Publication Date

Spring 2012

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Advisor

Elizabeth McGee

Keywords

Anabat, bat, echolocation, Myotis yumanensis, Tadarida brasiliensis mexicana, wetlands

Subject Areas

Wildlife conservation; Conservation biology; Ecology

Abstract

Research on bat habitat use within coastal estuaries is limited. The purposes of my study were to determine whether Yuma myotis (Myotis yumanensis) and Mexican free-tailed bats (Tadarida brasiliensis mexicana) differentiate between open water and marsh within saline and brackish habitats and to examine whether climatic factors are correlated with general activity and tidal height with foraging of the two species. I recorded echolocation sequences over 30 survey nights in Alviso, California. Two Anabat II® detectors were randomly deployed each survey night in open salt water and salt marsh or open brackish water and brackish marsh. I identified M. yumanensis and T. b. mexicana sequences within each of the four habitats and feeding buzzes in open brackish water and brackish marsh. Additionally, I logged air temperature and wind speed per hour, percent moonlight visibility per survey night, and tidal height at 15-min intervals. I recorded 1,896 sequences, 845 from M. yumanensis and 983 from T. b. mexicana. For both species, there was a significant difference in frequency of occurrence and mean number of echolocation sequences per survey night in open water versus marsh for saline but not for brackish habitats. Furthermore, T. b. mexicana demonstrated greater preference than M. yumanensis for open salt water. Although the call frequency of T. b. mexicana increased with higher air temperature and lower moonlight visibility, the presence/absence of echolocation calls from the two species could not be predicted from the three climatic variables. Mean tidal height did not differ between M. yumanensis and T. b. mexicana sequences with feeding buzzes and sequences without buzzes in open brackish water and brackish marsh. The results increase our knowledge about bat habitat use in estuaries and provide important information to enhance bat conservation in coastal wetlands.

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