Bat Maternity Colony Outflight Count

On Thursday night, Joy and I were joined by Dr. Pat Brown and her associate to conduct an outflight count of a Townsend's big-eared bat (Corynorhinus townsendii) maternity colony in an abandoned mine. Our western subspecies (C. t. townsendii) is the closest we have to a formally endangered bat in California, although bats are starting to get more attention, particularly since the outbreak of White-Nose Syndrome in the eastern US in 2006. Townsend's big-eared bats were previously considered a Category 2 candidate species by the Fish & Wildlife Service, though the term is no longer in use. They are now considered a Federal Species of Concern, along with a California Species of Special Concern, and BLM Sensitive Species in California. None of those designations packs a whole lot of punch, but at least people are paying some attention. While we do have to close mines to protect human health and safety, we do take the bats into consideration and use bat-friendly structures whenever possible.

To conduct an outflight count, we position ourselves in front of each mine opening. We use an infrared light pointed towards the mine entrance and watch with night vision goggles. I have to say it feels pretty surreal to be up in some random mountains, waiting in silence with black ops gear, but it was one of my coolest experiences on the job so far. I could hear the bats' wings as they flew by my head and out into the night. Between the four of us, we ended up counting over 200 bats flying out. I had 49 from my entrance. At this time of year, this includes the babies as well as the mothers. Dr. Pat says that this is the largest Townsend's maternity colony she knows about in California.

	ready to count with my night vision goggles and counter; we use two counters, one for "out" and one for "in"
	okay picture through one eye of the night vision goggles, showing the infrared light illuminating the mine entrance

Townsend's big-eared bat species account by the Western Bat Working Group (pdf)