Passive Acoustic Monitoring for Bats in Support of the Coyote Wind Project, Sweet Grass County, Montana

Scientific Disciplines
Biological Sciences - Terrestrial
acoustic monitoring
Wind energy
Bat activity
animal flight
Sweetgrass County, Montana
Garcia and Associates
energy development
wind project
wind speeds
coyote wind project
passive acoustic monitoring
sweet grass county montana
wind farms
Volume 16, No. 4

Passive acoustic monitoring for bats in support of the 
coyote wind project, Sweet grass county, Montana

Pam Spinelli,* Graham Neale, and Becky Parker,Garcia and Associates, 1716 West Main St., Ste. 
8-F, Bozeman, Montana 59715
Heather Johnson, Garcia and Associates, 1141 High St., Auburn, California 95603
Wind energy development in the United States has been increasing rapidly and is 
expected to continue to do so. There are many benefits to producing wind energy; however 

it is also important to understand potential negative effects and ways these impacts could 
be mitigated. Impacts to bats, and how to predict and mitigate impacts, are less well known 
than wind project impacts to birds. We conducted passive acoustic monitoring from 29 
August to 6 November 2008 in Sweet Grass County, Montana, as part of pre-construction 
surveys for Enerfin Energy Company‚Äôs proposed Coyote Wind Project. We deployed four 
Anabat acoustic detectors on two portable towers at 1.5- and 20-m heights, and recorded 
data nightly. We used these data to evaluate bat activity over the study period; within each 
night; relative to wind speed; relative to temperature; and relative to instrument heights. We 
recorded 668 echolocation files in 3 phonic groups. Bat activity was highest between 29 
August and 1 October, and within 3 hrs of sunset. Bat activity peaked at wind speeds of 2-3 
m/s and dropped off with increasing wind speeds to about 8 m/s. Bats were most active at air 
temperatures between 5 and 20 oC. Instrument height and bat phonic group were significantly 
correlated. These results are generally consistent with those found by Arnett et al. (2006) in 
Pennsylvania.  Increasing our understanding of environmental parameters and bat activity in 
Montana will contribute to appropriate wind project siting and mitigation.