Cool Critters: Holy springtime, Batwoman! Female bats emerging early in our region

With its streamlined body, acrobatic maneuvers and rapid wingbeats, Shari Miller thought she was seeing a tree swallow wheel through the air as she walked along the Snake River near the town of Asotin, Washington, last month.

“I remember thinking how odd it was that a swallow had arrived from migration so early in the season,” recalled Miller, a birder who walks the river bank several times a week.

She raised her binoculars expecting to see a swallow’s white underside and some steel-blue feathers. Instead, she saw something brown and furry with tiny round ears.

“It was a bat – in February! I could hardly believe it,” Miller said.

Not only that, but this creature of the night was flying in daylight.

“It was late afternoon and the sun was still out,” Miller explained. “I’m pretty sure I said under my breath, ‘Shouldn’t you be sleeping?’ ”

Yes, it should have been. As nocturnal mammals, bats sleep and rest during the day and are active at night. What’s more, bats in our region spend winters conserving energy in a state of sleep called torpor.

Yet it was late February that Miller spotted the bat flying overhead. Why wasn’t it still snoozing upside-down in a nearby tree cavity, rock crevice or canyon wall?

Blissfully unaware of the human calendar, it’s likely the bat was nudged from sleep several weeks before normal – as were plenty of other bats, according to bat biologist Abigail Tobin of the Washington Department of Fish and Wildlife.

“It’s been a warm winter, so we are seeing many bats emerging earlier than other years,” said Tobin, adding that they typically emerge in late March or early April.

Meteorological winter runs from December through February, but for bats and humans alike, it may have felt like winter never arrived to the Inland Northwest. Temperatures ran above normal and a lot more rain fell than snow. In the latter half of February, some parts of the region saw days in the mid-50s and even the 60s.

So when bats began to emerge early, Tobin wasn’t surprised. Mild weather lured them out, just as it did mountain bluebirds and tortoiseshell butterflies.

Whether a bat emerges in February or holds off until late March, it’s hungry and on the hunt for insects, she said.

“Their goal is to eat as much as they can to regain the fat they lost during hibernation,” Tobin explained. “Sometimes they will even forage during the day. It’s not a sign that a bat is unhealthy. It’s just hungry.”

Along with being hungry, if you see a bat this time of year, it’s probably pregnant.

After bats mate in autumn, the females store sperm in their reproductive tract, delaying fertilization until warm weather rouses them from hibernation. Females typically emerge earlier than males to replenish their energy reserves for gestation and to search for maternity roosting sites, according to Bats Conservation International. Most species give birth to one baby, called a pup, in early summer.

Early-emerging bats in our region – ranging from big and little brown bats, Yuma myotis and the Townsend’s big-eared bat – will return to torpor if insects are scarce or cold temperatures come roaring in, said Tobin.

But being that it’s mid-March and temperatures are predicted to rise into the 60s this week, it won’t be long before bat silhouettes dart across our dusky skies.