Little brown bat
Encyclopedia
The little brown bat (Myotis lucifugus) is a species
of the genus
Myotis (mouse-eared bat
s), one of the most common bat
s of North America
. The little brown bat has been a model organism
for studying bats.
of 22–27 cm (8.7–10.6 in). 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 g (0.17636981052556–0.493835469471567 oz). Females tend to be larger than males. The fore and hind limbs have five metapodials. The skull of the brown bat lacks a sagittal crest
. Its rostrum is shortened and has upslope profile of the forehead. Its braincase flattened and sub-circular when observed dorsally. The bat has 38 teeth all of which including molars
are relatively sharp, as is typical for an insectivore
, and canine
s are prominent to enable grasping hard-bodied insect
s in flight.
The little brown bat can be distinguished from the Indiana bat
by the lack of a keel on the caclar and the presence of hairs on the hind feet that extend pass the toes. Compared to the long-legged bat
, the brown bat has a shorter tibia and lesser amounts of hair on the undersurface of the wing in addition to the lack of a keel on the caclar.
. It is most common in the northern half of the continental United States and southern Canada. Most specimens from the northern edge of its range are males although nursery roosts have been found in the Yukon. Brown bats have been found in Iceland and Kamchatka, likely due to accidental ship transportation by humans.
s, wasp
s, beetle
s, gnat
s, mosquito
es, midge
s 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. Brown bats feed along the margins of lakes and streams, zig-zagging in and out of vegetation 2–5 cm above the ground. Later in the evening, they usually forage in groups over water staying within 1-2m above the surface. They echolocate
to find their prey. They are very effective predators when the insect are in patches and at close range. As with other insectivorous bats, little brown bats catch prey by aerial hawking and gleaning tactics. When taken in flight, the prey is taken by swooping or dipping maneuvers. When above water, prey is taken by the mouth.
Brown bat do not claim feeding areas like a territory, however individuals frequently return to the same feeding sites. When hunting swarms, brown bats focus on one or two species to feed on. When insect are more scattered, they are less selective and will feed on multiple species. If they do not catch any food, they will enter a torpor
similar to hibernation that day, awakening at night to hunt again. A bat will eat half of their body weight per night with lactating females eating more than their body weight per night.
The bats' diet makes this species beneficial to agriculture as it eats many species of agricultural pests. Other than that, it can pollinate crops.
in eastern North America. Many states have made special considerations with respect to the disease, including listing them as a sensitive or protected species.
Accidents are more common causes of mortality than predator or parasites. Bats are impaled on barbed wire and burdocks and drown by floodings in hibernacula. Pesticides also cause great mortality. However DDT
has little effect on the bats and they also seem to have low levels of rabies
.
When on a collision course, feeding bats will alert each other by vocalizing or "honking". These honks are made by reducing the frequency of the terminal portion of a sweep call to 25 kHz. They are the only non-echolocation sound done by this species when feeding. The bats also seem to use echolocation calls of conspecifics to locate roosting sites. These calls are usually used by males calling from mating sites within hibernacula. Mother and young communicate through a few, complex vocalizations.
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. These colonies sometimes reach numbers of bats as great as 1,000 per cave/forest. Gestation lasts 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 three weeks, they learn to fly. By fours weeks, they are adult sized. 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 during their first autumn.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Myotis (mouse-eared bat
Mouse-eared bat
The mouse-eared bats are a diverse and widespread genus of bats within the family Vespertilionidae.-Relationships:Myotis has historically been included in the subfamily Vespertilioninae, but was classified in its own subfamily, Myotinae, by Nancy Simmons in 1998...
s), one of the most common bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. The little brown bat has been a model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
for studying bats.
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, greyish fur underneath. Wing membranes are dark brown on a typical wingspanWingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...
of 22–27 cm (8.7–10.6 in). 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 g (0.17636981052556–0.493835469471567 oz). Females tend to be larger than males. The fore and hind limbs have five metapodials. The skull of the brown bat lacks a sagittal crest
Sagittal crest
A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull of many mammalian and reptilian skulls, among others....
. Its rostrum is shortened and has upslope profile of the forehead. Its braincase flattened and sub-circular when observed dorsally. The bat has 38 teeth all of which including molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
are relatively sharp, as is typical for an insectivore
Insectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
, and canine
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
s are prominent to enable grasping hard-bodied insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s in flight.
The little brown bat can be distinguished from the Indiana bat
Indiana bat
The Indiana bat is a medium-sized mouse-eared bat native to North America. It lives primarily in eastern and midwestern states and in parts of the south of the United States. The Indiana bat is gray, black, or chestnut in colour and is 1.2–2 inches and weighs about 1/4 an ounce...
by the lack of a keel on the caclar and the presence of hairs on the hind feet that extend pass the toes. Compared to the long-legged bat
Long-legged Bat
The Long-legged Bat, Macrophyllum macrophyllum, is a bat species from South and Central America. It is monotypic in its genus.It hunts close over the water surfaces of lakes and slowly flowing streams, where it seizes insects right above or directly off the surface in a manner similar to Noctilio...
, the brown bat has a shorter tibia and lesser amounts of hair on the undersurface of the wing in addition to the lack of a keel on the caclar.
Range and ecology
The little brown bat is found throughout much North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. It is most common in the northern half of the continental United States and southern Canada. Most specimens from the northern edge of its range are males although nursery roosts have been found in the Yukon. Brown bats have been found in Iceland and Kamchatka, likely due to accidental ship transportation by humans.
Habitat and roosting
The little brown bat lives in three different roosting sites: day roosts, night roost and hibernation roosts. Day and night roosts are used by active in spring, summer and fall while hibernacula are used in winter. Day roost sites are typically found in buildings, trees, under rock in wood piles and sometimes in caves. Nursery roosts are found in hollow trees and other natural crevices as well as around buildings. Nursery roosts have also been found under sheet metal roofs of trapper’s caches and attics of buildings. Night roosts tend to be in the same buildings as day roosts, however these roosts tend to be confined spaces with many bats packing themselves together to increase roost temperature. Bats congregate in night roosts after feeding in the evening. Thus night roosting could result in the accumulation of feces away from the day roosts which could make the latter less conspicuous to predators. Brown bats usually hibernate in caves and sometimes abandoned mines. Northern populations of bats enter hibernation in early September and end in mid-May while southern populations enter in November and ends in mid-March.Diet
Little brown bats are insectivores, eating mothMoth
A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...
s, wasp
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
s, beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, gnat
Gnat
A gnat is any of many species of tiny flying insects in the Dipterid suborder Nematocera, especially those in the families Mycetophilidae, Anisopodidae and Sciaridae.In British English the term applies particularly to Nematocerans of the family Culicidae...
s, mosquito
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...
es, midge
Midge
A midge is a very small, two-winged flying insect. "Midge" may also refer to:-Real:* Midge Costanza , American politician* Mildred Gillars , aka "Midge", American broadcaster of Nazi propaganda during World War II...
s and mayflies
Mayfly
Mayflies are insects which belong to the Order Ephemeroptera . They have been placed into an ancient group of insects termed the Palaeoptera, which also contains dragonflies and damselflies...
, among others. Since many of their preferred meals are insects with an aquatic life stage, such as mosquitoes, they prefer to roost near water. Brown bats feed along the margins of lakes and streams, zig-zagging in and out of vegetation 2–5 cm above the ground. Later in the evening, they usually forage in groups over water staying within 1-2m above the surface. They echolocate
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
to find their prey. They are very effective predators when the insect are in patches and at close range. As with other insectivorous bats, little brown bats catch prey by aerial hawking and gleaning tactics. When taken in flight, the prey is taken by swooping or dipping maneuvers. When above water, prey is taken by the mouth.
Brown bat do not claim feeding areas like a territory, however individuals frequently return to the same feeding sites. When hunting swarms, brown bats focus on one or two species to feed on. When insect are more scattered, they are less selective and will feed on multiple species. If they do not catch any food, they will enter a torpor
Torpor
Torpor, sometimes called temporary hibernation is a state of decreased physiological activity in an animal, usually characterized by a reduced body temperature and rate of metabolism. Animals that go through torpor include birds and some mammals such as mice and bats...
similar to hibernation that day, awakening at night to hunt again. A bat will eat half of their body weight per night with lactating females eating more than their body weight per night.
The bats' diet makes this species beneficial to agriculture as it eats many species of agricultural pests. Other than that, it can pollinate crops.
Mortality
Brown bats live approximately 6 to 7 years and often live well beyond 10 years. Little brown bats are preyed on by a variety of animals including, small carnivores, birds, rats and snakes. 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. Brown bats are also hosts for various parasites such as fleas, bed bugs and lice. Little brown bats are now at a higher threat due to white nose syndromeWhite nose syndrome
White nose syndrome is a poorly understood disease associated with the deaths of more than a million bats. The condition, named for a distinctive fungal growth around the muzzles and on the wings of many affected animals, was first identified in a cave in Schoharie County, New York, USA, in...
in eastern North America. Many states have made special considerations with respect to the disease, including listing them as a sensitive or protected species.
Accidents are more common causes of mortality than predator or parasites. Bats are impaled on barbed wire and burdocks and drown by floodings in hibernacula. Pesticides also cause great mortality. However DDT
DDT
DDT is one of the most well-known synthetic insecticides. It is a chemical with a long, unique, and controversial history....
has little effect on the bats and they also seem to have low levels of rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...
.
Sleep
The average sleep time of a little brown bat in captivity is said to be 19.9 hours per day. This long period of sleep is thought to be a way of conserving energy, by only hunting for a few hours each night when their insect prey are available.Behavior
As with most bats, the little brown bat is nocturnal, emerging its roosts at dusk. Most activity occurs two or three hours after dusk. They are also active before dawn. Brown bats return to their roost around 4-5 o’clock in the morning. 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 raise the young. When fall comes, both sexes 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 communityEcholocation and communication
Little brown bats produce calls that are high intensity frequency modulated (FM) and that last from less than one millisecond (ms) to about 5 ms and sweep from about 80–40 kHz, with most of their energy at 45 kHz. When cruising, bats usually produce 20 calls per second to detect prey and objects. The rate of call production while chasing prey is 200 calls per second. The bat emits a high-pulse repetitive call when nearing a landing site.When on a collision course, feeding bats will alert each other by vocalizing or "honking". These honks are made by reducing the frequency of the terminal portion of a sweep call to 25 kHz. They are the only non-echolocation sound done by this species when feeding. The bats also seem to use echolocation calls of conspecifics to locate roosting sites. These calls are usually used by males calling from mating sites within hibernacula. Mother and young communicate through a few, complex vocalizations.
Mating and reproduction
At least in Ontario, brown bat mating occurs in two phases, active and passive. In the active phase, both partners are awake and alert. In the passive state, male will mate with torpid individuals of both sexes, with 35% of mating being homosexual. Most mating occurs in the active phase, corresponding to the peak in testosterone levels in plasma. There is some conflicting reports on whether active females store sperm. Active mating peaks in August but passive mating continues into the winter. During mating, the male mounts the female from the rear and may use copulation call to calm her and stop struggling. The mating system is described as indiscriminate and promiscuous. Neither males nor females can protect any investment in choosing their mates. Torpid males cannot have a monopoly on females and torpid females are often inseminated by other males when they are in the passive phase. Males will mate with as many females as possible and females mate more than once.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. These colonies sometimes reach numbers of bats as great as 1,000 per cave/forest. Gestation lasts 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 three weeks, they learn to fly. By fours weeks, they are adult sized. 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 during their first autumn.
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
- IUCN Red List of Threatened Species: Myotis lucifungus
- 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