White Nose Syndrome Update

By Craig Stihler

The fungal disease White Nose Syndrome (WNS) was first documented in West Virginia in early 2009.  Since then, there have been significant declines in the numbers of bats observed in hibernacula.  Species most impacted have been the little brown bat, Indiana bat, northern long-eared bat, and tricolored bat.   During winter 2016-2017, WVDNR biologists conducted bat surveys in 20 caves, including the state’s most important bat hibernaculum, Hellhole.  Nineteen of these caves were also surveyed in winter 2014-2015.  The results of the 2017 surveys contained both good news and bad news.

Virginia big-eared bats, an endangered species, do not seem to be impacted by White Nose Syndrome, and their numbers are increasing.  The winter count was the highest on record with 15,354 Virginia big-eared bats tallied.  Over 13,000 were in Hellhole.  Unlike other bats in the state, Virginia big-eared bats also form summer maternity colonies that use caves.  West Virginia Department of Natural Resources biologists monitor the bats in these colonies each June using nightvision equipment to count the bats as they emerge in the evening to feed.  The June 2016 count was also the highest summer count on record.

Little brown bats were once one of the most common bats in the state.  By 2014, White Nose Syndrome reduced the population by around 97%.  Winter surveys conducted in 2016 showed that the number of little brown bats in caves surveyed in both 2014 and 2016 increased 17% between the two surveys.  The number observed in cave surveys this past winter showed an increase of 19% over the 2015 total.  While the number of bats remaining is still much lower than pre-WNS numbers, an increase in numbers is a welcome change.

Unfortunately, we are still not seeing increases in other species.  The winter 2017 surveys documented a further 50.8% decline in Indiana bats and a 23.9% decline in tricolored bats (formerly called eastern pipistrelles) since 2015.  Hellhole has the largest concentration of endangered Indiana bats in the state.  There used to be over 18,500 Indiana bats hibernating in the cave; the 2017 survey counted only 794 Indiana bats, a decrease of nearly 96%.  Northern long-eared bats are not often observed in caves in West Virginia, so winter surveys don’t provide a good way to monitor their populations.  Summer bat mist netting data suggest that this species has declined, but the decline does not seem to be as severe as it has been for little brown bats.

Because White Nose Syndrome affects bats during hibernation, migratory bats that move south rather than enter hibernation are not affected.  Migratory bats include the eastern red bat, hoary bat, and silver-haired bat.