The bat came swooping out of the darkness into researchers’ nets just before 1 a.m. — a small brown female with a secret.
As the scientists untangled its tiny limbs from the fine webbing, they didn’t notice anything unusual. Not until they got back to the processing station did the puzzle emerge. The bat’s size was all wrong: Too small for a big brown bat, too heavy for a little brown bat.
Measuring its slim forearm and sneaking a look at its teeth, the researchers realized they had netted a big discovery in bat ecology.
They had nabbed an evening bat — a species new to Minnesota and the first such discovery in more than a century.
Researchers from the Minnesota Department of Natural Resources (DNR) and Central Lakes College caught the bat last month while studying the summer breeding habits of a different bat species.
The evening bat is typically found farther south and east, with its northern limit historically limited to central Iowa, said Rich Baker, endangered species coordinator with the DNR.
“Very rarely do we discover a new mammal in the state,” Baker said.
The last time it happened, in fact, was in 1991, with the discovery of a shrew. But it’s been more than a century since a new bat species has fluttered into the state, wildlife officials said.
This particular evening bat glided into netting suspended from two 30-foot poles at the Army National Guard’s Training Site in Arden Hills. The female’s weight, forearm length and two front teeth — other similar species have four — helped the crew identify it as an evening bat.
To confirm their findings, they took a tiny sample from its wing and sent it to a lab in Arizona, where its identity was verified last week.
Scientists are now exploring whether it’s an isolated critter blown north, or whether a population of evening bats has established itself in the state, bumping the number of documented bat species in Minnesota to eight.
Last month crews set up acoustic detectors around the Arden Hills site to help determine if other evening bats are winging through the area. Every bat species uses echolocation on a different frequency.
Researchers plan to start analyzing the bat sounds later this week, said Brian Dirks, an animal survey coordinator with the DNR who helped make the discovery.
The female bat came with an added surprise: She was nursing. Scientists suspect she may have a pair of pups tucked away near Arden Hills but don’t know if she arrived pregnant or has a mate nearby.
The discovery comes at a time of grave concern about Minnesota’s bat population, which suffered its first confirmed losses from a fungus known as white-nose syndrome earlier this year.
The lethal fungus has ravaged colonies farther east, with more than 6 million bats succumbing since 2007, said Jonathan Reichard, white-nose syndrome assistant coordinator for the U.S. Fish and Wildlife Service.
The disease, known for its trademark white fuzz on the faces and wings of infected bats, has especially battered species that hibernate in caves, mines and wells. But evening bats roost primarily in trees and haven’t yet been affected by the fungus, Reichard said.
Scientists aren’t sure what their discovery means about Minnesota’s habitat or environment, but they suspect it is good news to Minnesotans sick of summer bugs.
“A typical bat will eat its weight in insects every night,” Baker said. “If you don’t like mosquitoes, you need to like bats.”