THE EFFECTS OF LIVESTOCK GRAZING ON THE BOG TURTLE [GLYPTEMYS ( =  CLEMMYS) MUHLENBERGII]

Abstract

The bog turtle Glyptemys ( = Clemmys) muhlenbergii is an inhabitant of groundwater-fed sedge meadows in the northeastern and southeastern United States. Observations of bog turtle habitats throughout the species' range demonstrate that livestock grazing has been an important factor in staving off successional processes and abating large-scale invasions by tall-growing, competitively dominant plants—many of which are exotic in origin. The demise of small-scale dairy farming over the past three decades has led to the pastoral abandonment of the majority of bog turtle habitats in the Northeast. As a consequence, habitats are being degraded by the growth of invasive flora, changes in hydrology, and loss of turtle microhabitats created by livestock. In this study we compared the number of bog turtle captures, bog turtle demographic parameters, bog turtle densities, and vegetation at sites that are currently grazed (n = 12) and at sites in which grazing had recently ceased (n = 12). This analysis demonstrated that grazed sites contained greater numbers of turtles, greater turtle density, and greater frequency of occurrence for juvenile turtles. Grazed sites also contained greater cover of low-growing herbaceous vegetation and lower heights of tall-growing exotic and/or invasive vegetation than the formerly grazed sites. We hypothesize that nutrient enrichment from manure and agricultural run-off has promoted the establishment and growth of invasive plant species at many of the sites, but livestock grazing has kept these plants in check. When livestock are removed, invasive species proliferate, and the hummocky microtopography maintained by the livestock traffic is often reduced to a mat of vegetation. This investigation showed that efforts to preserve viable populations of bog turtles may depend on the preservation of low-intensity, pasture-based dairy and beef farming.