Each year on April 17th, National Bat Appreciation Day reminds us of the roles bats play in our daily lives. April is also the best time of the year to observe bats, as they are now beginning to emerge from hibernation.
The Bay Area is home to up to 16 species of bats, all of which are insectivores, a carnivorous plant or animal that eats insects. Some of the more common bat species you might see in the Bay Area include the Mexican free-tailed bat (Tadarida brasiliensis), the big brown bat (Eptesicus fuscus), and various mouse-eared bats (in the genus Myotis). The three most common
Bats are the number-one predator of insects that fly at night, and they can reduce mosquito problems substantially. According to the U.S. Fish and Wildlife Service, a colony of bats with approximately 100 members will consume more than 600 million insects in a 200-day feeding season. It is easy to see that bats provide a benefit to humans, including insect control and plant pollination.
There are 13 to 15 species of bats in the East Bay, but you need to be out at dusk to glimpse them in action, said East Bay Regional Park naturalist Cat Taylor, noting that bats use a dozen publicly accessible structures at Sunol Regional Wilderness, Black Diamond, and Big Break, with each structure housing 200 to 300 bats.
Taylor said your best chance of seeing bats is to look toward the sun as it sets, as the bats emerge from their roost.
“It illuminates the water, and you should be able to see bats feeding furiously on insects as they fly over the water for about 20 minutes, after which they go hang upside down to digest it all,” said Taylor, who recommends going on a full moon.