Myotis lucifugus

"Echolocation of little brown bats has been well studied since the invention of bat detectors, electronic devices that can ""hear"" the ultrasonic calls bats make, which are usually beyond the range of human hearing. Little brown bats typically produce calls lasting about 4 milliseconds. While cruising, they emit echolocation calls about 20 times per second, spacing the pulses at 50 millisecond intervals. When attacking airborne prey, the pulse rates rise drastically, to 200 per second, with only 5 millisecond gaps between calls. The information the bats receive through echolocation allows them to orient themselves, and to locate, track, and evaluate their insect prey. Little brown bats feed near or over water, mainly on aquatic insects such as caddis flies, mayflies, and midges, and typically consume half their body weight in insects each night. Nursing females may eat up to 110 percent of their body weight each night."

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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Wide range includes North America from the Alaska-Canada boreal forest south through most of the contiguous United States, though the species is generally absent fom the southern Great Plains region. Southwestern populations formerly assigned to this species have now been assigned to M. occultus (Piaggio et al. 2002; Wilson and Reeder 2005), so the southwestern boundary of the range includes southern California (except extreme southeast), Nevada, northern Utah, northern Colorado, and perhaps northeastern New Mexico (Piaggio et al. 2002; Valdez, pers. comm.).

The high density of caves in the Appalachian Mountain range and eastern Midwest (Culver et al. 1999) likely "support much larger populations of this species than in other parts in the species' range. The largest known colonies of little brown myotis are in the northeastern and mid-western United States, with the northeastern population considered the core range of the species" Kunz and Reichard 2010). Smaller populations occur in the southern and western United States (Davis et al. 1965).

Little brown bats are found in most parts of North America. They are not found in the far north of Canada or in the far southern parts of the United States, except in the forested high mountains of Mexico. Some little brown bats have been observed in Iceland and Kamchatka, but those probably got there as the result of accidental ship transportation by people.

Biogeographic Regions: nearctic (Native )

The range encompasses southeastern California, Arizona (Hoffmeister 1986, Arizona Game and Fish Department 2003), New Mexico (except perhaps extreme northeast; Frey 2004), southern Colorado, and perhaps southern Utah and western Texas (Piaggio et al. 2002; Valdez pers. comm.). In Arizona, this bat is distributed predominantly in the highlands and upper stream reaches (Piaggio et al. 2002). In New Mexico, it is known from low-elevation riparian areas in the Rio Grande Valley and montane highlands. In California, it occurs only along the Colorado River lowlands and in the adjacent desert mountain ranges. The range meets that of M. lucifugus in central Colorado; that species occupies the northern third of the state (Valdez pers. comm.). The only record from Texas is an unusual, perhaps intermediate specimen collected in the early 1900s near Fort Hancock in Hudspeth County (Piaggio et al. 2002; Valdez pers. comm.; Schmidly 2004).
Range limits in northcentral Mexico are uncertain; the species has been recorded from several localities in Chihuahua and a disjunct site near Texcoco in the Distrito Federal (Piaggio et al. 2002; Valdez pers. comm.). In Arizona, this bat is most common at elevations of 1,830-2,806 meters, but it also occurs much lower along rivers in desert regions (Arizona Game and Fish Department 2003).

Alaska (USA) to Labrador and Newfoundland (Canada), south to Southern California, Northern Arizona, Northern New Mexico (USA). It is found in Mexico.

Little brown bats, Myotis lucifugus, are abundant in southern Alaska, Canada, across the United States from the Pacific to Atlantic coasts, and the higher elevation forested regions of Mexico. Although little brown bats are not found in northern Canada, individuals have been observed in Iceland and Kamchatka. Those outlying records are presumed to have been the result of accidental ship transportation by humans. Little brown bats are also absent from much of Florida, the southern Great Plains regions of the U.S., southern California, and parts of coast Virginia and the Carolinas.

Biogeographic Regions: nearctic (Native )

endemic to a single nation

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) The range encompasses northern Mexico, southeastern California, Arizona (Hoffmeister 1986, Arizona Game and Fish Department 2003), New Mexico (except perhaps extreme northeast; Frey 2004), southern Colorado, and perhaps southern Utah and western Texas (Piaggio et al. 2002; Valdez, pers. comm.). In Arizona, this bat is distributed predominantly in the highlands and upper stream reaches (Piaggio et al. 2002). In New Mexico, it is known from low-elevation riparian areas in the Rio Grande Valley and montane highlands. In California, it occurs only along the Colorado River lowlands and in the adjacent desert mountain ranges. The range meets that of M. lucifugus in central Colorado; that species occupies the northern third of the state (Valdez, pers. comm.). The only record from Texas is an unusual, perhaps intermediate specimen collected in the early 1900s near Fort Hancock in Hudspeth County (Piaggio et al. 2002; Valdez, pers. comm.; Schmidly 2004). Range limits in northcentral Mexico are uncertain; the species has been recorded from several localities in Chihuahua and a disjunct site near Texcoco in the Distrito Federal (Piaggio et al. 2002; Valdez, pers. comm.). In Arizona, this bat is most common at elevations of 1,830-2,806 meters, but it also occurs much lower along rivers in desert regions (Arizona Game and Fish Department 2003).

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Little brown bats are appropriately named. Their fur is glossy, and can be dark-brown, golden-brown, reddish, or olive-brown. Albino individuals have also been observed. The fur on the belly is lighter than the fur on the back. Wings and membranes between the legs are dark brown or black, and have almost no hair. Little brown bats have small ears and large hind feet. The hind foot has hairs that extend past the toes.

Little brown bats are tiny, and weigh between 5 and 14 g. They are between 60 and 102 mm long, and have a wingspan between 222 and 269 mm. Females are larger than males, especially during the winter. Little brown bats fly at speeds as high as 35 km/hour and average 20 km/hour.

Range mass: 5 to 14 g.

Range length: 60 to 102 mm.

Average length: 87 mm.

Range wingspan: 222 to 269 mm.

Other Physical Features: endothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: female larger

Average basal metabolic rate: 0.051 W.

The fur of M. lucifugus is glossy, and varies in color from dark brown, golden brown, reddish, to olive brown. Albino individuals have also been observed. The ventral side has lighter pelage. The wing and interfemoral membranes are nearly hairless and dark brown or black. The tragus is blunt and of medium height. Their ears usually do not extend past the nose when laid forward. Myotis lucifugus has small ears and large hind feet. The fore and hind limbs have five metapodials. The hind foot has hairs that extend past the toes.

The skull has some distinguishing characteristics. Myotis lucifugus lacks a saggital crest, has a shortened rostrum, 38 teeth, and a upslope profile of the forehead. In addition, the braincase is flattened and subcircular when observed dorsally.

Myotis lucifugus does not possess a keel on the calcar and has a short tibia relative to the length of the hind foot (~55% of the tibial length). Myotis lucifugus lacks choroidal papillae and folded retinas, and therefore does not exhibit eye shine.

Myotis lucifugus weighs between 5 and 14 g. The length varies between 60 and 102 mm, and the wingspan between 222 and 269 mm. The forearm, including claw, measures 33 to 41 mm, and tail length measures 28 to 65 mm. The hind foot is between 8 and 10 mm in length, ears are 11 to 15.5 mm, and the tragus is 7 to 9 mm. Little brown bats fly at speeds as high as 35 km/hour and average 20 km/hour. Females are larger than males, especially during the winter.

Range mass: 5 to 14 g.

Range length: 60 to 102 mm.

Average length: 87 mm.

Range wingspan: 222 to 269 mm.

Other Physical Features: endothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: female larger

Average basal metabolic rate: 0.051 W.

Length: 9 cm

Weight: 14 grams

Sexual Dimorphism: Females are slightly larger than males.

Length:
Average: 87 mm
Range: 60-102 mm

Weight:
Average: 10 g
Range: 7-13 g

This is the only long-footed (i.e. hind foot length >8.0 mm [0.32 inches]) Myotis in Arizona with a gradually sloping forehead and the only Myotis in Arizona with only 1 small upper premolar behind the canine. In the rare individual with 2, it is on 1 side only or 1 is crowded out of alignment. [From Arizona Game and Fish Department Heritage Data Management System]

The genus Myotis is distinguished from other bat species in Arizona by lack of a nose-leaf, or enlarged facial glands, or a tail extending beyond the tail membrane, or fur on the tail membrane. Myotis are initially identified by their uniform shades of brown and by their straight and relatively narrow tragus with a pointed tip. When compared to other Myotis, the lack of a keeled calcar distinguishes M. occultus from M. californicus, M. ciliolabrum, and M. volans. Shorter ears (11-16 mm) distinguish M. occultus from M. evotis (20-24 mm), M. auriculus (19-21 mm) and usually from M. thysanodes (12-19 mm). [From Arizona Game and Fish Department Heritage Data Management System]

Myotis occultus may also be distinguished from M. thysanodes by the lack of a macroscopic fringe of hairs on trailing edge of the tail membrane in M. occultus. Lack of bare spot between scapulae and lack of grayish back distinguish M. occultus from M. velifer. Darker ears and longer forearm (36.0-41.0 mm [1.44-1.64 inches]), and a glossier coat distinguish M. occultus from M. yumanensis which usually has light-colored ears, a shorter forearm (31.0-36.0 mm [1.24-1.44 inches]), and a dull coat. [From Arizona Game and Fish Department Heritage Data Management System]

Characters that are potentially useful for differentiating M. occultus and M. lucifugus carissima include the number of upper premolars (complete set in lucifugus), length of maxillary toothrow, presence or absence of sagittal crest (present in occultus, not in lucifigus), and pelage coloration (sometimes reddish in occultus, glossy brown in lucifigus) (Findley and Jones 1967), and rostrum length and slope of forehead (Hoffmeister 1986). However, morphologically intermediate specimens have been found, and at least some of these group genetically with M. occultus (Piaggio et al. 2002).

Differs from M. sodalis in unkeeled calcar. Differs from M. austroriparius in smaller size, glossy rather than dull pelage, and usual absence of a sagittal crest. Differs from M. grisescens in banded dorsal hairs banded (vs. unicolored) and wing attached to the foot at the base of the toe rather than at the ankle. Differs from M. velifer in smaller size, glossy rather than dull pelage, and lack of sagittal crest. Differs from M. keenii and M. septentrionalis in shorter ears that do not extend beyond the nose when laid forward. Differs from M. volans in smaller size, glossy rather than dull pelage, and unkeeled calcar. Differs from M. yumanensis in larger size, larger skull (greatest length usually more than 14 mm rather than usually less than 14 mm), and usually glossy pelage rather than dull pelage. Differs from M. thysanodes in absence of a conspicuous fringe of hairs along the edge of the interfemoral membrane. Differs from M. californicus in larger size, unkeeled calcar, and skull rising gradually from rostrum. Differs from M. leibii in larger size and unkeeled calcar. (Hall 1981).

Comments: These bats use a wide range iof habitats and often use human-made structures for resting and maternity sites; they also use caves and hollow trees. Foraging habitat requirements are generalized; foraging usually occurs in woodlands near water. Winter hibernation sites (caves, tunnels, abandoned mines, and similar sites) generally have a relatively stable temperature of about 2-12 C (see Kunz and Reichard 2010). Maternity colonies commonly are in warm sites in buildings (e.g., attics) and other structures; also infrequently in hollow trees. Miicroclimate conditions suitable for raising young are relatively narrow, and availability of suitable maternity sites may limit the species' abundance and distribution.

One of the most important aspects of little brown bat habitat is the presence of good roosts. Little brown bats use three different kinds of roosts: day, night, and hibernation roosts. In order for a place to serve as a roost, the air temperature there must remain about the same all the time. Day and night roosts are used by active bats. These roosts can be found in buildings, in trees, under rocks, and in piles of wood. Day roosts have very little or no light, and provide good shelter. Day roosts often have southwestern exposures, which provide heat to wake the bats up from their daily sleep.

Night roosts have closed-in spaces where lots of bats can cluster together. This helps to make the roost warmer. Little brown bats use night roosts when temperatures are below 15°C. These roosts are usually not in the same place as day roosts. Separation of day and night roosts may keep feces from piling up, which may help to keep the roost's location a secret from predators. Day and night roosts are used during spring, summer, and fall. During the winter, little brown bats use hibernaculum sites.

Nursery roosts are like day roosts, but they are warmer than the surrounding air. They are usually occupied only by females and their babies. Females use the same nursery colony every year.

Roosts used during the winter are called hibernaculum sites. These may be shared with Myotis_yumanensis. Winter roosts include abandoned mines or caves where the temperature is continuously above freezing and humidity is high. In the north, little brown bats enter hibernation in early September and end in mid-May. In the south, hibernation begins in November and ends in mid-March. Unlike some bats, little brown bats do not make long migrations during the change of seasons.

Little brown bats are most often found in forested areas near water. Some subspecies live in dry climates where there is not much water to drink. In these habitats, drinking water comes from moisture on cave walls or dew that settles on the fur.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral ; forest ; mountains

Other Habitat Features: urban ; suburban ; agricultural ; riparian ; caves

Habitat and Ecology

Systems

• Terrestrial

Habitat and Ecology

Systems

• Terrestrial

Myotis lucifugus occupies three types of roosts: day, night, and hibernation roosts. Locations of roosts are chosen based upon the presence of stable ambient temperatures. Day and night roosts are used by active bats and include, but are not limited to, buildings, trees, under rocks, and in piles of wood. Day roosts have very little or no light, provide good shelter, and typically have southwestern exposures to provide heat for arousal from daily torpor.

Night roosts are selected for their confined spaces where large concentrations of bats can cluster together to increase the temperature in the roost. These roosts are primarily occupied when temperatures are below 15°C. Night roosts are usually away from day roosts; this may diminish the accumulation of feces at day roosts and avoid signaling predators. Day and night roosts are inhabited during spring, summer, and fall months, whereas during the winter, hibernacula sites are used.

Nursery roosts are similar to day roosts but are warmer than ambient temperature. They are usually occupied only by females and their offspring. Females use the same nursery colony every year.

Hibernaculum sites may be shared with Myotis yumanensis. These sites usually include abandoned mines or caves where the temperature is continuously above freezing and humidity is high. Northern populations of bats enter hibernation in early September and end in mid-May; southern populations enter in November and end their hibernation in mid-March. Myotis lucifugus does not make tremendously long migrations during the change of seasons.

Myotis lucifugus inhabits forested lands near water, but some subspecies can be found in dry climates where water is not readily available. In those habitats, drinking water is provided by moisture on cave walls or condensation on the fur. Little brown bats live over a wide latitudinal and elevational range.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral ; forest ; mountains

Other Habitat Features: urban ; suburban ; agricultural ; riparian ; caves

Comments: Habitats in Arizona include ponderosa pine and oak-pine woodland near water; this bat is also known from wooded riparian areas in desert areas (Hoffmeister 1986). In New Mexico, the species is usually associated with large bodies of water without respect to associated vegetation type (Findley et al. 1975); it is known from low elevation riparian areas in the Rio Grande Valley and montane highlands (Piaggio et al. 2002). Maternity colonies have been found in buildings (e.g., the attics of abandoned houses; Hoffmeister 1986; Chung-MacCoubrey 1999), in crevices between timbers of a highway bridge (Arizona Game and Fish Department 2003), and in snags. A few individuals have been found hibernating in mines in California and Sonora (Howell 1989).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

In the northeast, may migrate hundreds of miles between winter and summer habitats; in the west, believed to hibernate near their summer range (Schmidly 1991).

Little brown bats eat insects. They are very good at catching insects, especially when they are in patches and are less than one meter away. These bats will catch whatever insects are available. Their food may be captured straight out of the air, or may be picked off of surfaces.

Little brown bats fly faster near the end of an attack when the prey is very close. They usually feed on swarms of insects. Large swarms of insect make it easier for the bats to capture them.

These bats do not protect feeding terrietories, but individuals do return to areas where they have had prior feeding success.

Females who are nursing young need more food than other bats. These females usually select larger insects than male bats or female bats without young. Little brown bats usually eat insects that are from 3 to 10 mm long. An active bat can eat half of its own body weight in insects each night. Females with nursing young eat 110 percent of their body weight per night.

These animals eat their food quickly. The food takes only 35 to 54 minutes to pass through the digestive system.

The echolocation calls used by little brown bats work the best for finding prey insects between 3 and 8 mm long. This is close to the size of insects most often eaten by these bats, which is between 3 and 10 mm. The same call is used to locate both flying and sitting insects.

Little brown bats catch insects in wooded areas, fields, and over water. These insects are captured as the bats swoop and dip through the air. Insects on the water surface may also be caught. Bats do most of their feeding about two hours after dark.

Little brown bats eat a lot of insects that live in the water. Chironomidae provide these bats with most of their food, but other aquatic insects are eaten, too. Coleoptera, Trichoptera, Lepidoptera, Ephemeroptera, Neuroptera, and Diptera are all eaten sometimes.

Animal Foods: insects

Myotis lucifugus is an efficient insect predator, especially when insects are in patches and at close range (approximately less than one meter). Little brown bats, along with many other insectivorous bats, are opportunistic feeders and catch prey by aerial hawking and gleaning tactics. Myotis lucifugus flies faster near the end of the attack, when approaching prey. During gleaning, these bats hover approximately 30 cm from the prey. Myotis lucifugus typically feeds on swarms of insects, saving time and energy to search for food. There is no evidence of territorial protection of feeding areas, but individuals return to areas where they have had prior feeding success. Myotis lucifugus has different selectivity based upon the arrangements of insects. In large swarms of mating insects, these bats concentrate one or two species to feed on, but when insects are dispersed, little brown bats are less selective and feed on multiple species. Food demand of lactating females increases and pregnant or lactating females usually select larger insects than males or nonpregnant females. Normally, these bats feed on insects whose length ranges from 3 to 10 mm. These bats typically eat half of their body weight per night (when active) and lactating females eat approximately 110 percent of their body weight per night. Myotis lucifugus chews and processes food relatively quickly. Mastication rate is seven jaw cycles per second, and food takes only 35 to 54 minutes to pass items through the digestive system.

Myotis lucifugus uses FM echolocation, downward sweeping pulses of 80 to 40 kHZ that last from 1 to 5 msec. These wavelengths give the greatest quality of detection for 3 to 8 mm size prey, and M. lucifugus consumes prey averaging 3 to 10 mm in size. The same FM call is used for location of both flying and stationary insects. The approach phase of their call has second and third harmonics, but during the feeding buzz, the frequency is focused at 47kHz. The rate of call production while chasing prey is 200 calls per second. Myotis lucifugus emits a high-pulse repetitive call when nearing a landing site.

Myotis lucifugus catches free-flying insects in wooded areas, fields, and over water, but also preys on insects on the water surface. Insects caught during flight are taken by swooping or dipping maneuvers. Most activity over water occurs between 1 to 2 m over the surface and the insects are taken by the mouth. Most feeding activity occurs about two hours after dark.

Little brown bats feed largely on aquatic insects. Midges are the primary source of food of M. lucifugus, but a large part of their diet comes from other aquatic insects. When available, beetles are easily identified by echolocation and easily captured. Other insects consumed include caddisflies, moths, mayflies, lacewings, and occasionally mosquitoes.

Animal Foods: insects

Primary Diet: carnivore (Insectivore )

Comments: Often hunts over water or along the margins of lakes and streams; consumes flying insects, especially mosquitoes, midges, caddisflies, moths, various hoppers, and smaller beetles, sometimes spiders (e.g., see Whitaker and Lawhead 1992). Insects with wingspans of 1/8-1/2" are pursued (Schwartz and Schwartz 1981). Prey are detected by echolocation at a range of 1 m (Fenton and Bell 1979).

Little brown bats have a major impact on the insect populations around their roosts. Active bats eat half of their body weight per night and lactating females eat more than their body weight per night. One M._lucifugus consumes approximately 3 to 7 grams of insects each night.

Cestoda, and ectoparasites such as Siphonaptera, Parasitiformes and Cimicidae are carried by little brown bats.

Commensal/Parasitic Species:

• Cestoda
• Siphonaptera
• Parasitiformes
• Cimicidae

House cats are good at catching bats, and have many chances since bats often roost near human habitations. Predators such as Martes americana and Martes pennanti take advantage of weak young that fall, or hibernating individuals that are dislodged by grooming activities. Other predators of little brown bats include Peromyscus, Strigiformes, Mustela, Accipitridae, Squamata, Procyon, Felis silvestris, and other small carnivores.

Known Predators:

• mice (Peromyscus)
• owls (Strigiformes)
• weasels (Mustela)
• hawks (Accipitridae)
• snakes (Squamata)
• raccoons (Procyon)
• martens (Martes_americana)
• fishers (Martes_pennanti)
• domestic cats (Felis_silvestris)

Anti-predator Adaptations: cryptic

Little brown bats have a major impact on the insect populations around their roosts. Active bats eat half of their body weight per night and lactating females eat more than their body weight per night. One M. lucifugus consumes approximately 3 to 7 grams of insects each night.

Tapeworms, and ectoparasites such as fleas, mites and bed bugs are carried by little brown bats.

Commensal/Parasitic Species:

• Tapeworms
• Fleas
• Mites
• Bed bugs

Domestic cats have become adept at catching bats due to the close proximities of roosts to human habitations. Many predators take advantage of the high concentrations of bats in roosts. Predators such as martens and fishers take advantage of weak young that fall or hibernating individuals that are dislodged by grooming activities. Other predators of M. lucifugus include mice, owls, weasels, hawks, snakes, raccoons, domestic cats, and other small carnivores.

Known Predators:

• mice (Peromyscus)
• owls (Strigiformes)
• weasels (Mustela)
• hawks (Accipitridae)
• snakes (Squamata)
• raccoons (Procyon)
• martens (Martes americana)
• fishers (Martes pennanti)
• domestic cats (Felis silvestris)

Anti-predator Adaptations: cryptic

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: This species is represented by a large number of occurrences (subpopulations and locations) well spread over a vast geographic range.

100,000 to >1,000,000 individuals

Comments: Total adult population size is unknown but certainly exceeds 100,000 and was estimated at around 6.5 million as of 2006 (Frick et al. 2010). Individual maternity colonies often include (or at least recently included) hundreds (sometimes thousands) of individuals. Population size is now much smaller.(see trend comments). For general information on population size in Mexico see Arita (1993).

10,000 - 1,000,000 individuals

Comments: Total adult population size is unknown but presumably exceeds 10,000. Stager (1943) estimated that Myotis occultus made up about 40 percent of 2,000 bats in a mixed-species colony roosting under a bridge in May near Blythe, California. Hayward (1963) recorded an Arizona maternity colony that included 67 females in one year and 41 the next year.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 80

Comments: The total number of occurrences or subpopulations is unknown but is at least a few dozen.

Winter concentrations may include tens of thousands. Summer home range is poorly understood. Experiences low survival during first winter, higher in subsequent years.

Little brown bats use echolocation to find prey. In echolocation, the bat blasts out calls and listens for the echo. From the echo, the bat can determine where an object is located. Echolocation allows them to find bugs to eat, and to avoid hitting objects while flying.

Little brown bats make other calls to communicate with each other. An example of such a call is when two bats are flying on a collision course during feeding.

These animals may use echolocation calls, visual cues (such as landmarks), and possibly scent cues to locate roosts. A roost can be located from 180 miles away.

Mother and young communicate through vocalizations. There is also some information transmitted in physical contact between the mother and her young.

Scientists do not know if these bats make alarm or distress calls.

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: pheromones

Perception Channels: visual ; acoustic ; ultrasound ; echolocation

Myotis lucifugus produces frequency modulated (FM) calls at 45kHz, their fundamental frequency. These calls last 1 to 5 milliseconds and sweep from 80 to 40 kHz. Cruising bats typically produce 20 calls per second to detect prey and objects.

Myotis lucifugus alert other bats with non-echolocation calls if they are flying on a collision course during feeding. They emit this call by reducing the frequency of the terminal portion of a sweep call to 25 kHz. Additionally, they may use echolocation calls, visual cues, such as landmarks, and possibly chemical cues to locate roosts; they can find their roosts from 180 miles away. Mother and young communicate through a few, complex vocalizations. There is no information about alarm or distress calls.

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: pheromones

Perception Channels: visual ; acoustic ; ultrasound ; echolocation

Comments: Most active during the first 2-3 hours after sunset. Following a mid-night roost is a second foraging period. Cool temperatures and a low abundance of prey will lengthen the mid-night roost. Hibernates September-October to April-May. In Indiana, a few bats flew outside a hibernation site periodically throughout the winter, especially in mild weather; feeding apparently did not begin until mid-March (Whitaker and Rissler 1992).

Little brown bats can find food almost anywhere and can use a variety of roosts. This allows them to survive in changing conditions.

A normal life span for these animals is 6 to 7 years, though some live well beyond 10 years. Males usually live longer than females. One 31 year-old male was discovered in southeastern Ontario, although these bats usually don't live so long. A little brown bat is most likely to die during its first winter, since new pups have considerably less weight than adults do at the start of hibernation.

Range lifespan
Status: wild: 31 (high) years.

Typical lifespan
Status: wild: 6 to 7 years.

Average lifespan
Status: wild: 6 to 7 years.

Average lifespan
Status: captivity: 30.0 years.

The lifespan of M. lucifugus is extended by their ability to find food and inhabit a variety of roosts. These characteristics allow expansion of their habitat to new ranges, but also contribute to their survival. Myotis lucifugus live approximately 6 to 7 years and often live well beyond 10 years. A 31 year-old male was discovered in southeastern Ontario. Evidence indicates that males tend to live longer than females. Mortality rate is the greatest during the first winter when new pups have considerably less weight than their adult counterparts at the start of hibernation.

Range lifespan
Status: wild: 31 (high) years.

Typical lifespan
Status: wild: 6 to 7 years.

Average lifespan
Status: wild: 6 to 7 years.

Average lifespan
Status: captivity: 30.0 years.

Maximum longevity: 34 years (wild) Observations: The little brown bat is unique amongst mammals, and maybe even amongst vertebrates, due to its large range of body temperatures. Animals can be cooled to 279.5 K without apparent harm and have also been found at 327 K (Roger Barbour and Wayne Davis 1969). They attain adult weight in about one month.

Little brown bats mate in two different ways. Mating occurs right before hibernation in the hibernaculum roost. Sometimes both the male and female are awake and alert when mating takes place. But sometimes, males mate with other bats who have already entered hibernation. Mating is random and both males and female mate with more than one other bat.

Mating System: polygynandrous (promiscuous)

Little brown bats hibernate in a special roost called a hibernaculum. When the temperature falls during late summer and autumn, bats begin swarming at the hibernaculum. Swarming helps young bats find suitable hibernation roosts. The first bats to arrive at the hibernaculum in late July are adult males, and females without young. Females and subadults arrive in August.

Even though little brown bats mate in autumn, females delay ovulation and store sperm for about seven months before they actually get pregnant in spring. Pregnancy lasts 50 to 60 days. Pups are born in June and July. Females give birth to only one pup each year.

Normally, bats hang with their heads pointed down. When females give birth, they reverse their position so the head is up. Mothers catch their newborn young in a special membrane between their legs. A pup is born with a full set of teeth. Its eyes and ears open within hours of birth. A pup clings to to its mother's nipple using its teeth, thumbs, and hind feet.

When the bat pups are 9.5 days old, they can control the temperature of their bodies. They can hear as well as adults by the time they are 13 days old. Young can fly by the time they are 3 weeks old. Pups become independent and self-supporting about 4 weeks after they are born. By this time they are as big as adults.

Breeding interval: Both sexes mate more than once per year and produce one young per year.

Breeding season: Mating begins in mid-August during the active phase and continues in passive phase throughout the winter.

Range number of offspring: 1 to 2.

Average number of offspring: 1.

Range gestation period: 50 to 60 days.

Range weaning age: 21 to 28 days.

Average weaning age: 26 days.

Average time to independence: 4 weeks.

Average age at sexual or reproductive maturity (female): 210 days.

Average age at sexual or reproductive maturity (male): 210 days.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous ; sperm-storing ; delayed fertilization

Average birth mass: 1.96 g.

Average number of offspring: 1.

Average age at sexual or reproductive maturity (male)
Sex: male: 210 days.

Average age at sexual or reproductive maturity (female)
Sex: female: 210 days.

Mother little brown bats provide all of the parental care. A mother can identify her own pup by its odor and its calls.

The mother provides milk to her young, and for 18 to 21 days this is all the pup eats. At about 3 weeks of age, the permanent teeth of a pup come in, allowing it to feed on insects along with the mother's milk.

Weaned pups lose weight when they are first learning to catch insects. Scientists are not sure if mothers bring insects to their young or actively teach them to hunt. However, because mothers and their young stay together, scientists believe that the young are learning from their mother before they become independent.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

Mating occurs between adult females and adult males; subadult males are not sexually mature until after their first year. Mating occurs in two phases: active and passive. During the active phase, both partners are awake and alert. In the passive phase, active males mate with torpid individuals of both sexes; passive phase mating is approximately 35% homosexual. Mating is random and promiscuous. Females in active phase usually mate with more than one male. In both active and passive phase matings, males mate with multiple females.

Mating System: polygynandrous (promiscuous)

Swarming at the hibernacula occurs during late summer and fall; activity decreases with lower temperatures. Swarming serves a prenuptial function, along with showing the young suitable hibernation roosts. During late July, bats arriving at the hibernacula are adult males and nonparous females; females and subadults appear in early August. Swarming M. lucifugus may travel large distances, causing mixing of populations from different areas. During the swarming period, little brown bats are receptive to calls of conspecifics.

Myotis lucifugus has enlarged pararhinal glands during the mating season. Mating occurs when a male mounts a female from the rear. The male may bite the female on her back. Upon female struggle, the male may emit a copulation call to ease the female. Males inseminate females that are are active as well as those that are torpid. Little brown bats delay ovulation and store sperm for about seven months between copulations in the fall and fertilization in the spring. Pups are born and reared in June and July after a 50 to 60 day gestation period. The greatest energy demand on females occurs during lactation and toward the end of pregnancy. Females lose the ability to thermoregulate well when approaching parturition.

Normally, bats hang head down; females giving birth reverse their position, so their head is up. Young are born into the interfemoral membrane; only one young is born per year. The pups’ eyes and ears open within hours of birth, and deciduous teeth are fully erupted. Pups must cling to the female’s nipple using their deciduous incisors, large thumbs, and hind feet. The young start hearing at day 2 and develop auditory sensitivity similar to that of an adult by day 13. On approximately day 9.5, pups are able to thermoregulate and in three weeks they are able to fly.

Independence from the mother comes when the pups start to fly and become self-supporting at about 4 weeks of age. Adult weight is attained at about 4 weeks of age as well. Spermatogenesis starts in May and ends in August.

Breeding interval: Both sexes mate more than once per year and produce one young per year.

Breeding season: Mating begins in mid-August during the active phase and continues in passive phase throughout the winter.

Range number of offspring: 1 to 2.

Average number of offspring: 1.

Range gestation period: 50 to 60 days.

Range weaning age: 21 to 28 days.

Average weaning age: 26 days.

Average time to independence: 4 weeks.

Average age at sexual or reproductive maturity (female): 210 days.

Average age at sexual or reproductive maturity (male): 210 days.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous ; sperm-storing ; delayed fertilization

Average birth mass: 1.96 g.

Average number of offspring: 1.

Average age at sexual or reproductive maturity (male)
Sex: male: 210 days.

Average age at sexual or reproductive maturity (female)
Sex: female: 210 days.

Mothers nurse their own young and distinguish from other pups by odor and calls. For 18 to 21 days, pups ingest only milk from their mother. Weaning takes place at about three weeks; at this time, the permanent teeth fully erupt and pups start to feed on insects along with the mother's milk. After weaning, the pups have a drop in body weight as they learn to catch insects. It is not clear if mothers bring insects to their young or help to teach them to hunt. However, many female/young pairs are captured together, suggesting that there is some period of supervised learning before independence. Males play no role in parental care.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

Usually mates in September-October. Ovulation and fertilization are delayed until spring. Gestation lasts 50-60 days. Gives birth to 1 litter of 1 young, late spring-early summer. Females produce first young usually in first (Indiana, New Mexico) or second year (British Columbia) (Herd and Fenton 1983). In British Columbia, may delay or forego reproduction in wet years (Grindal et al. 1992). Survival for a decade may be fairly common; a few live as long as 20-30 years; females may be reproductive to an age of at least 12 years (Hall et al. 1957, Keen and Hitchcock 1980). Most summer colonies range from 50 to 2500 individuals (average 400) (Mumford and Cope 1964).

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N3 - Vulnerable

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Widespread in North America from Alaska-Canada boreal forest south through most of the contiguous United States to central Mexico; formerly very abundant, recently underwent severe decline in abundance in the core of the range in northeastern North America as a result of high mortality caused by an introduced, rapidly spreading fungal disease (white-nose syndrome). Version 3.09 of NatureServe's rank estimator yielded a rank of "G3?"

Year Assessed

Assessor/s

Reviewer/s

Justification

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 1996
  Lower Risk/least concern

Myotis lucifugus is under no special conservation status as the species is abundant across North America. These bats thrives with expansion of human populations, as many of their roosting sites are built by humans. In spite of their overall abundance, some populations have suffered declines due to control measures and build-up of fat-soluble pesticides in their bodies.

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Relatively small range in the mountains of the American southwest and northern Mexico; some populations have declined; better information is needed on current status and threats.

Global Short Term Trend: Unknown

Global Long Term Trend: Relatively stable to decline of 50%

Comments: Overall trend is unknown, but some subpopulations 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 (AGFD 2003). Populations that were formerly common along the Colorado River in California and Arizona have apparently declined, perhaps drastically (K. Stager, P. Leitner, pers. comm.).

Global Short Term Trend: Decline of 50-80%

Comments: Range-wide trend over the past three generations (probably roughly 25-30 years) is not precisely known, but abundance has declined severely in the eastern (core) portion of the range (Frick et al. 2010, Kunz and Reichard 2010). Population decreases in bats at infected hibernacula range from 30 to 99 percent annually, with a regional mean of 73 (Frick et al. 2010). The large majority of the global population of M. lucufugus occurs in the region now infected with WNS (Kunz and Reichard 2010).

Population is "in sharp decline due to the rapidly spreading white-nose syndrome (WNS) that has already resulted in several local extirpations and that is ultimately expected to cause regional and likely rangewide extinction of the little brown myotis in a very short ecological time frame...." Frick et al. (2010) projected that "regional species extinction will likely occur, with 99% certainty, in or before 2026...eliminating at least the core northeastern range of the species, which clearly constitutes a significant portion of the species' range in terms of population numbers, geographical distribution, resiliency, and habitat composition." Source: Kunz and Reichard (2010).

More recently, Langwig et al. (2012) reported that (as of 2010) sampled populations in New York, Vermont, Connecticut, and Massachusetts had stabilized at about 2-20 percent of the pre-WNS population size. Population stabilization apparently was facilitated by increases in the number and fraction of little brown myotis roosting individually after populations declined, which likely resulted in each bat having fewer neighbours during hibernation and lower pathogen exposure.

Global Long Term Trend: Decline of 50-80%

Population

Population Trend

Population

Population Trend

Degree of Threat: Medium

Comments: Without citing specific examples, Schmidly (2004) reported that this species has declined as a result of pesticide use, control measures in nursery colonies, and disturbance at hibernation sites.

Comments: Primary threat is a recently recognized fungal pathogen that causes a generally fatal condition known as white-nose syndrome (WNS), which attacks hibernating bats and killed at least 1 million M. lucifugus in the four years following detection of WNS in 2006 (Frick et al. 2010, Kunz and Reichard 2010). WNS has spread rapidly (confirmed in more than 100 bat hibernacula) and now has been documented throughout northeastern North America. The fungus that causes WNS (Geomyces destructans) likely was recently introduced from Europe (Warnecke et al. 2012).

Other threats include deforestation (Parker 1996, Parker et al. 1996), use of pesticides (Fenton and Barclay 1980, Agosta 2002), use of cyanide in mining (Helfferich 1991), and destruction of caves and shafts associated with karst topography (Agosta 2002), along with control measures being implemented in nursery colonies and collecting of bats for experimentation (Fenton and Barclay 1980).

Special precautions should be taken when mine and cave surveys are conducted during breeding periods and winter hibernation. Hibernating bats are sensitive to human disturbance (Thomas 1995). Disturbance during hibernation can cause bats to use up stored fat reserves and starve to death. Disturbance of breeding colonies can cause young to lose their grasp and fall to their death.

Major Threats

Major Threats

Conservation Actions

Conservation Actions

Management Requirements: See Greenhall (1982) for information on house bat management.

Little brown bats are abundant, and because they have some possible negative effects on humans, people have spent a lot of money trying to eliminate them from some areas. These bats live in attics, roofs, trees, and other areas that put them into contact with humans. These bats sometimes carry rabies, although transmission to humans rarely occurs. Still, other parasites such as Cestoda, Siphonaptera, Parasitiformes and Cimicidae are common in these bats, and make them unwanted additions to the community in many areas.

Negative Impacts: injures humans (bites or stings, causes disease in humans , carries human disease); causes or carries domestic animal disease ; household pest

Members of this species are heavily researched and provide scientists with a bat model to test and study many aspects of the order, including echolocation, social behavior, feeding, and habitat use. Additionally, little brown bats eat pests that transmit diseases and eat agricultural products. They are also predators of mosquitoes and other pest around human habitats.

Positive Impacts: research and education; controls pest population

Myotis lucifugus is the target of control measures due to the abundance of the species. These bats inhabit attics, roofs, trees, and other areas in close proximity to humans; therefore, homeowners have spent large amounts of money trying to erradicate M. lucifugus from these areas. Rabies transmission to humans is extremely low, and only a small percentage of M. lucifugus are infected with the disease. Although rabies in M. lucifugus is low, other parasites such as tapeworms, fleas, mites and bed bugs are common.

Negative Impacts: injures humans (bites or stings, causes disease in humans , carries human disease); causes or carries domestic animal disease ; household pest

Members of this species are heavily researched and provide scientists with a bat model to test and study many aspects of the order, including echolocation, social behavior, feeding, and habitat use. Additionally, little brown bats eat pests that transmit diseases and eat agricultural products. They are also predators of mosquitoes and other pest around human habitats.

Positive Impacts: research and education; controls pest population