Little brown bats are just as their name suggests. These long-lived bats are abundant across most of North America, their numbers having grown with the increased availability of suitable roosting sites, such as attics and mines, provided by the ever-growing human population.

Life span
Up to 33 years, males living longer than females.

Statistics
Wing span 222-269mm,

Physical description
Little brown bats can be a variety of colours. Their glossy fur coats can be pale tan, reddish brown, olive brown, dark yellowish brown or dark brown, with a paler coloured underside. They have small black ears and hairy toes (hairs extend further than their claws).

Distribution
North America. Highest concentrations in the northern states, southern Canada and southern Alaska. Also a few in Northern Mexico.

Habitat
Temperate forest and rainforest, temperate grassland, mountains.

Diet
Little brown bats are insectivores, eating organisms such as moths, wasps, beetles and gnats. Prey are detected by echo-location, caught on the bat's wingtips, transferred to a cup formed by curling the bat's tail forwards and then grabbed in the teeth. The bats aren't always successful at catching prey, so may enter a state of 'torpor' (short term hibernation) during the day whereby their metabolism is reduced to conserve energy.

Behaviour
During April and May females congregate in large maternity colonies of up to 1000 individuals in warm dark attics or similar places. Males join the females later on in the summer after a solitary winter existence. Once the young are weaned the adults disperse to their summer ranges. The bats stay alert on warm days, but do not emerge from their roosts to feed until dusk. Individuals follow the same flight path when foraging, returning to the roost at dawn.

Reproduction
Little brown bats were originally thought to be promiscuous, although it is now thought that mating is biased towards particular males. Although mating occurs in autumn and early winter, fertilisation does not occur until the spring months when the bats come out of hibernation. The male's sperm is stored and kept viable in the females uterus over the winter months. Gestation lasts for 50-60days, with births occurring from May to mid July. Females usually give birth to one young a year, but will occasionally have twins. The female gives birth by hanging head first and forming a cup with her tail to catch the young. The blind infant will then find its way to one of her nipples and stay there for about 2 weeks until it is half grown. The infant opens its eyes on the second day, can fly after three weeks and is fully grown by 4 weeks.

Conservation status
They are not listed by the 2000 IUCN Red List.