White-Nose Syndrome having devastating impact on Minnesota bats

TOWER, Minn. (KMSP) - If you hate mosquitos, then you should care that our bats in Minnesota are dying at an alarming rate. 

Most insects that fly at night, including the dreaded mosquito, are no match for the winged mammals.

But it's a fungus, which causes White-Nose Syndrome, that's bringing down bats by the thousands.

The fungus irritates a bat's ears, nose, and wings, jarring them from hibernation and results in a deadly awakening.

Bats at Lake Vermilion-Soudan Underground Mine State Park near Tower have been hit hard by the disease.

The long abandoned, deep shaft iron ore mine is home to the largest concentration of hibernating bats in Minnesota. Some 10,000 to 15,000 bats winter there.

James Pointer oversees the park's naturalist program and he is concerned.

"What we're seeing is in the winter time they're coming out, leaving the mine shaft and going to find food,” said Pointer. “Here in northern Minnesota during December and January, they're not going to find any because they're all insect eaters. So what happens in the cold, cold days is they die from exposure."

And if it’s not the cold, the bats may succumb to ravens and other birds, waiting for them to surface from the cave.

White Nose began on the East Coast ten years ago. It has progressively made its way west, killing hundreds of thousands of bats along the way. For the last couple years Minnesota was surrounded by it with cases in Canada, Wisconsin, and Iowa and then it hit the Soudan mine last year.

But it was this year that bat mortality in the mine hit the devastating level with 70 percent of the bats in the mine dying.

“It's huge in terms of the number of insects that might not get eaten now,” said Pointer. “All these bats are insect eaters. You think about the mosquitos and everything they eat. The studies say that anywhere from 100 to 1,000 insects a night each bat will eat."

Descending down into the mine, it's clear the bats hibernating in the depths of the Soudan mine were hit hard.

Deep down on level 12 many bats are alive, but just as many are already dead. Some still cling to the granite walls, while others have fallen to the floor - the white fuzz of the fungus evident on some.

The cave, which stays at a constant 50 degrees, is a perfect environment for hibernating bats. But since there is such a large concentration bats, the fungus gets transmitted very easily. Hibernating bats cling to each other and walk over each other, passing the fungus from bat to bat.

Jim Essig, who manages the park and mine, says the disease could alter the bat population for decades to come

“About middle of December, we started to see bats coming to the surface at that area where we lowered the cage and with the cold temperatures, 20 to 30 below zero,” said Essig. “They just weren't surviving well. They died from exposure.”

Some of these bats will survive White-Nose Syndrome though, either through luck or a natural resistance. Though the numbers are small and dwindling, biologists hope it is enough  to eventually repopulate the Soudan Mine and other habitats in Minnesota.