Kathlean Wolf
Wild Warner
In early September on the shore of Cherokee Marsh, 20 Northside bat lovers gathered to listen in on the calls of some of Wisconsin’s most interesting and mysterious mammals — bats. The dusky purple light on the horizon backlit the small animals as they flew over the water in swift, nimble patterns. We were delighted when one of them swooped low through the middle of our group; one less mosquito in our midst.
Bats navigate and hunt using sound, emitting ultrasonic calls. The soundwaves bounce off trees, the land and water below, and other creatures in flight, back to the bat’s sensitive ears. This reflected sound allows them to create a three-dimensional image of the world around them and to locate their insect prey.
The high frequency sound of their calls can’t be heard by human ears, so we listened in by using echometers, small devices plugged into an iPad that translated the calls into a lower register.
We counted six of Wisconsin’s eight species of bat: little brown bat, big brown bat, hoary bat, tricolored bat, evening bat and eastern red bat. The two species not represented that night were the silver-haired bat and the northern long-eared bat.
Bats are some of the most influential and numerous species on Earth, making up one-fifth of all mammals. With 1,400 known species, bats have a wide variety of lifestyles: some are active during the day, others are nocturnal. Some eat only fruit, others rely on nectar, and some catch and eat fish. All of Wisconsin’s bats are insectivores, taking advantage of the abundance of beetles, flies, mosquitoes and moths.
For centuries, farmers have relied on bats to reduce the insect damage to their crops and forests. This “ecosystem service” provided by bats saves Wisconsin farmers $650 million to $1.5 billion dollars every year.
In recent years, our bats have faced an existential threat, white nose fungus, brought into the United States on the equipment of people who explore caves. Arriving in New York in 2006, this disease spread rapidly to caves where bats hibernate through the winter. The fungus arrived in Wisconsin in 2014, and by 2019 had wiped out over 99% of little brown bats.
Their recovery from this disease has been remarkable: their population has grown to 50% of what it was before white nose arrived. This is largely due to bats’ excellent maternal care. Although they only have one pup per year, 60% of their pups make it to adulthood.
We can all help bats by ensuring they have enough food and habitat to reproduce and thrive. Add native plants to your yard, garden or balcony flowerbox; find alternatives to pesticide use; or join a citizen science project to monitor bats in your neighborhood.
To learn more about Wisconsin’s bats, visit dnr.wisconsin.gov and type “bats” in the search bar. To join the citizen science project, visit wiatri.net/inventory/bats/index.cfm.
