bat

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Bats are
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fu ...

s of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as
wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic force In fluid mechanics, an aerodynamic force is a force exerte ...

s, they are the only mammals capable of true and sustained
flight Flight or flying is the process by which an object (physics), object motion (physics), moves through a space without contacting any planetary surface, either within an atmosphere (i.e. air flight or aviation) or through the vacuum of outer space ...

. Bats are more agile in flight than most
birds Birds are a group of warm-blooded vertebrate Vertebrates () comprise all animal Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, b ...

, with their very long spread-out digits covered with a thin or
patagium The patagium (plural: patagia) is a membranous Animal body, body part that assists an animal in obtaining lift (force), lift when gliding flight, gliding or flight. The structure is found in extant taxon, extant and extinct groups of flying and g ...
. The smallest bat, and arguably the smallest extant mammal, is Kitti's hog-nosed bat, which is in length, across the wings and in mass. The largest bats are the flying foxes, with the giant golden-crowned flying fox, ''Acerodon jubatus'', reaching a weight of and having a wingspan of . The second largest order of mammals after , bats comprise about 20% of all classified mammal species worldwide, with over 1,400 species. These were traditionally divided into two suborders: the largely fruit-eating megabats, and the s. But more recent evidence has supported dividing the order into
Yinpterochiroptera The Yinpterochiroptera (or Pteropodiformes) is a suborder of the Chiroptera, which includes taxa formerly known as megabats and five of the microbat families: Rhinopomatidae, Rhinolophidae, Hipposideridae, Craseonycteridae, and Megadermatidae. T ...
and Yangochiroptera, with megabats as members of the former along with several species of microbats. Many bats are
insectivore file:Common brown robberfly with prey.jpg, A Asilidae, robber fly eating a hoverfly An insectivore is a carnivore, carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the Entomophagy i ...
s, and most of the rest are
frugivore A frugivore is an animal that thrives mostly on raw fruits or succulent fruit-like produce of plants such as roots, shoots, nuts and seeds. Approximately 20% of mammalian herbivores eat fruit. Frugivores are highly dependent on the abundance and ...
s (fruit-eaters) or
nectarivore In zoology, a nectarivore is an animal which derives its energy and nutrient requirements from a Diet (nutrition), diet consisting mainly or exclusively of the sugar-rich nectar produced by Angiosperms, flowering plants. Nectar as a food source ...
s (nectar-eaters). A few species feed on animals other than insects; for example, the
vampire bat Vampire bats, species of the subfamily Desmodontinae, are leaf-nosed bats found in Central and South America. Their food source is blood of other animals, a dietary trait called hematophagy. Three extant bat species In biology, a specie ...
s feed on blood. Most bats are
nocturnal Nocturnality is an ethology, animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatures generally have ...
, and many roost in caves or other refuges; it is uncertain whether bats have these behaviours to escape
predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation (wh ...

s. Bats are present throughout the world, with the exception of extremely cold regions. They are important in their ecosystems for
flower A flower, sometimes known as a bloom or blossom, is the reproduction, reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providin ...

s and dispersing seeds; many tropical plants depend entirely on bats for these services. Bats provide humans with some direct benefits, at the cost of some disadvantages. Bat dung has been mined as
guano Guano (Spanish from qu, wanu) is the accumulated excrement of Seabird, seabirds or bats. As a manure, guano is a highly effective fertilizer due to the high content of nitrogen, phosphate, and potassium, all key nutrients essential for plant ...

from caves and used as fertiliser. Bats consume insect pests, reducing the need for
pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, ...
s and other insect management measures. They are sometimes numerous enough and close enough to human settlements to serve as tourist attractions, and they are used as food across Asia and the Pacific Rim. However, fruit bats are frequently considered pests by fruit growers. Due to their physiology, bats are one type of animal that acts as a natural reservoir of many
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ ...
s, such as rabies; and since they are highly mobile, social, and long-lived, they can readily spread disease among themselves. If humans interact with bats, these traits become potentially dangerous to humans. Some bats are also predators of
mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small Diptera, flies within the family Culicidae (from the Latin ''culex'' meaning "gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish ...

es, suppressing the transmission of
mosquito-borne disease Mosquito-borne diseases or mosquito-borne illnesses are diseases caused by microorganism, bacteria, viruses or parasites transmitted by mosquitoes. Nearly 700 million people get a mosquito-borne illness each year resulting in over 725,000 deaths. ...
s. Depending on the culture, bats may be symbolically associated with positive traits, such as protection from certain diseases or risks, rebirth, or long life, but in the West, bats are popularly associated with darkness, malevolence, witchcraft,
vampire A vampire is a mythical creature that subsists by feeding on the Vitalism, vital essence (generally in the form of blood) of the living. In European folklore, vampires are undead, undead creatures that often visited loved ones and caused mi ...

s, and death.

# Etymology

An older English name for bats is flittermouse, which matches their name in other
Germanic languages The Germanic languages are a branch of the Indo-European languages, Indo-European language family spoken natively by a population of about 515 million people mainly in Europe, North America, Oceania and Southern Africa. The most widely spoken ...

(for example German ''Fledermaus'' and Swedish ''fladdermus''), related to the fluttering of wings.
Middle English Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman conquest of England, Norman conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments ...
had ''bakke'', most likely cognate with Old Swedish ''natbakka'' ("night-bat"), which may have undergone a shift from ''-k-'' to ''-t-'' (to Modern English ''bat'') influenced by Latin ''blatta'', "moth, nocturnal insect". The word "bat" was probably first used in the early 1570s. The name "Chiroptera" derives from grc, χείρ''cheir'', "hand" and πτερόν''pteron'', "wing".

# Phylogeny and taxonomy

## Evolution

The delicate
skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

s of bats do not fossilise well; it is estimated that only 12% of bat genera that lived have been found in the fossil record. Most of the oldest known bat fossils were already very similar to modern microbats, such as ''Archaeopteropus'' (32 million years ago). The extinct bats '' Palaeochiropteryx tupaiodon'' (48 million years ago) and '' Hassianycteris kumari'' (48 million years ago) are the first fossil mammals whose colouration has been discovered: both were reddish-brown. Bats were formerly grouped in the superorder , along with the treeshrews (Scandentia), s (Dermoptera), and
primate Primates are a diverse order (biology), order of mammals. They are divided into the Strepsirrhini, strepsirrhines, which include the lemurs, galagos, and lorisids, and the Haplorhini, haplorhines, which include the Tarsiiformes, tarsiers and ...

s. Modern genetic evidence now places bats in the superorder
Laurasiatheria Laurasiatheria ("laurasian beasts") is a superorder of Placentalia, placental mammals that groups together true insectivores (Eulipotyphla, eulipotyphlans), bats (Chiroptera, chiropterans), Carnivora, carnivorans, pangolins (Pholidota, pholidotes ...

, with its sister taxon as Fereuungulata, which includes
carnivora Carnivora is a monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population Populatio ...
ns,
pangolin Pangolins, sometimes known as scaly anteaters, are mammals of the order Pholidota (, from Ancient Greek wikt:ϕολιδωτός, ϕολιδωτός – "clad in scales"). The one Neontology, extant family, the Manidae, has three genera: ''Mani ...

s,
odd-toed ungulate Odd-toed ungulates, mammals which constitute the Taxonomy (biology), taxonomic Order (biology), order Perissodactyla (, ), are animals—ungulates—who have reduced the weight-bearing toes to three (rhinoceroses and tapirs, with tapirs still ...
s,
even-toed ungulate The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
s, and
cetacea Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel thems ...

ns. One study places Chiroptera as a sister taxon to odd-toed ungulates (Perissodactyla). The flying primate hypothesis proposed that when adaptations to flight are removed, megabats are allied to
primate Primates are a diverse order (biology), order of mammals. They are divided into the Strepsirrhini, strepsirrhines, which include the lemurs, galagos, and lorisids, and the Haplorhini, haplorhines, which include the Tarsiiformes, tarsiers and ...

s by anatomical features not shared with microbats and thus flight evolved twice in mammals. Genetic studies have strongly supported the
monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...
of bats and the single origin of mammal flight.

## Inner systematic

evidence indicates that megabats originated during the early
Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek Anci ...
, and belong within the four major lines of microbats. Two new suborders have been proposed;
Yinpterochiroptera The Yinpterochiroptera (or Pteropodiformes) is a suborder of the Chiroptera, which includes taxa formerly known as megabats and five of the microbat families: Rhinopomatidae, Rhinolophidae, Hipposideridae, Craseonycteridae, and Megadermatidae. T ...
includes the Pteropodidae, or megabat family, as well as the families Rhinolophidae, Hipposideridae, Craseonycteridae, Megadermatidae, and Rhinopomatidae. Yangochiroptera includes the other families of bats (all of which use laryngeal echolocation), a conclusion supported by a 2005 DNA study. A 2013 phylogenomic study supported the two new proposed suborders. The 2003 discovery of an early fossil bat from the 52-million-year-old
Green River Formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River (Colorado River), Green River in Colorado, Wyoming, and Utah. The sedimen ...
, '' Onychonycteris finneyi'', indicates that flight evolved before echolocative abilities. ''Onychonycteris'' had claws on all five of its fingers, whereas modern bats have at most two claws on two digits of each hand. It also had longer hind legs and shorter forearms, similar to climbing mammals that hang under branches, such as
sloth Sloths are a group of Neotropical realm, Neotropical xenarthran mammals constituting the suborder Folivora, including the extant Arboreal locomotion, arboreal tree sloths and extinct terrestrial Ground sloth, ground sloths. Noted for their sl ...
s and
gibbon Gibbons () are apes in the Family (biology), family Hylobatidae (). The family historically contained one genus, but now is split into four extant genera and 20 species. Gibbons live in subtropical and tropical rainforest from eastern Bangladesh ...
s. This palm-sized bat had short, broad wings, suggesting that it could not fly as fast or as far as later bat species. Instead of flapping its wings continuously while flying, ''Onychonycteris'' probably alternated between flaps and glides in the air. This suggests that this bat did not fly as much as modern bats, but flew from tree to tree and spent most of its time climbing or hanging on branches. The distinctive features of the ''Onychonycteris'' fossil also support the hypothesis that mammalian flight most likely evolved in arboreal locomotors, rather than terrestrial runners. This model of flight development, commonly known as the "trees-down" theory, holds that bats first flew by taking advantage of height and gravity to drop down on to prey, rather than running fast enough for a ground-level take off. The molecular phylogeny was controversial, as it pointed to microbats not having a unique common ancestry, which implied that some seemingly unlikely transformations occurred. The first is that laryngeal echolocation evolved twice in bats, once in Yangochiroptera and once in the rhinolophoids. The second is that laryngeal echolocation had a single origin in Chiroptera, was subsequently lost in the family Pteropodidae (all megabats), and later evolved as a system of tongue-clicking in the genus ''Rousettus''. Analyses of the sequence of the vocalization gene ''FoxP2'' were inconclusive on whether laryngeal echolocation was lost in the pteropodids or gained in the echolocating lineages. Echolocation probably first derived in bats from communicative calls. The Eocene bats '' Icaronycteris'' (52 million years ago) and '' Palaeochiropteryx'' had cranial adaptations suggesting an ability to detect
ultrasound Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...
. This may have been used at first mainly to forage on the ground for insects and map out their surroundings in their gliding phase, or for communicative purposes. After the adaptation of flight was established, it may have been refined to target flying prey by echolocation. Analyses of the hearing gene ''Prestin'' seem to favour the idea that echolocation developed independently at least twice, rather than being lost secondarily in the pteropodids, but
ontogenic Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the ovum, egg to adult. The term can also be used to refer to t ...
analysis of the cochlea supports that laryngeal echolocation evolved only once.

## Classification

Bats are
placental mammal Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished ...
s. After
rodent Rodents (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around ...
s, they are the largest order, making up about 20% of mammal species. In 1758,
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
classified the seven bat species he knew of in the genus '' Vespertilio'' in the order
Primates Primates are a diverse order (biology), order of mammals. They are divided into the Strepsirrhini, strepsirrhines, which include the lemurs, galagos, and lorisids, and the Haplorhini, haplorhines, which include the Tarsiiformes, tarsiers and ...
. Around twenty years later, the German naturalist
Johann Friedrich Blumenbach Johann Friedrich Blumenbach (11 May 1752 – 22 January 1840) was a German physician A physician (American English), medical practitioner (English in the Commonwealth of Nations, Commonwealth English), medical doctor, or simply doctor, ...
gave them their own order, Chiroptera. Since then, the number of described species has risen to over 1,400, traditionally classified as two suborders: Megachiroptera (megabats), and Microchiroptera (microbats/echolocating bats). Not all megabats are larger than microbats. Several characteristics distinguish the two groups. Microbats use echolocation for navigation and finding prey, but megabats apart from those in the genus '' Rousettus'' do not. Accordingly, megabats have a well-developed eyesight. Megabats have a claw on the second finger of the forelimb. The external ears of microbats do not close to form a ring; the edges are separated from each other at the base of the ear. Megabats eat fruit,
nectar Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollination, pollinating animals, or by extrafloral nectaries, which provide a nutrient source to anim ...
, or pollen, while most microbats eat insects; others feed on fruit, nectar, pollen,
fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...
, frogs, small mammals, or
blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the Cell (biology), cells, and transports Metabolic waste, metabolic waste products away from th ...
. Below is a table chart following the bat classification of families recognized by various authors of the ninth volume of ''Handbook of the Mammals of the World'' published in 2019:

# Anatomy and physiology

## Skull and dentition

The head and teeth shape of bats can vary by species. In general, megabats have longer snouts, larger eye sockets and smaller ears, giving them a more dog-like appearance, which is the source of their nickname of "flying foxes". Among microbats, longer snouts are associated with nectar-feeding. while vampire bats have reduced snouts to accommodate large incisors and canines. Small insect-eating bats can have as many as 38 teeth, while vampire bats have only 20. Bats that feed on hard-shelled insects have fewer but larger teeth with longer canines and more robust lower jaws than species that prey on softer bodied insects. In nectar-feeding bats, the canines are long while the cheek-teeth are reduced. In fruit-eating bats, the cusps of the cheek teeth are adapted for crushing. The upper incisors of vampire bats lack enamel, which keeps them razor-sharp. The bite force of small bats is generated through
mechanical advantage Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for t ...
, allowing them to bite through the hardened armour of insects or the
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
of fruit.

## Wings and flight

Bats are the only mammals capable of sustained flight, as opposed to
gliding Gliding is a recreational activity and competitive air sports, air sport in which pilots fly glider aircraft, unpowered aircraft known as Glider (sailplane), gliders or sailplanes using naturally occurring currents of rising air in the atmospher ...
, as in the
flying squirrel Flying squirrels (scientifically known as Pteromyini or Petauristini) are a tribe of 50 species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodi ...
. The fastest bat, the
Mexican free-tailed bat The Mexican free-tailed bat or Brazilian free-tailed bat (''Tadarida brasiliensis'') is a medium-sized bat native to the Americas, so named because its tail can be almost half its total length and is not attached to its uropatagium. It has been ...
ground speed Ground speed is the horizontal speed of an aircraft relative to the Earth’s surface. It is vital for accurate navigation that the pilot has an estimate of the ground speed that will be achieved during each leg of a flight. An aircraft diving ve ...
of . The finger bones of bats are much more flexible than those of other mammals, owing to their flattened cross-section and to low levels of
calcium Calcium is a chemical element A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substance consisting only of that species. Unlike chemica ...
near their tips. The elongation of bat digits, a key feature required for wing development, is due to the
upregulation In the biological Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that ...
of
bone morphogenetic protein Bone morphogenetic proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Originally discovered by their ability to induce the formation of bone and cartilage, BMPs are now considered to constitute a group of piv ...
s (Bmps). During
embryonic development An embryo is an initial stage of development of a multicellular organism. In organisms that Sexual reproduction, reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell ...
, the gene controlling Bmp signalling, '' Bmp2'', is subjected to increased expression in bat forelimbsresulting in the extension of the manual digits. This crucial genetic alteration helps create the specialized limbs required for powered flight. The relative proportion of extant bat forelimb digits compared with those of Eocene fossil bats have no significant differences, suggesting that bat wing morphology has been conserved for over fifty million years. During flight, the bones undergo
bending In applied mechanics, bending (also known as flexure) characterizes the behavior of a slender structural element subjected to an external Structural load, load applied perpendicularly to a longitudinal axis of the element. The structural elemen ...
and shearing stress; the bending stresses felt are smaller than in terrestrial mammals, but the shearing stress is larger. The wing bones of bats have a slightly lower breaking stress point than those of birds. As in other mammals, and unlike in birds, the
radius In classical geometry, a radius (plural, : radii) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', ...
is the main component of the forearm. Bats have five elongated digits, which all radiate around the wrist. The thumb points forward and supports the
leading edge The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, ...
of the wing, and the other digits support the tension held in the wing membrane. The second and third digits go along the wing tip, allowing the wing to be pulled forward against aerodynamic drag, without having to be thick as in
pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the Order (biology), order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cre ...
wings. The fourth and fifth digits go from the wrist to the
trailing edge The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge meets.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 521. Aviation Supplies & Academics, 1997. ...
, and repel the bending force caused by air pushing up against the stiff membrane. Due to their flexible joints, bats are more maneuverable and more dexterous than gliding mammals. The wings of bats are much thinner and consist of more bones than the wings of birds, allowing bats to maneuver more accurately than the latter, and fly with more lift and less drag. By folding the wings in toward their bodies on the upstroke, they save 35 percent energy during flight. The membranes are delicate, tearing easily, but can regrow, and small tears heal quickly. The surface of the wings is equipped with touch-sensitive receptors on small bumps called
Merkel cell Merkel cells, also known as Merkel-Ranvier cells or tactile epithelial cells, are oval-shaped mechanoreceptors essential for light touch sensation and found in the skin of vertebrates. They are abundant in highly sensitive skin like that of the f ...
s, also found on human fingertips. These sensitive areas are different in bats, as each bump has a tiny hair in the center, making it even more sensitive and allowing the bat to detect and adapt to changing airflow; the primary use is to judge the most efficient speed at which to fly, and possibly also to avoid stalls. Insectivorous bats may also use tactile hairs to help perform complex maneuvers to capture prey in flight. The
patagium The patagium (plural: patagia) is a membranous Animal body, body part that assists an animal in obtaining lift (force), lift when gliding flight, gliding or flight. The structure is found in extant taxon, extant and extinct groups of flying and g ...
is the wing membrane; it is stretched between the arm and finger bones, and down the side of the body to the hind limbs and tail. This skin membrane consists of
connective tissue Connective tissue is one of the four primary types of animal tissue (biology), tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Con ...
, elastic fibres,
nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the E ...
s,
muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other ...
s, and
blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide aw ...
s. The muscles keep the membrane taut during flight. The extent to which the tail of a bat is attached to a patagium can vary by species, with some having completely free tails or even no tails. The skin on the body of the bat, which has one layer of
epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the ...
and
dermis The dermis or corium is a layer of skin between the epidermis (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from s ...
, as well as
hair follicle The hair follicle is an Organ (anatomy), organ found in mammalian skin. It resides in the Dermis, dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a compl ...
s,
sweat gland Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin that produce sweat. Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial sur ...
s and a fatty subcutaneous layer, is very different from the skin of the wing membrane. Depending on the bat species the presence of
hair follicle The hair follicle is an Organ (anatomy), organ found in mammalian skin. It resides in the Dermis, dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a compl ...
s and
sweat gland Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin that produce sweat. Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial sur ...
s will vary in the
patagium The patagium (plural: patagia) is a membranous Animal body, body part that assists an animal in obtaining lift (force), lift when gliding flight, gliding or flight. The structure is found in extant taxon, extant and extinct groups of flying and g ...
. This
patagium The patagium (plural: patagia) is a membranous Animal body, body part that assists an animal in obtaining lift (force), lift when gliding flight, gliding or flight. The structure is found in extant taxon, extant and extinct groups of flying and g ...
is an extremely thin double layer of epidermis; these layers are separated by a
connective tissue Connective tissue is one of the four primary types of animal tissue (biology), tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Con ...
center, rich with
collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...
and
elastic fiber Elastic fibers (or yellow fibers) are an essential component of the extracellular matrix composed of bundles of proteins (elastin) which are produced by a number of different cell types including fibroblasts, endothelial, smooth muscle, and air ...
s. In some bat species sweats glands will be present in between this
connective tissue Connective tissue is one of the four primary types of animal tissue (biology), tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Con ...
. Furthermore, if hair follicles are present this supports the bat in order to adjust sudden flight maneuvers. For bat embryos,
apoptosis Apoptosis (from grc, wikt:ἀπόπτωσις, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemistry, Biochemical events lead to characteristic cell changes (Morp ...
(cell death) affects only the hindlimbs, while the forelimbs retain webbing between the digits that forms into the wing membranes. Unlike birds, whose stiff wings deliver bending and torsional stress to the shoulders, bats have a flexible wing membrane that can resist only tension. To achieve flight, a bat exerts force inwards at the points where the membrane meets the skeleton, so that an opposing force balances it on the wing edges perpendicular to the wing surface. This adaptation does not permit bats to reduce their wingspans, unlike birds, which can partly fold their wings in flight, radically reducing the wing span and area for the upstroke and for gliding. Hence bats cannot travel over long distances as birds can. Nectar- and pollen-eating bats can hover, in a similar way to
hummingbird Hummingbirds are birds native to the Americas and comprise the Family (biology), biological family Trochilidae. With about 361 species and 113 genus, genera, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are ...
s. The sharp leading edges of the wings can create
vortices In fluid dynamics, a vortex (plural, : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools ...
, which provide
lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobile ...
. The vortex may be stabilized by the animal changing its wing curvatures.

## Roosting and gaits

When not flying, bats hang upside down from their feet, a posture known as roosting. The femurs are attached at the hips in a way that allows them to bend outward and upward in flight. The ankle joint can flex to allow the trailing edge of the wings to bend downwards. This does not permit many movements other than hanging or clambering up trees. Most megabats roost with the head tucked towards the belly, whereas most microbats roost with the neck curled towards the back. This difference is reflected in the structure of the cervical or neck vertebrae in the two groups, which are clearly distinct. Tendons allow bats to lock their feet closed when hanging from a roost. Muscular power is needed to let go, but not to grasp a perch or when holding on. When on the ground, most bats can only crawl awkwardly. A few species such as the New Zealand lesser short-tailed bat and the
common vampire bat The common vampire bat (''Desmodus rotundus'') is a small, leaf-nosed bat native to Latin America. It is one of three extant species of vampire bat, the other two being the Hairy-legged vampire bat, hairy-legged and the white-winged vampire bats ...
are agile on the ground. Both species make lateral gaits (the limbs move one after the other) when moving slowly but vampire bats move with a bounding gait (all limbs move in unison) at greater speeds, the folded up wings being used to propel them forward. Vampire bat likely evolved these gaits to follow their hosts while short-tailed bats developed in the absence of terrestrial mammal competitors. Enhanced terrestrial locomotion does not appear to have reduced their ability to fly.

## Internal systems

Bats have an efficient
circulatory system The blood circulatory system is a organ system, system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascula ...
. They seem to make use of particularly strong venomotion, a rhythmic contraction of
venous Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary vein, pulmonary and umbilical veins, both of which ca ...
wall muscles. In most mammals, the walls of the veins provide mainly passive resistance, maintaining their shape as deoxygenated blood flows through them, but in bats they appear to actively support blood flow back to the heart with this pumping action. Since their bodies are relatively small and lightweight, bats are not at risk of blood flow rushing to their heads when roosting. Bats possess a highly adapted
respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
to cope with the demands of powered flight, an energetically taxing activity that requires a large continuous throughput of oxygen. In bats, the relative alveolar surface area and pulmonary capillary blood volume are larger than in most other small quadrupedal mammals. During flight the respiratory cycle has a one-to-one relationship with the wing-beat cycle. Because of the restraints of the mammalian lungs, bats cannot maintain high-altitude flight. It takes a lot of energy and an efficient circulatory system to work the flight muscles of bats. Energy supply to the muscles engaged in flight requires about double the amount compared to the muscles that do not use flight as a means of mammalian locomotion. In parallel to energy consumption, blood oxygen levels of flying animals are twice as much as those of their terrestrially locomoting mammals. As the blood supply controls the amount of oxygen supplied throughout the body, the
circulatory system The blood circulatory system is a organ system, system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascula ...
must respond accordingly. Therefore, compared to a terrestrial mammal of the same relative size, the bat's
heart The heart is a muscular organ Organ may refer to: Biology * Organ (biology), a part of an organism Musical instruments * Organ (music), a family of keyboard musical instruments characterized by sustained tone ** Electronic organ, an el ...
can be up to three times larger, and pump more blood. Cardiac output is directly derived from heart rate and
stroke volume In cardiovascular physiology, stroke volume (SV) is the volume of blood pumped from the left ventricle (heart), ventricle per beat. Stroke volume is calculated using measurements of ventricle volumes from an Echocardiography, echocardiogram and s ...
of the blood; an active can reach a heart rate of 1000
beats per minute Beat, beats or beating may refer to: Common uses * Patrol, or beat, a group of personnel assigned to monitor a specific area ** Beat (police), the territory that a police officer patrols ** Gay beat, an area frequented by gay men * Batter ...
. With its extremely thin membranous tissue, a bat's wing can significantly contribute to the organism's total gas exchange efficiency. Because of the high energy demand of flight, the bat's body meets those demands by exchanging gas through the patagium of the wing. When the bat has its wings spread it allows for an increase in surface area to volume ratio. The surface area of the wings is about 85% of the total body surface area, suggesting the possibility of a useful degree of gas exchange. The subcutaneous vessels in the membrane lie very close to the surface and allow for the diffusion of oxygen and carbon dioxide. The
digestive system The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller compone ...
of bats has varying adaptations depending on the species of bat and its diet. As in other flying animals, food is processed quickly and effectively to keep up with the energy demand. Insectivorous bats may have certain
digestive enzyme Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption into the cells of the body. Digestive enzymes are found in the digestive tracts of anima ...
s to better process insects, such as
chitinase Chitinases (EC 3.2.1.14, chitodextrinase, 1,4-β-poly-N-acetylglucosaminidase, poly-β-glucosaminidase, β-1,4-poly-N-acetyl glucosamidinase, poly ,4-(N-acetyl-β-D-glucosaminide)glycanohydrolase, (1→4)-2-acetamido-2-deoxy-β-D-glucan glyc ...
to break down
chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting of very large molecules called macromolecules, ...
, which is a large component of insects. Vampire bats, probably due to their diet of blood, are the only vertebrates that do not have the enzyme
maltase Maltase (, ''alpha-glucosidase'', ''glucoinvertase'', ''glucosidosucrase'', ''maltase-glucoamylase'', ''alpha-glucopyranosidase'', ''glucosidoinvertase'', ''alpha-D-glucosidase'', ''alpha-glucoside hydrolase'', ''alpha-1,4-glucosidase'', ''alp ...
, which breaks down malt sugar, in their intestinal tract. Nectivorous and frugivorous bats have more maltase and
sucrase Sucrase is a digestive enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the subs ...
enzymes than insectivorous, to cope with the higher sugar contents of their diet. The adaptations of the
kidney The kidneys are two reddish-brown bean-shaped organ (anatomy), organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal ...
s of bats vary with their diets. Carnivorous and vampire bats consume large amounts of protein and can output concentrated
urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra. Cel ...
; their kidneys have a thin cortex and long renal papillae. Frugivorous bats lack that ability and have kidneys adapted for
electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electron The electron ( or ) is a subatomic particle with a negative one elementary charge, elementary electr ...
-retention due to their low-electrolyte diet; their kidneys accordingly have a thick cortex and very short conical papillae. Bats have higher metabolic rates associated with flying, which lead to an increased respiratory water loss. Their large wings are composed of the highly vascularized membranes, increasing the surface area, and leading to
cutaneous Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
evaporative water loss. Water helps maintain their ionic balance in their blood,
thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
system, and removal of wastes and toxins from the body via urine. They are also susceptible to blood urea poisoning if they do not receive enough fluid. The structure of the uterine system in female bats can vary by species, with some having two uterine horns while others have a single mainline chamber.

## Senses

### Echolocation

Microbats and a few megabats emit ultrasonic sounds to produce echoes. Sound intensity of these echos are dependent on subglottic pressure. The bats' cricothyroid muscle controls the orientation pulse frequency, which is an important function. This muscle is located inside the larynx and it is the only tensor muscle capable of aiding phonation. By comparing the outgoing pulse with the returning echoes, bats can gather information on their surroundings. This allows them to detect prey in darkness. Some bat calls can reach 140
decibels The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a ...
. Microbats use their
larynx The larynx (), commonly called the voice box, is an organ (anatomy), organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal ...
to emit echolocation signals through the mouth or the nose. Microbat calls range in frequency from 14,000 to well over 100,000 Hz, extending well beyond the range of human hearing (between 20 and 20,000 Hz). Various groups of bats have evolved fleshy extensions around and above the nostrils, known as nose-leaves, which play a role in sound transmission. In low-duty cycle echolocation, bats can separate their calls and returning echoes by time. They have to time their short calls to finish before echoes return. The delay of the returning echoes allows the bat to estimate the range to their prey. In high-duty cycle echolocation, bats emit a continuous call and separate pulse and echo in frequency using the
Doppler effect The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who ...
of their motion in flight. The shift of the returning echoes yields information relating to the motion and location of the bat's prey. These bats must deal with changes in the Doppler shift due to changes in their flight speed. They have adapted to change their pulse emission frequency in relation to their flight speed so echoes still return in the optimal hearing range. In addition to echolocating prey, bat ears are sensitive to sounds made by their prey, such as the fluttering of moth wings. The complex geometry of ridges on the inner surface of bat ears helps to sharply focus echolocation signals, and to passively listen for any other sound produced by the prey. These ridges can be regarded as the acoustic equivalent of a
Fresnel lens A Fresnel lens ( ; ; or ) is a type of composite compact lens (optics), lens developed by the French physicist Augustin-Jean Fresnel (1788–1827) for use in lighthouses. It has been called "the invention that saved a million ships." The desi ...
, and exist in a large variety of unrelated animals, such as the
aye-aye The aye-aye (''Daubentonia madagascariensis'') is a long-fingered lemur Lemurs ( ) (from Latin ''lemures'' – ghosts or spirits) are Strepsirrhini, wet-nosed primates of the Superfamily (biology), superfamily Lemuroidea (), divided into ...
, lesser galago,
bat-eared fox The bat-eared fox (''Otocyon megalotis'') is a species of fox Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightl ...
,
mouse lemur The mouse lemurs are nocturnal lemurs of the genus ''Microcebus''. Like all lemurs, mouse lemurs are native to Madagascar. Mouse lemurs have a combined head, body and tail length of less than , making them the smallest primates (the smallest spe ...
, and others. Bats can estimate the elevation of their target using the
interference pattern In physics, interference is a phenomenon in which two waves combine by adding their displacement together at every single point in space and time, to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructive ...
s from the echoes reflecting from the tragus, a flap of skin in the external ear. By repeated scanning, bats can mentally construct an accurate image of the environment in which they are moving and of their prey. Some species of moth have exploited this, such as the tiger moths, which produces
aposematic Aposematism is the Advertising in biology, advertising by an animal to potential predation, predators that it is not worth attacking or eating. This unprofitability may consist of any defences which make the prey difficult to kill and eat, suc ...
ultrasound signals to warn bats that they are chemically protected and therefore distasteful. Moth species including the tiger moth can produce signals to jam bat echolocation. Many moth species have a hearing organ called a tympanum, which responds to an incoming bat signal by causing the moth's flight muscles to twitch erratically, sending the moth into random evasive manoeuvres.

### Vision

The eyes of most microbat species are small and poorly developed, leading to poor
visual acuity Visual acuity (VA) commonly refers to the clarity of visual perception, vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpn ...
, but no species is blind. Most microbats have
mesopic vision Mesopic vision, sometimes also called twilight vision, is a combination of photopic vision, photopic and scotopic vision under low-light (but not necessarily dark) conditions. Mesopic levels range approximately from 0.01 to 3.0 candela per s ...
, meaning that they can detect light only in low levels, whereas other mammals have
photopic vision Photopic vision is the visual perception, vision of the human eye, eye under well-lit conditions (luminance levels from 10 to 108 candela per square metre, cd/m2). In humans and many other animals, photopic vision allows color vision, color ...
, which allows colour vision. Microbats may use their vision for orientation and while travelling between their roosting grounds and feeding grounds, as echolocation is effective only over short distances. Some species can detect
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
(UV). As the bodies of some microbats have distinct coloration, they may be able to discriminate colours. Megabat species often have eyesight as good as, if not better than, human vision. Their eyesight is adapted to both night and daylight vision, including some colour vision.

### Magnetoreception

Microbats make use of magnetoreception, in that they have a high sensitivity to the
Earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic ...
, as birds do. Microbats use a polarity-based compass, meaning that they differentiate north from south, unlike birds, which use the strength of the magnetic field to differentiate
latitude In geography, latitude is a Geographic coordinate system, coordinate that specifies the north–south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south ...
s, which may be used in long-distance travel. The mechanism is unknown but may involve
magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to be ...
particles.

## Thermoregulation

Most bats are
homeothermic Homeothermy, homothermy or homoiothermy is thermoregulation that maintains a stable internal body temperature regardless of external influence. This internal body temperature is often, though not necessarily, higher than the immediate environmen ...
(having a stable body temperature), the exception being the vesper bats (Vespertilionidae), the horseshoe bats (Rhinolophidae), the free-tailed bats (Molossidae), and the bent-winged bats (Miniopteridae), which extensively use
heterothermy Heterothermy or heterothermia (from Ancient Greek, Greek ἕτερος ''heteros'' "other" and θέρμη ''thermē'' "heat") is a physiological term for animals that vary between self-regulating their body temperature, and allowing the surrounding ...
(where body temperature can vary). Compared to other mammals, bats have a high
thermal conductivity The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials ...
. The wings are filled with blood vessels, and lose body heat when extended. At rest, they may wrap their wings around themselves to trap a layer of warm air. Smaller bats generally have a higher metabolic rate than larger bats, and so need to consume more food in order to maintain homeothermy. Bats may avoid flying during the day to prevent overheating in the sun, since their dark wing-membranes absorb solar radiation. Bats may not be able to dissipate heat if the ambient temperature is too high; they use saliva to cool themselves in extreme conditions. Among megabats, the flying fox '' Pteropus hypomelanus'' uses saliva and wing-fanning to cool itself while roosting during the hottest part of the day. Among microbats, the Yuma myotis (''Myotis yumanensis''), the Mexican free-tailed bat, and the pallid bat (''Antrozous pallidus'') cope with temperatures up to by panting, salivating, and licking their fur to promote evaporative cooling; this is sufficient to dissipate twice their metabolic heat production. Bats also possess a system of
sphincter A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning. Sphincters are found in many animals. There are over 60 types in the hum ...
valves on the arterial side of the vascular network that runs along the edge of their wings. When fully open, these allow oxygenated blood to flow through the
capillary A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...
network across the wing membrane; when contracted, they shunt flow directly to the veins, bypassing the wing capillaries. This allows bats to control how much heat is exchanged through the flight membrane, allowing them to release heat during flight. Many other mammals use the capillary network in oversized ears for the same purpose.

### Torpor

Torpor Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time ...
, a state of decreased activity where the body temperature and
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
decreases, is especially useful for bats, as they use a large amount of energy while active, depend upon an unreliable food source, and have a limited ability to store fat. They generally drop their body temperature in this state to , and may reduce their energy expenditure by 50 to 99%. Tropical bats may use it to avoid predation, by reducing the amount of time spent on foraging and thus reducing the chance of being caught by a predator. Megabats were generally believed to be homeothermic, but three species of small megabats, with a mass of about , have been known to use torpor: the common blossom bat (''Syconycteris australis''), the long-tongued nectar bat (''Macroglossus minimus''), and the eastern tube-nosed bat (''Nyctimene robinsoni''). Torpid states last longer in the summer for megabats than in the winter. During
hibernation Hibernation is a state of minimal activity and Metabolism, metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic ra ...
, bats enter a torpid state and decrease their body temperature for 99.6% of their hibernation period; even during periods of arousal, when they return their body temperature to normal, they sometimes enter a shallow torpid state, known as "heterothermic arousal". Some bats become dormant during higher temperatures to keep cool in the summer months. Heterothermic bats during long migrations may fly at night and go into a torpid state roosting in the daytime. Unlike migratory birds, which fly during the day and feed during the night, nocturnal bats have a conflict between travelling and eating. The energy saved reduces their need to feed, and also decreases the duration of migration, which may prevent them from spending too much time in unfamiliar places, and decrease predation. In some species, pregnant individuals may not use torpor.

## Size

The smallest bat is Kitti's hog-nosed bat (''Craseonycteris thonglongyai''), which is long with a wingspan and weighs . It is also arguably the smallest
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...
species of mammal, next to the Etruscan shrew. The largest bats are a few species of ''
Pteropus ''Pteropus'' (suborder Yinpterochiroptera) is a genus of megabats which are among the largest bats in the world. They are commonly known as fruit bats or flying foxes, among other colloquial names. They live in South Asia, Southeast Asia, Austra ...
'' megabats and the giant golden-crowned flying fox, (''Acerodon jubatus''), which can weigh with a wingspan of . Larger bats tend to use lower frequencies and smaller bats higher for echolocation; high-frequency echolocation is better at detecting smaller prey. Small prey may be absent in the diets of large bats as they are unable to detect them. The adaptations of a particular bat species can directly influence what kinds of prey are available to it.

# Ecology

Flight has enabled bats to become one of the most widely distributed groups of mammals. Apart from the Arctic, the Antarctic and a few isolated oceanic islands, bats exist in almost every habitat on Earth. Tropical areas tend to have more species than temperate ones. Different species select different habitats during different seasons, ranging from seasides to mountains and deserts, but they require suitable roosts. Bat roosts can be found in hollows, crevices, foliage, and even human-made structures, and include "tents" the bats construct with leaves. Megabats generally roost in trees. Most microbats are
nocturnal Nocturnality is an ethology, animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatures generally have ...
and megabats are typically diurnal or
crepuscular In zoology, a crepuscular animal is one that is active primarily during the twilight period, being matutinal, vespertine (biology), vespertine, or both. This is distinguished from diurnality, diurnal and nocturnality, nocturnal behavior, where ...
. Microbats are known to exhibit diurnal behaviour in temperate regions during summer when there is insufficient night time to forage, and in areas where there are few avian predators during the day. In temperate areas, some microbats migrate hundreds of kilometres to winter hibernation dens; others pass into torpor in cold weather, rousing and feeding when warm weather allows insects to be active. Others retreat to caves for winter and hibernate for as much as six months. Microbats rarely fly in rain; it interferes with their echolocation, and they are unable to hunt.

## Food and feeding

Different bat species have different diets, including insects, nectar, pollen, fruit and even vertebrates. Megabats are mostly fruit, nectar and pollen eaters. Due to their small size, high-metabolism and rapid burning of energy through flight, bats must consume large amounts of food for their size. Insectivorous bats may eat over 120 percent of their body weight, while frugivorous bats may eat over twice their weight. They can travel significant distances each night, exceptionally as much as in the spotted bat ('' Euderma maculatum''), in search of food. Bats use a variety of hunting strategies. Bats get most of their water from the food they eat; many species also drink from water sources like lakes and streams, flying over the surface and dipping their tongues into the water. The Chiroptera as a whole are in the process of losing the ability to synthesise
vitamin C Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a Topical medication, topical 'serum' ingredient to treat melasma (dar ...
. In a test of 34 bat species from six major families, including major insect- and fruit-eating bat families, all were found to have lost the ability to synthesise it, and this loss may derive from a common bat ancestor, as a single mutation. At least two species of bat, the frugivorous bat (''Rousettus leschenaultii'') and the insectivorous bat (''Hipposideros armiger''), have retained their ability to produce vitamin C.

### Insects

Most microbats, especially in temperate areas, prey on insects. The diet of an insectivorous bat may span many species, including
flies Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwing ...
,
mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small Diptera, flies within the family Culicidae (from the Latin ''culex'' meaning "gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish ...

s,
beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, Elytron, elytra, distinguishing them from most other insects. The Coleoptera, wit ...
s, moths,
grasshopper Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshoppe ...
s,
cricket Cricket is a Bat-and-ball games, bat-and-ball game played between two teams of eleven players on a cricket field, field at the centre of which is a cricket pitch, pitch with a wicket at each end, each comprising two Bail (cricket), bails b ...
s,
termite Termites are small insects that live in colonies and have distinct castes (Eusociality, eusocial) and feed on wood or other dead plant matter. Termites comprise the infraorder Isoptera, or alternatively the Taxonomic rank#All ranks, epifamily ...
s,
bee Bees are winged insects closely related to wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which lo ...
s,
wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. ...
s,
mayflies Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four Census Bureau Region, census regions ...
and
caddisflies The caddisflies, or order Trichoptera, are a group of insect Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects ...
. Large numbers of Mexican free-tailed bats (''Tadarida brasiliensis'') fly hundreds of metres above the ground in central Texas to feed on migrating moths. Species that hunt insects in flight, like the
little brown bat The little brown bat or little brown myotis (''Myotis lucifugus'') is an endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction ...
(''Myotis lucifugus''), may catch an insect in mid-air with the mouth, and eat it in the air or use their tail membranes or wings to scoop up the insect and carry it to the mouth. The bat may also take the insect back to its roost and eat it there. Slower moving bat species, such as the brown long-eared bat (''Plecotus auritus'') and many horseshoe bat species, may take or glean insects from vegetation or hunt them from perches. Insectivorous bats living at high latitudes have to consume prey with higher energetic value than tropical bats.

### Fruit and nectar

Fruit eating, or frugivory, is found in both major suborders. Bats prefer ripe fruit, pulling it off the trees with their teeth. They fly back to their roosts to eat the fruit, sucking out the juice and spitting the seeds and pulp out onto the ground. This helps disperse the seeds of these fruit trees, which may take root and grow where the bats have left them, and many species of plants depend on bats for
seed dispersal In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...
. The Jamaican fruit bat (''Artibeus jamaicensis'') has been recorded carrying fruits weighing or even as much as . Nectar-eating bats have acquired specialised adaptations. These bats possess long muzzles and long, extensible
tongue The tongue is a muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper surfa ...
s covered in fine bristles that aid them in feeding on particular flowers and plants. The tube-lipped nectar bat (''Anoura fistulata'') has the longest tongue of any mammal relative to its body size. This is beneficial to them in terms of pollination and feeding. Their long, narrow tongues can reach deep into the long cup shape of some flowers. When the tongue retracts, it coils up inside the rib cage. Because of these features, nectar-feeding bats cannot easily turn to other food sources in times of scarcity, making them more prone to extinction than other types of bat. Nectar feeding also aids a variety of plants, since these bats serve as
pollinator A pollinator is an animal that moves pollen from the male anther of a flower to the female carpel, stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains. Insects are ...
s, as pollen gets attached to their fur while they are feeding. Around 500 species of flowering plant rely on bat pollination and thus tend to open their flowers at night. Many rainforest plants depend on bat pollination.

### Vertebrates

Some bats prey on other vertebrates, such as fish, frogs, lizards, birds and mammals. The fringe-lipped bat (''Trachops cirrhosus,'') for example, is skilled at catching frogs. These bats locate large groups of frogs by tracking their mating calls, then plucking them from the surface of the water with their sharp canine teeth. The
greater noctule bat The greater noctule bat (''Nyctalus lasiopterus'') is a rare carnivorous bat found in Europe, West Asia, and North Africa. It is the largest and least studied bat in Europe with a wingspan of up to and is one of the few bat species to feed on pa ...
can catch birds in flight. Some species, like the greater bulldog bat ('' Noctilio leporinus'') hunt fish. They use echolocation to detect small ripples on the water's surface, swoop down and use specially enlarged claws on their hind feet to grab the fish, then take their prey to a feeding roost and consume it. At least two species of bat are known to feed on other bats: the spectral bat (''Vampyrum spectrum''), and the
ghost bat The ghost bat (''Macroderma gigas'') is a species of bat found in northern Australia. The species is the only Australian bat that preys on large vertebrates – birds, reptiles and other mammals – which they detect using acute sight and heari ...
(''Macroderma gigas'').

### Blood

A few species, specifically the common, white-winged, and hairy-legged vampire bats, feed only on animal blood (
hematophagy Hematophagy (sometimes spelled haematophagy or hematophagia) is the practice by certain animals of feeding on blood (from the Ancient Greek, Greek words αἷμα ' "blood" and φαγεῖν ' "to eat"). Since blood is a fluid tissue rich in ...
). The common vampire bat typically feeds on large mammals such as
cattle Cattle (''Bos taurus'') are large, domestication, domesticated, Cloven hoof, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referr ...
; the hairy-legged and white-winged vampires feed on birds. Vampire bats target sleeping prey and can detect deep breathing. Heat sensors in the nose help them to detect blood vessels near the surface of the skin. They pierce the animal's skin with their teeth, biting away a small flap, and lap up the blood with their tongues, which have lateral grooves adapted to this purpose. The blood is kept from clotting by an
anticoagulant Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquito Mosqu ...
in the saliva.

## Predators, parasites, and diseases

Bats are subject to predation from
birds of prey Birds of prey or predatory birds, also known as raptors, are hypercarnivorous bird species that actively predation, hunt and feed on other vertebrates (mainly mammals, reptiles and other smaller birds). In addition to speed and strength, these p ...
, such as
owls Owls are birds from the Order (biology), order Strigiformes (), which includes over 200 species of mostly Solitary animal, solitary and Nocturnal animal, nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vi ...
,
hawks Hawks are birds of prey Birds of prey or predatory birds, also known as raptors, are hypercarnivorous bird species that actively predation, hunt and feed on other vertebrates (mainly mammals, reptiles and other smaller birds). In addition ...
, and falcons, and at roosts from terrestrial predators able to climb, such as cats. Low-flying bats are vulnerable to
crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...
s. Twenty species of tropical New World
snake Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...
s are known to capture bats, often waiting at the entrances of refuges, such as caves, for bats to fly past. J. Rydell and J. R. Speakman argue that bats evolved nocturnality during the early and middle
Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek Anci ...
period to avoid predators. The evidence is thought by some zoologists to be equivocal so far. As most mammals, bats are hosts to a number of internal and external parasites. Among
ectoparasite Parasitism is a close relationship between species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as th ...
s, bats carry
flea Flea, the common name for the order Siphonaptera, includes 2,500 species of small flightless insects that live as external parasites of mammals and birds. Fleas live by ingesting the blood of their hosts. Adult fleas grow to about long, ar ...
s and
mite Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...
s, as well as specific parasites such as bat bugs and bat flies ( Nycteribiidae and Streblidae). Bats are among the few non-aquatic mammalian orders that do not host
lice Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insect Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biol ...
, possibly due to competition from more specialised parasites that occupy the same niche.
White nose syndrome White-nose syndrome (WNS) is a fungal disease in North American bats which has resulted in the dramatic decrease of the bat population in the United States and Canada, reportedly killing millions as of 2018. The condition is named for a distincti ...
is a condition associated with the deaths of millions of bats in the
Eastern United States The Eastern United States, commonly referred to as the American East, Eastern America, or simply the East, is the region of the United States to the east of the Mississippi River. In some cases the term may refer to a smaller area or the East C ...
and Canada. The disease is named after a white
fungus A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...
, ''
Pseudogymnoascus destructans ''Pseudogymnoascus destructans'' (formerly known as ''Geomyces destructans'') is a Psychrophile, psychrophilic (cold-loving) fungus that causes white-nose syndrome (WNS), a fatal disease that has devastated bat populations in parts of the United ...
'', found growing on the muzzles, ears, and wings of affected bats. The fungus is mostly spread from bat to bat, and causes the disease. The fungus was first discovered in central New York State in 2006 and spread quickly to the entire Eastern US north of Florida; mortality rates of 90–100% have been observed in most affected caves.
New England New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts Massachusetts (Massachusett language, Massachusett: ''Muhsachuweesut assachusett writing systems, məhswatʃəwiːsət ...
and the mid-Atlantic states have, since 2006, witnessed entire species completely extirpated and others with numbers that have gone from the hundreds of thousands, even millions, to a few hundred or less. Nova Scotia, Quebec, Ontario, and New Brunswick have witnessed identical die offs, with the Canadian government making preparations to protect all remaining bat populations in its territory. Scientific evidence suggests that longer winters where the fungus has a longer period to infect bats result in greater mortality. In 2014, the infection crossed the Mississippi River, and in 2017, it was found on bats in Texas. Bats are natural reservoirs for a large number of
zoonotic A zoonosis (; plural zoonoses) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that has Cross-species transmission, jumped from a non-human (usuall ...
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ ...
s, including
rabies Rabies is a viral disease that causes encephalitis Encephalitis is inflammation of the brain. The severity can be variable with symptoms including reduction or alteration in consciousness, headache, fever, confusion, a stiff neck, a ...
, endemic in many bat populations,
histoplasmosis Histoplasmosis is a fungal infection caused by ''Histoplasma capsulatum''. Symptoms of this infection vary greatly, but the disease affects primarily the lungs. Occasionally, other organs are affected; called disseminated histoplasmosis, it can b ...
both directly and in guano, Nipah and Hendra viruses, and possibly the
ebola virus ''Zaire ebolavirus'', more commonly known as Ebola virus (; EBOV), is one of six known species within the genus ''Ebolavirus''. Four of the six known ebolaviruses, including EBOV, cause a severe and often fatal viral hemorrhagic fever, hemorrhag ...
, Note: This is a lay summary of the various scientific publications cited in the preceding sentence. whose natural reservoir is yet unknown. Their high mobility, broad distribution, long life spans, substantial
sympatry In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sh ...
(range overlap) of species, and social behaviour make bats favourable hosts and vectors of disease. Reviews have found different answers as to whether bats have more zoonotic viruses than other mammal groups. One 2015 review found that bats, rodents, and primates all harbored significantly more
zoonotic A zoonosis (; plural zoonoses) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that has Cross-species transmission, jumped from a non-human (usuall ...
viruses (which can be transmitted to humans) than other mammal groups, though the differences among the aforementioned three groups were not significant (bats have no more zoonotic viruses than rodents and primates). Another 2020 review of mammals and birds found that the identify of the taxonomic groups did not have any impact on the probability of harboring zoonotic viruses. Instead, more diverse groups had greater viral diversity. They seem to be highly resistant to many of the pathogens they carry, suggesting a degree of adaptation to their immune systems. Their interactions with livestock and pets, including predation by vampire bats, accidental encounters, and the scavenging of bat carcasses, compound the risk of zoonotic transmission. Bats are implicated in the emergence of
severe acute respiratory syndrome Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1), the first identified strain of the SARS coronavirus species, '' ...
(SARS) in China, since they serve as natural hosts for
coronavirus Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the c ...
es, several from a single cave in
Yunnan Yunnan , () is a landlocked Provinces of China, province in Southwest China, the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is ...
, one of which developed into the SARS virus. However, they neither cause nor spread
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was COVID-19 pandemic in Hubei, identified in Wuhan, China, in December ...
.

# Behaviour and life history

## Social structure

Some bats lead solitary lives, while others live in colonies of more than a million. For instance, the
Mexican free-tailed bat The Mexican free-tailed bat or Brazilian free-tailed bat (''Tadarida brasiliensis'') is a medium-sized bat native to the Americas, so named because its tail can be almost half its total length and is not attached to its uropatagium. It has been ...
fly for more than one thousand miles to the wide cave known as Bracken Cave every March to October which plays home to an astonishing twenty million of the species, whereas a
mouse-eared bat The mouse-eared bats or myotises are a diverse and widespread genus (''Myotis'') of bats within the family Vespertilionidae. The noun "''myotis''" itself is a New Latin construction, from the Greek language, Greek "''muós'' (meaning "mouse") and ...
lives an almost completely solitary life. Living in large colonies lessens the risk to an individual of predation. Temperate bat species may
swarm Swarm behaviour, or swarming, is a collective animal behaviour, collective behaviour exhibited by entities, particularly animals, of similar size which aggregate together, perhaps milling about the same spot or perhaps moving ''en masse'' or a ...
at hibernation sites as autumn approaches. This may serve to introduce young to hibernation sites, signal reproduction in adults and allow adults to breed with those from other groups. Several species have a fission-fusion social structure, where large numbers of bats congregate in one roosting area, along with breaking up and mixing of subgroups. Within these societies, bats are able to maintain long-term relationships. Some of these relationships consist of
matrilineal Matrilineality is the tracing of kinship through the female line. It may also correlate with a social system in which each person is identified with their matriline – their mother's Lineage (anthropology), lineage – and which can in ...
ly related females and their dependent offspring. Food sharing and mutual grooming may occur in certain species, such as the common vampire bat (''Desmodus rotundus''), and these strengthen social bonds.

## Communication

Bats are among the most vocal of mammals and produce calls to attract mates, find roost partners and defend resources. These calls are typically low-frequency and can travel long distances. Mexican free-tailed bats are one of the few species to "sing" like birds. Males sing to attract females. Songs have three phrases: chirps, trills and buzzes, the former having "A" and "B" syllables. Bat songs are highly stereotypical but with variation in syllable number, phrase order, and phrase repetitions between individuals. Among greater spear-nosed bats (''Phyllostomus hastatus''), females produce loud, broadband calls among their roost mates to form group cohesion. Calls differ between roosting groups and may arise from vocal learning. In a study on captive Egyptian fruit bats, 70% of the directed calls could be identified by the researchers as to which individual bat made it, and 60% could be categorised into four contexts: squabbling over food, jostling over position in their sleeping cluster, protesting over mating attempts and arguing when perched in close proximity to each other. The animals made slightly different sounds when communicating with different individual bats, especially those of the opposite sex. In the highly
sexually dimorphic Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different Morphology (biology), morphological characteristics, particularly characteristics not directly involved in reproduction. The conditio ...
hammer-headed bat (''Hypsignathus monstrosus''), males produce deep, resonating, monotonous calls to attract females. Bats in flight make vocal signals for traffic control. Greater bulldog bats honk when on a collision course with each other. Bats also communicate by other means. Male little yellow-shouldered bats (''Sturnira lilium'') have shoulder glands that produce a spicy odour during the breeding season. Like many other species, they have hair specialised for retaining and dispersing secretions. Such hair forms a conspicuous collar around the necks of the some Old World megabat males. Male greater sac-winged bats (''Saccopteryx bilineata'') have sacs in their wings in which they mix body secretions like saliva and urine to create a perfume that they sprinkle on roost sites, a behaviour known as "salting". Salting may be accompanied by singing.

## Reproduction and lifecycle

Most bat species are
polygynous Polygyny (; from Neoclassical Greek πολυγυνία (); ) is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women. Incidence Polygyny is more widespread in Africa than in any o ...
, where males mate with multiple females. Male pipistrelle, noctule and vampire bats may claim and defend resources that attract females, such as roost sites, and mate with those females. Males unable to claim a site are forced to live on the periphery where they have less reproductive success.
Promiscuity Promiscuity is the practice of engaging in sexual activity frequently with different partners or being indiscriminate in the choice of sexual partners. The term can carry a moral judgment. A common example of behavior viewed as promiscuous by ma ...
, where both sexes mate with multiple partners, exists in species like the Mexican free-tailed bat and the little brown bat. There appears to be bias towards certain males among females in these bats. In a few species, such as the yellow-winged bat and spectral bat, adult males and females form
monogamous Monogamy ( ) is a form of dyadic relationship in which an individual has only one partner during their lifetime. Alternately, only one partner at any one time ( serial monogamy) — as compared to the various forms of non-monogamy (e.g., po ...
pairs.
Lek mating A lek is an aggregation of male animals gathered to engage in competitive displays and courtship rituals, known as lekking, to entice visiting females which are surveying prospective partners with which to mate. A lek can also indicate an avail ...
, where males aggregate and compete for female choice through display, is rare in bats but occurs in the hammerheaded bat. For temperate living bats, mating takes place in late summer and early autumn. Tropical bats may mate during the dry season. After copulation, the male may leave behind a
mating plug A mating plug, also known as a copulation plug, sperm plug, vaginal plug, or sphragis (Latin, from Greek σφραγίς ''sphragis'', "a seal"), is gelatinous secretion used in the mating In biology, mating is the pairing of either opposite-se ...
to block the sperm of other males and thus ensure his paternity. In hibernating species, males are known to mate with females in torpor. Female bats use a variety of strategies to control the timing of pregnancy and the birth of young, to make delivery coincide with maximum food ability and other ecological factors. Females of some species have delayed fertilisation, in which sperm is stored in the reproductive tract for several months after mating. Mating occurs in late summer to early autumn but fertilisation does not occur until the following late winter to early spring. Other species exhibit delayed implantation, in which the egg is fertilised after mating, but remains free in the reproductive tract until external conditions become favourable for giving birth and caring for the offspring. In another strategy, fertilisation and implantation both occur, but development of the foetus is delayed until good conditions prevail. During the delayed development the mother keeps the fertilised egg alive with nutrients. This process can go on for a long period, because of the advanced gas exchange system. For temperate living bats, births typically take place in May or June in the northern hemisphere; births in the southern hemisphere occur in November and December. Tropical species give birth at the beginning of the rainy season. In most bat species, females carry and give birth to a single pup per litter. At birth, a bat pup can be up to 40 percent of the mother's weight, and the pelvic girdle of the female can expand during birth as the two-halves are connected by a flexible ligament. Females typically give birth in a head-up or horizontal position, using gravity to make birthing easier. The young emerges rear-first, possibly to prevent the wings from getting tangled, and the female cradles it in her wing and tail membranes. In many species, females give birth and raise their young in maternity colonies and may assist each other in birthing. Most of the care for a young bat comes from the mother. In monogamous species, the father plays a role. Allo-suckling, where a female suckles another mother's young, occurs in several species. This may serve to increase colony size in species where females return to their natal colony to breed. A young bat's ability to fly coincides with the development of an adult body and forelimb length. For the little brown bat, this occurs about eighteen days after birth. Weaning of young for most species takes place in under eighty days. The common vampire bat nurses its offspring beyond that and young vampire bats achieve independence later in life than other species. This is probably due to the species' blood-based diet, which is difficult to obtain on a nightly basis.

## Life expectancy

The maximum lifespan of bats is three-and-a-half times longer than other mammals of similar size. Six species have been recorded to live over thirty years in the wild: the brown long-eared bat (''Plecotus auritus''), the little brown bat (''Myotis lucifugus''), the Siberian bat (''Myotis sibiricus''), the lesser mouse-eared bat (''Myotis blythii'') the
greater horseshoe bat The greater horseshoe bat (''Rhinolophus ferrumequinum'') is an Insectivore, insectivorous bat of the genus ''Rhinolophus''. Its distribution covers Europe, Northern Africa, Central Asia and Eastern Asia. It is the largest of the horseshoe bats i ...
(''Rhinolophus ferrumequinum''), and the Indian flying fox (''Pteropus giganteus''). One hypothesis consistent with the rate-of-living theory links this to the fact that they slow down their
metabolic rate Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
while hibernating; bats that hibernate, on average, have a longer lifespan than bats that do not. Another hypothesis is that flying has reduced their mortality rate, which would also be true for birds and gliding mammals. Bat species that give birth to multiple pups generally have a shorter lifespan than species that give birth to only a single pup. Cave-roosting species may have a longer lifespan than non-roosting species because of the decreased predation in caves. A male Siberian bat was recaptured in the wild after 41 years, making it the oldest known bat.

# Interactions with humans

## Conservation

Groups such as the Bat Conservation International aim to increase awareness of bats' ecological roles and the environmental threats they face. In the United Kingdom, all bats are protected under the Wildlife and Countryside Acts, and disturbing a bat or its roost can be punished with a heavy fine. In
Sarawak Sarawak (; ) is a States and federal territories of Malaysia, state of Malaysia. The largest among the 13 states, with an area almost equal to that of Peninsular Malaysia, Sarawak is located in northwest Borneo Island, and is bordered by the M ...
, Malaysia, "all bats" are protected under the Wildlife Protection Ordinance 1998, but species such as the hairless bat (''Cheiromeles torquatus'') are still eaten by the local communities. Humans have caused the extinction of several species of bat in modern history, the most recent being the Christmas Island pipistrelle (''Pipistrellus murrayi''), which was declared extinct in 2009. Many people put up bat houses to attract bats. The 1991
University of Florida The University of Florida (Florida or UF) is a public university, public land-grant university, land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853 ...
bat house is the largest occupied artificial roost in the world, with around 400,000 residents. In Britain, thickwalled and partly underground World War II pillboxes have been converted to make roosts for bats, and purpose-built bat houses are occasionally built to mitigate damage to habitat from road or other developments.
Cave gate A cave gate is a manmade barricade typically placed at, or just inside, the entrance to a cave in an effort to impede or mitigate human access to a cave's interior. The reason for gating a cave can be varied, but may include protecting sensitive o ...
s are sometimes installed to limit human entry into caves with sensitive or endangered bat species. The gates are designed not to limit the airflow, and thus to maintain the cave's micro-ecosystem. Of the 47 species of bats found in the United States, 35 are known to use human structures, including buildings and bridges. Fourteen species use bat houses. Bats are eaten in countries across Africa, Asia and the Pacific Rim. In some cases, such as in Guam, flying foxes have become endangered through being hunted for food. There is evidence that
wind turbine A wind turbine is a device that wind power, converts the kinetic energy of wind into electrical energy. Hundreds of thousands of list of most powerful wind turbines, large turbines, in installations known as wind farms, now generate over 650 gi ...
s create sufficient
barotrauma Barotrauma is physical damage to body Fluid compartments, tissues caused by a difference in pressure between a gas space inside, or contact with, the body and the surrounding gas or liquid. The initial damage is usually due to over-stretching th ...
(pressure damage) to kill bats. Bats have typical mammalian lungs, which are thought to be more sensitive to sudden air pressure changes than the lungs of birds, making them more liable to fatal rupture. Bats may be attracted to turbines, perhaps seeking roosts, increasing the death rate. Acoustic deterrents may help to reduce bat mortality at wind farms.

## Cultural significance

Since bats are mammals, yet can fly, they are considered to be liminal beings in various traditions. In many cultures, including in Europe, bats are associated with darkness, death, witchcraft, and malevolence. Among Native Americans such as the Creek,
Cherokee The Cherokee (; chr, ᎠᏂᏴᏫᏯᎢ, translit=Aniyvwiyaʔi or Anigiduwagi, or chr, ᏣᎳᎩ, links=no, translit=Tsalagi) are one of the indigenous peoples of the Southeastern Woodlands of the United States. Prior to the 18th century, th ...
and
Apache The Apache () are a group of culturally related Native American tribes in the Southwestern United States, which include the Chiricahua, Jicarilla, Lipan, Mescalero, Mimbreño, Ndendahe (Bedonkohe or Mogollon and Nednhi or Carrizaleño ...
, the bat is identified as a
trickster In mythology and the study of folklore and religion, a trickster is a character in a story (God (male deity), god, goddess, spirit, human or anthropomorphism, anthropomorphisation) who exhibits a great degree of intellect or secret knowledge and ...
. In Tanzania, a winged batlike creature known as Popobawa is believed to be a shapeshifting
evil spirit Evil, in a general sense, is defined as the opposite or absence of good In most contexts, the concept of good denotes the conduct that should be preferred when posed with a choice between possible actions. Good is generally considered to b ...
that assaults and sodomises its victims. In
Aztec The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different Indigenous peoples of Mexico, ethnic groups of central Mexico, particularly those g ...
mythology Myth is a folklore genre consisting of narratives that play a fundamental role in a society, such as foundational tales or origin myths. Since "myth" is widely used to imply that a story is not objectively true, the identification of a narra ...
, bats symbolised the land of the dead, destruction, and decay. An East Nigerian tale tells that the bat developed its nocturnal habits after causing the death of his partner, the bush-rat, and now hides by day to avoid arrest. More positive depictions of bats exist in some cultures. In China, bats have been associated with happiness, joy and good fortune. Five bats are used to symbolise the "Five Blessings": longevity, wealth, health, love of virtue and peaceful death. The bat is sacred in
Tonga Tonga (, ; ), officially the Kingdom of Tonga ( to, Puleʻanga Fakatuʻi ʻo Tonga), is a Polynesia, Polynesian country and archipelago. The country has List of islands and towns in Tonga, 171 islands – of which 45 are inhabited. Its tota ...
and is often considered the physical manifestation of a separable
soul In many religious and philosophical traditions, there is a belief that a soul is "the immaterial aspect or essence of a human being". Etymology The Modern English noun '':wikt:soul, soul'' is derived from Old English ''sāwol, sāwel''. The ea ...
. In the Zapotec civilisation of Mesoamerica, the bat god presided over corn and fertility. The Weird Sisters in Shakespeare's ''
Macbeth ''Macbeth'' (, full title ''The Tragedie of Macbeth'') is a Shakespearean tragedy, tragedy by William Shakespeare. It is thought to have been first performed in 1606 in literature, 1606. It dramatises the damaging physical and psychologica ...
'' used the fur of a bat in their brew. In
Western culture image:Da Vinci Vitruve Luc Viatour.jpg, Leonardo da Vinci's ''Vitruvian Man''. Based on the correlations of ideal Body proportions, human proportions with geometry described by the ancient Roman architect Vitruvius in Book III of his treatise '' ...
, the bat is often a symbol of the night and its foreboding nature. The bat is a primary animal associated with fictional characters of the night, both villainous
vampire A vampire is a mythical creature that subsists by feeding on the Vitalism, vital essence (generally in the form of blood) of the living. In European folklore, vampires are undead, undead creatures that often visited loved ones and caused mi ...

s, such as
Count Dracula Count Dracula () is the title character of Bram Stoker's 1897 gothic horror novel ''Dracula''. He is considered to be both the prototypical and the archetypal vampire in subsequent works of fiction. Aspects of the character are believed by some ...
and before him '' Varney the Vampire'', and heroes, such as the
DC Comics DC Comics, Inc. (doing business as DC) is an American comic book publisher and the flagship unit of DC Entertainment, a subsidiary of Warner Bros. Discovery. DC Comics is one of the largest and oldest American comic book companies, with their f ...
character
Batman Batman is a superhero appearing in American comic books published by DC Comics. The character was created by artist Bob Kane and writer Bill Finger, and debuted in Detective Comics 27, the 27th issue of the comic book ''Detective Comics'' on ...
. Kenneth Oppel's Silverwing novels narrate the adventures of a young bat, based on the silver-haired bat of North America. The bat is sometimes used as a heraldic symbol in Spain and France, appearing in the coats of arms of the towns of
Valencia Valencia ( va, València) is the capital of the Autonomous communities of Spain, autonomous community of Valencian Community, Valencia and the Municipalities of Spain, third-most populated municipality in Spain, with 791,413 inhabitants. It is ...
,
Palma de Mallorca Palma (; ; also known as ''Palma de Mallorca'', officially between 1983–88, 2006–08, and 2012–16) is the capital and largest city of the Autonomous communities of Spain, autonomous community of the Balearic Islands in Spain. It is situate ...
,
Fraga Fraga (; ) is the major town of the ''comarca'' of Bajo Cinca ( ca, Baix Cinca) in the province of Huesca (province), Huesca, Aragon, Spain. It is located by the river Cinca River (Spain), Cinca. According to the 2014 census,Instituto Nacional de ...
,
Albacete Albacete (, also , ; ar, ﭐَلبَسِيط, Al-Basīṭ) is a city and municipality in the Spanish autonomous communities of Spain, autonomous community of Castilla–La Mancha, and capital of the province of Albacete. Lying in the south-ea ...
, and Montchauvet. Three US states have an official state bat. Texas and Oklahoma are represented by the Mexican free-tailed bat, while Virginia is represented by the
Virginia big-eared bat The Virginia big-eared bat (''Corynorhinus townsendii virginianus'') is one of two endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political juris ...
(''Corynorhinus townsendii virginianus'').

## Economics

Insectivorous bats in particular are especially helpful to farmers, as they control populations of agricultural pests and reduce the need to use
pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, ...
s. It has been estimated that bats save the agricultural industry of the United States anywhere from $3.7billion to$53billion per year in pesticides and damage to crops. This also prevents the overuse of pesticides, which can pollute the surrounding environment, and may lead to resistance in future generations of insects. Bat dung, a type of
guano Guano (Spanish from qu, wanu) is the accumulated excrement of Seabird, seabirds or bats. As a manure, guano is a highly effective fertilizer due to the high content of nitrogen, phosphate, and potassium, all key nutrients essential for plant ...

, is rich in nitrates and is mined from caves for use as
fertiliser A fertilizer (American English) or fertiliser (British English; American and British English spelling differences#-ise, -ize (-isation, -ization), see spelling differences) is any material of natural or synthetic origin that is applied to soil ...
. During the
US Civil War The American Civil War (April 12, 1861 – May 26, 1865; also known by other names) was a civil war A civil war or intrastate war is a war between organized groups within the same Sovereign state, state (or country). The aim ...
,
saltpetre Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate Salt (chemistry), salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ...
was collected from caves to make
gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). Th ...
. At the time, it was believed that the nitrate all came from the bat guano, but it is now known that most of it is produced by
nitrifying bacteria Nitrifying bacteria are lithotroph, chemolithotrophic organisms that include species of genera such as ''Nitrosomonas'', ''Nitrosococcus'', ''Nitrobacter'', ''Nitrospina'', ''Nitrospira'' and ''Nitrococcus''. These bacteria get their energy from the ...
. The Congress Avenue Bridge in
Austin, Texas Austin is the capital city of the U.S. state of Texas, as well as the county seat, seat and largest city of Travis County, Texas, Travis County, with portions extending into Hays County, Texas, Hays and Williamson County, Texas, Williamson co ...
, is the summer home to North America's largest urban bat colony, an estimated 1,500,000 Mexican free-tailed bats. About 100,000 tourists a year visit the bridge at twilight to watch the bats leave the roost.

* Bat detector

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