Bat Counts Shrink as White-nose Syndrome Spreads in Georgia

Social Circle, GA
Tuesday, May 17, 2016 - 10:15

 

 

The disease that has killed more than 6 million bats in North America hasn’t spared Georgia.

Since white-nose syndrome was first found here in 2013, the number of bats has plummeted by about 90 percent in caves and mines the Georgia Department of Natural Resources surveys each winter.

“They’re just gone,” said Katrina Morris, lead bat researcher for DNR’s Nongame Conservation Section.

The surveys help gauge the impact of white-nose, or WNS, in the state. Nongame Conservation checked 20 hibernacula or refuges this winter, all but two of them in north Georgia. Morris’ report notes that:

  • Sixteen either tested positive for the fungus that causes white-nose, Pseudogymnoascus destructans, or showed signs of being infected.
  • In 10 caves checked annually since at least 2014, bat counts are down overall by 92 percent.
  • Except for gray bats, no other Myotis bats were seen. While counts of bats in this genus are always low in north Georgia caves, this was the first time researchers found none, Morris said.

First documented in North America in New York in 2007, white-nose has spread through the eastern U.S. and into Canada. The disease took a 1,300-mile leap from Minnesota to Washington in March, when a sick bat near Seattle tested positive. In Georgia, white-nose is confirmed or suspected in 11 counties. White-nose poses no known risk to humans.

The fungus Pd thrives in the cold and humid conditions characteristic in caves and mines used by hibernating bats. The disease Pd causes is named for the white fungus often found growing on the muzzle and skin of affected bats. The fungus results in bats being awakened too often from hibernation or less intense torpor, and using fat reserves needed for hibernation long before winter is over.

Death rates of 90-100 percent have been seen at some hibernacula. Causes of death vary from starvation to stressed immune systems.

One of the first sites in Georgia documented with white-nose is also one of the most telling examples of the fallout. Counts at Sitton’s Cave, a popular grotto at Cloudland Canyon State Park in northwest Georgia, have shrunk from more than 1,700 bats in 2013 to 62 this year, a 96 percent decline.

Morris said that unlike at some affected hibernacula in the North, where dead or dying bats are found in the snow near entrances, in Georgia “we don’t usually see piles of dead bats. We see missing bats.”

While DNR biologists can only survey a small number of caves, those checked likely represent the larger picture of what’s happening to bats in the northern part of the state, according to Morris. Preliminary data from sampling with mist nets in summer also show that fewer bats are being caught, she said.

There is good news. Some bats are surviving for years at affected sites, and some species, including the federally endangered gray bat, don’t appear to be developing white-nose, though they carry the fungus.

Also, scientists are working to combat white-nose, including an effort involving the U.S. Fish and Wildlife Service and Georgia State University researchers testing a bacterium aimed at inhibiting growth of the fungus.

DNR is following a response plan that outlines steps for raising awareness of the disease, combating its spread, reporting and analyzing bats, and managing related natural resources. DNR has increased surveys to better assess bat populations and worked with cavers to spread the word about white-nose, reduce trips in Georgia caves and follow disinfectant protocols for clothes and gear. Only about 15 percent of Georgia’s caves are on state-managed lands. Learn more at www.georgiawildlife.com/WNS.

DNR’s Nongame Conservation Section works daily to conserve Georgia’s endangered and other wildlife not legally fished for or hunted, as well as rare plants and natural habitats. The agency depends primarily on fundraisers, grants and contributions for this vital work.

Georgians can provide help conserve native bats and other wildlife species and rare plants through buying or renewing a DNR eagle or hummingbird license plate. These tags cost only $25 more than a standard plate, and most of the fee from sales and renewals is dedicated to nongame conservation.

Upgrade to a wild tag for only $25! Details at www.georgiawildlife.com/conservation/support and www.georgiawildlife.com/conservation/annualreport.

WHY BATS MATTER

The loss of bats can contribute to widespread ecological effects. Why? Bats help …

  • Control insects: A little brown bat can eat its weight in insects in a night; 1 million bats can consume nearly 700 tons a year. Bats save corn farmers worldwide an estimated $1 billion per year in crop damages. This natural pest control also reduces pesticide use.
  • Enrich cave ecosystems: Nutrient-packed guano from cave-roosting bats qualify them as keystone species in these habitats.
  • Feed other animals: Wildlife varying from owls to raccoons prey on bats.
  • Pollinate plants and disperse seeds: More than 300 species of fruit, including mangoes, depend on bats for pollination. Bats are critical to seed dispersal in tropical forests.
  • Benefit science: Research on bats has led to developments in sonar, vaccines and other areas.
  • Serve as indicator species: Population changes can indicate broader ecological issues such as the loss of forest habitat.

Sources include: Bat Conservation International, U.S. Fish and Wildlife Service, U.S. Forest Service