|The Mammals of Texas -
Chiroptera : Family
Vespertilionidae : Myotis thysanodes Miller
Description. A relatively large Myotis
with large ears and a distinct fringe of short, stiff
hairs on free edge of the membrane between hind legs;
tail from 75 to 81% of length of head and body; foot from
50 to 75% of length of tibia; ears projecting about 5 mm
beyond snout when laid forward; pelage full and about 9
mm long on the back; upperparts uniform warm buff, tips
of hairs shiny, bases fuscus black; underparts dull
whitish. Dental formula as in M. californicus. External measurements average: total length,
86 mm; tail, 35 mm; foot, 9 mm; ear, 16.5 mm; forearm, 43
Distribution in Texas. A western bat
known from Texas in the Trans-Pecos region in summer. Two
specimens have been captured from northwest Texas (Crosby
County), but these were probably seasonal migrants. The
fringed myotis has been captured in habitats ranging from
mountainous pine, oak, and pinyon-juniper to desert scrub
but seems to prefer grassland areas at intermediate
Habits. These bats roost in
caves, mine tunnels, rock crevices, and old buildings in
colonies that may number several hundred. This is a
highly migratory bat that arrives in Trans-Pecos Texas by
May, at which time it forms nursery colonies. These
colonies begin to disperse in October, and the winter
locales and habits of this bat remain a mystery.
This species appears late in the
evening to forage. They fly slowly and are highly
maneuverable, allowing the bats to forage close to the
vegetative canopy or about the face of small cliffs. No
data are available on their specific food habits in
Texas, but specimens from New Mexico contained mostly
The single young is born in late June
or early July after a gestation period of 50-60 days.
Gravid females captured on June 28 each contained a
single fetus nearly ready for birth. Immature individuals
have been found in July and August in colonies of adult
females. The young are able to fly at 16-17 days of age.
As with other species of Myotis, adult males and
females do not associate with each other in summer.
Photo credit: Merlin D. Tuttle, Bat Conservation
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