For Halloween, here is a reminder that the holiday's favorite flying mammal lives right in San Francisco.
Hidden in plain sight
By day, Golden Gate Park's bats sleep in the branches, hollows and bark of old cypress and eucalyptus trees. At night they hunt insects over the park's lakes. “They're there, and there's a lot of them,” filmmaker Kristin Tièche told The San Francisco Standard. Her documentary is called “The Invisible Mammal.”
No one is counting the park's bats. But Winifred Frick, chief scientist at Bat Conservation International, told the Standard the park likely hosts many of the Bay Area's native species. On a late-August evening at Blue Heron Lake, Tièche's detector picked up calls the device identified as big brown, silver-haired and little brown bats, and possibly hoary or Mexican free-tailed bats.
How to listen
Tièche uses a $179 Echo Meter Touch 2, a small detector that plugs into a phone or tablet and turns bats' ultrasonic calls into sound. Peak season is summer and early fall. Lakes are the best spots because they draw the insects bats eat, and activity starts about 10 minutes after sunset. Hobby detectors can confuse species, so treat the readings as a guess.
Why they matter
The National Park Service says the biggest threats to Bay Area bats are habitat loss and disturbance of roosts. Seven of the region's 13 species are believed to be of special concern. The park service and partners run summer acoustic monitoring at Golden Gate National Recreation Area and Point Reyes. White-nose syndrome, a deadly fungal disease, has not reached the Bay Area.