Precipitation Gradient and its Effect on Species Composition and Sex Ratios

Noe, Michelle

Eleven of the 16 species of bats detected in Washington state may be present within Olympic National Park. The objective of this study is to observe species composition and sex ratios within species at the extremes of the precipitation gradient in Olympic National Park and the surrounding area. Great precipitation, elevation, and habitat gradients occur in the park, making Olympic National Park a good place to observe differences in species composition and sex ratios. The low/wet sites of this study were near Quinault Lake in the southern part of Olympic National Park, northwest of the town of Quinault, and the low/dry sites were in Miller Peninsula State Park which is west of Sequim across Sequim Bay. We used Tuttle traps to collect capture and species presence data during the sampling period of June and July 2003. Eptesicus fuscus, Lasionycteris noctivagans, and Myotis thysanodes were found only on the dry side. Plecotus townsedii was found only on the wet side. Myotis californicus was the most abundant species on both sides of the park. Precipitation appeared to only affect species presence and not sex ratios, as sex ratios were not skewed on either side of the park.