Water Table Depth, Surface Saturation, and Drought Response in Bog Turtle (Glyptemys muhlenbergii) Wetlands

Abstract

The bog turtle (Glyptemys muhlenbergii) is known to select wetland areas that are near water with deep mud, but water table dynamics in their habitats have not been well described. We installed and monitored shallow groundwater wells to evaluate hydrology over a continuous 28-month period on six wetlands known to be frequently used by bog turtles and six similar wetlands not known to be used. Overall, water tables remained high, with mean monthly depth to the water table for all 12 wetlands varying between −1 cm and −35 cm below the soil surface. Wetlands frequently used by bog turtles had higher mean water tables and surface saturation than wetlands not known to be used, particularly during summer months. Differences in mean water table (17 cm) and saturation (25 %) were greatest during southwestern Virginia’s 2008 drought. A differential remained after the resumption of normal rainfall, demonstrating the importance of groundwater recharge to bog turtle wetlands. Relatively small differences in water table hydrology have the potential to affect bog turtle biology and wetland use because bog turtles primarily use the top 15 cm of the soil and select saturated locations even when the availability of saturated soil is limited.