Bats in Buildings
Common Roosting Species

Common Roosting Species


Bats Most Likely to Occupy Bat Houses in the United States and Canada

Throughout the northern two-thirds of the United States and southern Canada, the little brown myotis and big brown bat are the most likely species to be encountered in bat houses. In the southern United States, Mexican free-tailed, south-eastern myotis and evening bats are most common. Almost any bat that will roost in buildings or under bridges is a candidate for a bat house. These species have been documented as bat house users:

credit: MerlinTuttle.org
Pallid bat
Antrozous pallidus
Western and southwestern United States and extreme south-central British Columbia, mostly in arid areas. Roosts in various human structures such as bridges, barns, porches, bat boxes, and human-occupied as well as vacant buildings. Winter habitat unknown, presumed to hibernate locally in deep rock crevices.
credit: MerlinTuttle.org
Jamaican fruit-eating bat
Antrozous pallidus
North America’s only fruit-eating bat, this species occurs in the lower Florida Keys, and occasionally uses buildings throughout its range.
credit: MerlinTuttle.org
Mexican long-tongued bat
Choeronycteris mexicana
Occasionally roosts in human structures, but is easily disturbed and will readily flee.
credit: MerlinTuttle.org
Rafinesque’s big-eared bat
Corynorhinus rafinesquii
These bats are known to form nursery colonies in large hollow trees, but as trees in the swamps of the southeastern U.S. have been harvested, they have moved their maternity roosts into old buildings or attics.
credit: MerlinTuttle.org
Townsend’s big-eared bat
Corynorhinus townsendii
Females form maternity colonies in mines, caves or buildings..
credit: MerlinTuttle.org
Big brown bat
Eptesicus fuscus
One of the most widespread bats in North America, found across most of the United States and Canada, except for extreme southern Florida and south and central Texas. Maternity roosts are commonly found across North America in buildings, barns, bridges and bat houses. These bats are cold-hardy and occasionally are found hibernating in caves, abandoned mines and buildings in winter. Frequent bat house users, they have overwintered in bat houses from Texas to New York.
credit: MerlinTuttle.org
Florida bonneted bat
Eumops floridanus
Florida’s largest and rarest bat may be one of the most critically endangered mammals in North America, listed as Critically Endangered by the IUCN. Today this bat is only known to occupy a few bat houses, an abandoned house, and a few tree cavities in south Florida. At least one maternity colony was confirmed using a bat house with a 11⁄2-inch chamber.
Please see our Florida bonneted bats in buildings guide, in English or Spanish to learn how you can protect the Florida bonneted bat in your home or bat box.
Guide [English]
Guide [Spanish]
credit: MerlinTuttle.org
Greater bonneted bat
Eumops perotis
This is the largest bat in North America, north of Mexico, with a wingspan approaching two feet. It is known to roost in human structures in parts of its range.
credit: MerlinTuttle.org
Silver-haired bat
Lasionycteris noctivagans
A solitary tree-roosting bat that usually day-roosts behind loose bark but has been found roosting in open sheds, garages and outbuildings, in woodpiles and on fence posts. Sometimes hibernates in buildings.
credit: MerlinTuttle.org
Lesser long-nosed bat
Leptonycteris yerbabuenae
These bats feed exclusively on the fruit and nectar of night-blooming cacti including saguaro and organ pipe, as well as many species of agave. They are both pollinators and seed-dispersers, and are known to night-roost after feeding in open buildings like barns and carports.
credit: MerlinTuttle.org
California leaf-nosed bat
Macrotus californicus
These bats may night-roost in open buildings, cellars, porches, bridges, rock shelters, or shallow mines and caves.
credit: MerlinTuttle.org
Peters’s ghost-faced bat
Mormoops megalophylla
These bats most often roost in caves, rock crevices and abandoned mines, but also occasionally move into old buildings.
credit: MerlinTuttle.org
Pallas’s mastiff bat
Molossus molossus
In the United States, this species is found only the Florida Keys where they roost in the roof spaces of flat-roofed buildings. Individuals have been found roosting in palm fronds. Throughout the Caribbean, northern Mexico, Central America and northern South America, its roosts include hollow trees, palm fronds, rock crevices, caves, bridges, culverts and buildings. Uses bat houses year-round in Cayman Islands and Puerto Rico.
credit: MerlinTuttle.org
Southwestern myotis
Myotis auriculus
Southwestern myotis have been found night-roosting in buildings, mines and caves.
credit: MerlinTuttle.org
Southeastern myotis
Myotis austroriparius
Mostly restricted to Gulf Coast states. Rears young in caves, tree hollows, buildings, bridges, culverts and bat houses. Often non-migratory, hibernates in caves in its northern range and sometimes in tree hollows or buildings farther south. Confirmed bat house user in Florida and Georgia; believed to use bat houses in other Gulf states.
credit: MerlinTuttle.org
California myotis
Myotis californicus
California myotis are known to form small maternity colonies in cliff crevices, buildings and bridges.
credit: MerlinTuttle.org
Western small-footed myotis
Myotis ciliolabrum
These bats have been found, in Arizona, roosting under loose bark on trees and in buildings. In Montana, small maternity colonies were found in buildings, caves and mines. One of only two western forest bats that have been found regularly roosting at ground level.
credit: MerlinTuttle.org
Long-eared myotis
Myotis evotis
Primarily in forests of southwestern Canada and the western United States. Often lives alone or in small groups; females form small maternity colonies in summer. Roosts in hollow trees, under bark, in cliff crevices, timbers of unused railroad trestles, caves, mines and abandoned buildings. Confirmed bat house user in Washington. Day roosts have been found in New Mexico in buildings and mine tunnels. Winter habitat unknown. This western forest bat that roosts regularly at ground level.
credit: MerlinTuttle.org
Gray myotis
Myotis grisescens
One of the first bat species listed as Endangered by the U.S. Fish and Wildlife Service, 95% of the known population roosts in just nine U.S. caves. Over the years, a few colonies, two of them maternity colonies, have been found roosting in storm sewers, and there have been a few reports of Gray myotis roosting in mines and buildings.
credit: MerlinTuttle.org
Eastern small-footed myotis
Myotis leibii
This is the smallest myotis species in the eastern U.S. Nursery colonies of 12-20 bats are sometimes found in buildings.
credit: MerlinTuttle.org
Little brown myotis
Myotis lucifugus
Wooded areas throughout most of Canada and the northern half of the United States, except desert and arid areas. A few isolated populations farther south. Rears young in tree hollows, buildings, rock crevices and bat houses. This is one of the species most commonly found in bat houses. Travels to nearest suitable cave or abandoned mine for hibernation. This species is especially associated with humans, often forming nursery colonies containing hundreds, sometimes thousands of individuals in buildings, attics and other man-made structures. Little brown myotis has been heavily impacted by White-nose Syndrome, resulting in this once-abundant species becoming uncommon throughout much of its eastern range.
credit: MerlinTuttle.org
Dark-nosed small-footed myotis
Myotis melanorhinus
Widespread across western North America, from central Mexico to British Columbia, Canada. Most scientists consider this bat to be a sub-species of M. ciliolabrum (Western small-footed myotis), but IUCN designated species status in 2008. They hibernate in caves and abandoned mines.
credit: MerlinTuttle.org
Arizona myotis
Myotis occultus
Some subpopulations of this species have apparently declined or been eliminated. One or two of the three or four known maternity colonies in Arizona have been eliminated, and another has been partially excluded from available buildings. Maternity colonies have been found in the attics of abandoned houses and in crevices between timbers of a highway bridge. A few individuals have been found hibernating in mines in California and Sonora.
credit: MerlinTuttle.org
Northern long-eared myotis
Myotis septentrionalis
Found in the Upper Midwest, eastern, and some southern states and into Canada. Summer roosts vary. This species, in some parts of their North American and Canadian range, form maternity roosts in buildings and bat houses. Hibernation sites are caves and underground mines. They have also been found roosting beneath tree bark, in rock crevices, as well as caves and mines.
This species is heavily impacted by White-nose Syndrome and in 2015 the species was listed as Threatened by the U.S. Fish and Wildlife Service.
credit: MerlinTuttle.org
Indiana myotis
Myotis sodalis
One of the earliest bat species designated Endangered by the U.S. Fish and Wildlife Service, hibernating populations of Indiana myotis occur in just three states: Kentucky, Missouri and Indiana, where they form large, highly vulnerable aggregations. In summer, these bats mostly rear their young under loose bark or in tree hollows, but rare maternity colonies have been found in utility pole crevices and bat boxes. Occasionally they use buildings, bridges and bat houses; reported in bat houses in Illinois, Indiana and Pennsylvania. This species is associated mainly with forests and limestone caves.
credit: MerlinTuttle.org
Fringed myotis
Myotis thysanodes
Night and day roosts of the fringed myotis include caves, mines and abandoned buildings. Little is known about their whereabouts during winter, but they sometimes hibernate in caves and buildings.
credit: MerlinTuttle.org
Cave myotis
Myotis velifer
Found in southern California and Arizona into central Texas, Oklahoma and south-central Kansas. This species forms nursery colonies, usually numbering in the thousands, in caves, mines, barns, buildings and sometimes under bridges, making them very susceptible to human disturbance. The eastern subspecies hibernates in caves, but the winter habitat of the western subspecies is unknown. Shares bat houses with Mexican free-tailed bats in Texas.
credit: MerlinTuttle.org
Long-legged myotis
Myotis Volans
This species roosts in trees and rock crevices, and in buildings, and hibernate in caves and mines.
credit: MerlinTuttle.org
Yuma myotis
Myotis yumanensis
Found in southern British Columbia, Washington, Idaho, Oregon, California, Arizona, extreme western Nevada, eastern Utah, southern Wyoming to western New Mexico. Though occasionally roosting in mines or caves, Yuma myotis are most often found raising their young in buildings or bridges. Winter habitat unknown. Usually found in areas near water. Lives in bat houses from Arizona to British Columbia. Bachelors sometimes roost in abandoned cliff swallow nests.
credit: MerlinTuttle.org
Evening bat
Nycticeius humeralis
Evening bats get their common name from being one of the first bat species to emerge and forage in the early evening. They are true forest bats, almost never found in caves. Nursery colonies form in hollow trees, behind loose bark, and in buildings and attics. Nursery colonies often share roosts with Mexican free-tailed bats. Winter habitat largely unknown, but often found in buildings and bat houses.Found east of the Appalachians, ranges from southern Pennsylvania to Florida; west of the mountains, from southern Michigan and Wisconsin into Nebraska and south into Texas.
credit: MerlinTuttle.org
Pocketed free-tailed bat
Nyctinomops femorosaccus
These bats mainly live in desert areas and roost in crevices high on cliff faces, but sometimes also use buildings.
credit: MerlinTuttle.org
Big free-tailed bat
Nyctinomops macrotis
Desert and arid grassland bats, they typically inhabit rocky out-crops, canyons and cliffs, but occasionally will roost in buildings.
credit: MerlinTuttle.org
Canyon bat
Parastrellus hesperus
Formerly known as the western pipistrelle, the canyon bat day-roosts in rock crevices, beneath rocks, in burrows, mines and buildings. They hibernate in mines, caves and rock crevices.
credit: MerlinTuttle.org
Tri-colored bat
Perimyotis subflavus
Found in eastern North America into Canada, except northern Maine, and south to Texas and central
Florida. In summer, the tri-colored bat roosts in rock crevices, caves, buildings and tree foliage. Several tri-colored bats have been reported in bat houses. In the fall, they are sometimes found roosting on apartment building walls, especially on upper levels that are open on both ends. Hibernation occurs deep within caves and mines. Because they prefer humid hibernation sites, tri-colored bats are impacted by White-nose Syndrome.
credit: MerlinTuttle.org
Mexican free-tailed bat
Tadarida brasiliensis
Common in southern and southwestern United States and north to Nebraska, Colorado, Utah, Nevada and Oregon. The largest maternity colonies are found in limestone caves, but they also roost in large numbers in abandoned mines, under bridges and in buildings. Smaller colonies have been found in hollow trees and frequently in bat houses. Many populations migrate south to overwinter in Mexico and Central America, although colonies in the southeastern U.S. and West Coast typically do not migrate. The densest concentrations of this migrating species are found in Texas, where maternity colonies number in the millions of individuals. Active year round.

RECOGNIZE THE SIGNS OF ROOSTING BATS

It is usually not necessary to enter an attic, basement or other areas to look for bats in structural voids (the spaces between exterior and interior envelopes of a building). Evidence that bats are occupying voids includes seeing them entering or exiting a roost, staining and guano accumulations near active roost entries, audible roost chatter (high-pitched chirping), a distinct musky odor, or repeatedly finding bats on the ground or roosting on an exterior wall.

 

CREDIT: Austin Bat Refuge

 

The size and shape of bat guano differs among bat species, but what all insect-eating bat guano have in common is the presence of shiny insect parts in the droppings, and the dry, crumbly texture. Bat guano can sometimes be confused with gecko, lizard, frog or rodent droppings. Rodent droppings are similar in color and size, but are hard and not easily crushed. Gecko droppings are soft and easily crushed, but pellets are tipped with white uric acid deposits not found on bat guanos.

 

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