Distribution of Populations and Suitable Habitat for Spotted Turtles (Clemmys guttata) and Blanding’s Turtles (Emydoidea blandingii) in Indiana

2019-01-04T03:06:38Z (GMT) by Jessica Hinson
The spotted turtle (Clemmys guttata) and Blanding’s turtle (Emydoidea blandingii) are two state-endangered species in Indiana whose populations are in decline. Historically, both species were found across the northern portion of Indiana in various wetland habitats. There are multiple causes of population decline for both species, including habitat fragmentation, habitat loss and degradation, urban development and encroachment, poaching, and road mortality. Despite efforts to record these species across the state, there has been no intensive population assessments. Based on this need, I conducted both visual encounter surveys across the state and used Maximum Entropy (MaxEnt) modeling to facilitate understanding the current distribution of both species in Indiana. Twenty-three locations were visited and surveyed in Indiana, with trapping being conducted at an additional four locations where populations were known to be larger. Surveys aided in delineation of six populations of Blanding’s turtles and five populations of spotted turtles. A total of 69 Blanding’s turtles and 70 spotted turtles were observed between surveying and trapping. Delineated populations were mainly found in the northern third of Indiana. This data and other occurrences were used to predict suitable habitat across Indiana. The Blanding’s turtle models were sufficiently resolved to predict potential localities or potential sites for focused management or repatriation. Spotted turtle model performance reflected the need for more samples, but also the likelihood of fewer numbers due to declining habitat availability. Both Blanding’s turtle and spotted turtle models argue for the need of more intense survey efforts based on historical occurrences, as well as restoration efforts across the state. Most models for both species were observed to have a trend towards suitable habitat in the northern third of the state, correlating with the results of the survey efforts. The results of this project indicate that Blanding’s turtle and spotted turtle populations are still in decline likely due to limited habitat availability.