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  The Mammals of Texas - Online Edition

Little Brown Myotis
Order Chiroptera : Family Vespertilionidae : Myotis lucifugus (Le Conte)

Little Brown Myotis (Myotis lucifugus).  Photo by Merlin D. Tuttle, Bat Conservation International.Description. A small bat; hairs of back with long, glossy tips that produce a conspicuous sheen; pelage long and full, longest hairs about 10 mm; upperparts ranging from bronzy brown to olive brown; underparts grayish with rich, buffy suffusion; interfemoral membrane sparsely haired above about to line joining knees; foot relatively large, a little more than half the length of tibia; ratio of tail to head and body less than 80; dorsal profile of skull gradually rising from relatively short rostrum. Dental formula as in M. californicus. External measurements average: total length, 85 mm; tail, 35 mm; foot, 9 mm; ear, 13 mm; forearm, 39.5 mm. Weight, 7-9 g.

Distribution in Texas. This species is known in Texas by only one specimen (U.S. Nat. Mus., 21083/36121) from Fort Hancock in Hudspeth County.

Habits. This bat spends the daytime in crevices in canyon walls, caves, attics, or other places of concealment and emerges shortly before dark. Its flight is erratic and relatively slow.

In the northeastern United States, these bats may migrate up to 320 km between winter and summer ranges, but in the west they are believed to hibernate near their summer range. As cold weather approaches the bats move to suitable caves, mine tunnels, or other quarters where they hibernate and sleep through the winter. During the period of preparation for winter, males and females are found together and breeding takes place, but the ova are not fertilized at that time. This habit of breeding in the fall has led some students to estimate the gestation period of this species to be 300 days; however, the period of gestation is actually 50-60 days. The sperm from the fall mating are retained in the reproductive tract of the female and fertilization of the ova does not take place until the following spring, shortly before the bats leave their winter quarters. This ability is known as "delayed fertilization." A short breeding period may also occur in the spring. The single young is born in June or July.

Food consists of insects captured in flight. Remains of small, night-flying beetles, bugs, and flies have been identified in their stomachs. These bats forage primarily over or near water.

Photo credit: Merlin D. Tuttle, Bat Conservation International.