How Many Bats are in That House?

Bat houses at Kootenai National Wildlife

It is easy to miss the bat houses when you drive into the maintenance yard at Kootenai National Wildlife Refuge. Four small structures, mounted on the side of one of the buildings, don’t look like much. But in summer, those boxes are home to a LOT of bats. The refuge installed the houses in 2010 hoping to relocate a colony of bats that roosted in an old building – a building slated to be torn down. It worked, and the bats moved into their new digs. Refuge staff could tell the bats were living there by the growing pile of guano accumulating under the structures each summer and when staff members stood by the houses, they could hear the bats inside, scratching against the walls and twittering to each other. But refuge staff did not know what kind of bats they were or how many bats lived in the houses each summer.

Meantime, White-nose Syndrome was devastating bats in the east and bat biologists in the West were working to gather more information about their bats in anticipation of eventual spread of the disease. The Inventory & Monitoring (I&M) Program in the Pacific Region began working with National Wildlife Refuges to learn more about the bat populations. Kootenai Staff and I&M began to work on Kootenai’s summer residents. Through acoustic work and genetics analysis (funded by Idaho Department of Fish and Game), we learned that little brown and Yuma myotis live in the colony. And we started an annual exit count in order to learn the population size.

Kootenai National Wildlife Refuge

The Friends of Kootenai National Wildlife Refuge became important partners in the annual bat colony exit count. They conduct the survey! Each summer, on night in June or July, 4 to 8 volunteers gather around the bat colony before sunset. They record information on the weather, sun rise and set time, moon rise and set time, and they count the bats as they leave their house to hunt for insects. Through this work, we know that 500 to 1000 bats use the bat boxes to raise young each year. The survey not only provides data for wildlife managers, it gives a small group of volunteers to experience watching a large number of bats fly off into the night. And that is a truly wonderful experience.