Bat activity over wetlands: temporal and spatial variation

Foraging animals face decisions about when and where to forage based, in part, on prey availability, which can fluctuate temporally as well as spatially. For temperate insectivorous bats, wetlands are important forage habitats because they provide water and high abundances of insects. My overall objective was to identify abiotic and biotic factors that influence bat foraging activity over wetlands in the channeled scablands of eastern Washington. I surveyed 12 wetland sites at Turnbull National Wildlife Refuge (TNWR) in Cheney, Washington, 3 or 4 times during summer 2012. Ten stations were set up at each site to measure insect abundance using floating aquatic emergence traps and pan traps. Bat feeding activity was measured using ultrasonic recording devices. I measured vegetation abundance, water temperature and depth, presence/absence of fish, and wetland type at each site. I collected 3,127 aquatic insects from 5 different orders. I recorded calls from ten bat species, including two species that have not been previously detected at TNWR. Feeding buzzes were recorded at all 12 sites during at least one sampling period. There was spatial variation in water depth, cattail abundance, and calls from high-frequency bats. Water depth was deeper at one permanent wetland than at one permanent and one non-permanent wetland. Cattail abundance varied across sites. Calls from high-frequency bats were higher at one permanent wetland compared to one wetland that dried up during July. There was temporal variation in wetland characteristics, insect biomass, and bat activity. Water temperature, insect biomass, and bat activity (both total calls and total feeding buzzes) were highest during the first sampling period. Overall, my study showed that bats utilize wetlands as foraging habitat. Because wetlands exhibit temporal and spatial fluctuation, a broad-scale conservation effort to maintain quality wetlands would provide the greatest benefit to bat species at TNWR --Document