Bats of the Apostle Islands: Up to Seven Species, and White-nose Syndrome Nearby

Apostle Islands National Lakeshore hosts up to seven bat species: the big brown bat (Eptesicus fuscus), eastern red bat (Lasiurus borealis), hoary bat (Lasiurus cinereus), silver-haired bat (Lasionycteris noctivagans), little brown bat (Myotis lucifugus), northern long-eared bat (Myotis septentrionalis) and tricolored bat (Perimyotis subflavus). Wisconsin lists the big brown, little brown and tricolored bats as threatened, and the northern long-eared bat is listed as threatened by both the state and the federal government.

How bats live

Bats are the only mammals that truly fly, which they do with elongated hands and wing membranes called patagia. There are more than 1,000 species worldwide. Like other mammals, bats make milk for their young, which are called pups, and females typically have one pup a year. Many bats see well, but most species rely on echolocation at night, "seeing" with their ears.

Bats help ecosystems and agriculture by controlling pests. The park says they provide billions of dollars a year in economic value, mostly through the insects they eat. All the bats found in the park are insect-eaters, and a little brown bat can eat up to 1,000 mosquitoes in a night. The eastern red, hoary and silver-haired bats migrate, while the big brown, little brown, northern long-eared and tricolored bats hibernate. No bats are known to spend the winter in the park.

White-nose syndrome

A little brown bat affected by white-nose syndrome. Image: National Park Service.

White-nose syndrome (WNS) is a fungal disease in which spores grow on the skin of hibernating bats that live in caves. It rouses the bats from hibernation too early, so they use up their energy reserves and starve before spring arrives. Since the disease reached the United States in 2006, more than one million little brown bats have died of it, and the disease is known to have a mortality rate of 75 to 98 percent. Local bats also face other threats, including climate change, increased wind and habitat loss.

The park adds that white-nose syndrome does not affect humans and that fewer than 1 percent of bats carry rabies.

Listening for bats

An ultrasonic recorder on North Twin Island. Image: National Park Service.

In 2015 the National Park Service's Biological Research Division began an ongoing bat-monitoring survey in four parks of the Great Lakes Inventory and Monitoring Network (GLKN), Apostle Islands among them. Five more parks joined in 2016, and all of the work is coordinated from the network's office in Ashland, Wisconsin.

The project aims to learn which species are present and how common each is, and to follow changes in which calls are heard at a given location. As of 2017, white-nose syndrome was known to be present in the area around the Apostle Islands. The data will help show how local bat populations respond to the disease and will inform management plans.

The park has 26 sampling sites for acoustic bat data. Each is visited twice a summer: once to set out a recorder, and again to collect the recorder and its data.

Sources

• National Park Service, Apostle Islands National Lakeshore, Bats of the Apostles; rewritten in hubnx's own words.