Somatic Growth and Maturity for Four Species of River Cooter Including Pseudemys concinna suwanniensis, P. nelsoni, P. peninsularis, and P. texana

Simple Summary: River Cooters commonly occur in many freshwater ecosystems, but little is known about their growth and maturity. We used nearly 20 years of turtle tracking to estimate the growth, length at maturity, age at maturity, and sexual dimorphism of four River Cooters in five freshwater springs, four in Florida and one in Texas. We found that River Cooter juveniles grow exceptionally fast, doubling or tripling in size in the first year, while adults grow very slowly after maturing. Female River Cooters grow larger than males and mature later for the four taxa we studied but much more so for Suwannee River Cooters. Environmental differences among springs affected the growth rate of turtles more than the maximum size. Our efforts elucidate more about the life history of River Cooters and define baseline information to track potential changes to growth from natural and human disturbances in the future. Pseudemys is a genus of commonly occurring freshwater turtles with limited growth information across their long lifespans. We used 11,361 mark-recapture events to estimate the somatic growth rates of P. nelsoni, P. peninsularis, P. concinna suwanniensis, and P. texana from freshwater springs and developed a Bayesian growth model to estimate the species-specific, site-specific, and individual effects on growth. We corroborated evidence for fast juvenile growth and slower adult growth in Pseudemys but found uncommonly fast growth rates, with turtles doubling or tripling in size in the first year. P. texana males had the smallest average maximum size (L-infinity, 243 mm), while P. c. suwanniensis females had the largest (423 mm). Environmental conditions at springs had significant effects on k, the growth coefficient, but not L-infinity. We derived, using a ratio of length at maturity to L-infinity (71.7% and 87%, males and females), that females matured 1.15-1.57 times older than males except for P. c. suwanniensis, which matured three times older. Given the local abundance declines in many Pseudemys from anthropogenic impacts, this study provides important baseline life history information for Pseudemys species for use in ongoing conservation efforts and presents a novel hierarchical modeling approach using a long-term mark-recapture dataset.