Countywide Bat Study Reports First Results

— from Russel Barsh —

The best available scientific evidence is in, and it’s a fact: San Juan County is very batty, and Orcas is the battiest island!

Kwiaht director Russel Barsh has announced results of the first systematic survey of the county’s bats in 75 years.

The study included 105 nights of ultrasound recordings, visits to homes and barns where bats were reported roosting, and visual observations including dead or injured bats received by Wolf Hollow Wildlife Rehabilitation Center. “Over ten thousand bats were heard,” Barsh says, “and that is only perhaps one percent of what’s out there.” The most bat flyovers per hour were heard above lakes and ponds on Orcas.

Nine species of bats were identified by acoustic analyses; a tenth species (Keen’s Myotis) is probably also present but must be confirmed genetically. “This is a significant portion of the 15 species of bats that are known from Washington State as a whole,” says Barsh. All nine confirmed species were observed on Lopez, Orcas, and San Juan Islands, but in different proportions, which Barsh attributes to differences in the kinds of habitats that are available on each island. “For example,” Barsh says, “Yuma Myotis, which like to hunt over open water, were more abundant on Lopez, while California Myotis, which seem to prefer to hunt wooded areas, were more abundant on Orcas.”

Results of the 2014 study are consistent with an acoustic survey of Lopez in July 2013 conducted by Western Bat Working Group co-chair Ella Rowan with assistance by Barsh and Kwiaht. That study has already been submitted for publication.

The Kwiaht study also confirmed that San Juan County is an important reservoir of Townsend’s Big-Eared Bat, a federal and state species of concern found at only about a dozen maternity roosts in Washington.  Townsends were identified on four islands.  The reason for their relative abundance in San Juan County remains unclear, but farmers and gardeners should rejoice: this relatively large, sociable bat specializes in eating moths, in particular the moths that are most destructive of orchard trees.  “Older, untended orchards must be a feast for them,” Barsh says.

The Kwiaht study also confirmed that many species of bats remain in the islands over the winter, dispersing locally rather than migrating to the mainland or hibernating. “Next year’s focus will be the dispersal pattern of winter bats,” Barsh says, “and what it is they are eating.”  He is particularly interested in a tribe of moths that tend to emerge in January and February in the islands’ woodlands.

Data summaries and graphs will be posted on the Kwiaht website and Facebook page in the next few weeks.

The American Wildlife Conservation Foundation helped fund the Kwiaht study. Barsh also expressed appreciation for the professional support and encouragement of Ella Rowan, Greg Falxa, and Nancy Williams, and the generosity of homeowners that allowed him to record on their property.

For further information contact: Russel Barsh via email.