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Unintended Victims

A bat that weighs less than half an ounce can eat as many as 1,000 mosquitoes in a single hour.

Most have faces only a mother could love, but bats play an essential role in the balance of life on our planet. Contrary to their reputation, bats are not blind, aggressive or disease-ridden pests. In fact, they’re rather timid creatures that generally avoid humans. They are, however, voracious predators of agricultural pests such as corn ear worms, cucumber beetles and grasshoppers. A little brown bat weighs less than half an ounce but can eat as many as 1,200 mosquitoes in a single hour. Think about that next time you’re swatting madly during a riverside cookout!  

Sadly, more than half the bat species in the U.S. are in serious decline. Although bats have relatively long life spans –20 to 30 years for some species -- they reproduce very slowly; so those numbers are troubling. Bats can be found almost everywhere in the state, in cities and the countryside, but because they’re nocturnal, we don’t often take notice. Even so, seven of the 15 species in Montana are listed as species of concern and two as potential species of concern. Pesticides and drought have played a part in the decline. But so have the negative misconceptions we hold of bats. Because they cluster in large colonies, bats are extremely vulnerable to attacks, and every year, humans kill tens of thousands. 

Wind facilities present a whole new level of risk. Some bats die when they collide with the turbine blades. The majority are killed when they’re caught in the backwash of the rotating blades, where the rapid change in barometric pressure literally bursts their tiny lungs – a condition known as barotrauma. 

Scientists aren’t sure what draws bats into contact with turbines. Tree-roosting species – such as most of those in Montana -- may mistake the tall spindly turbines for tree snags. Perhaps they’re pursuing insects that are attracted to the turbine sites. Sound emitted by the rotors may attract bats or disorient their delicate echolocation systems.    Our ability to avoid or mitigate the threats to bats is complicated by these gaps in our understanding.   But if we don’t consider the habits of these rarely seen creatures, The Nature Conservancy in Montana’s study, “An Ecological Risk Assessment of Wind Energy Development in Montana,” suggests that wind farms could result in local bat extinctions. Scientists are studying whether visual or acoustic deterrents might help reduce the threats to bats; but for now, our best strategy is to locate wind farms away from migration paths and the areas where bat populations are concentrated.


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