Field Guide to Mammals
of Southern California
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Spotted Bat (Euderma maculatum)
Spotted bat occurs throughout much of western North America from south-central British Columbia to southern Mexico (Harvey and others 1999). The species has a scattered distribution throughout California (Philpott 1997). As reported in Brown (2002) prior to 1990, the majority of California records (mostly single, dead or moribund animals) came from low elevation, xeric settings (e.g., Red Rock Canyon State Park in Kern County, Mecca in Riverside County, and several from the Indian Wells Valley in Kern County and Owens Valley, Inyo County) (Bleich and Pauli 1988, Brown 2002, Constantine and others 1979, Grinnell 1910, Hall 1939). More recent surveys (Pierson and Rainey 1998, as reported in Brown 2002) have detected the distinctive low frequency echolocation signals (audible to many humans) emitted by spotted bats at several sites in the mountains of Shasta and Siskiyou counties. Most of the widely distributed Sierra Nevada localities are at elevations of 3,500–4,000 feet (about 1,200–1,400 m), but one or more individuals have been heard at several sites up to 8,500 ft (2,880 m). Other recent auditory detections have been made at Mt. Palomar in San Diego County; and near Bishop, Inyo County. North of Bishop, a roost site was discovered in the cliffs at Owen's Gorge in Mono County (Brown 2002). They are found in foothill and desert areas in southern California.
Spotted bat is the only species in the genus Euderma (Handley 1959).
Spotted bats are found in a variety of habitats ranging from below sea level desert, sagebrush, montane forests and up to high-elevation coniferous forests. This includes foraging habitat in forest openings, pinyon juniper woodlands, large riverine/riparian habitats, and riparian habitat associated with small to mid-sized streams in narrow canyons, wetlands, meadows, and old agricultural fields. As reported in Brown (2002), most of the widely distributed Sierra Nevada localities are at elevations of around 3,500– 4,000 feet (1,070–1,220 m), but one or more individuals have been heard at several sites up to 8,500 ft (2,600 m). The spotted bat is rare, but could be anywhere suitable cliff habitat is found (Stokes 2003). They are closely associated with rock cliffs, where they roost in crevices (Philpott 1997). The abundance and distribution of suitable cliff habitats may limit the distribution of this species (Luce 1998, Stephenson and Calcarone 1999). Mines and caves may also be used during winter (Philpott 1997). Roost sites are often located in the vicinity of open water (Arizona Game and Fish Department 1998).
Little information is available on spotted bat reproduction, but scanty data suggest that mating takes place in the fall, implantation is delayed, and females give birth to one young per year between June and July (Philpott 1997). When born, the babies lack the spotted coloration of adults (Harvey and others 1999).
Spotted bats emerge approximately 1 hour after dark to forage, and return to the day roost approximately 1 hour before sunrise (Harvey and others 1999). As reported in Brown (2002) seasonal patterns and movements for this species are not well known. No evidence exists for longitudinal migration. In the colder portions of their range, they have been found hibernating (Hardy 1941, as reported in Brown 2002), yet spotted bats are periodically active throughout the winter in southwestern Utah (Poché 1981, as reported in Brown 2002; Ruffner and others 1979), and in the upper Sacramento River drainage of northern California (Miller pers. comm., as reported in Brown 2002).
Diet and Foraging
Spotted bats subsist almost entirely on moths. To locate their prey, they use very low frequencies (9- 12khz). This low frequency is outside of the hearing range of most moths. While this low frequency makes the spotted bat very efficient at finding large prey at long distances, it is ineffective for locating small insects. These bats typically forage over meadows, along forest edges, and in open coniferous woodlands. They commonly forage above the canopy from 33–98 feet (10–30 meters) above the ground (Philpott 1997). Spotted bats are continuously airborne during the foraging period. This is in contrast to many other bat species that feed just after dusk and before dawn, and roost during the middle of the night. Spotted bats are quite predictable in their daily movements, usually following a set route to the nighttime feeding area and returning to the same roost night after night (Harvey and others 1999). They may move as far as 6.2 miles (10 kilometers) between the day roost and feeding areas.
No information is available on territorial behavior or home range movements for spotted bats.
Bats are occasional prey to owls and falcons, although there are no published accounts of this predator-prey relationship for spotted bats. Released animals have been captured by a kestrel and chased by a peregrine falcon and a red-tailed hawk (Watkins (1977).
Arizona Game and Fish Department. 1998. Heritage data management system animal abstract: Euderma maculatum. Arizona Game and Fish Department.
Bleich, V.C.; Pauli, A.M. 1988. Additional records of the spotted bat (Euderma maculatum) from California. Great Basin Nat. 48(4): 563 or 214.
Brown, P. 2002. Species account for West Mohave Planning Area. Brown-Berry Biological Consulting, 134 Wilkes Crest, Bishop, California 93514.
Constantine, D.G.; Humphrey, G.L.; Herbenick, T.B. 1979. Rabies in Myotis thysanodes, Lasiurus ega, Euderma maculatum and Eumops perotis in California. J. Wildlife Dis. 15(2): 343-345. Grinnell, J. 1910. A second record of the spotted bat (Euderma maculatum) for California. University of California Publ. Zool. 5(10): 317-320.
Hall, E.R. 1939. The spotted bat in Kern County, California. J. Mammal. 20(1): 103.
Hall, E.R. 1981. The Mammals of North America. Vol. 2. John Wiley and Sons, Inc., New York.
Handley Jr., C.O. 1959. A revision of American bats of the genera Euderma and Plecotus. Proceedings of the U.S. Natural History Museum 110: 95–246.
Hardy, R. 1941. Some notes on Utah bats. J. Mammal. 22(3): 289-295.
Harvey, M.J.; Altenbach, J.S.; Best, T.L. 1999. Bats of the United States. Arkansas Game and Fish Commission.
Leonard, M. L. and M. B. Fenton. 1983. Habitat use by spotted bats (Euderma maculatum, Chiroptera: Vespertilionidae): Roosting and foraging behaviour. Canadian Journal of Zoology 61: 1487-1491.
Luce, B. 1998. Spotted bat: Euderma maculatum. In: Ecology, conservation and management of western bat species: Bat species accounts. Distributed at the Western Bat Working Group Workshop, February 9– 13, 1998, Reno NV.
Pierson, E.D.; Rainey, W.E. 1998. Distribution of the spotted bat, Euderma maculatum, in California, with notes on habitat associations and status. Submitted to J. Mammal.
Poché, R.M. 1975. New record of Euderma maculatum from Arizona. J. Mammal. 56(4): 931-933.
Philpott, W. 1997. Summaries of the life histories of California bat species. United States Forest Service. Unpublished document. Sierra National Forest, Pineridge Ranger Station.
Poché, R.M. 1981. Ecology of the spotted bat (Euderma maculatum) in southwest Utah. Utah Division of Wildlife Resources. Publication No. 8181-1.
Ruffner, G.A.; Poché, R.M.; Meierkord, M.; Neal, J.A. 1979. Winter bat activity over a desert wash in southwestern Utah. Southwestern Nat. 24(3): 447-453.
Stephenson, J.R.; Calcarone, G.M. 1999. Southern California mountains and foothills assessment: Habitat and species conservation issues. General Technical Report GTR-PSW-175. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture.
Watkins, L.C. 1977. Euderma maculatum. Mammalian Species 77: 1-4.
Information gathered from California DFG - California Interagency Wildlife Task Group