Semester

Fall

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Forestry and Natural Resources

Committee Chair

Donald Brown

Committee Member

Andrew Badje

Committee Member

James Anderson

Committee Member

John Edwards

Abstract

Due to range-wide population declines, wood turtles (Glyptemys insculpta) are under review for federal listing under the United States Endangered Species Act. Understanding how habitat associations and environmental conditions influence population dynamics and spatiotemporal activity patterns is fundamental for designing effective management strategies. Previous work on wood turtle abundance-habitat relationships focused on broad-scale habitat relationships in northeastern North America. However, regional differences in climate, habitat conditions, and land use patterns limit their applicability to much of the wood turtle’s Upper Midwest distribution. Much of our understanding of wood turtle activity patterns is based on radiotelemetry studies, which are biased towards daytime hours and typically have relatively low temporal resolution. There is a general understanding of wood turtle activity patterns during the spring, but patterns become unclear and inconsistent after the nesting period. Many studies report that wood turtles become primarily terrestrial during the summer months, but few studies have investigated nighttime habitat use during the summer months. Thus, further research is required to better understand wood turtle population dynamics and spatiotemporal activity patterns in the Upper Midwest region.

In Chapter 1, I provide information on the ecology and behavior of wood turtles, their current conservation status, and threats affecting populations. I discuss the importance of ii vegetation structure in wildlife studies, emphasizing how it affects microclimate. I also provide background information on Light Detection and Ranging (LiDAR) technology and its application to quantifying vegetation structure. Lastly, I state the goals of this thesis research and give a summary of the chapters.

In Chapter 2, we conducted wood turtle population surveys across northern Wisconsin and northeastern Minnesota and gathered numerous aquatic and terrestrial habitat data, including measures of 3-dimensional vegetation structure derived from LiDAR. We created a hierarchical N-mixture model to estimate adult abundance and used a multistage model selection approach to rank habitat covariates. We found aquatic and terrestrial habitat characteristics to be strong predictors of abundance, particularly stream velocity, stream width, mean return height, and vertical coefficient of variation (CV) of height. The most supported model suggested that abundance was high at sites containing comparatively narrow streams with moderate velocities, low mean return heights, and extremes in vertical CV of height.

In Chapter 3, we characterized the daily movement patterns of wood turtles between aquatic and terrestrial habitats throughout the active period in northeastern Minnesota. We modeled the influence of temporal, demographic, and environmental covariates using generalized linear mixed models. We found open canopy air temperature to be the strongest predictor of aquatic-terrestrial habitat use. The most supported model included an interaction between air temperature and sex, and the most supported temporal model contained an interaction among the hour of the day, day of the year, and sex. We found that terrestrial activity was positively associated with air temperature, resulting in daytime terrestrial and nighttime aquatic activity during pre-nesting (i.e., May). During the post-nesting period (i.e., July), females became more terrestrial than males at night, influenced by females moving farther from the river.

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