First Advisor

Catherine de Rivera

Date of Award

Spring 6-16-2024

Document Type

Thesis

Degree Name

Bachelor of Science (B.S.) in Environmental Science and University Honors

Department

Environmental Science and Management

Language

English

Subjects

Invasive species management, Red-eared slider turtle, Trachemys scripta elegans, Western painted turtle, Chrysemys scripta elegans, Biological invasions

DOI

10.15760/honors.1560

Abstract

The red-eared slider is considered one of the most ubiquitous freshwater turtles globally. Several key ecological advantages and life history traits of this species jointly impact growth rates and survivorship of native freshwater turtles where sympatry occurs. Evaluation of current management actions for red-eared slider turtles is limited, resulting in a paucity of information to guide management for the species and conservation of declining native freshwater turtles. We used previously collected mark-recapture and removal sampling data from sites with sympatric populations of red-eared slider and western painted turtles. We examined the effects of control (trapping and removal) of red-eared sliders on (1) red-eared slider abundance (2) western painted turtle abundance and body condition (3) community composition. The estimated population size of western painted turtles decreased over time, though with wide confidence intervals, in Peninsula Drainage Canal and increased substantially in Smith and Bybee. However, in Smith and Bybee the estimated population size of red-eared sliders increased, despite continuous removal of the species. We did not detect a difference in the average body condition for western painted turtles as more red-eared sliders were removed. We also showed moderate evidence that management actions can change community composition by removing red-eared sliders, increasing the proportion of western painted turtles relative to red-eared sliders within the community. The questions we set out to answer are imperative to the management of these species and our study highlights the need to make improvements to mark-recapture study design and more systematic sampling to enable rigorous conclusions.

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Persistent Identifier

https://archives.pdx.edu/ds/psu/42161

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