Geographic Variation in Roost-Site Selection of Long-Legged Myotis in the Pacific Northwest

Several species of bats in the Pacific Northwest of the United States, including long-legged myotis (Myotis volans), are dependent on snags in coniferous forests during summer for roosting and rearing young. Thus, data on roosting preferences of this species are needed to integrate their habitat requirements into shifting plans for management of forests in this region. Therefore, from 2001 to 2006, we radiotracked adult female long-legged myotis (n = 153) to day roosts (n = 395) across 6 watersheds in Washington, Oregon, and Idaho, USA, and compared characteristics associated with roosting sites to those of random snags (n = 260) sampled in the same watersheds using use-availability logistic regression and an information-theoretic approach. Model rankings varied among geographic locations, with quantity of stem surface for roosting the best model for explaining roost-site selection of long-legged myotis in both Washington and Oregon. Model rankings for populations of bats in Idaho found stand- and landscape-scale features to be important in roost-site selection, with a habitat fragmentation model and a foraging habitat quality model both demonstrating strong support as best model. Choice of day roosts by long-legged myotis was associated with snags that were taller, intact at the top of the stem, possessing a greater amount of exfoliating bark, in stands with a larger basal area of dead stems, and in landscapes that were unfragmented (i.e., supporting lesser amounts of edge). Results indicate that roost-site selection of bats in western coniferous forests, particularly long-legged myotis, is likely to be region-specific. We encourage land managers to consider importance of geographic variation in intraspecific habitat use in forest-dwelling bats when implementing silvicultural systems to promote biological diversity in actively managed forests of the Pacific Northwest region.