Publication Date

2024

Document Type

Dissertation/Thesis

First Advisor

King, Richard B.

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Biological Sciences

Abstract

Across the globe, biodiversity is threatened due to anthropogenic changes to the environment and large numbers of freshwater species, especially turtles, are facing population declines. Resources for conservation are limited, making empirically based conservation planning of utmost importance. Effective management strategies incorporate relevant biological information to outline specific and feasible actions that will mitigate the greatest threats to a species. Blanding’s Turtles (Emydoidea blandingii) are a long-lived, semi-aquatic, freshwater species that are classified as endangered in Illinois and internationally. As with other species of concern, Blanding’s Turtles are threatened by habitat loss, fragmentation, and degradation. They are also threatened by increased populations of human-subsidized predators, road mortality, poaching, loss of genetic diversity, and disease. The combination of these threats causes unsustainably high rates of adult mortality and decreased juvenile recruitment, leading many turtle populations into an extinction vortex. Several management strategies are aimed at addressing threats to Blanding’s Turtle populations, such as habitat restoration, headstarting, meso-predator control, and health monitoring. However, the efficacy of these management strategies needs evaluation.

In Chapter 2, I looked at the effects of habitat quality by comparing spatial ecology of adult female Blanding’s Turtles and provided a first test for covariation between spatial ecology and health for a free-ranging turtle species. Although I did not find a difference between spatial ecology among sites, movement distance was sometimes correlated with health, possibly resulting from temporal variation in stress associated with reproduction. In Chapter 3, I identified variables that affect headstarted Blanding’s Turtle survival. I found that headstarts that are larger at release, released with concurrent predator removal, and have lower stress (heterophil-lymphocyte ratio) had higher post-release survival. In Chapter 4, I explored how population recovery targets can be met using a variety of release strategies within differing initial population conditions. I found that headstarting can lead to population growth by releasing older larger headstarts with concurrent predator removal, releasing larger numbers of younger smaller headstarts, or implementing predator removal to allow natural recruitment without headstarting. Overall, management for Blanding’s Turtles seems to achieve positive outcomes for populations, but the implementation of these strategies can be fine-tuned to maximize effects. These results will help maintain important populations of an endangered turtle species, protect them against future threats, and continue to provide scientifically-backed guidance for Blanding’s Turtle conservation, and freshwater turtle management more generally.

Extent

142 pages

Language

en

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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