduction and slow maturation of turtles hinder basic and applied biomedical research. To overcome these limitations, we developed the first adult stem cell-derived turtle hepatic organoids, which provide 3D self-assembled structures that mimic their original tissue and allow for in vitro testing and experimentation without constantly harvesting donor tissue and screening offspring. Our pioneering work with turtles represents the first for this vertebrate Order and complements the only other organoid lines from non-avian reptiles, derived from snake venom glands. Here we report the isolation and characterization of hepatic organoids derived from painted, snapping, and spiny softshell turtles spanning ∼175 million years of evolution, with a subset being preserved in a biobank. Morphological and transcriptomics revealed organoid cells resembling cholangiocytes, which was then compared to the tissue of origin. Deriving turtle organoids from multiple species and life stages demonstrates that our techniques are broadly applicable to chelonians, permitting the development of functional genomic tools currently missing in most herpetological research. When combined with genetic editing, this platform will further support studies of genome-to-phenome mapping, gene function, genome architecture, and adaptive responses to climate change, among others. We discuss the unique abilities of turtles, including their overwintering potential, which has implications for ecological, evolutionary, and biomedical research. SIGNIFICANCE: Here we developed the first turtle-derived organoid biobank from the liver of multiple chelonians with a subset characterized via histology, RNA sequencing transcriptomics, single-nuclei RNA sequencing, and transmission electron microscopy. Furthermore, we discuss the potential of the 3D organoid model to investigate unique physiological adaptations of turtles which could unravel the molecular mechanisms underlying their overwintering capacity, opening the door for in vitro biomedical studies relevant to hepatic ischemia-reperfusion injury to organ cryopreservation, beyond fundamental ecology and evolution. This organoid biobank represents a novel resource for the scientific community to support research regarding the unique adaptations of this understudied Order of vertebrates.

Wood turtles (Glyptemys insculpta) are considered rare or threatened throughout their range. Populations in Iowa occur at the western periphery of the species' range and may be particularly vulnerable to extirpation due to low population density, geographic isolation with restricted opportunities for gene flow, a small range, and a high percentage of land that has been converted for agriculture. To improve our understanding of the ecological needs of the species and to provide targeted conservation of required habitat, determining home range size, site fidelity, and movement patterns is needed. We conducted a 2-yr radiotelemetry study on wood turtles in Iowa to provide baseline data on movement patterns (including estimated total distance moved in an active season and mean daily movement) and home range size and site fidelity between years of survey. Home range size of adult male and female wood turtles differed significantly for 100%, 95%, and 50% minimum convex polygon home range, with male mean home range being nearly 3 times the mean size of female home range. Stream home range length also differed significantly between males and females, with males utilizing a larger portion of lotic habitat. Both sexes showed a high degree of site fidelity to annual home ranges but not to specific overwintering locations. Our study provides important data on home range size, degree of site fidelity, and movement patterns of wood turtles from an isolated population in Iowa at the southwest periphery of the species' range. These data will inform conservation agencies on relevant habitat protection and management strategies of riparian areas that are necessary for the continued survival and protection of the species in the state.