Date of Graduation

12-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Biology (PhD)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

DeGregorio, Brett A.

Committee Member

Naithani, Kusum J.

Second Committee Member

Sperry, Jinelle

Third Committee Member

Willson, John D.

Keywords

Activity; Dynamic; Movement; Occupancy; Turtle

Abstract

Wetland ecosystems are often spatially patchy across a landscape and exhibit seasonal patterns in water levels, resulting in the need for aquatic wildlife to use several different wetland patches across a season. The ecology of semi-aquatic freshwater turtles is especially complex because individuals often move among a variety of habitats to meet life history needs and these habitat requirements often differ across a season. Understanding the temporal and spatial scale in which turtles move and distribute across the landscape is vital for effective management, especially in the face of continued habitat fragmentation and climate change. Thus, we sought to understand the spatio-temporal variation in activity, movement, and occupancy dynamics of an imperiled freshwater turtle, the spotted turtle (Clemmys guttata), in a dynamic wetland ecosystem.

In Chapter I, I used near-continuous automated radiotelemetry to quantity diel activity patterns of spotted turtles over 19 months across different seasons. I also examined how season, turtle characteristics (age and sex), and climatic conditions influenced diel activity patterns and nocturnal behaviors. Diel activity of spotted turtles remained constant across the year, but there was seasonal variation in total activity and nocturnal behaviors. As expected, adult spotted turtles were more active than juveniles, though there was no difference between adult male or females. Nocturnal activity was best predicted by recent climatic conditions. I consider automated radiotelemetry to be effective at documenting fine-scale activity patterns of spotted turtles and recommend widespread adoption of continuous monitoring methods to better understand how widespread nocturnal behavior is among turtles and identify the mechanisms driving nocturnal activity.

In Chapter II, I used VHF radio-transmitters to radio-locate adult and juvenile turtles and estimate movement and space-use during their active and aestivation seasons (March - August). I then explored how movement and space-use varied based on intrinsic turtle characteristics (sex and age class) and extrinsic wetland and climatic features. I demonstrated that spotted turtle movement is influenced by season, as well as climatic conditions and wetland characteristics. Spotted turtle movement peaked in late spring. Across this time, adult spotted turtles moved farther than juvenile turtles and occupied larger home-ranges, though there was no difference in movement or space-use between adult males and females. Turtle response to variation in season and wetland configuration highlight the need for complex and dynamic landscapes that are required to sustain this species.

In Chapter III, conducted repeated surveys across three spring seasons (March – June) to determine the spatio-temporal occupancy dynamics and habitat associations of spotted turtle across wetland complexes. We then explored how wetland characteristics influenced occupancy and abundance, and how climatic conditions influenced detection of spotted turtles. Occupancy and abundance varied across the spring sampling season, with a peak in the number of occupied wetlands and abundance estimates in the middle of the season. There was a seasonal trend in occupancy based on wetland size, but not habitat type across the season. Abundance estimates were best predicted by presence of prey availability and wetland configuration. These results help to provide more accurate predictions of dynamic distributions and population persistence.

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