Field Guide To The San Gabriel Mountains: Bats

Bats are the only mammals that fly. (Flying squirrels glide.) They have furry bodies and membranous wings. Bats have small eyes, but excellent vision. However, they find their food by echolocation, meaning they produce a sound either through their mouth or nose, that bounces back to them, somewhat in the same manner as radar or sonar, enabling them to zoom in on their prey and capture it.

Bats, which usually fly at night, are found in areas with nearby water and plenty of insects. Any place you know?

This excellent page is a superb introduction to bats: Bat Species: Natural History

Bat Species in the San Gabriel Mountains

Bats recorded at Eaton Canyon (Source: Windows into the Wild, Docent Naturalist Training Manual, County of Los Angeles, Department of Parks and Recreation, in cooperation with Nature Center Associates of Los Angeles County, 1982, Mammal Checklist):

Additional bats recorded at Placerita Canyon (from the same source as Eaton Canyon):

Bats recorded at San Dimas Experimental Forest

Bats listed as Potentially Vulnerable Species in the Angeles National Forest (Source: Southern California Mountains and Foothills Assessment, United States Department of Agriculture Forest Service, General Technical Report PSW-GTR-172):

Most of the time you won't get close enough to a bat to reveal all these features, but just in case you get lucky here is A Key to the Bats of California

Locating Bats to Watch

Bats, when they first wake up at dusk, go searching for water, then for their food, insects. They follow certain pathways through the air. To locate bats to watch, first find some water nearer than 1/4 to 1/2 mile away. Then locate some really buggy spot and wait for the sun to set. Eaton Canyon Wash is a very successful spot.

Bat Habits

Different bats species eat different kinds of insects. Each species has a unique flight pattern and different sound as well.

Watch for bats in sky zigzaging after the insects. They fly a commute (rather straight) pattern until they locate an insect by echolocation. They turn immediately (zigzag) to go after it.

Since bats can locate very tiny insects using their hearing only, it is extremely unlikely that they will fly into your hair. Instead, because people attract insects, the bats are zooming in after their prey, the insect, for dinner.

Listen to the echolocation clicks of bats and view the sonagrams

What do bats eat?

Bats hibernate and can only be seen from about April 15 through September 15. There are no bats flying at Halloween.

Bats spend much of their time sleeping and resting; this (in)activity is called roosting.

Our local bats typically roost in rock crevices or in trees. Others use man-made structures; but bat houses are rarely successful in attracting bats. Even bird houses fail to attract an occupant 90% of the time; the vacancy rate for bat houses is even higher. Furthermore, bats are loyal to their roosting sites.

California doesn't have large colonies of bats because there aren't any large karst caves. But bats do inhabit old mines.

Bat Connections

Bat Press

What to do if you find an injured bat

Many years ago, in 1984, I (Jane) was on a nature walk with Pat Sullivan, then the director of the Nature Center. We saw a bat flying and determined that it was a hoary bat. A little farther on on our walk, I found one roosting in the sun on a rock, quite visible, but well camouflaged, the blond-brownish frosted coat perfectly matching the rocks on the north-facing cliffside. Since this was daytime and since this bat behavior was so unusual, we were admonished not to touch bats. Pat later collected these bats in a cage using heavy protective gloves. They turned out to have rabies. The point to be made here is to be very careful and not touch the bats especially if they are exhibiting ususual behavior like day flying and roosting in the sunlight.

"Wild animals accounted for nearly 92.0% of reported cases of rabies in 1996. The 6,550 cases reported in 1996...Raccoons continued to be the most frequently reported rabid wildlife species (50.4% of all animal cases during 1996), followed by skunks (23.2%), bats (10.4%), foxes (5.8%), and other wild animals, including rodents and lagomorphs (2.1%)."
Source: Rabies surveillance in the United States during 1996

Bats bibliography online and in print

Go to: Field Guide to the San Gabriel Mountains: Natural History: Animals

Copyright © 2001 by Jane Strong and Tom Chester.
Permission is freely granted to reproduce any or all of this page as long as credit is given to us at this source:
Comments and feedback: Jane Strong | Tom Chester
Updated 18 August 2001