Date of this Version
Wagner J.L. 2023. Bat Use of Afforested and Encroached Patches and Their Role in Extending Bat Habitat into the Nebraska Sandhills. Thesis, University of Nebraska - Lincoln.
The Nebraska Sandhills are currently undergoing a state shift to a redcedar dominated woodland due to anthropologic planting of eastern redcedar (Juniperus virginiana) and woody encroachment from the periphery of the Sandhills. To better understand this novel ecosystem and how bats are utilizing it I collected data at Barta Brothers Ranch with acoustic sensor grids consisting of 24 100m spaced acoustic sensors placed adjacent to planted windbreaks. Supplemental data from the Nebraska North American Bat Monitoring Program was used for data analysis at larger spatial scales. I used linear regressions and kriging interpolation maps to see how bats used windbreaks during nightly activity. Eptesicus fuscus, Lasiurus borealis, and Nycticeius humeralis showed close usage activity around windbreaks while Lasiurus cinereus and Lasionycteris noctivagans showed even usage activity throughout the sensing area, while still showing a relationship with trees at a larger scale. I used multi model inference and model averaging to find the best models to explain bat species richness and call count. I found that distance to trees, with a preference for deciduous trees, and time through the summer to be the best predictors of bat species richness and call count. I used linear regressions of first instance calls in my grids to determine if bats are using windbreaks to roost or travel from roosts to feeding grounds. Across all species, Eptesicus fuscus and Lasionycteris noctivagans showed greater numbers of first instances closer to the windbreak, which indicates that, in general, bats are using windbreaks for roosting or for pathways between roosts and feeding grounds. Lasiurus cinereus first instances were not related to windbreaks hinting that this species may travel across open grassland from roost to feeding grounds. Bat presence and use of trees in the Sandhills presents a dilemma of ecosystem service tradeoffs, in which management aimed at controlling the spread of woody plants for grassland diversity and forage quality and quantity may reduce habitat for bat species.
Advisor: Craig Allen