Surveys show numbers taking drastic drop as WNS cases increase

Last updated: October 13. 2013 12:09AM - 1101 Views
By - tvenesky@timesleader.com

Biologist Rich Fritsky watches as Amber Nolder measures a little brown bat that was trapped in a Glen Lyon mine.
Biologist Rich Fritsky watches as Amber Nolder measures a little brown bat that was trapped in a Glen Lyon mine.
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The numbers don’t lie…

Following is a list of what used to be the top sites in the state for bat populations, and what those numbers are today:

Glen Lyon, Luzerne County (mine): 50,000 - 75,000 down to 1,500

Long run Mine, Armstrong County: 90,000 down to 10

Lawrence County (mine): 35,000 down to 8

Canoe Creek State Park, Blair County (limestone mine): 35,000 down to 155

Gateway Mine (along Ohio border): 40,000 down to 125

Hanover Township (mine): 50,000 to 75,000 down to 0

Durham Iron Mine, Bucks County: 10,000 down to 23

Cause for hope?

Greg Turner said there are two sites in New York where bats appear to be holding their own against white-nose syndrome, to a degree. He said biologists are taking a close look at each site to determine a reason, such as something in the soil that is keeping the fungus under control.

Also, research is beginning to indicate that adult bats are starting to weigh more going into hibernation - two to three grams heavier than what was typical in the past. Turner said the heavier weight could be a response to the increased energy demands resulting from white-nose syndrome. The discouraging part, he said, is the same change hasn’t been seen in juvenile bats.

Pennsylvania Game Commission biologist Richard Fritsky clearly remembers the thousands of bats that were trapped in the Glen Lyon mine each year as biologists conducted annual population surveys. The bats would be hauled out in baskets and biologists worked at a feverish pace to count, measure and release them all before another load was brought up.

“We couldn’t keep up there were so many, Fritsky said.

That was only a few years ago, and times have changed.

Last Tuesday, biologists returned to the mine to do another population count. This time, it was different.

While at one time bat trapping required hustle and bustle, on this night all the biologists could do was wait.

No longer did they have thousands of bats to process. Now, they only had a handful.

Greg Turner, a mammalogist with the Game Commission, estimates the Glen Lyon mine holds 1,500 bats — at most. In 2009, he said, the population estimate approached 75,000.

The cause for the drastic drop is clear — a fungus that causes white-nose syndrome. The fungus causes bats to awaken during their winter hibernation. The more time they spend awake, the more energy they burn until finally the small mammals exit their hibernaculum in search of insects. It’s a fatal move as the bats find nothing to eat in the winter skies and quickly succumb to starvation and bitter cold temperatures.

White-nose syndrome is believed to have surfaced in Pennsylvania in 2008. Since then, Turner has seen plenty of hibernacula, taking areas that once held tens of thousands of bats to be reduced to a handful of survivors.

“It’s pretty damn shocking when you see it and it first hits you,” he said. “The worst part, by far, is going back to a site and within two years the bats are all gone. It’s the same story at every location.”

A mine in Armstrong County, for example, used to yield nightly catches of 3,000 bats when biologists conducted surveys. Turner said the site was surveyed last week and only 10 bats were found.

At the Glen Lyon site, biologists used harp traps to capture bats as they exited the mine during the night. The trap consists of two rows of fishing line strung vertically across the mine openings. Bats are able to pass through the first row, but when they hit the second row of line they fall into a padded basin and are collected. The traps are checked every hour throughout the night, and biologists identify each species caught, determine its sex, weigh and measure each bat before banding and releasing it.

The majority, if not all of the approximately 1,500 bats in the mine are little browns. The site held other species, but white-nose has basically wiped them out, according to Turner.

“I think the Northern long-eared and Indiana bats are all but gone here,” he said.

While a cure or remedy for white-nose has yet to be identified, Turner said they are gaining a better understanding of how it’s impacting bats. During hibernation, bats drop their body temperature and metabolic rate. They do go through periods when their body temperatures warm — called arousals, and bats have just enough body fat to accommodate 15 arousals each winter.

White-nose syndrome causes the amount of arousals to double — up to 35, Turner said.

“By January and February they have burned through their fat supplies, don’t have enough energy, and fly out and die,” he said.

The annual population surveys are also used to provide more insight into the white-nose issue. Turner said close attention is being paid to those adult bats that are surviving and the environmental conditions, which could yield a possible control for the fungus. Biologists are also looking for juvenile bats that have survived so far as a sign that a new generation of bats will be able to eventually replace the adults. The lifespan of a bat is up to 30 years.

“We have yet to find any juvenile survivors,” Turner said. “Bats are dying of old age and they’re not being replaced.”

The decline at the Glen Lyon mine, which is a hibernation site, began in 2010. The estimated population of 1,500 makes it one of the best locations left in the state, Turner said, and there are no sites showing any type of increase.

Turner has 34 sites across the state where he has collected population data before and after white-nose appeared. The overall decline is 98 percent, he said.

“The true hibernating bats are getting whacked. We have one site in the state, here at Glen Lyon, where there is some little brown bat survival,” Turner said. “It’s pretty immense what is happening.”

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