Bats are an important part of our environment and provide us with many benefits, including insect control and fertilizer. However, bat populations in the United States are being threatened by the spread of the fungal disease known as white-nose syndrome (WNS) and the rapid growth of wind energy development. Bats are susceptible to wind turbine fatalities for reasons we don't fully understand yet. Although we are aware of bat fatalities at wind facilities, it is difficult to know how these fatalities are affecting our environment without a better knowledge of basic bat ecology, which is sparse in many areas including northeast Iowa. Relatively little is known about species distribution and density, migration timing and pattern, and feeding, roosting, and mating behavior. Also, most of what we understand about turbine impacts comes from studies conducted at large-scale, multi-turbine wind farms. Virtually no studies have examined the impacts of single-turbine facilities, such as the one at Luther College.
The goal of our study is to examine bat activity and fatality at the Luther College wind turbine in Decorah, IA, an area that has not yet been affected by white-nose syndrome but is at the edge of the infection zone. Student researchers are searching the turbine daily for bat carcasses from June 15-October 15, 2015. Additionally, we have set up bat acoustic recording devices at the turbine and nearby areas to track the bat activity at these locations. We have started a community-based volunteer program to collect additional data on bat activity around the Decorah area.
A pilot study conducted at the Luther wind turbine last year suggested some surprising patterns. First, we found 27 bat carcasses underneath the turbine throughout the summer, which is higher than values reported per turbine at wind farms in the Midwest. Second, we found a surprising diversity of species represented among the carcasses. Whereas studies often report that only a couple of species are most at risk (those that are migratory and roost in trees), we found 6 different species among the fatalities, and the resident cave-dwelling species were slightly more common. Finally, by recording the ultrasonic sounds that bats use to navigate and track their insect prey, we found that bat activity (i.e., highest number of recording calls) peaked in late July, but fatality events occurred intermittently throughout the entire study period. This contrasts to most other studies, where fatalities show a pronounced peak in late summer/early fall coinciding with the peak in total bat activity.