Snack-Sized Turtles? Investigating Size Class Distributions and Predation of the Endangered Spotted Turtle (Clemmys guttata)

Abstract

Reptiles are experiencing decreased population sizes and declines in number of populations. Despite this overall pattern, for many species, there remains insufficient data to understand population trends, let alone the specific causes of these declines. One species experiencing severe declines, but sparse assessment is the spotted turtle (Clemmys guttata), a freshwater species found in wetlands in Eastern North America and classified as endangered under the IUCN Red List. This decline likely has occurred because of potential threats such as predation, collection for the pet trade, and habitat loss. I studied the size class distributions of turtles in Maryland and Delaware populations based on frequency of juvenile and adult turtles. I found that C. guttata populations had a negatively skewed size distributions at all study sites. However, they were primarily individuals in the 90–100 mm plastron length size range, while larger, older, individuals were not typically present. Additionally, I analyzed the potential predation of C. guttata based on predator-caused injuries and assessing predator abundance via camera traps. Clemmys guttata had a greater rate of predator-caused injuries compared to other common turtle species; however, there was no correlation between injury rate and predator activity, specifically regarding raccoons (Procyon lotor). My results suggest while there was a large proportion of adults in populations of C. guttata at my sites, very old adults were absent. This was potentially caused, in part, due to predation, but the explanation for high injury rates of C. guttata is complicated and likely involves other factors such as human removal for the pet trade.