Bats (Order: Chiroptera)

Vesper bats (Vespertilionidae Family)

Several bats in the genus Myotis may occur at Quail Ridge, and some may be difficult to distinguish except by experienced biologists. In the absence of any surveys, it is somewhat unclear which species occur here. Little brown myotis (Myotis lucifugus) have yellowish glossy brown hair with the tips a bit darker on the backside and a lighter underside. The fur is shiny or burnished, and somewhat yellowish brown in coloration. These bats can be found foraging above streams and around the edges of forests. They emerge from their day roosts at dusk and forage on insects, capturing them on the wing. Yuma myotis (M. yumanensis) is one of the most common of the western Myotis. Yuma myotis have a characteristic dull brownish color with hairs that are darker at the base. The undersides of these bats are whitish in color. Yuma bats are late-night fliers that stick close to the ground when foraging and are typically found in oak savannas. These generally have duller fur than little brown myotis, and they are slightly larger (e.g., forearm length 35-40 mm as opposed to 32-37 mm). Other species which may occur at Quail Ridge include fringed myotis (M. thysanodes), long-legged myotis (M. volans), long-eared myotis (M. evotis), California myotis (M. californicus), and the western small-footed myotis (M. ciliolabrum).

Western Pipistrelle; Photo courtesy of Glenn and Martha Vargas © California Academy of SciencesThe big brown bat (Eptesicus fuscus) is one of the most common bat species in the United States. The coats of these bats are long with a brown to black color and a glossy hue. Another distinctive characteristic is the dark black coloring of their patagia (wing membranes). Big brown bats tend to roost alone in caves, crevices, buildings, or trees, but have also been known to roost in small groups. They feed mainly on beetles and are known to hibernate for months during the winter.The western pipistrelle (Pipistrellus hesperus), or “Pips”, are small bats, and have a distinctive yellow-gray smoke-like coloration on their backs, and a whitish belly. They are found near water sources in more arid areas, and they roost in caves, cliffs, under loose rocks, and in buildings. These bats can be found foraging on insects in the early evening, sometimes even before sundown.

Townsend's Bid-eared Bat; Photo courtesy of Merlin TuttleAn unusual, and aptly named bat, Townsend’s big-eared bat (Corynorhinus (previously Plecotus) townsendii) has remarkably long ears – roughly one third of forearm length – that meet basally at the top of the forehead. They have a brown coat with a grayish tint and have distinctive lumps between the nostrils and eyes. Big-eared bats forage at the edge between forest and grassland habitats. These bats are of conservation concern because they appear to be extraordinarily sensitive to human disturbance – a single human visit may cause abandonment of a roost site – and their numbers are declining in California.

Three species of related bats, the Lasiurine bats, are notable for having furry tail membranes. The western red bat (Lasiurus blossevillii) is readily distinguished by its rusty, brick-red coloration, with white-tipped hairs. Red bats roost among the foliage of trees and are solitary. However, they forage in pairs, and forage over the same area repeatedly. Red bats migrate south in the fall.Hoary Bat; Photo courtesy of William Leonard © 2005 William Leonard Because of their apparent dependence on riparian vegetation, these bats may be faring poorly in California, where riparian habitats have been largely degraded or destroyed. Hoary bats (Lasiurus cinereus) have a yellowish brown coat with white-tipped hairs over most of their body and patches of white fur on their elbows and wrists. These bats are also solitary and can be found foraging late at night or roosting in trees during the day. Silver-haired bats (Lasionycteris noctivagans) have a dark brown coat with hairs tipped with white/silver. Only the proximal half of the interfemoral membrane is well furred. Silver-haired bats roost among foliage in forested areas and forage among the trees.

Pallid bats (Antrozous pallidus) are colonial, roosting in caves, buildings, trees, and mine tunnels. They are a gray to dull yellow color and have long ears that extend beyond the snout when bent forward, but do not touch basally. Pallid bats feed near the ground on Jerusalem crickets, beetles, and other invertebrates.

Free-tailed bats (Molossidae Family)

The Brazilian free-tailed bat (Tadarida brasiliensis) is readily distinguishable by its tail, which extends beyond the interfemoral membrane, and the reddish brown coat. The ears generally do not touch basally, and are distinguished by having a series of little bumps on their edges. Brazilian free-tailed bats are colonial, roosting in caves and buildings, emerging at dusk to forage on moths. The largest colonies of mammals known are this species; at Bracken Cave in Texas some 20 million bats emerge to forage every evening in the summer.

Species Accounts

Mammals Page

Photo Credits: Title, Mule Deer (Mike Benard),Western Pipistrelle (Glenn and Martha Vargas), Townsend's Big-eared Bat (Merlin Tuttle), Hoary Bat (William Leonard). For more pictures see:

This page last updated: June 24, 2005  

Contact: Dr. Virginia Boucher
John Muir Institute of the Environment
109 The Barn, University of California, Davis, CA 95616
Phone: 530-752-6949; email:

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