Friday, August 8, 2008

PS 83-124: The demographics and spatial utilization of Blanding's turtle (Emydoidea blandingii) at Richard Bong State Recreation area in southeastern Wisconsin

Robert C. Jagla, Chris Coleman, Sean Murphy, Gregory C. Mayer, and Joy Wolf. University of Wisconsin-Parkside

Background/Question/Methods

Identifying suitable habitat for small populations is a critical concern for land managers and in conservation efforts. Species that naturally exist in fragmented habitats must move among habitat patches suitable for feeding, breeding, and nesting.  Anthropogenic alterations to the landscape can affect reproductive success for some populations. Blanding’s turtle (Emydoidea blandingii) is a semi-aquatic species vulnerable to loss of wetland habitats, and is now listed as threatened in most midwestern states. In Richard Bong State Recreation Area (RBSRA), located in southeastern Wisconsin, a mark/recapture study and telemetry of radio-tagged turtles was performed to determine their population size, spatial utilization, and nesting habitat. The radio telemetric data collected were analyzed using spatial analysis software to describe the habitat use of the turtles at RBSRA.
Results/Conclusions

Thirty one Blanding's turtles, 171 painted turtles (Chrysemys picta), and 25 common snapping turtles (Chelydra serpentina) were captured at RBSRA between May 1st and August 24th 2007. All Blanding's turtle captures occurred within or near the wildlife refuge area. The peak numbers of captures, which were mostly by hand, were fourteen in June and eight in July. The adult sex ratio of 0.76M:1F (13M:17F) was not significantly different from 1:1. All of the gravid females were tracked to a grassland habitat five hundred meters or more from their initial capture sites. Habitat utilization was divided between two distinct upland and wetland use areas based on 95% fixed kernel density estimation. The results show that Blanding’s turtles at RBSRA inhabit an isolated wetland, and utilize a highly disturbed area for nesting activity. Understanding the habitat usage and nesting behavior for species that are in decline is vital for conservation and management decisions.