Bat signals: Tracking white-nose syndrome along the Mississippi River
By Quentin Ikuta (He, Him), Community Volunteer Ambassador, Mississippi National River and Recreation Area
and Elyse Mallinger, Bat Monitoring Technician, Mississippi National River and Recreation Area
Edited by Katy R. Goodwin, Research Biologist/Bat Monitoring Project Coordinator, NPS Great Lakes Inventory & Monitoring Network
A bat with white-nose syndrome hanging in a cave. Credit: USGS. Public domain. 2016.
A very brief introduction to the bat monitoring program coordinated by the Great Lakes Inventory and Monitoring Network within the Mississippi National River and Recreation Area.
North American bat populations are threatened by a variety of environmental pressures including habitat loss, climate change, mortality from wind turbines, and the fungal disease white-nose syndrome (WNS). Since 2006, hibernating bat colonies on the east coast have decreased 80-97% as a result of WNS and researchers are predicting similar population declines in the Midwest region as WNS spreads.
USFWS and MA Division of F&W biologists in Massachusetts mine containing bats with WNS. Credit: Kim Miller, USGS National Wildlife Health Center. Public domain. 2008.
WNS infects bats as they hibernate. Bats catch the fungus from other infected bats or from parts of the cave or mine where they are hibernating. However, bats that pick up the fungus don’t necessarily have the WNS disease. Humans are also able to spread the fungus on their shoes, clothes, and equipment. WNS slowly grows upon the muzzle and wings of bats during hibernation.
As a result of the fungal infection, bats wake up more frequently during hibernation and use more energy than healthy bats. The result of this infection during hibernation paired with more frequent, energy-sapping waking up means a slow death due to starvation as the bat’s fat reserves are drained.
There are some disease treatments in the works that will either prevent or lessen the effects of the disease. However, until these treatments come out, monitoring bat populations is crucial to gaining a better understanding of the disease. The Great Lakes Inventory and Monitoring Network has established a bat acoustic monitoring program focused on documenting the impacts of WNS.
In 2016, monitoring began at the Mississippi National River and Recreation Area. Ultrasonic microphones are used to record bat echolocation calls. Bats use echolocation to navigate and find food by bouncing sound off objects in their environment. While typical microphones pick up sounds only within the range of human hearing, ultrasonic microphones are used to detect sounds at higher frequencies, such as bat echolocation calls. Humans are able to hear sounds from about 20 Hz to 20 kHz whereas bats in Minnesota echolocate at frequencies of about 15 to 120 kHz, generally much higher than we can hear.
Echolocation sound data are recorded at 28 locations (see Map “Bat Monitoring Sites”) throughout the park. The data that are collected are fed into a sound analysis software, which assigns bat species classification to each recording. Within the Mississippi River corridor, eight species of bats have been detected. The species found include: Big Brown Bat, Eastern Red Bat, Hoary Bat, Silver-haired Bat, Little Brown Bat, Northern Long-eared Bat, Evening Bat, and Tricolored Bat.
Five of these species appear to be stable, however activity levels for the other three species - the Little Brown Bat, Northern Long-eared Bat, and Tricolored Bat - are decreasing. These three species are highly susceptible to WNS, which is likely causing the observed decline.
Since 2013, the National Park Service has funded hundreds of projects related to WNS. These projects are all working towards slowing down the spread of the fungus by increasing awareness, resources, and surveillance. The continuation of this research will provide proper management guidelines and techniques to help preserve future bat populations.