Relative Species Composition of Bats in Sitka spruce and Western hemlock forests on the Olympic Peninsula

Adam, Patrick

Species composition of bats may differ substantially between comparable age class stands of Sitka spruce and western hemlock forests within Olympic National Park. This study investigates previous indications of this phenomenon for a more thorough understanding of habitat requirements and niche partitioning for vespertilionid bat species. Our goals are to compare relative activity and species composition between Sitka spruce and western hemlock forests using both direct capture and echolocation detection techniques. Positive species identification and acquisition of basic morphological and biological characteristics was attained through use of both harp traps and mist nets. Relative activity levels between sites were made with the use of automated bat echolocation equipment. ArcView GIS was used to analyze land cover data for plots chosen as trapping sites to determine percent coverage of a given tree species. Four species of bat, M. californicus, M. yumanensis, M. lucifigus, and M. evotis were as likely to be found in Sitka spruce forests ... as in western hemlock forests .... Although these values are statistically insignificant ... the analysis does not take into consideration the interactive effects of elevation which may have an effect on the final analysis. The results imply no difference in bat species composition between forest types which may in part be due to a lack of sharp segregation between Sitka spruce and western hemlock trees.