Buzz killers: Big brown bats get head start on mosquito control

As spring tips past the threat of freezing temperatures, watch for the first glimpse of bats at dusk. They might be mistaken for birds until you catch the steep dives and high-flying maneuvers more like barnstormers and aerialists.

Minnesota has nine species of bats. About half of them overwinter in caves or buildings that stay just above freezing. The rest are migrating back from warmer climates.

One of the year-round residents, the big brown bat, is considered the hardiest. It doesn’t need the regulated temperatures and humidity of caves, where the fungus that causes White-Nose Syndrome has killed millions of bats across the country.

The downside of the spring warmup — the emergence of biting mosquitoes and other flying pests — would be much worse without the pivotal role of bats. They use echolocation, which helped inspire sonar and radar, to find and capture insects while flying through the dark.

Bats can consume their body weight in insects each night, which can mean up to 1,500 mosquitoes or similar-sized insects. They also help control pests that can damage crops and forests.

“They help keep the ecosystem in balance,” said Melissa Boman, mammal specialist for the Minnesota Biological Survey.

Despite having “big” in their name, big brown bats measure 10 to 14 cm long, weigh barely an ounce, and can wedge into spaces just half an inch wide.

Look for and seal up gaps on your home’s exterior as part of spring maintenance to keep out bats. To provide them a place to live, consider building a multi-chambered Johnson bat house designed by Earl Johnson, a former Minnesota Department of Natural Resources area wildlife manager.

Chambers let bats, especially females nursing babies in the early summer, move around and find the warm temperatures they need. You can learn more about bats on the DNR website and find more bat house information through Bat Conservation International.

Lisa Meyers McClintick has freelanced for the Minnesota Star Tribune since 2001 and volunteers as a Minnesota master naturalist.