Bats and Wind Turbines

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Bat Fatalities Overview

In a 2003 report, Erickson et al compiled information about birds and bats from previous reports and noted the long history of bat fatalities due to collisions with communication towers, power lines, fences, lighthouses and tall buildings. The report noted dead bats found near wind turbines in Colorado, Minnesota, Oregon, Wisconsin and Wyoming. Prior to the discovery of hundreds of dead bats at the Moutaineer Wind Energy Center in West Virginia, the largest previous discovery was 32 dead bats found over a 15 month period at a 3 turbine wind farm in Tennessee.

Although there was a significant amount of data available for documented bat fatalities at wind facilities, only 536 had approximate dates of fatality reported. Nearly 90% of those fatalities occurred from mid-July through mid-September, which helps bolster the hypothesis that most bat fatalities at wind farms occur during late summer and early fall.

The data also showed that migratory tree bats were mostly harmed compared to bats that reside year-round near wind facilities. Large resident populations of big brown and little brown bats were found near a Minnesota wind farm but little or no wind collision deaths were recorded. From the data compiled, hoary bats were the prominent species affected, comprising 61.7% of the reported fatalities. Eastern red bats accounted for 17.2% of the deaths and silver-haired bats 7.1%. If resident species were harmed, the researchers should have expected to discover a pattern due to the commuting practices of resident species between roosts and foraging areas. Instead, researchers found random patterns of reported deaths.

The report also noted that most wind turbine facilities at the time were located in grasslands and crop fields, while most bats prefer to forage near trees. A possible reason for the surprisingly high number of fatalities in West Virginia and Pennsylvania may be due to the fact that the turbines were erected within wooded areas and thus prone to higher bat activity.

Bat Facts

There are over 900 species of bats on Earth, and are the only mammals truly capable of flying. Bats are primary nocturnal but are capable of flying during dusk hours. Most bats live long lives of up to 30 years, and the females usually give birth to one offspring per year, although some species have three or four offspring per year (USFWS(a), 2007).

Bats rely on their echolocation (sonar) system to locate food while active at night. The majority of bat species eat insects, while some feed on plant nectar. In the continental United States there are 45 species of bats, including six listed as endangered under the Endangered Species Act of 1973 (USFWS(b), 2007):

Endangered Species Bats in the United States Gray bat (Myotis grisescens) Indiana bat (Myotis sodalis) Ozark big-eared bat (Corynorhinus (=Plecotus) townsendii ingens) Virginia big-eared bat (Corynorhinus (=Plecotus) townsendii virginianus) Lesser long-nosed bat (Leptonycteris curasoae yerbabuenae) Mexican long-nosed bat (Leptonycteris nivalis)

Gray Bat www.mnh2.si.edu