By Dr. Becker
Millions of hibernating bats have died in North America due to white-nose syndrome (WNS), a disease so-named because it leads to the growth of white fungus on the bat’s muzzle. The U.S. is home to 47 bat species, half of which depend on hibernation to survive through the winter.
Bats with WNS, however, venture out into the cold during the winter months and exhibit other strange behaviors like flying during the daytime and clustering near cave entrances. The bats, unable to find food, often freeze to death after venturing outside of the hibernacula (the caves and mines where bats hibernate).
It’s also been suggested that WNS causes bats to overheat and burn energy quickly. With no available food to replenish their energy, they starve, leading to devastating losses.1
Minnesota Bats Decline by 70 Percent Due to WNS
Lake Vermilion-Soudan Underground Mine State Park in Minnesota is home to the largest bat colony in Minnesota. Up to 15,000 bats hibernate there each year, but according to the 2017 annual survey, the population has dropped 70 percent due to WNS.
More than 2,000 dead bats were counted at the surface of the mine. In other areas of the U.S., particularly in the east where WNS was first observed, losses from WNS have reached 90 percent to 100 percent. Inforum reported:2
“Bats can live more than 30 years in the wild but have a very low reproductive rate, which means it is very difficult for populations to rebuild after the disease hits.
Even if some bats survive at Soudan, it would take decades to rebuild their numbers, [Jim] Essig [manager at Lake Vermilion-Soudan Underground Mine State Park] noted.
Experts say they are considering options to try to keep the disease out of specific caves, but once it enters it is impossible to eradicate.”
White-Nose Syndrome Is Spreading Rapidly
WNS was first detected in New York in 2006. Since then, it’s spread to the central U.S. and Canada and was recently detected in Washington state. So far, 31 states and five Canadian provinces have been affected.3
Although the disease originated in Europe, the bats there seem to be immune to the condition. In North America, seven bat species, two of which are endangered and one threatened, have had confirmed cases of WNS.4
What’s known is that WNS is caused by the fungus Pseudogymnoascus destructans. It’s thought that the fungus is spread from bat to bat, although they may also pick up the spores from contaminated caves (possibly contaminated by fungal spores brought in by human cave explorers).
According to the U.S. Geological Survey (USGS), “The relatively widespread mortality associated with WNS is unprecedented in hibernating bats.” They noted that little brown bats, populations of which have been seriously hurt by WNS, could even become locally or regionally extirpated as a result.5
This would be tragic, as bats, though often viewed as pests, are extremely valuable and beneficial animals. Bats not only assist with pollination but also have a voracious appetite for insects.
By eating insects and suppressing pest-associated fungal growth on crops, it’s been shown that bats save farmers more than $1 billion worldwide — for corn crops alone.6
Another study estimated the value of bats to the agriculture industry at nearly $23 billion per year, but explained the estimate could be as far ranging as $3.7 billion to $53 billion a year.7
What You Can Do to Help Bats
According to the U.S. Fish and Wildlife Service, there have been suspicious jumps of WNS across distances longer than bats are likely to have traveled. Such “jump sites” are often popular spots for human visitors. While scientists believe WNS is primarily transmitted bat-to-bat, human-assisted transmission of WNS is also likely.8
While research is underway to understand how WNS is transmitted, experts recommend the following to help prevent its spreads as well as protect bat species in your area:9
✓ Avoid caves and mines where bats are hibernating, or suspected of hibernating, during winter.
✓ Encourage natural bat habitats around your home by reducing outdoor lighting, minimizing tree clearing and protecting streams and wetlands. Install a bat house.
✓ Adhere to cave closures. Check with your state and federal agencies or a local chapter of the National Speleological Society for the status of caves and caving in your area.
Follow the national WNS Decontamination Protocol to clean and disinfect clothes, footwear and equipment used in caves or mines.
✓ Talk to your family and friends about the benefits of bats and the fact that white-nose syndrome is decimating entire populations of bats across North America.
✓ Report unusual bat behavior, such as bats flying during the daytime in late-winter months, or bat deaths, to your state wildlife agency.