Little Brown Myotis Little Brown Myotis
Myotis lucifugus
Little Brown Bat


Variable shades of glossy brown above, with tips of hairs burnished brown; buff below. Tragus rounded and short (about 1/4" or 7–8 mm). Calcar lacks keel or sometimes has weak keel. Hairs on toes project beyond ends of toes. Length 3 1/8"–3 5/8" (79–93 mm); Weight 1/16–1/2 oz (3.1–14.4 g).


Bats are susceptible to rabies, a serious viral disease that results in death if untreated. Rabid bats rarely attack humans or other animals, but bats found lying on the ground may be rabid. Never touch or pick up any bat. Stay away from any animal that seems to be acting strangely and report it to animal-control officers. If you are bitten by a possibly rabid animal, you must immediately consult a doctor for a series of injections; there is no cure once symptoms emerge.

Little Brown Myotis

Similar Species

In East, Southeastern Myotis often has white belly, as well as sagittal crest on skull; Indiana Myotis has prominent keel on calcar, and hairs do not project beyond ends of toes; Keen’s Myotis has longer ears and longer, thinner tragus. In West, Long-legged and California myotises have keeled calcar; Long-eared and Southwestern myotises have longer ears and longer, thinner tragus; Yuma Myotis has slightly shorter forearms and duller fur.


Mates in fall and sometimes again in winter or spring. Sperm remains in female’s reproductive tract until spring, when eggs are fertilized. 1 young born late May–early July, usually in a building, occasionally in a hollow tree.

Little Brown Myotis


Areas along streams and lakes. In summer, forms nursery colonies, usually in buildings or other structures. In winter, hibernates in caves and mines in the East.


Much of North America from middle Alaska south throughout most of Canada and U.S. except s California and much of se and sc U.S.


The Little Brown Myotis, whose nitrate-rich guano was sold as fertilizer in the first half of this century, is one of the most common bats in the U.S. and Canada. Nursery colonies begin forming in April or May and disperse from late July through October. They may number in the thousands (one observed maternity colony had 6,700 individuals, others have had 4,000). The first two to three days after the young are born, their mothers suckle them constantly, except while foraging. Until they are ready to fly on their own, at about four weeks, the young remain in the roost while the mother hunts for small insects, especially flies and moths. Bats usually do not carry their young in flight. However, if disturbed, the mother may take flight with the young, carrying it crosswise, with the infant’s mouth grasping one teat and its hindlegs tucked under the opposite armpit. Besides echolocation clicks, this species produces warning "honks" when on a collision course with other bats during feeding or near roosts. In the fall, these bats may fly several hundred miles to a hibernating site; they often can be seen swarming at cave entrances. From September, October, or early November through March or April, they hibernate in irregular clusters, some tight, some loose. They wake an average of once every two weeks during hibernation and may fly about outdoors on warm winter nights, but without feeding. They store about 1/16 ounce (2 g) of fat as winter sustenance, using nearly three-quarters of it during winter awakenings and emergence. The remainder must sustain them through the winter.