The U.S. Forest Service Northern Region has conducted bat surveys each year during 2005-2007 to gather information on the distribution and status of bats on Forest Service lands in Montana. During 2005, 57 sites were surveyed on selected National Forest (NF) Ranger Districts (RD); the 2005 field season provided information for areas previously without documented bat activity and resulted in numerous new county records for several species. In 2006, with an increased number of surveyors, 75 new sites were surveyed using both mist-net and acoustic sampling methods. A pilot project was undertaken following the 2006 field season to investigate bat detection probabilities for surveys using more than one detection method (mistnetting and acoustic sampling). During the 2007 field season, 87 new sites were surveyed: 59 acoustically, 28 mist-netted. Areas targeted for survey included RDs and/or backcountry areas of select RDs lacking any survey coverage. These included the Dillon, Jefferson, Madison, Pintler, Wisdom, and Wise River RDs of the Beaverhead-Deerlodge NF; the Ashland and Beartooth RDs of the Custer NF; Glacier View, Hungry Horse, Spotted Bear, Swan Lake, and Tally Lake RDs of the Flathead NF; the Gardiner RD of the Gallatin NF; the Rocky Mountain RD of the Lewis and Clark NF; and the Seeley Lake and Superior RDs of the Lolo NF. Ten species of bats, represented by 218 individuals, were captured by mist-net during mid June-late August 2007. Species captured included Little Brown Myotis (Myotis lucifugus), Western Long-eared Myotis (M. evotis), Long-legged Myotis (M. volans), California Myotis (M californicus), Big Brown Bat (Eptesicus fuscus), Hoary Bat (Lasiurus cinereus), Silver-haired Bat (Lasionycteris noctivagans), Townsend's Big-eared Bat (Corynorhinus townsendii), Eastern Red Bat (Lasiurus borealis), and Pallid Bat (Antrozous pallidus); the latter two are the first of their respective species to be detected by any method during the first three years of the USFS Northern Region inventory. Call analysis on the 2007 acoustic surveys has not been completed at the time this report was prepared. Genetic analysis is needed to confirm tentative identifications of some Myotis taxa at several netting sites. No bats were detected at ten sites and are not included in the total number of site surveys for 2007. The 2007 surveys filled important gaps in documented bat distributions in Montana, as well as on Ranger Districts formerly lacking any surveys. However, a summary of all existing Northern Region bat records continues to show large distribution gaps for all species, underscoring the need for additional surveys. In particular, large portions of the Bitterroot, Flathead, Gallatin, Kootenai, and Lewis and Clark National Forests lack records for any bat species or any recently documented activity. Up-to-date distribution maps for Montana's species can be queried and viewed with a variety of map layers on the Montana Natural Heritage Program's TRACKER website at: http://mtnhp.org/Tracker. Morphometric data collected in Montana, Idaho, and South Dakota during 2005-2007 were comparable with previously documented measurements in the region, although a few records were outside the limits of published ranges. For the eight species where a significant difference was detected, females exceeded males in mean forearm length in all but Western Long-eared Myotis. Mean weight and ear length were not clearly differentiated by sex. Data collected from captured bats during the USFS Northern Region surveys can help identify regional differences in bat morphometrics, supplement regional natural history information, and assist in refining in-hand identification techniques.
Report includes 1)inventory results of the 2007 field season, 2) summary of grid cell coverage for the effort to date (2005-2007), and 3) analysis of all standard morphometric traits taken from bats captured during 2005-2007, with discussion of their utility for making species determinations.