It’s baby bat season on San Juan Island

A Townsend’s Big Eared Bat, the rarest bat in the San Juan Islands — Contributed photo

Russel Barsh of Kwaiht shares insights into the late summer activity of some of San Juan Island’s most interesting residents.

Encounters with bats inside island homes peak in mid- to late August each year. Biologists at Kwiaht study the diets and health of island bats, and the explanation is simple.

After a two-month pregnancy beginning as early as mid-April, but more often in mid- to late May, mouse-eared bats return to the maternity roost one or twice each night to nurse their pups for up to a month before the young bats can begin to fly and feed on their own. Here in the islands, most bat pups fledge in August and, if they survive, grow to adult size by the time that their mothers are ready to disperse for the winter.

Naïve young bats, like fledgling birds, are at first somewhat clumsy flyers, complicated by the need to learn how to navigate in the dark by echolocation. In addition, like human teenagers, young bats are curious to the point of recklessness as they explore the world that lays outside the enclosed roost in which they have lived thus far. Although they learn very quickly, young bats are more likely than experienced adults to fly into open unscreened windows, doors, and chimneys — or to pop through a tiny crack in a ceiling that separates an attic or crawlspace roost from rooms occupied by their unwitting human hosts.

At this stage of life, young bats are still quite small and have flexible bones like hard rubber, so that they can squeeze through surprisingly narrow openings. And while they are not yet expert navigators and pilots like their mothers, they fly swiftly and almost silently. Opening a door for an evening dog walk can be enough for a young bat to dive inside for a look.

Once inside a room, young bats frequently cannot relocate their point of entry, especially if it was a temporarily open door or window. Bright lights also confuse them; their eyes and ears are giving them conflicting information. Panicking, a young bat will seek a high point near the ceiling, such as a beam or a small niche, where it will try to hide. If it does not find its way out in a few days, it will die of dehydration; bats must drink almost nightly.

Give trapped baby bats a break by opening a nearby window, turning off all lights, and leaving the room for at least 15 to 20 minutes after twilight. Left to itself in the dark, young bats can find the open window acoustically — like sonar — and will take the opportunity to go out in search of fresh water and flying food. Avoid handling bats; they are very fragile, especially the thin bones in their wings, and that’s when people get bitten. No rabid bats have been found in the islands, but people and bats share other diseases as well.

If you want to learn more, help the island conservation laboratory Kwiaht expand its bats-and-bees technical assistance program for homeowners, gardeners and farmers. Kwiaht is raising money through the San Juan Island Community Foundation’s 2022 County Fair Giving Campaign, which will match the first $1,000 in donations dollar-for-dollar.

To be eligible, donations must be made during the 2022 County Fair, August 17–20. Donations can be made in person at the SJICF booth at the Fair; online at the SJICF website; by phone at 360-378-1001; or by mailing a check payable to SJICF (and dated between August 17–20) with Kwiaht in the memo line to P.O. Box 1352, Friday Harbor, WA 98250.

And if you find a trapped, injured or ill bat, phone Wolf Hollow Wildlife Rehabilitation Center at 360-378-5000. They have expertise to handle and help bats in need of medical attention. Consider a donation to Wolf Hollow as well.

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