Fall 2003

Table of Contents

Rare bats saga continues with radio telemetry

The very rare bat colony in an old log cabin north of Spokane that is featured on WDFW’s website “Bat Cam” continues to be monitored by Eastern Washington University graduate students, this year with the help of radio telemetry equipment.

The Townsend’s big-eared bat, Corynorhinus townsendii, is a candidate for state listing as a threatened or endangered species and is considered one of the rarest mammals in the northwest. They have low populations and low annual natality rates, probably because they have very specific hibernacula requirements involving caves, mines, and buildings and are very sensitive to human disturbance. Of the twelve maternity roosts known in Washington, only two are in the eastern part of the state, both in man-made structures.

Like last year, the first 40 or so of these migratory bats arrived back at the cabin in early April. Also like last year, bat presence at the roost was sporadic throughout the rest of April, May, and June.

But their overall presence and numbers were consistently lower than last year. Only five bats were observed in late May, and with the exception of one day when 22 bats were present, after mid June there were only two or four bats.

Researchers began to wonder if the bats had abandoned this roost. In an effort to locate where the bats were roosting, three lactating bats were captured on July 2 and radio telemetry transmitters were placed on two of them.

The radioed bats were tracked to two different locations, both within three miles of the original location. One roost was located in the attic of an abandoned log cabin similar to the original roost (but painted a gaudy red) where 175 bats were present. The other was located, along with about 45 bats, in the crawl space of a building at a very active youth summer camp. Both colonies had young.

On July 11 both radioed bats were at their respective new locations and the original cabin roost (featured on BatCam) had 30 bats. On July 13, one radioed bat was at the “red” cabin and the other was found in the original cabin along with 140 bats.

By August the original cabin was hosting up to 300 bats, including young of the year. By early September the bats were beginning to disperse, with around 150 left. At the same time, the newly discovered red roost had around 25 bats.

This movement between roosts is still a mystery so research will continue next year when the bats hopefully return again.