Honors Program Theses

Award/Availability

Honors Program Thesis (UNI Access Only)

First Advisor

Jeffrey Tamplin, Professor, Honors Thesis Advisor, Department of Biology

Keywords

Wood turtle--Seasonal variations--iowa; Wood turtle--Habitat--Iowa;

Abstract

The wood turtle (Glyptemys insculpta) is endangered in the state of Iowa and populations are declining throughout their native range. Forty-two wood turtles from Black Hawk County (11 females and 7 males) and Butler County (17 females and 7 males), Iowa, were tracked biweekly to bimonthly with radio telemetry from January 2017 through December 2021. I analyzed data collected from 2017– 2021 to determine if water depth selection in aquatic habitats differed between sexes and/or five seasonal activity periods (Hibernation, Prenesting, Nesting, Postnesting, and Prehibernation). Activity period had a statistically significant effect on Iowa wood turtle water depth selection and both female and male wood turtles selected deeper water during hibernation than during the other four activity periods. However, sex, and the interaction between sex and activity period, were not significant factors; female and male wood turtles chose similar water depths during each of the five activity periods.

Mean water depth of adult wood turtles in Iowa across all activity periods from 2017–2021 was: 87.55 cm ± 0.84 SE (± 35.29 SD; >200 = censored; n = 1,587); 99.97 ± 1.15 SE (± 48.48 SD; >200 = 200 cm; n = 1,784); and 105.49 ± 1.44 SE (± 60.84 SD; >200 = 250 cm; n = 1,784). Mean water depth during Hibernation from 2017–2021 was: 94.77 cm ± 1.17 SE (± 32.41 SD; >200 = censored; n = 657); 110.56 ± 1.73 SE (± 48.03 SD; >200 = 200 cm; n = 773); and 118.07 cm ± 2.27 SE (± 63.02 SD; >200 = 250 cm; n = 773).

Water depth of individual turtle locations was coded as one of five categories: Shallow (0.0–40.9 cm), Medium (41.0–80.9 cm), Deep (81.0–120.9 cm), Very Deep (121.0–160.9 cm), and Extremely Deep (>161.0 cm) water depth. Iowa wood turtles chose Deep water most frequently (35.6% of observations) during Hibernation, but used locations categorized as Medium-water depth most frequently during the other activity periods (range: 32.9–52.9% of observations). During Hibernation, 66.6% of all turtle locations were at depths >80.0 cm; during other activity periods, selection of water depths >80.0 cm ranged from 32.3–60.2% of observations. Wood turtles chose Shallow water least frequently during Hibernation (1.2% of observations; range of other active periods: 5.4–19.5% of IV observations).

Wood turtles remain aerobic during winter dormancy and require high levels of dissolved oxygen for survival. Selection of deep, flowing-water areas near river banks may be an adaptation in Iowa wood turtles that provides protection from thickening river ice and fluctuating water levels, yet minimizes exposure to strong stream currents that have the potential to dislodge them from their hibernaculum while they are largely inactive.

Year of Submission

2022

Department

Department of Biology

University Honors Designation

A thesis submitted in partial fulfillment of the requirements for the designation University Honors

Date Original

12-2022

Object Description

1 PDF file (xi, 57 pages)

Language

en

File Format

application/pdf

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