|The Mammals of Texas -
Chiroptera : Family
Vespertilionidae : Pipistrellus subflavus (F.
Description. A small bat with leading
edge of wing and the edges of the membrane between the
hind legs much paler than rest of membranes; tragus long
and slender; upperparts pale yellowish brown, with
grizzled effect; the individual hairs tricolored, dark
basally, grayish-yellow medially, and tipped with dusky.
Dental formula: I 2/3, C 1/1, Pm 2/2, M 3/3 X 2 = 34.
External measurements average: total length, 85 mm; tail,
41 mm; foot, 8 mm; ear, 14 mm; forearm, 35 mm. Weight,
Distribution in Texas. Eastern half of
state including the Rolling Plains west to Armstrong
County and central Texas as far west as Val Verde County,
and a recent record from Lubbock County.
Habits. These small bats are
some of the earliest to emerge in the evening from their
daytime retreats in caves, crevices in cliffs, buildings,
and other man-made structures offering concealment. They
are relatively slow and erratic in flight and often
flutter and flit along watercourses or over pastures and
woodlands like large moths. They appear to favor
watercourses as foraging grounds. They are much more
closely associated with woodlands than is the western
This species is known to spend the
winter hibernating in suitable caves within its summer
range. Its hibernation is more complete than that of most
other American bats and they generally roost singly or in
small groups. Individuals may hang in one spot for weeks
on end, and their torpor is so deep that they are not
easily disturbed. They emerge from hibernation early in
the spring and remain active well into the fall.
Little is known of their food habits in
Texas. In Indiana they are known to eat small
leafhoppers, ground beetles, flies, moths, and ants.
Insects are caught by the bats in considerable quantities
in a short period and within 20 minutes they are gorged.
They probably feed at intervals throughout the night and
hang up to digest their meals between feeding times.
Mating takes place in the fall. They
have been observed copulating as late as November. Both
males and females have been observed roosting together as
early as August, however. During the period from March to
August adult males and females usually occupy separate
roosts. Data suggest that the sperm may remain viable in
the vaginal tract of the female until spring, when
ovulation occurs (in March or April) and fertilization of
the ova takes place. However, copulation in the spring
also has been observed.
The exact period of gestation is not
known, but it probably does not begin until the bats have
left their winter quarters. The young, usually two in
number, are born from May to July. They grow rapidly and
when about 3 weeks old are able to take care of
Photo credit: John L. Tveten.