BAT ACTIVITY ALONG INTERMITTENT STREAMS IN NORTHWESTERN CALIFORNIA

Abstract

Bats are known to use areas above perennial streams and rivers for foraging and traveling; however, little is known about bat use of smaller streams that flow intermittently. We compared bat activity among 3 size classes of streams and upland sites in a northwestern California watershed during summers 1996 and 1997. Stream size was classified based on channel width. Ultrasonic Anabat II® bat detectors were placed in stream channels and at upland sites, and bat activity was recorded remotely at night. Analysis of bat detector data revealed a significant difference in activity among the 4 habitat types in both years. In 1996, bat activity was greatest along medium and large intermittent streams, was intermediate at small intermittent streams, and was least at upland sites. In 1997, a similar pattern was found, but no significant difference was found in bat activity between small stream and upland sites. To determine species presence, bats were captured in mist nets at stream sites with the highest bat activity. Results are presented indicating differences in number of captures by species between medium and large streams.