O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
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nas Mountains of New Mexico, Chung-MacCoubrey (1996) found maternity colonies numbering 
3CMK) individuals roosting in ponderosa pine snags or live ponderosa pines with long, vertical 
cracks and loose bark. These trees were in isolated stands or “stringers” along arroyos, and at the 
pinyon-juniper woodland-ponderosa pine forest ecotone. Year-to-year reuse of roosts in trees was 
documented (Chung-MacCoubrey, 2003). 
Warm Season Roosts in Caves, Mines, Buildings, and Bridges: Fringed myotis will also 
roost in caves and mines during warm seasons. Nursery clusters numbering 400-500 in each clus¬ 
ter were noted in “several rooms” of a cave in Chihuahua, Mexico near Big Bend National Park 
(Easterla, 1973:41). A “semi-dormant” clump of 18 adult males was observed in mid-August in a 
mine tunnel in oak-walnut-sycamore habitat in the Huachuca Mountains of southeastern Arizona, 
and a colony of adult females and young were found at a separate mine at the lower edge of the 
oak belt; these bats were also taken at the lower edge of the pine belt (Hoffmeister and Goodpaster, 
1954). A colony of about 250 females and young was observed in a cave in the Chiricahua Moun¬ 
tains of Arizona in 1954, with about 50 seen at this location the following summer (Cockrum and 
Ordway, 1959). About 2,000 individuals were observed roosting during summer in an abandoned 
mine in the Santa Rita Mountains of Arizona, with other colonies also reported using other aban¬ 
doned min es during summer in the same region (von Bloeker, 1967). Two colonies of unspecified 
function numbered up to 121 individuals in one Arizona cave and up to 71 bats in a second cave 
during summer (Arizona Game and Fish Department data cited in Ellison et al., 2003). 
Banding records of fringed myotis from roosts in Mohave County, Arizona indicated strong 
year-to-year fidelity to colonial roosts in abandoned mine tunnels (Cockrum et al., 1996). 
Altenbach and Sherwin (2002) report a decline of a maternity colony at a New Mexico cave from 
over 500 adult females in 1990 to zero bats in 2001, while an abandoned mine about eight kilo¬ 
meters distant became occupied instead, apparently through displacement of the colony in the cave 
by disturbance. An abandoned mine with unusually cool temperatures was used as a roost during 
June when females were pregnant, and this use was suggested to be a possible mechanism to induce 
an embryonic diapause (Altenbach et al., 2000); they are known to give birth in maternity colonies 
with a high degree of synchrony among individuals (O’Farrell and Studier, 1973). In late summer 
and early fall, dormant bats were found roosting solitarily or in very small groups in several aban¬ 
doned mine tunnels in Mohave County, Arizona (Cockrum et al., 1996). 
Fringed myotis will also roost in buildings and bridges during warm seasons. The species was 
discovered and named in part based on specimens from the attic of an adobe building that housed 
a maternity colony at Old Fort Tejon, California in 1891 (Miller, 1897). This building was re-vis- 
ited in 1904, but the colony was absent (Grinnell, 1918); in 1945, three were captured at 0300 h 
returning to the building to roost (Dalquest and Ramage, 1946). A colony of about 50 adults and 
young was documented using the roof of a building near Angwin, Napa County, California in July 
1945 (Dalquest 1947a), and smaller numbers were reported from attics in Kem, Santa Cruz, and 
San Mateo counties (Dalquest, 1947b). A maternity colony of about 200 was reported from the attic 
of a building in northern New Mexico at about 2,040 meters elevation during late June 1967 (Studi¬ 
er, 1968). This colony was later reported to consist of 1,000 to 1,200 individuals (nearly all adult 
females and young) in 1970 (O’Farrell and Studier, 1975). Bridges were found to house both diur¬ 
nal- and night-roosting bats in the central Sierra Nevada of California (Pierson et al., 2001). Only 
a single transient individual was reported roosting under a bridge over the Rio Grande in southern 
New Mexico, despite multiple surveys of 17 bridges over a two-year period when many individu¬ 
als of several other species were recorded (Geluso and Mink, 2009). 
Night Roosts: Fringed myotis are well known to use night roosts in caves, buildings, mines, 
and other sites not used as diurnal roosts. As examples, they were documented night-roosting in 
buildings at two locations in Kem County, California (Dalquest and Ramage, 1946; Dalquest, 
