Vespertilionidae, Evening

Elliott, William R., Reddell, James R., Rudolph, D. Craig, Graening, G. O., Briggs, Thomas S., Ubick, Darrell, Aalbu, Rolf L., Krejca, Jean & Taylor, Steven J., 2017, The Cave Fauna of California, Proceedings of the California Academy of Sciences 64, pp. 1-311 : 46-48

Family Vespertilionidae, Evening bats

Antrozous pallidus, Pallid Bat , was formerly thought to be common in caves of central and southern California, but few recent records are available. A colony on the order of 100 was seen in Painted Rock Cave, San Luis Obispo County, in 1911 (Grinell 1918). It is known from three abandoned mines in Inyo County (Ellison et al. 20003; U.S. Geological Survey 2016b). Perhaps 50 were seen in Swordfish Cave on Santa Cruz Island, Santa Barbara County , in 1997–99, the only bats reliably reported from a California sea cave. Pallid Bat has been found in seven mines, two crevices, and 15 caves across the state. This species probably is a permanent resident in most of its range (Barbour and Davis 1969). Pallid Bat roosts in small colonies in rock crevices and buildings, and occasionally caves, mines, and tree cavities. (See, for example, a photo of a colony of roosting Pallid Bats ( Antrozous pallidus ) at Madera Canyon , Santa Rita Mountains , southeastern Arizona . (Photo by Geoff Gallice — <http://www.flickr.com/photos/dejeuxx/4844640621/>, CC BY 2.0, <https://commons.wikimedia.org/w/index.php?curid=12165921>).

Corynorhinus townsendii , Townsend’s big-eared bat (Fig. 83), has several subspecies with two in California: C. t. townsendii , western big-eared bat or Pacific Townsend’s big-eared bat, and C. t. pallescens, pale Townsend’s big-eared bat. The subspecies C. t. intermedius was synonymized with C. t. pallescens.

Townsend’s big-eared bat is by far the most commonly reported bat in California’s caves and mines. Few of the recorded field identifications noted the subspecies, which are difficult to distinguish, so our species list lumps the two subspecies. Generally C. t. townsendii occurs in most of northern California on the west side of the Sierra Nevada , and C. t. pallescens in the deserts. Our species list has 308 localities, including 123 mines and 185 caves from 31 counties in most regions of the state, from Klamath and Marble Mountains to Mojave Desert , Coast Ranges to Sierra Nevada .

Corynorhinus t. townsendii has been a Species of Concern in California since 2013, and it was considered for listing by the state because of a significant loss of population size, maternity colonies, and hibernation colonies throughout the state. Few sites were protected, but colonies that have come under protection at Lava Beds National Monument, Pinnacles National Park, and Sequoia National Park have increased again. California denied a petition to list the subspecies as threatened or endangered ( California Department of Fish and Wildlife 2016; Pierson and Fellers 1998) .

Large colonies of C. t. townsendii used to exist. A colony of 1,000 was seen on July 1, 1935 in Alice Mine, Riverside County, Mojave Desert , the largest count of this species yet reported in a California mine or cave. The second largest colony was 425 on June 1, 2002 in Bear Gulch Cave, Pinnacles National Park, San Benito County, Coast Ranges (Pierson and Fellers 1998). Two colonies of 210 and 230 were observed in Inyo County mines in 1992–1993 ( U.S. Geological Survey 2016b).

Graham (1966) reported that disturbance by humans had caused the abandonment of several nursery (maternity) colonies in limestone caves. He thought that C. townsendii did not roost in many California limestone caves, especially for hibernation, because most of the caves are at lower elevations and thus are relatively warm. Pierson and Rainey (1994) and Pierson and Fellers (1998) reported a significant decline in big-eared bats in California caves, mines, and buildings; there has been a 52% decline in the number of known maternity colonies. The species is sometimes frightened out of caves by humans, but it may re-establish later, especially bachelor colonies. There are few sites that have had regular, long-term bat counts. Parrish Cave, a lava tube in Shasta County , had winter bat counts in 1948–1951, 1955, 1957, 1960, 1966, 1987, 1988, 1991, and 2015. The largest count was 201 in 1948, the smallest was 11 in 1988 and 1991. A graph of the counts, grouped by decades, could be interpreted as a long-term decline except that there were two data gaps of 21 and 24 years, then the colony peaked again at 177 in 1987. The cave is heavily visited by tourists.

Although C. t. townsendii was being considered for listing, it is still listed as Least Concern by IUCN because of its wide distribution, presumed large population, occurrence in a number of protected areas, and because it is unlikely to be declining at the rate for listing in a threatened category. There are two subpopulations/subspecies that are listed as endangered by the U.S. Fish and Wildlife Service (ingens and virginianus ) (International Union for the Conservation of Nature 2016). A series of further, regular hibernation and maternity colony counts at a few sites would help in monitoring the status of this species, but they must be done carefully by professionals to limit disturbance.

Eptesicus fuscus, Big Brown Bat , is common across North America , and it has been reported from five caves, one crevice, three mines, and two tunnels across California. Suggett (1982) report- ed the subspecies E. f. bernardinus Rhoads in Upstairs-Downstairs Cave, Siskiyou County. Most summer roosts are attics, barns, bridges or other man-made structures; they move into caves, mines and crevices to hibernate only during the coldest weather conditions, and they usually vacate within weeks.

Euderma maculatum, Spotted Bat , was reported from a spring cave, San Bernardino County , in 1948 by Parker (1952) and V. Johnson (1990). It is otherwise known from southern California from a few buildings and a cliff face, and in one instance from a garage in Shasta County.

Lasionycteris noctivagans , Silver-haired Bat, is widespread in North America but has only been found in a mine in Inyo County (V. Johnson 1990; Szewczak et al. 1998). The bat is solitary, dark-colored, and difficult to identify on cave or mine walls.

Myotis californicus , California Myotis (Fig. 95 and front cover), is known in small numbers in eight caves and five mines from the Mojave Desert to northern California. The species also roosts in rock crevices, tree cavities and loose bark, and buildings.

Myotis ciliolabrum , Western Small-footed Myotis , seeks cover in crevices, caves, mines and buildings. Besides five mines in the Mojave Desert , it is known from two lava caves in Siskiyou County , where five to 12 bats were caught with harp traps in 1990 and 1999. One was a lactating female in Heppe Ice Cave. These records hint that many cave bat colonies are still unidentified in California.

Myotis evotis , Long-eared Myotis , has daytime roosts in buildings, tree cavities, caves, mines, and rock crevices. The species has been found in one tunnel, one mine, and ten caves.

Myotis lucifugus, Little Brown Myotis , is widespread in the U.S. and Canada, although it has declined greatly in the east because of White Nose Syndrome, and it is being considered for listing as endangered. The disease was found in this species in March 2016 in King County, Washington ( U.S. Geological Survey 2016a). In summer M. lucifugus inhabits attics or other shelters near water, and it hibernates in caves and mines, formerly in large numbers in the eastern U.S.A. In California it has been found in small numbers in six caves and one mine, from the Mojave Desert to Lava Flows North.

Myotis melanorhinus , Dark-nosed Small-footed Myotis , roosts in rock-face crevices and riverbanks, and may use talus, tree bark or buildings; hibernation sites include mines and caves. The species has been seen in two mines in far southern California.

Myotis occultus , Arizona Myotis , another obscure vespertilionid, it has only been seen in an abandoned copper mine in the Riverside Mountains, Mojave Desert.

Myotis thysanodes, Fringed Myotis , known only in small numbers from seven mines from San Diego to Lake County. Danehy (1952) noted that this bat occurs in caves in central and southern California; roosts in caves, mines, and buildings.

Myotis velifer, Cave Myotis , is common across the southwestern U.S. to Central America . Danehy (1952) reported that this bat is common in the summer in sandstone and conglomerate caves near the Colorado River (Imperial, Riverside, San Bernardino counties). The subspecies M. v. brevis barely ranges into southeastern California. In summer, it congregates in caves and mines, and less often, buildings; winter roosts are primarily caves. California populations may be migratory, however we only have scant records from four mines in Riverside County.

Myotis volans , Long-legged Myotis . Danehy (1952) reported that this was an uncommon bat in central and southern California caves, but is sometimes found with M. thysanodes . Barbour and Davis (1969) claim that this bat uses caves as night roosts only. Primarily inhabits forested mountain regions, where it roosts in trees, rock crevices, stream banks, and buildings; hibernation sites are primarily caves and mines. Records consist of three caves and three mines from southern to northern California.

Myotis yumanensis, Yuma Myotis . Danehy (1952) notes only that this species is sometimes found with M. velifer in caves. Maternity colonies utilize buildings, caves, mines, or bridges. In 1918 600 were observed in Old Senator Mine, Imperial County ( U.S. Geological Survey 2016b). Fifty Yuma bats were counted in a Dam Canyon cave, San Diego County, in 2003. Our records include six mines, two tunnels, and five caves from southern to northern California.

Parastrellus hesperus , Western Pipistrelle or Canyon Bat. Danehy (1952) reports that this bat is found in cracks in caves, but uncommonly. Primarily a desert species, it inhabits a variety of habitats from rocky canyons, cliffs, and outcroppings, to creosote bush flats; day roosts usually in rock crevices, mines, or buildings; hibernates in mines, caves, and rock crevices. Records include small numbers from nine caves and seven mines from southern to northern California .