Reducing Bat Fatalities at Wind Farms

As wind farms grow in popularity, there is also rising concern about wildlife fatalities. (Photo credit: Glen Allison/Photodisc/Getty Images

Energy generated by the wind is quickly becoming one of the fastest-growing sectors in the alternative-energy industry. Unlike fossil fuels, wind energy is renewable and emission-free. However, one downside to wind farms is that the turbines are responsible for a significant number of wildlife fatalities. Though bird deaths initially brought the first cause for concern, it has since been found that bat deaths greatly outweigh bird fatalities.

The majority of bat deaths occur between late August and early September, a time period that coincides with the migratory season for many tree-roosting bat species. In a study published in the Journal of Wildlife Management, researchers used thermal infrared cameras to capture video of bat flight behavior around wind turbines. Video evidence shows that bats actively forage around wind turbines and approached both moving and nonmoving turbine blades. The study authors hypothesize that bats may be attracted to the turbines by thinking that the structures are dead trees, and therefore a potential roosting place. The researchers also discovered that bats were more likely to be struck by turbine blades that were moving slowly; that is, in periods of low wind speed.

In another study published in the Journal of Wildlife Management, scientists found that bats are more likely to fly when wind speeds are low. They also noted a jump in bat fatalities in the time periods just before and just after a storm front passes through an area. The authors suggest that one way to prevent bat deaths would be to turn off wind turbines under certain weather conditions, particularly when bat activity in the area is high.

The tree-dwelling hoary bat is one species affected by wind turbine fatalities. (Photo credit: James Hager/Robert Harding World Imagery/Corbis)

The wind speed at which the blades of wind turbine begin to spin is called the cut-in speed. The majority of wind turbine blades are set to begin rotating as soon as wind speed reaches eight or nine miles per hour. Research published in Frontiers in Ecology and the Environment (a journal of the Ecological Society of America) indicates that raising the cut-in speed just a few miles per hour could significantly reduce bat fatalities. When the cut-in speed is raised to about 11 miles per hour, the researchers reported that bat deaths are reduced by at least 44 percent and up to 93 percent. In addition, they found that this raising the cut-in speed just a few miles per hour doesn’t affect energy production much–in fact, the wind farms experienced a decline in power production of less than one percent.

Given bats important roles as insect eaters, pollinators, and seed dispersers, it is important that their populations are protected. By implementing a simple change in the way power is generated at wind farms, bat fatalities may significantly be reduced and wind energy can maintain its environmentally-friendly reputation.

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Bats Dying Off in Huge Numbers

This little brown bat shows symptoms of white-nose syndrome. (Greg Turner/Pennsylvania Game Commission)

For many people, bats bring to mind images of blood-sucking vampires, rabies infections, and other nightmarish scenarios. However, these misunderstood mammals are actually a very important part of the local environment in which they are found. Insect-eating species eat huge numbers of insects at night. They save you from bug bites and also save farmers millions of dollars that they would otherwise have to spend on pesticides and other forms of insect control. Recently, massive numbers of bats have been dying off in the northeastern United States. Scientists are in a rush to discover what is behind the mysterious ailment that is causing their deaths.

Wildlife researchers are not sure what is behind the mysterious white-nose syndrome that is affecting bat species on the East Coast of the United States. (Greg Thompson/USFWS)

Bats are perhaps among the most misunderstood of animals. Though hearing the word bats might make you think of rabid, blood-sucking blind flying furballs that like to dive bomb into peoples hair, such ideas are mostly untrue. Though vampire bats (found mainly in Central and South America) do feed on blood, they feed on animals such as pigs, cows, horses, and birds much more often than on humans. And, technically speaking, vampire bats do not suck blood. Instead, they make a small cut in the animals skin and then use their tongues to lap up the flowing blood. Though most bats are active at night, they are not blind; they actually have a highly-developed sense of vision. They do, however, mainly rely on sonar to detect objects in their way–helping them to avoid things such as flying into a persons hair by accident. While rabies is common in bats, not all bats carry the disease.

Rapid Die-Off of Bats

Regardless of the true nature of bats, their mysterious nature makes them common sights in Halloween decorations and horror movies. However, bats in the northeastern United States are currently facing their own nightmares. Tens of thousands of bats have died as a result of a mysterious ailment in bat colonies throughout New York, Vermont, and Massachusetts.

Many scientists, including Paul Cryan, a bat ecologist with the United States Geological Survey, are puzzled by the rapid die-off of bats. “This is probably one of the strangest and most puzzling problems we have had with bats,” Cryan said in an article reported by The New York Times. “It’s really startling that we’ve not come up with a smoking gun yet.”

White-Nose Syndrome

One clue the scientists have is the white fungus found on the faces of affected bats, which has led to the illness being named white-nose syndrome. Scientists are unsure, however, whether the fungus is a primary cause of death, or just one of many symptoms working together to kill the bats. So far, scientists have come up with three possible hypotheses to explain the mystery affliction.

Dehydration and emaciation, exhibited by this cluster of bats, are two symptoms of white-nose syndrome. (Greg Thompson/USFWS)

One hypothesis is that an unidentified pathogen such as a virus, bacterium, or fungus is causing the problem. A second hypothesis is that climate change is affecting the bats ability to get food and/or properly hibernate. In addition to the white fungus, many of the dead or dying bats are found to be in very poor condition when discovered, and lack the fat reserves necessary for winter hibernation. A third hypothesis is that pesticide use in the area is decreasing the amount of insects available for food. Pesticides also impact the bats metabolism and ability to hibernate. In recent years, agencies in the northeastern United States have increased their use of pesticides to fight the spread of West Nile virus, carried by mosquitoes.

A World Without Bats

A massive die-off of bats is a problem for many reasons. As consumers of insects, bats effectively control pests. For example, a single little brown bat can catch and eat up to 1200 mosquito-sized insects in an hour. Many bats species are important to the agricultural industry. They consume pest species such as cucumber beetles, June beetles, leafhoppers, cutworm moths, and corn earworm moths that can seriously harm crops. So far, white-nose syndrome only appears to have affected northeastern species such as little brown bats, the endangered Indiana bats, northern bats, eastern small-footed bats, and eastern pipistrelles. Scientists think that the affliction could spread to other species across the United States and even to species across borders. For example, Mexican free-tail bats migrate yearly from central Mexico to the southwestern United States. Bats are key pollinators of several desert plant species. For example, while feeding, the lesser long-nosed bat also pollinates agave plants and saguaro cacti in the southwestern desert. A massive die-off of southwestern bat species would also negatively impact desert plants.

More Research is Needed

Researchers worry that this ailment could spread through bat populations across the United States. According to an article in The New York Times, Merlin Tuttle, the president of Bat Conservation International, an education and research group based in Austin, Texas, is extremely concerned. “So far as we can tell at this point, this may be the most serious threat to North American bats weve experienced in recorded history,” said Tuttle. “It definitely warrants immediate and careful attention.”

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Scientists Suggest Short-Term Solution for Afflicted Bats

This little brown bat shows symptoms of white-nose syndrome. (Greg Turner/Pennsylvania Game Commission)

This little brown bat shows symptoms of white-nose syndrome. (Greg Turner/Pennsylvania Game Commission)

Scientists are still struggling to determine the cause behind white-nose syndrome, a disease which has a mortality rate of 75 – 100 percent among affected populations. This mysterious disease has killed almost 500,000 bats in the Northeast since its discovery in 2006. Last month scientists finally identified the fungus that gives the disease its name. Scientists think that the fungus causes a disruption to the bats’ hibernation, forcing the bats to use more energy than they have reserved for their winter hibernation.

Justin Boyles, a graduate student at Indiana State University, and Craig Willis, a professor at the University of Winnipeg, created a mathematical computer simulation to test this hypothesis. The variables they inputted into their simulation included patterns of arousal and the body mass and body fat percentage of the little brown bat, one of the affected bat species. The scientists’ simulation indicated that the patterns and proportion of mortality in affected bat populations was similar to the researchers’ theory of hibernation disruption.

Boyles and Willis have proposed a short-term solution to protect affected bat populations from catastrophe. When bats are forced to arouse themselves from a state of hibernation, they must use a lot of energy to heat up their bodies. The scientists suggest that providing hibernating bats with a heat source in their caves could prevent bats from needing to expend large amounts of energy to re-heat their bodies. The researchers are currently developing a system to create warm pockets within caves.

The scientists are quick to point out that installing a heat source for bats is only a short-term solution to the problem. This solution does not solve the problem of preventing the spread of white-nose syndrome or curing the disease itself. More research is necessary to resolve these serious issues.

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