Date of this Version
Hellman, M.L. 2013. Amphibian Occupancy and Functional Connectivity of Restored Wetlands in the Missouri River Floodplain. MS thesis. University of Nebraska, Lincoln.
Wetland decline may threaten many taxa including shorebirds, amphibians, and fish. As agencies increase restoration of wetland habitat, monitoring is crucial to inform the process. Permeable skin sensitive to water quality and biphasic life histories requiring both terrestrial and aquatic habitat make amphibians good indicators of wetland health. I modeled amphibian occupancy in restored Missouri River bends to determine habitat characteristics associated with the presence of amphibians.
Occupancy modeling acknowledges imperfect detection and allows the inclusion of detection covariates. To assess detection I examined two methods currently used to assess anuran occupancy in wetlands, aural anuran surveys and tadpole dip-netting. I assessed survey and site-specific factors that may influence detection success of anuran species using these two methods and found that water temperature appears to play a role in aural detection of some species during call surveys. Slope impacts detection of tadpoles and may be indicative of a sampling bias.
I incorporated the top detection models into my candidate models testing the effect of habitat characteristics on amphibian occupancy. My results indicate that the slope of a wetland is driving occupancy of many species at the research sites. In most cases slope had a negative impact on occupancy. Landscape characteristics, like connectivity of wetlands, facilitate between-patch dispersal and may be just as important to the local persistence of amphibians. I assessed connectivity for anurans of wetlands within a bend and recommend locations for new restorations that can improve connectivity of the bend. I found that average connectivity of a bend may not be the best indicator of functional connectivity. All of the research bends had clusters of wetlands that were highly connected to one another but relatively unconnected to the rest of the complex.
I suggest that future site selection should focus on shallow, gently sloping wetlands and that a few well-placed restorations could increase functional connectivity of the complex and improve the resilience of amphibian populations to droughts, floods, and localized disturbances like land-use changes.
Advisor: Craig Allen