Our Central California Bats

Twenty species of bats occur within California’s Central Coast Region. Several species are rare in the area, including the Western Small-footed Myotis, a xeric habitat specialist; the Little Brown Bat, a mesic habitat specialist in southern portions of its range (incl. the Central Coast); the Western Mastiff Bat, a cliff-dwelling, riparian-corridor-foraging super-bat; and the "Eastern" Red Bat (Lasiurus borealis). Although not yet detected during our surveys, the Eastern Red Bat has been documented by chiropterologists Pat Brown and Bill Rainey during their studies of bats on the Channel Islands.

A 21st Central California bat species that is not found in the Central Coast region, the Spotted Bat, occurs in the foothills and canyons of the western slopes of the Sierra Nevada eastward into high-elevation deserts.

The most exciting results of our survey so far are the confirmations of the regular occurrence of two “free-tailed” bats, Pocketed and Big Free-tailed Bats, and the discovery of and widespread distribution in Central California of the Western Yellow Bat (Dasypterus xanthinus), a species known primarily in California from its southern deserts and especially palm-laden oases. Previously, the species was not recorded along the Pacific Coast north of Los Angeles County nor from the San Joaquin Valley, where it has become, if not common, a regular and widespread species.

Here’s a list of all of our 21 *Central California bats with a few notes about each, including their key features:

*Data primarily from Fresno, Inyo, Kern, San Luis Obispo, Santa Barbara, Monterey, San Bernardino, and Tulare counties.

Canyon Bat (Parastrellus hesperus)
Key features: Smallest North American bat (body length: 60-70mm); forearm 25-30mm; dark facial mask; unique (blunt) tragus (unlike Myotis); keeled calcar; one tiny premolar – Myotis have two – however, this is an in-hand only identification trait.

Townsend’s Big-eared Bat (Corynorhinus townsendii pallescens)
Key features: Just slightly larger than large Myotis species (body length 90-115mm); forearm 39-44mm; large ears (30-40mm); distinct horseshoe-shaped lump on nose.

California Myotis (Myotis californicus)
Key features: All-around small bat – body length 65-90mm; forearm 32-38mm; dorsal pelage typically long (shaggy); base of hairs typically much darker than tips; foot is very small (5-8mm); forearm is small (< 35mm); calcar is keeled.

Small-footed Myotis (Myotis ciliolabrum)
Key features: Rare or absent along coast. Similar to California Myotis: Small size (body length 65-85mm); forearm 30-35mm; foot similarly small (5-8 mm), calcar is keeled; dorsal surface of interfemoral membrane furred on anterior half; skull flattened; ears black; typically has distinctive black facial mask.

Long-eared Myotis (Myotis evotis)
Key features: Body length 75-95mm; forearm 36-41mm; extremely long ears for a Myotis (18-25mm); also, ears black, shiny, and hairless.

Little Brown Bat (Myotis lucifugus)
Key features: Rare in SLO, MON, and SBA counties. Small bat; body length 80-95mm; forearm length 36-40mm; wingspan 220-270mm; fur darker on dorsum than ventrum; feet w/long toe hairs that extend to tips of toes.

Fringed (Fringe-tailed) Myotis (Myotis thysanodes)
Key features: Body length 75-105mm; relatively long ears (16-20mm); often with notable facial mask; only Myotis w/fringe of (stiff) hairs along edge of interfemoral membrane.

Long-legged Myotis (Myotis volans)
Key features: Body length 95-103mm; forearm 36-42mm; underwing furred near body from knee to elbow; obvious keel on calcar.

Long-eared Myotis (Myotis evotis)
Key features: Body length 75-95mm; forearm 36-41mm; extremely long ears for a Myotis (18-25mm); also, ears black, shiny, and hairless.

Yuma Myotis (Myotis yumanensis)
Key features: Noticeably two-toned (darker on back, lighter on underside); small bat (body length 85-90mm); forearm 32-36mm; large feet (≈10 mm); short ears (13-15mm), lacks keel on the calcar.

Spotted Bat (Euderma maculatum)
Key features: Spotted Bats have black bodies with two white spots on their shoulders and one white spot on the rump. Ventral coloration is black with white-tipped hair, giving a white appearance. Ears hairless, 45 to 50 mm in length with a simple tragus, erect when active but folded and curled back against the body when resting or in torpor. Body length 107 to 115 mm; forearm 48 to 51 mm; tail 47 to 50mm.

Pallid Bat (Antrozous pallidus)
Key features: Medium-sized (length 92-135mm); forearm 48-60mm; large eyes; often feeds on the ground; can run on folded wings and hind feet; can hop from ground to catch insects

Big Brown Bat (Eptesicus fuscus)
Key features: Largest locally occurring bat with uniform brown fur (body length 105-120mm); forearm 45-52mm; tragus blunt (as opposed to pointed in all Myotis species)

Silver-Haired Bat (Lasionycteris noctivagans)
Key features: Medium-sized bat (body length 90-115mm); forearm 39-43mm; interfemoral membrane lightly furred; fur color typically black with silver tips – similar to hoary bat but face NOT distinctly lighter than back.

Western ( aka "Peters") Red Bat (Lasiurus frantzii)
Key features: Medium-sized (body length 90-120mm); forearm 38-42mm; males typically brick-red, females are rusty (i.e., browner); body hairs often tipped with white; interfemoral membrane heavily (densely) furred.

Hoary Bat (Lasiurus cinereus)
Key features: Large bat (body length 130-145mm); forearm 50-55mm; face lighter than dorsum (often yellowish); ears distinctively rounded, glossy black in color with naked edges; all-over densely furred.

Mexican (Brazilian) Free-tailed Bat (Tadarida brasiliensis)

Key features: A small bat (body length 90-105mm) with long narrow wings (extremely fast flier); forearm 36-46mm; tail extends out from the interfemoral membrane; long hairs extend from toes; unlike the mastiff bat, ears do not meet in the middle of forehead; short snouted with notably wrinkled lips.

Western Mastiff Bat (Eumops perotis)

Key features: Rare in SLO, MON, and SBA counties. Largest U.S. bat; body length 140-185mm; forearm 72-82mm; long, narrow wings; approx. half of tail is free from the membrane between hind legs; large ears join at the midline of forehead, noticeable underbite.

Pocketed Free-tailed Bat (Nyctinomops femorosaccus)

Key features: Rare in SLO, MON, and SBA counties. Pelage is red-brown to gray-brown ventrally (white at their base), paler dorsally. Body length is 105mm to 120mm, weigh 10-14 g; females average slightly smaller than males with notably smaller heads. Typical (avg.) measurements: tail length, 46mm; hind foot, 10mm; ear length, 23mm; forearm, 46mm; wingspan, 35cm (13.8in). A pocket-like fold of skin is on the underside of the uropatagium and there are long hairs above the uropatagium that extend beyond the normal pelage length. Ears are joined at the middle of the head above the forehead and present are vertical wrinkles on the lips along the muzzle.

Big Free-tailed Bat (Nyctinomops macrotis)

Key features: Rare in SLO, MON, and SBA counties. Migratory and peregrinatious. Adult male body length, 145-160mm; adult females, 120-140mm. Pelage is bi-colored, dorsally dark red to dark brown, ventrally contrastingly lighter in color. Tail extends 40 to 50 mm behind a small tail membrane. Face is black; the ears lay forward (as if bonneted like the Mastiff Bat), joined at their bases (also like the Mastiff Bat).