Bat Inventories in San Diego County

In 2002, the US 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 district of the Cleveland National Forest, Santa Ysabel Ranch Preserve, and the Multi-Species Planning Area (MSCP) of eastern San Diego County.

Several survey methods are being utilized to conduct these bat inventories including 1) use of mist-nets to capture bats at foraging and roosting sites, 2) use of hand-nets to capture bats at day and night roosts, 3) use of acoustic techniques including Anabat bat detectors and audible listening to detect bats at foraging and roosting sites, and 4) use of artificial lights to visually inspect for bats at roost sites and to visually observe foraging bats. Most of the survey effort has occurred from May through September, however, surveys are being conducted year-round with a reduced but consistent, almost weekly, effort throughout the fall, winter, and spring.

As of February 1, 2003 a total of 17 of the 23 bat species known from San Diego County have been detected during the USGS bat inventory studies. Thirteen of these 17 species have been documented by capture at roosting and/or foraging sites, with the remaining four species having been detected only acoustically.

Western red bat. Photo courtesy of Merlin D. Tuttle © Bat Conservation International.
Photo courtesy of Merlin D. Tuttle © Bat Conservation International.
Click on a common name in the table below to see images (photos or sonograms) of the species that have been detected during these studies. Photos on the web pages for the various species below were taken by Drew Stokes and Cheryl Brehme of USGS unless otherwise noted.

Common NameScientific NameStatus1Detected 20022
Phyllostomatidae (American Leaf-nosed Bats)
California leaf-nosed batMacrotus californicusCSC,FSS,BLMA,V
Mexican long-tongued batChoeronycteris mexicanaCSCV
Lesser long-nosed batLeptonycteris curasoaeFENot Detected
Vespertilionidae (Mouse-eared Bats)
Little brown batMyotis lucifugusnoneNot Detected
Yuma myotisMyotis yumanensisFSC,BLMA,C,V
Long-eared myotisMyotis evotisFSC,BLMA,C,V
Fringed myotisMyotis thysanodesCSC*,FSC,BLMA,C
Long-legged myotisMyotis volansCSC*,FSC,BLMNot Detected
California myotisMyotis californicusnoneA,C,V
Small-footed myotisMyotis ciliolabrumFSC,BLMA,C,V
Silver-haired batLasionycteris noctivagansnoneNot Detected
Western pipistrellePipistrellus hesperusnoneA,C,V
Big brown batEptesicus fuscusnoneA,C,V
Red batLasiurus blossevilliiCSC*,FSSA,C
Yellow batLasiurus xanthinusCSC*Not Detected
Hoary batLasiurus cinereusnoneA,C
Spotted batEuderma maculatumCSC,FSC,BLMNot Detected
Townsend's big-eared batCorynorhinus townsendiiCSC,FSC,FSS,BLMA,C,V
Pallid batAntrozous pallidusCSC,FSS,BLMA,C,V
Molossidae (Free-tailed Bats)
Mexican free-tailed batTadarida brasiliensisnoneA,V
Pocketed free-tailed batNyctinomops femorosaccusCSCA
Big free-tailed batNyctinomops macrotisCSCA
Western mastiff batEumops perotisCSC,FSC,BLMA

1Legal Status categories include California Species of Special Concern (CSC), species proposed to become California Species of Special Concern (CSC*, Betsy Bolster pers. comm.),Federal Species of Special Concern (FSC), Forest Service Sensitive (FSS), and Bureau of Land Management Sensitive (BLM), and Federally Endangered (FE). Source: Calif. Dept. of Fish and Game, Special Animals List, July 2002.
2Detection method: A = Acoustic, C = Mist-net capture, V = Visual observation in roost

Last update: 17 March 2003