Graduate Degree Type
Urban development is a global threat to native wildlife. The process of urbanization reduces and degrades the useable habitat of a region, and creates novel “urban ecosystems” that possess new threats and stressors to local species. Turtles are one of the most threatened vertebrate groups worldwide, and are particularly at risk of decline in urban ecosystems due to reduced nesting success, increased road mortality events, altered movement patterns, and increased predation rates. Eastern box and Blanding’s turtles are two at-risk turtle species in the state of Michigan, USA, primarily due to land use change. Presently, there are urban populations of eastern box and Blanding’s turtles in the city of Grand Rapids, Michigan, a major urban center, however little is known about the status of these populations. I studied the urban populations of eastern box and Blanding’s turtles within the city limits of Grand Rapids in order to determine demographic and spatial movement patterns within this developmentally intense environment. I conducted mark-recapture and radio telemetry surveys across 2019 and 2020. A total of 1,041 locations were collected for 20 adult turtles, and 406 trap nights were completed across the 2019 and 2020 seasons. Comparisons of home range estimations were made using minimum convex polygons and kernel density estimators, and habitat use was analyzed using Brownian bridge movement models. Only one instance of mortality was noted from telemetered individuals, and sex ratios did not differ from parity for either focal species, or for other native turtles captured during the study. Age classes were skewed towards adults, and home range sizes were highly reduced (mean = 1.58 ha SE +/- 0.486 for Blanding’s turtles; mean = 2.88 ha SE+/- 0.913 for eastern box turtles) when compared to previous studies in more naturalistic environments. These populations of eastern box and Blanding’s turtles will likely require human intervention in order to continue to persist within this urban landscape.
Brouwers, Carly E., "Spatial and demographic patterns of two threatened turtle species in an urban environment" (2021). Masters Theses. 1006.
Available for download on Saturday, May 07, 2022