Habitat Characteristics, Population Size, and Home Range of the Bog Turtle, Clemmys muhlenbergii, in Maryland

Abstract

Twenty bog turtle, Clemmys muhlenbergii, colonies were studied in Carroll, Baltimore, and Harford counties, Maryland, to determine habitat characteristics, population size, and movements and home range. Thirty-six habitat variables at each colony site were used in statistical analyses to examine the relationship between indexes of population size and habitat characteristics. Based on principal components analysis, the greater the index of population size, the more likely the colony was located in a circular basin with (1)spring-fed pockets of shallow water, (2) a bottom substrate of soft mud and rock, (3) dominant vegetation of low grasses and sedges, and (4) interspersed wet and dry pockets. Of the nine sites where populations could be estimated, we found from 7 to 213 turtleslha of wetland habitat. Bog turtles were active for six months in Maryland. Home ranges were larger in males (0.176 ha) than in females (0.066 ha) and overlapped considerably among individuals of both sexes. Home ranges rarely extended far beyond the transitional edge of the wetland. Although turtles had small activity areas, they moved extensively within those areas. Winter retreats were shallow, just below the upper surface of frozen mud and/or ice. Four of eight turtles monitored moved in and out of winter retreats from November through March. Conservation efforts should focus on protection of a wetland network that allows movement and gene flow among populations to minimize the effects of local extinctions.