General Distribution
During 1996-1998, bat surveys were conducted at 76 sites located throughout the four forests of
southern California. These surveys were in partnership with the Biological Resources Discipline within
the U.S. Geological Survey. The fringed myotis was found at 15 of 76 sites (Stephenson and Calcarone
1999). It was found only at elevations above 4,600 feet (1,954 meters), primarily in montane conifer
forests, but also in pinyon-juniper woodland forests.
Localities where the fringed myotis was found include Indian Creek (at Bluff Camp) and Pine Springs
(north of Cuddy Valley) on the Los Padres National Forest; Dorr Canyon Spring, Islip Saddle, and Big
Rock Campground on the Angeles National Forest; Arrastre Creek, North Slope, Cactus Flats, and Big
Bear Lake on the San Bernardino National Forest; and Laguna Mountain on the Cleveland National
Forest (Stephenson and Calcarone 1999; Stamer pers. comm.).
In 2002, the U.S. Geological Survey began a series of bat inventory studies in San Diego County funded
by several federal, state, and local agencies including the National Park Service, United States Forest
Service, California Department of Fish and Game, and the County of San Diego. Four study areas are
being surveyed including the Cabrillo National Monument, Descanso Ranger District of the Cleveland
National Forest, Santa Ysabel Ranch Preserve, and the Multi-Species Planning Area (MSCP) of eastern
San Diego County. Systematics
Three subspecies are recognized (O'Farrell and Studier 1980) with M. t. thysanodes occupying most of
the range. Habitat Requirements
Fringed myotis occupies a wide variety of habitats from low desert scrub to high-elevation coniferous
forests (Philpott 1997). In California, the species occurs in mixed deciduous/coniferous forests,
redwood and giant sequoia groves, and Joshua tree woodlands (Philpott 1997).
Roost sites are essential for metabolic economy, for juvenile growth and as night roosts to consume
prey. The fringed myotis roosts in crevices in a variety of situations such as caves, buildings,
mineshafts, cliff faces, trees, and bridges for maternity and night roosts. Hibernation has only been
documented in buildings and mines (Stephenson and Calcarone 1999).
In the Laguna Mountains of San Diego County, a radio-telemetry study provided a means to locate
hidden roosting bats (Miner and Brown 1996). Five roosting fringed myotis were discovered along the
eastern escarpment in separate rock crevices on inaccessible cliff faces. One post-lactating female
roosted in a south-facing cliff face in chaparral and was located 7.9 miles (12.8 km) away from the
capture site. Reproduction
Mating occurs during autumn, but ovulation, fertilization, and implantation take place from April to May
(Harvey and others 1999). Females give birth to one young per year in May, June (Philpott 1997), or
early July (Harvey and others 1999). Maternity colonies are typically small (fewer than 40 females), but
may contain up to several hundred individuals (Philpott 1997). Due to thermoregulatory requirements,
maternity colonies may shift locations within a roost (Harvey and others 1999). Daily/Seasonal Activity
Fringed myotis are year-round residents of California, where they hibernate but are also capable of
periodic winter activity (Philpott 1997). Excluding periods of hibernation, individual bats emerge from
the roost to forage approximately 1-2 hours after sunset (Arizona Game and Fish Department 1999).
There may be some level of activity throughout the night (Arizona Game and Fish Department 1999). Diet and Foraging
Fringed myotis feeds on a variety of insect prey, including small beetles and moths (Philpott 1997). The
species may forage in and among vegetation along forest edges and over the forest canopy (Philpott
1997). Territoriality/Home Range
Probably not territorial (Zeiner and others 1990). Predator-Prey Relations
Similar to many other bat species, they are susceptible to predation by mammals, raptors and snakes
upon entering or leaving a roost. Literature Cited
Arizona Game and Fish Department. 1999. Arizona wildlife views (special edition). Phoenix, AZ:
Arizona Game and Fish Department.
Brown, P. 2002. Species accounts for the Western Mojave Planning Area. Bureau of Land Management.
Harvey, M.J.; Altenbach, J.S.; Best, T.L. 1999. Bats of the United States. Arkansas: Arkansas Game and
Fish Commission.
Miner, K.; Brown, P. 1996. A report on the southern California forest bat survey and radio telemetry
study of 1996.
O'Farrell, M.J.; Studier, E.H. 1980. Myotis thysanodes. Mammalian Species 137: 1-5. American Society
of Mammalogists.
Philpott, W. 1997. Summaries of the life histories of California bat species. Unpublished
document. USDA Forest Service, Sierra National Forest, Pineridge Ranger Station.
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.
Western Bat Working Group. 1998. Western bat species: regional priority matrix. Developed at
Western Bat Working Group Workshop, Reno, Nevada, February 9-13, 1998.
Zeiner, D.C.; Laudenslayer, W.F., Jr.; Mayer, K.E.; White, M. 1990. California's wildlife. Volume III:
Mammals. California Statewide Wildlife Habitat Relationships System. Sacramento, CA: California
Department of Fish and Game.
Information gathered from California DFG - California Interagency Wildlife Task Group
