Posted tagged ‘what is killing our bats’

One Million Bats Dead … and counting

October 26, 2011

Scientists have just officially confirmed that White-nose Syndrome, a swiftly-spreading disease responsible for the deaths of over a million bats, is caused by a previously unknown cold-loving fungus called Geomyces destructans.  The just-released study in Nature maintains that “the disease has the potential to decimate North American bat populations and cause species extinctions.”  It urges that “future research … focus on mitigating the effects of WNS before hibernating bat populations suffer losses beyond the point of recovery…”.

In popular culture, October is the month for bats.

In fact, by Halloween, it’s cold for the bats of the Northeast , and they are disappearing from the forests, fields and city streets.  Yes, city streets. New York City is home to bats.  Last summer, Richard Simon of NYC’s Urban Park Rangers told Amy Zimmer of that Central Park is probably home to hundreds of bats, although they go mostly undetected due to their nocturnal habits, speed and tiny size.

Like this federally endangered Indiana bat, many bats are a mere two inches in length.

Three of New York State’s nine bat species are migratory, heading south with the birds for the cold winter months. The other six species spend the winter in hibernation, often congregating en masse in the region’s caves, where they will stay until spring brings the return of flying insects, their only prey.

Hibernating bats. credit USFWS/Ann Froschauer

Sadly, the last few years have seen an astonishingly rapid mass die-off of hibernating bats, due to a virulent emerging disease known as White-nose Syndrome. Our bats really are disappearing.  First discovered in bats hibernating in a cave near Albany, NY in 2006, WNS has now been reported in 19 states and four Canadian provinces.

Map of white-nose syndrome by county/district as of 10/03/2011. Courtesy of Cal Butchkoski, PA Game Commission.

WNS is caused by Geomyces destructans, a fungus that thrives in the cold soil of caves.  During hibernation, when the bats’ immune systems are virtually suspended and their body temperatures drop to within a degree of the surrounding air, the white fungus lodges on their muzzles and attacks the sensitive membranes of the wings. The origins of the recently discovered fungus are unclear. While it has been found in European caves, it does not appear to be causing fatalities in European bats.

Little Brown Bat with White-Nose Syndrome; photo: Marvin Moriarty/USFWS

Under normal circumstances, bats rouse themselves several times during their winter hibernation to warm their bodies, groom, urinate and, possibly, reactivate their immune systems.  WNS appears to irritate the bats so that they rouse more frequently, depleting their fat reserves and sometimes even flying out of the hibernaculum in search of food. They may freeze to death or starve, since there is no food for them in winter and they cannot survive the cold unless in a state of torpor. Even those that survive the winter may have suffered damage to the wings that impairs their hunting ability, leading to further deaths in the spring.

Aside from their incalculable intrinsic worth, bats are an essential part of the ecosystem, not least because of their phenomenal insect-eating abilities. All of New York’s bats are insectivores, eating 20-50% of their body weight in insects each night.  According to Bat Conservation International, one million bats – the number that have been killed so far by White-nose Syndrome – eat  “just under 700 tons” of insects each year, including vast numbers of mosquitoes and agricultural pests. If we lose our bats, our world will suffer.

Today’s report has also confirmed that the disease can be transmitted from one bat to another.  Bats gather together in huge numbers to hibernate, then carry the disease with them when they disperse in the spring.  The fungus survives in the soil of the cave, waiting to infect surviving bats when they return in the fall. It also may be tracked out of caves by spelunkers and sightseers. For this reason, many caves have been closed to visitors.

With their extremely low reproductive rates, bats cannot easily recover from any drop in population, let alone one as catastrophic as is currently underway. Many bat species produce only one pup each year; under normal circumstances, a bat may live 20 years or more (one bat is known to have lived 34 years).  White-nose Syndrome poses the very real risk of extinction for some of North America’s bats.

To find out more about bats and WNS, visit any of the sites below:

National Wildlife Federation (NWF) Wildife Library: Bats

Nature: Culprit Behind Bat Scourge Confirmed

U.S. Fish & WIldlife Service: White-Nose Syndrome – Something Is Killing Our Bats

USGS: White-Nose Syndrome Threatens the Survival of Hibernating Bats in North America

With thanks to Kristi Sullivan of Cornell University Extension’s Master Naturalist Program for her presentation at the Arnot Forest last month.

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