Basking dynamics among sympatric turtle species (Trachemys scripta elegans, Pseudemys texana, and Graptemys pseudogeographica kohnii) in Waco Creek, Texas.

Abstract

The premise of this manuscript condenses into three words: turtles on logs. Turtles splaying their limbs and sunning themselves on emergent deadwood is commonly known as basking. Basking involves ectotherms taking advantage of solar radiation to boost their core temperature and fuel metabolic processes. This study examines a community assemblage of three turtle species within the Family Emydidae—Trachemys scripta elegans: Red-eared Slider, Pseudemys texana: Texas River Cooter, and Graptemys pseudogeographica kohnii: False Map Turtle—in Waco Creek, Texas, a tributary of the Brazos River, from 2010-2012. Turtles were collected daily via specialized traps which take advantage of repetitive basking habits, individually marked, measured, identified, and then released from June to October 2010, April to October 2011, and April to October 2012. Multiple recaptures allowed for observation of individual, population, and community progression over time. This manuscript asks three fundamental questions about the role of basking behavior in the Waco Creek emydid turtles: 1) What is the significance of the basking community assemblage composition in Waco Creek, 2) How do basking trap modifications and population demographic selection affect group trap response, and 3) How do polynomial and k-growth mixed models describe juvenile turtle logistic growth? Trachemys scripta elegans comprise 46%, Pseudemys texana 32%, and Graptemys pseudogeographica kohnii 23% sample composition within the Waco Creek basking turtle assemblage. All mature populations were significantly male skewed and turtle demographics exhibited several expected seasonal behavior patterns. The community has a large abundance of juveniles, young males, and immature females regardless of species. In addition, juvenile T. scripta appear to be the most actively basking demographic. Between individual demographic behavior and trap design as predictors for trap response, demographic behavior was significant across most response variables whereas trap design variables were not. This study pioneered a new technique for comparing turtle logistic growth models using a polynomial mixed model as a control. With an adequate sample size and consistent seasonal dispersal, results from this technique agree with reports from the literature and look promising.