Little brown bat

Little brown bat
Conservation status
Least Concern (IUCN 2.3)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Chiroptera
Family:	Vespertilionidae
Subfamily:	Myotinae
Genus:	Myotis
Species:	M. lucifugus
Binomial name
Myotis lucifugus (LeConte, 1831)

The little brown bat (sometimes called little brown myotis) (Myotis lucifugus) is one of the most common bats of North America, a species of the genus Myotis (mouse-eared bats), found throughout the world.

Description

As suggested by the bat’s name, its fur is uniformly dark brown and glossy on the back and upper parts with slightly paler, grayish fur underneath. Wing membranes are dark brown on a typical wingspan of 22–27 cm (8.7–11 in).^[1] Ears are small and black with a short, rounded tragus. Adult bats are typically 6–10 cm (2.4–3.9 in) long and weigh 5–14 grams (0.2–0.5 oz). All teeth including molars are relatively sharp, as is typical for an insectivore, and canines are prominent to enable grasping hard-bodied insects in flight.

Diet

Little brown bats are insectivores, eating moths, wasps, beetles, gnats, mosquitoes, midges and mayflies, among others. Since many of their preferred meals are insects with an aquatic life stage, such as mosquitoes, they prefer to roost near water. They echolocate to find their prey. Often they will catch larger prey with a wingtip, transfer it to a cup formed by their tail, then eat it - smaller prey are usually just caught in the mouth. They often use the same routes over and over again every night, flying 3-6 meters high above water or among trees. An adult can sometimes fill its stomach in 15 minutes; young have more difficulty. If they do not catch any food, they will enter a torpor similar to hibernation that day, awakening at night to hunt again.

Distribution

The little brown bat is found all over North America from northern Mexico to interior Alaska. It is the most abundant bat found in the United States and Canada.

Life Cycle

Little brown bat roosting in the eaves of a home in Pennsylvania. Brown bats frequently dwell in man-made structures.

Since little brown bats live in a temperate zone, they must find some way of dealing with winter. Most temperate bats either migrate or hibernate, but little brown bats do both. In summer, the males and females live apart, the females raising young. When fall comes, both genders fly south to a hibernaculum, where they mate and then hibernate.

Little brown bats undergo a prolonged period of hibernation during the winter due to the lack of food. They hibernate in caves as a community. Little brown bats mate in the autumn, before hibernation begins, and over winter the male's sperm is stored inside the female's body, and the infant is conceived in spring. When they arise in the spring, the females go to nursery colonies which may often be the same place where they were born.

These nursery colonies consist mainly of adult females and their young and can be located in the attics of warm buildings where there is high humidity. Gestation is 50-60 days. They usually have one baby per female each year, sometimes twins, born sometime from late May to early July. The young are born in an altricial state with their eyes closed and will hang in the nursery while their mothers forage at night. Their eyes open on their second day. They cling to a nipple constantly until they are two weeks old. At 3 weeks, they learn to fly. By 4 weeks, they are adult size.

The number of males in the nursery increases in September, and in October all of the bats migrate back to the caves to hibernate. They use the same hibernaculum and summer colonies year after year, except for yearling males going to the male summer colony upon reaching adulthood. While the females are at the nursing colonies during the summer, males roost in small groups in rock crevices or tree hollows.

Females may be sexually mature in the fall after their birth, but males may take a year longer. About half of females and most males breed in their first autumn. They can live up to 33 years, males living longer on average, though the average lifespan is shorter since about 50% of little brown bats die in their first year.

Social Status

The nursery colonies sometimes get to numbers as big as 1000 bats in one cave/forest.

Endangered Status

Little brown bats are not listed as endangered and have no special conservation status. Man-made roosting areas such as attics, caves and mines assist their particular abundance. Many states, though, have made special considerations for brown bats including listing them as a sensitive or protected species. Little brown bats are now at a higher threat due to white nose syndrome in eastern North America.

Genome Projects

The genome of M. lucifugus has already been sequenced at low (2x) coverage for the Mammalian Genome Project. It has also been selected for more complete (approximately 7x coverage) genome sequencing. This species is also part of the ENCODE comparative sequencing project.

External links

• Ohio Department of Natural Resources Life History Notes: Little Brown Bat
• Wild About Gardening.org's page on Little Brown Bats
• BBC - Science & Nature - Wildfacts - Little brown bat
• Little Brown Bat - Colorado Division of Wildlife
• Bat Man vs. White Nose, article with video, Sept 10, 2009

References

2. Eisenberg, John F. The Mammalian Radiations: An Analysis of Trends in Evolution, Adaptation, and Behavior. The University of Chicago Press: Chicago, 1981.