Bat Killers—White Nose Disease and Wind Turbines

Bats are long-lived, slow-breeding mammals that play vital roles in most of the Earth's ecosystems. Bats are important pollinators and seed dispersers in tropical regions, and serve as main predators of night flying insects in most parts of the world. Insect-eating bats are estimated to save farmers billions of dollars each year by providing pest control. (1) Prior to the year 2000, intentional killing by humans caused the greatest proportion of mortality events in bats globally. The reasons varied with region, but bats were hunted for human consumption, killed as pests, and to protect fruit crops. Although the proportion of international killing reports declined in recent times, such acts continue in some parts of the world. Since the dawn of the 21st century, however, white nose syndrome and collisions with wind turbines worldwide are the primary reported causes of mass mortality in bats.

Their biggest killer is white nose syndrome, an emerging disease in North American bats which as of 2012 was associated with 5.7 to 6.7 million bat deaths. The condition is named for a distinctive fungal growth around the muzzles and on the wings of hibernating bats and was first identified in February 2006 in a cave in Schoharie County, New York. It has rapidly spread. As of September 2014, the fungus has been found in caves and mines of 25 states throughout the Northeastern US, as far south as Mississippi, as far west as Missouri and as far north as five Canadian provinces. (2) And this isn't just happening in North America. Reports of bat deaths worldwide due to causes largely unique to the 21st century are markedly rising, according to a new analysis. White nose disease and wind turbine collisions led the reported causes of mass death in bats. These new threats now surpass all prior known causes of bat mortality, natural or attributed to humans. The comprehensive study reveals trends in the occurrence and causes of multiple mortality events in bats as reported globally for the past 200 years, shedding new light on the possible factors underlying populations declines. “Many of the 1300 species of bats on earth are already considered threatened or declining. Bats require high survival to ensure stability of growing populations,” said Tom O'Shea, a US Geological Society (USGS) emeritus research scientist and the study's lead author. (3)

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A team of researchers found the fungus in caves in northeast China where bats hibernate and found bats infected with the fungus. The discovery greatly expands the known distribution of the fungus which can survive in soil for months, even years, after the bats have departed. So bats entering previously infected sites may contract white nose disease from this environment. (4) It also casts a gloomy forecast for the curious flying mammals, which serve as critical food plant pollinators and offers important information used in medical research, particularly as it pertains to blindness. But there is an ecological consequence to bat extinction: a single bat can eat thousands of insects in a single night. Bats are critical to controlling bugs that threaten agriculture and forestry; their pest-control value to the economy is estimated in the billions of dollars. The findings have important implications for efforts to prevent further global spread of the disease. People need to start thinking about decontamination of caves said one researcher. (5)

Wind Turbines

Wind turbines killed almost 900,000 bats in 2013 alone, a species that the USGS estimate provides about $23 billion in benefits to America's agricultural industry each year. (6) Studies have highlighted that more than 200,000 bats are killed each year by German wind turbines. (7) The problem of bat fatalities at wind turbines could be easily solved, says researcher Christian Voigt. Bat activity is highest at dusk, most importantly during the time of autumn migration. If the turbines were switched off during this period for one to two hours, then this would drastically lower the frequency of bat fatalities and cause little loss of revenue to the companies that run the wind turbines. (8) This sounds to good to be true. References

1. "Decades of bat observations reveal uptick in new causes of mass mortality,” sciencedaily.com, January 20, 2016
2. “White nose syndrome,” en.wikipedia.org, January 2, 2016
3. Thomas J. O'Shea et al., “Multiple mortality events in bats: a global review,”Mammal Review, 2016; DOI:10.1111/mam.12064
4. Hannah T. Reynolds and Hazel A. Barton, “Comparison of the white nose syndrome agent pseudogymnoascus destructans to cave-dwelling relatives suggests reduced saprotrophic enzyme activity,” PloS ONE, 2014; 9 (1)
5. Joseph R. Hoyt et al, “Widespread bat white nose syndrome fungus, Northeastern China,” Emerging Infectious Diseases, 2015, 22, (1)
6. Travis Fisher and Alex Fitzsimmons, “All trick, no treat: how wind turbines kill bats and hurt farmers,” Canada Free Press, October 30, 2013
7. “German wind farms can kill bats from near and far, research suggests,” sciencedaily.com, July 2, 2012
8. Christian C.Voigt et al., “The catchment area of wind farms for European bats: a plea for international regulations,” Biological Conservation, 153, 80, 2012