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Little Brown Bat

Myotis lucifugus

Little brown bats can be golden, reddish, olive or dark brown with a dark brown or black face. (Garrett & Kitty Wilkins/Flickr)
Little brown bats can be golden, reddish, olive or dark brown with a dark brown or black face. (Garrett & Kitty Wilkins/Flickr)

The little brown bat is a small, mostly nocturnal flying mammal with long, brownish fur. It lives in buildings, trees, caves and similar areas throughout the Chesapeake Bay watershed.


  • Long, glossy fur that can be golden, reddish, olive or dark brown
  • Dark brown or black face, ears and wing membranes
  • Small ears that usually do not extend past the nose when laid forward
  • Large hind feet with long hairs that extend past the tips of the claws
  • Usually grows to about 3.5 inches with a wingspan of 9-11 inches
  • Usually weighs less than half an ounce
  • Females are slightly larger than males


  • Occupies different “roosts” depending on temperature and time of year
  • Spring, summer and autumn roosts include trees, buildings (mostly hot, dry attics or under shingles, shutters and siding), wood piles and under rocks.
  • Day roosts have little to no light and usually have a southwestern exposure to provide heat
  • Night roosts are typically confined spaces where many bats can cluster together to increase the temperature
  • Usually lives close to water
  • In winter, hibernates in caves and abandoned mines with high humidity and above-freezing temperatures
  • Nocturnal, like all other bats


  • Found throughout the entire Chesapeake Bay watershed


  • Mainly eats aquatic insects such as midges, mayflies and caddisflies
  • Also eat gnats, beetles, wasps, moths and crane flies
  • Feeds in fields, wooded areas, and near or over water while flying
  • Will also eat insects while they are on the water’s surface
  • Most feeding takes place about two hours after dark
  • Typically consumes half its body weight in insects every night. Nursing females may consume up to 110 percent of their body weight.
  • Uses echolocation – short, ultrasonic calls that humans cannot hear – to detect prey


  • Domestic cats are a major predator
  • Other predators include small carnivores such as mice, owls, hawks, snakes, weasels, martens, fishers and raccoons


  • Usually flies about 12 miles per hour, but can fly as fast as 21-22 miles per hour


  • Uses echolocation to orient itself, as well as to locate, track and evaluate its prey
  • Calls typically last about 4 milliseconds
  • While cruising, emits calls about 20 times per second; quickens to 200 times per second when attacking airborne prey
  • Most bat calls are beyond the range of human hearing, so humans need bat detectors to hear them
Little Brown Bat courtesy of Bat Call: Acoustic Call Library and Species Accounts

Reproduction and Life Cycle:

  • Mating occurs between random adult bats during late summer and early autumn in two phases: active and passive
  • During the active mating phase, both partners are awake and alert. Females in this phase usually mate with more than one male.
  • During the passive mating phase, active males mate with torpid bats of both sexes
  • Females delay ovulation, storing sperm for seven months between insemination in autumn and fertilization in spring
  • Gestationperiod is 50-60 days, with pups born between June-July
  • During this time, females roost in nursery areas that are typically only occupied by females and their young
  • Males play no role in parental care
  • Females give birth to just one pup per year
  • Young spend their first few weeks clinging to their mother’s nipple using their teeth and claws
  • Young are able to hear by day 2 and develop adult-like sensitive hearing by day 13
  • After three weeks, young are able to fly, and within four weeks of birth young are independent from their mothers
  • Usually lives 6-7 years, but can live for 10 or more years

Other Facts:

  • Also known as the little brown myotis
  • Spends a large amount of time every day grooming its fur and wing membranes
  • During the day and throughout the winter hibernation, little brown bats enter torpor: a state of reduced body activity in which temperature, breathing, heart rates and other bodily functions are lowered to conserve energy.

Sources and Additional Information:


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