Injuries and abnormalities of the southwestern pond turtle (Actinemys pallida) in the Mojave River of California

Abstract

The southwestern pond turtle ( Actinemys pallida ) is a semiaquatic turtle that occasionally spends time on land to bask, oviposit, make intermittent overland movements, and overwinter in terrestrial locations. Use of both aquatic and terrestrial environments exposes semiaquatic turtles to increased risk of injury or mortality from floods, predation attempts, and other environmental hazards (e.g., human activities such as vehicle strikes, etc.). We collected injury and morphological abnormality data from adult turtles at 3 study sites along the length of the Mojave River in San Bernardino County, California: 1 site on the upper half of the Mojave River (hereafter known as UHMRS) and 2 sites each on the lower half of the Mojave River (hereafter known as LHMRS). The studies were conducted when turtles were most active between May and October 1998–1999 and again from April to September 2016–2019. A total of 84 A. pallida were captured among all sites and all years. Seventeen percent ( n = 8) of the turtles captured at UHMRS exhibited shell abnormalities (natural variations in shell or bone morphology). Injuries (damage inflicted by force to the shell or body) occurred in 68% ( n = 26) of captured turtles at both the LHMRS sites combined and 78% ( n = 36) of turtles captured at the UHMRS alone. A total of 74% ( n = 62) of turtles had injuries at all sites combined. There was no statistical difference in the proportion of injured and noninjured turtles between the sexes for either the 2 LHMRS sites combined or the UHMRS. Mean carapace length was not significantly different between injured and noninjured turtles for these same sites. Injuries occurred in the majority of captured turtles at all sites and may be an indicator of the extent of threats facing these turtles.