The Impacts of Cattle Grazing on Bog Turtle Habitat Condition, Movement, and Resource Selection

Abstract

The involvement of the public in wildlife management is complex and increasingly necessary due to the occurrence of many threatened and endangered species primarily on private lands. One such species is the bog turtle (Glyptemys muhlenbergii [Schoepff 1801]), a small, freshwater turtle found in open-canopy wetland meadows throughout the eastern United States. Historically, the open nature of these fens was believed to have been maintained through natural and anthropogenic disturbance that limited the development of shrubby and woody vegetation; however, soil and hydrological conditions also play a role in maintaining the open nature of undisturbed fens. A management focus on disturbance-driven maintenance is largely a result of the past and current cattle grazing that occurs across a substantial portion of the known habitat of the bog turtle. While current management recommendations include forms of prescribed grazing, studies focused on the relationship between grazing impacts and bog turtles are relatively limited, and grazing cattle may directly and indirectly harm bog turtles. Current conservation goals for the bog turtles include identifying previously unknown populations and managing known habitat through protection and restoration efforts. This research informs both these conservation goals by expanding on the ability to remotely-sense habitat and quantifying the impact of grazing as a management practice on both habitat and on turtles themselves. I began by examining patterns of habitat selection across spatial scales to identify preferred environmental conditions that could be remotely sensed and, in future studies, used to refine occupancy and abundance field surveys. My results reveal turtle preference for wetland interiors, relatively lower elevations, and within scrub-shrub vegetation cover, regardless of the defined spatial scale. Next, I used game cameras to quantify cattle activity within occupied wetlands and related that activity to relevant habitat conditions including vegetation structure, hydrology, and nesting site temperatures. I found that higher cattle activity was correlated with increased surface water and mud presence, lower thatch and standing vegetation coverage, and higher and less consistent daily temperatures at potential nesting sites. Finally, I conducted a field experiment within two occupied wetlands and manipulated grazing stocking density and duration to investigate how trampling risk, habitat condition, and turtle movement observed via radiotelemetry varied across grazing treatments. My results suggest that a targeted grazing treatment such as flash grazing resulted in similar vegetation and soil conditions as a continuous, heavily grazed treatment but could have a significantly higher risk of trampling if implemented during the nesting season. Additionally, I saw no shifts in turtle movement or resource selection, suggesting that the temporary grazing manipulation had limited effect on turtle behavior. The growing need for land conversion for economic development is seemingly endless; therefore, managers must work to mitigate this demand by fostering responsible use of our natural resources. Additionally, conservation efforts for species on privately owned land must coexist with the financial and cultural ties that landowners have with their property. My results inform this responsible use, in addition to directing future research and conservation efforts for this rare species.