The National Park Service manages 84 million acres, in 419 parks, 1 in 4 of which have caves, and 1 in 3 of which have mines. Many of these caves and mines provide habitat for hibernating bats.

Bats are an essential part of many American ecosystems, but they're under threat from a hidden illness called white-nose syndrome. Since 2006, this fungal disease has killed millions of bats in North America. In some caves and mines, 90-100% of bat populations have died.

Parks in more than half of the United States are affected by the presence of White Nose Syndrom. Losing an important predator so quickly may have a drastic effect on the ecology of a given park. As the disease spreads, scientists consider the impact and potential for impact on national parks to be very high.

Today on America's National Parks, Bats of the Greater Yellowstone area - and how National Park Service scientists are working to learn how to protect them.