Trophic and Dietary Overlap Study Between Threatened and Common Riverine Turtles in Southeast New Mexico Using Stable Isotope Analyses

Published Date:

July 2021


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 (δ 13C) and nitrogen (δ 15N) 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 δ 15N values. Although stable isotopes showed niche overlap between   T. scripta  and   P. gorzugi  based on the ellipse area overlap (SEA B), 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