Trophic and Dietary Overlap Study Between Threatened and Common Riverine Turtles in Southeast New Mexico Using Stable Isotope Analyses
Thanchira Suriyamongkol, Ivana Mali
Aquatic turtles represent important biotic components of freshwater ecosystems. The Pecos River watershed is inhabited by six turtle species, including the widespread Trachemys scripta (Red-eared Slider) and a species of conservation concern, Pseudemys gorzugi (Rio Grande Cooter). We assessed isotopic niche widths of the Rio Grande Cooter and niche overlap where it co-occurs with the Red-eared Slider in the Pecos River tributaries, New Mexico, USA. We used carbon (δ13C) and nitrogen (δ15N) stable isotope analyses of blood and claws. Our results showed niche partitioning among populations of P. gorzugi and among sex classes. At sites where both species occur, we documented niche overlap, especially for δ15N values. Although stable isotopes showed niche overlap between T. scripta and P. gorzugi based on the ellipse area overlap (SEAB), the distribution of prey items in the diets of P. gorzugi and T. scripta revealed the differences in resource selection. We observed that differences in P. gorzugi diets among populations correspond to resource availability, suggesting opportunistic foraging behavior of P. gorzugi. Our study aids in understanding the ecology and natural history of P. gorzugi. Moreover, our study provides insights into interspecific relations of T. scripta in their native range.
Technical Report 394
Freshwater turtles, Pecos River, niche overlap, stable isotopes, Rio Grande Cooter