Wetland Characteristics Associated with Amphibian Presence in the Rocky Mountain Region
Hydroperiod (the annual period that open water is available) is an important factor in studies of wetland ecology. It has been linked to amphibian development, distribution, and rates of survival as well as the presence of exotic species. However, hydroperiod is rarely measured directly. Typically wetland size is used as a surrogate measurement of hydroperiod. Recent studies suggest that wetland size may not be as closely related to hydroperiod as was previously thought. To investigate the role of hydroperiod and its relationship with other habitat parameters, I conducted a study of 23 wetlands located in west-central Montana. Each wetland was surveyed three times during the summer of 2002 and estimates were made for: wetland size, area of open water, hydroperiod, rate of water loss, presence of Rana luteiventris, and presence of Ambystoma macrodactylum. Analysis showed that hydroperiod was not correlated with the other wetland measurements, nor was it an accurate predictor of the presence of amphibian species. Total wetland area was correlated with the presence of R. luteiventris, but was not an accurate predictor of the presence of A. macrodactylum. Area of open water was correlated with the presence of both species of amphibians. In this study area, there was not a large gradient of hydroperiods. Future studies should be conducted to minimize year-to-year variation within this wetland and more accurately assess the impact of hydroperiod. However, my results suggest that the area of open water may be a better predictor of amphibian presence than is hydroperiod.