||The Mammals of Texas -
Chiroptera : Family
Vespertilionidae : Lasionycteris noctivagans (Le
Description. A medium-sized, nearly black
bat with dorsal surface of interfemoral membrane densely
furred at least on the basal half and usually to near
margins; upper and lowerparts sooty brown or black with
white tips of hairs producing a frosted appearance;
membranes and ears sooty brown or black. Dental formula:
I 2/3, C 1/1, Pm 2/3, M 3/3 X 2 = 36 (upper incisors and
first lower premolar very small and easily overlooked).
External measurements average: total length, 100 mm;
tail, 40 mm; hind foot, 8 mm; ear, 16 mm; forearm, 41 mm.
Weight, 8-12 g.
Distribution in Texas. Broadly but
erratically distributed across northern North America;
recorded from six physiographic regions of Texas
(Pineywoods, Gulf Coastal Plains, Edwards Plateau,
Rolling Plains, High Plains, and Trans-Pecos, where it
apparently is a fall-spring migrant).
Habits. These bats are denizens
of forested areas and seldom are observed in xeric areas
except in migration. Cavities in trees and spaces under
loose bark are favorite daytime retreats but these bats
may also use buildings.
This species is migratory, at least in
part. It spends the summer in northern latitudes and
winters toward the south, even crossing several hundred
kilometers of ocean to reach Bermuda. Surprisingly few
winter records are available; thus, the mystery of just
where these bats spend the winter is still not completely
solved. It is likely that many of them winter on their
breeding grounds because occasional individuals have been
found hibernating as far north as New York and British
Columbia. Interestingly, most summer records of this bat
across the southwest are of males, suggesting that
geographical segregation of the sexes may occur during
the warmer months. Females appear to move north in spring
and summer to bear young, whereas the males remain behind
at more southern locales. A small population, apparently
comprised entirely of males, appears to be resident in
the Guadalupe Mountains (Culberson County) during summer.
This bat typically forages in or near
coniferous and/or mixed deciduous forests adjacent to
ponds or other sources of water. It is a relatively late
flier that often appears after other bats have begun
feeding. As with most other insectivorous bats, Lasionycteris
is opportunistic in its feeding habits and takes a wide
variety of small to medium-sized insects including moths,
bugs, beetles, flies, and caddisflies.
The one or two young are born in June
and July. Small maternity colonies may form in hollow
trees and abandoned bird nests. The young are black and
wrinkled at birth and are able to fly when about 3 weeks
Photo credit: Merlin D. Tuttle, Bat Conservation