Population dynamics of a desert riverine turtle, Pseudemys gorzugi, at the northern edge of its range

Abstract

Estimating the key demographic parameters of animal populations can enhance our understanding of system dynamics and assist in developing and improving conservation decision–support models. The Rio Grande cooter Pseudemys gorzugi is a conservation reliant freshwater turtle native to lower Rio Grande River Basin (USA and Mexico), with limited knowledge regarding its natural history and population dynamics. In this study, we used seven years of capture–mark–recapture data from the northern edge of the species' range to estimate survival probabilities, changes in abundance, and the probability of transitioning between different size classes while explicitly accounting for the sampling process. We found relatively high survival probabilities across different strata, with large juveniles exhibiting the highest survival (0.98) and small juveniles the lowest (0.71). However, transition probabilities between strata were low, indicating slow somatic growth rates. Our pattern‐oriented modelling revealed a low overall mean estimate of egg survival (0.024), warranting further empirical confirmation. Our study provides the first comprehensive demographic analysis of P. gorzugi encompassing an array of size and sex classes. Overall, we consider the population of P. gorzugi in the Black River robust, highlighting the importance of this river system to the species' persistence in the northern extent of its range, where the population is isolated from its broader distribution. The demographic estimates and ecological insights provided by our study offer critical data for parameterizing decision‐support models to ensure that P. gorzugi conservation strategies are grounded in the best available science.