The little brown bat (Myotis lucifugus) has a widespread range in North America from Alaska-Canada boreal forests south through most of the contiguous United States and into central Mexico. This species was once very abundant, but has experienced severe declines particularly in eastern North America due to white-nose syndrome, a novel fungal disease. This species is also subject to significant mortality by turbines at wind energy facilities. The little brown bat is still common in much of the historical range, apart from northeastern North America, but at least some of these populations may be subject to declines in the foreseeable future. The U.S. Fish and Wildlife Service is currently reviewing the status of the little brown bat as a result of these described threats.
Little brown bats use a wide range of habitats and often use human-made structures for resting and maternity sites. They typically roost in caves and mines in the winter, and they can be found in trees, artificial structures, bat houses, under rocks and in piles of wood in the summer. Foraging habitat requirements are generalized, occurring primarily over streams and other bodies of water, along the margins of lakes and streams or in woodlands near water. Winter hibernation sites like caves, tunnels and abandoned mines generally have a relatively stable temperature of about 2 to 12 Celsius, as documented by T.H. Kunz and J.D. Reichard in 2010. Maternity colonies commonly are in warm sites in buildings, like attics, bat houses, other human structures, and infrequently, in hollow trees.
A dense growth of trees and underbrush covering a large tract.
A natural chamber or series of chambers in the earth or in the side of a hill or cliff. An irregular limestone region with sinkholes, underground streams and caverns.
A considerable inland body of standing water.
A landmass that projects conspicuously above its surroundings and is higher than a hill.
A natural body of running water.
Of or relating to cities and the people who live in them.
Environments influenced by humans in a less substantial way than cities. This can include agriculture, silvaculture, aquaculture, etc.
Areas such as marshes or swamps that are covered often intermittently with shallow water or have soil saturated with moisture.
Areas where ground water meets the surface.
The diet of the little brown bat consists of a wide variety of flying insects, including mosquitoes, midges, caddisflies, moths, various hoppers, small beetles and spiders, as documented by J.O. Whitaker, Jr. and B. Lawhead in 1992. The wide and diverse prey selection for this species may have allowed the broad geographic distribution, as noted by L.A. Kaupas and R.M.R. Barclay in 2017. Individuals in the extreme northwest region of the range may consume more terrestrial insects, because flying insects are less available, as documented by R.P. Shively and others in 2018.
Little brown bats primarily hibernate in caves and cave-like structures. They emerge from hibernation and disperse on the landscape for the summer and early fall. Females begin to form maternity colonies that can consist of two to more than 100 individuals. Females may form maternity colonies in large tree cavities, attics or bat houses. Males often roost under exfoliating bark, within tree trunks and within tree cavities of live and dead trees during the summer. Males have also been observed roosting in human-made structures during the summer.
Large numbers of individuals may swarm around caves or mines in late summer and mating typically occurs in the fall. Females store sperm during the winter, a process known as delayed fertilization. Females typically give birth to a single pup in May or June after 50 to 60 days of gestation. The young are able to fly in about four weeks.
Bats of this species are known to live up to 30 years.
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