Learn About Bats

In this episode of the I Can't Sleep Podcast, fall asleep learning about bats. The only thing I can remember about bats is that they are an essential part of the ecosystem. Everything else on the subject put me to sleep. Happy sleeping!

Transcript

Welcome to the I Can't Sleep podcast, Where I read random articles from across the web To bore you to sleep with my soothing voice. I'm your host, Benjamin Boster. Today's episode is from a Wikipedia article titled, Bat. Bats are flying mammals of the order Chiroptera. With their forelimbs adapted as wings, They are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, Flying with their very long spread-out digits covered with a thin membrane or patagium. The smallest bat, And arguably the smallest extant mammal, Is Kitty's hog-nosed bat, Which is 29-34 mm in length, 150 mm across the wings, And 2-2. 6 g in mass. The largest bats are the flying foxes, With the giant golden-crowned flying fox reaching a weight Of 1. 6 kg and having a wingspan of 1. 7 m. The second-largest order of mammals after rodents, Bats comprise about 20% of all classified mammal species worldwide, With over 1, 400 species. These were traditionally divided into two sub-orders, The largely fruit-eating megabats And the echolocating microbats. But more recent evidence has supported dividing the order into Yin-Terra Chiroptera and Yango Chiroptera, With megabats as members of the former, Along with several species of microbats. Many bats are insectivores, And most of the rest are Frugivores, Fruit-eaters, Or nectivores, Nectar-eaters. A few species feed on animals Other than insects. For example, The vampire bats feed on blood. Most bats are nocturnal, And many roost in caves or other refuges. It is uncertain whether bats have these behaviors to Escape predators. Bats are present throughout the world, With the exception of extremely cold Regions. They are important in their ecosystems for pollinating flowers 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 from caves and used as fertilizer. Bats consume insect pests, Reducing the need for pesticides 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 pathogens, Such as rabies. And Since they are highly mobile, Social, And long-lived, They can readily spread diseases among themselves. If humans interact with bats, These traits become potentially dangerous to humans. Some bats are also predators of mosquitoes, Suppressing the transmission of mosquito-borne Diseases. 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, Vampires, And death. An older English name for bats is flittermouse, Which matches their name and other Germanic Languages, For example German Flittermaus and Swedish Flattermus, Related to the fluttering Of wings. Middle English had bakka, Most likely cognate from Old Swedish nattbakka, 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 ancient Greek, Chēr, Hand, And teron, Wing. The delicate skeletons of bats do not fossilize 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. The oldest complete bat skeleton is known from two skeletons Discovered in Wyoming. The extinct bats, Which lived 48 million years ago, Are the first fossil Mammals whose coloration has been discovered. Both were reddish-brown. Bats were formerly grouped In the superorder Archonta, Along with the tree shrews, Colugos, And primates. Modern genetic evidence now places bats in the superorder Lauraceatheria, With its sister taxon as Furungutila, Which includes carnivorans, Pangolins, Odd-toed eugulots, Even-toed ungulates, And cetaceans. One study placed chiroptera as a sister taxon to odd-toed ungulates. The flying primate hypothesis proposed that when adaptations to flight are removed, Megabats are allied to primates by anatomical features not shared with microbats, And thus flight evolved twice in mammals. Genetic studies have strongly supported the monopoly of bats and the single origin of mammal flight. An independent molecular analysis trying to establish the dates when bat ectoparasites Bedbugs evolved, Came to the conclusion that bedbugs similar to those known today Had already diversified and become established over 100 million years ago, Suggesting that they initially all evolved on non-bat hosts, And bats were colonized Several times independently, Unless the evolutionary origin of bats has been grossly underestimated. Fleas as a group are quite old. Most flea families formed around the end of the Cretaceous. But no analyses have provided estimates for the age of the flea lineages associated with bats. The oldest known members of a different lineage of bat ectoparasites, Bat flies, However, Are from roughly 20 million years ago, Well after the origin of bats. The bat ectoparasitic earwig has no fossil record, But is not believed to originate more Than 23 million years ago. Genetic evidence indicates that megabats originated during the Early Eocene and belong within the four major lines of microbats. The 2003 discovery of an Early fossil bat from the 52 million year old Green River Formation indicates that flight Evolved before echolocative abilities. This bat 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 sloths and Gibbons. This palm-sized bat had short, Broad wings, Suggesting that it could not fly as fast As or as far as later bat species. Instead of flapping its wings continuously while flying, It 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 this bat fossil also support the hypothesis that Mammalian flight most likely evolved in arboreal locomotors rather than terrestrial runners. This model of flight developed commonly known as the tree's 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 takeoff. 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 Younger Chiroptera and once in Rhinolophoids. The second is that laryngeal echolocation had a single origin in Chiroptera, Was subsequently lost in all megabats, And later evolved as a system of tongue-clicking 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 arrived in bats from communicative calls. The Eocene bats had cranial adaptation suggesting an ability to detect ultrasound. 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 PRESTON seem to favor the idea that echolocation developed Independently at least twice, Rather than being lost secondarily in the pteropodids, But ontogenic analysis of the cochlea supports that laryngeal echolocation evolved only once. Bats are placental mammals. Bats are placental mammals. After rodents, They are the largest order, Making up about 20% of mammal species. In 1758, Carl Linnaeus classified the seven Bat species he knew of in the genus Vespertilio in the order primates. Around 20 years later, The German naturalist Johann Friedrich Blumenbach Gave them their own order, Chiroptera. Since then, The number of described species Has risen to over 1, 400, Traditionally classified as two sub-orders, 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 Rousetus, 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 on the base of the ear. Megabats eat fruit, Nectar, Or pollen, While most microbats eat insects. Others feed on fruit, Nectar, Pollen, Fish, Frogs, Small mammals, Or blood. 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. This keeps them razor sharp. The bite force of small bats is generated through mechanical advantage, Allowing them to bite through the hardened armor of insects or the skin of fruit. Bats are the only mammals capable of sustained flight as opposed to gliding, As in the flying squirrel. The fastest bat, The Mexican free-tailed bat, Can achieve a ground speed of 160 kilometers an hour. 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 near their tips. The elongation of bat digits, A key feature required to wing development, Is due to the upregulation of bone morphogenetic proteins, BMPs. During embryonic development, The gene controlling BMP signaling, BMP2, Is subjected to increased expression in bat forelimbs, Resulting 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 50 million years. During flight, The bones undergo bending 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 animals and unlike in birds, The 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 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 wings. The fourth and fifth digits go from the wrist to the trailing edge, 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% 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 cells, 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 is the wing membrane. It is stretched between the arm and the finger bones, And down the side of the body to the hind limbs and tail. This skin membrane consists of connective tissue, Elastic fibers, Nerves, Muscles, And blood vessels. 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 and dermis, As well as hair follicles, Sweat glands, And a fatty subcutaneous layer, Is very different from the skin of the wing membrane. Depending on the bat species, The presence of hair follicles and sweat glands will vary in the Patagium. The patagium is an extremely thin, Double layer of epidermis. These layers are Separated by a connective tissue center rich with collagen and elastic fibers. In some bat species, Sweat glands will be present in between this connective tissue. Furthermore, If hair follicles are present, This supports the bat in order to adjust sudden flight Maneuvers. For bat embryos, Apoptosis, Programmed to sell death, Affects only the hind limbs, 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 wingspan, Unlike birds, Which can partly Fold their wings in flight, Radically reducing the wingspan 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 hummingbirds. The sharp leading edges of the wings can create vortices, Which provide lift. The vortex may be stabilized by the animal changing its wing curvatures. 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 their 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, Are agile on the ground. Both species make lateral gates. The limbs move one after the other when moving slowly, But Vampire bats move with a bounding gate. All limbs move in unison at greater speeds. The folded up wings being used to propel them forward. Vampire bats likely evolved these gates 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. Bats have an efficient circulatory system. They seem to make use of particularly strong venomotion, A rhythmic contraction of venous 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 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 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 must respond accordingly. Therefore, Compared to a terrestrial mammal of The same relative size, The bat's heart can beat up to three times larger and pump more blood. Cardiac output is directly derived from heart rate and stroke volume of the blood. An active microbat can reach a heart rate of a thousand beats per minute. 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 the surface area to volume ratio. The surface area of the wings is about 85 percent 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 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 the body warm. The digestive system of bats is Quickly and effectively to keep up with the energy demand. Insectivorous bats may have certain digestive enzymes to better process insects, Such as chitinase to break down chitin, 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, Which breaks down malt sugar in their intestinal tract. Nectivorous and frugivorous bats have more maltase and sucrase enzymes than insectivorous To cope with the higher sugar contents of their diet. The adaptations of the kidneys of bats vary with their diets. Carnivorous and vampire bats Consume large amounts of protein and can output concentrated urine. Their kidneys have a thin cortex and long renal papillae. Frugivorous bats lack the ability to Have kidneys adapted for electrolyte 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 evaporative water loss. Water helps maintain their ionic balance in their blood. Thermoregulation 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. Microbats and a few megabats emit ultrasonic sounds to produce echoes. Sound intensity of these echoes are dependent on subglottic pressure. The bat's cricothyroid muscle controls the orientation pulse frequency, Which is an important function. This muscle is responsible for the frequency of the bat's 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. Microbats use their larynx to emit Echolocation signals through the mouth or the nose. Microbat calls range in frequency from 14, 000 To well over 100, 000 hertz, Extending well beyond the range of human hearing, Between 20 and 20, 000 Hertz. 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 of their prey. In high-duty cycle echolocation, Bats emit a continuous call and separate pulse and echo In frequency, Using the Doppler effect 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 and exist in a large variety of unrelated animals, Such as the aye-aye, Lesser galago, Bat-eared fox, Moose lemur, And others. Bats can estimate the elevation of their target using the interference patterns 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 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 radically, Sending the moth into Random evasive maneuvers. The eyes of most microbat species are small and poorly developed, Leading to poor visual acuity, But no species is blind. Most microbats have mesopic vision, Meaning that they can detect light only on low levels, Whereas other mammals have otopic vision, Which allows color vision. Microbats may use their vision for orientation and while traveling Between their roosting grounds and feeding grounds, As echolocation is effective only over Short distances. Some species can detect ultraviolet. As the bodies of some microbats Have distinct coloration, They may be able to discriminate colors. 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 color vision. Microbats make use of magnetoreception, In that they have a high sensitivity to the earth's magnetic field, 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 latitudes, Which may be used in long distance travel. The mechanism is unknown, But may involve Magnetite particles. Most bats are homeothermic, Having a stable body temperature, The exception being the vesper bats, The horseshoe bats, The free-tailed bats, And the bent-winged Bats, Which extensively use heterothermy, Where body temperatures can vary. Compared to other Mammals, Bats have a high thermal conductivity. 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 uses Saliva and wing fanning to cool itself while roosting during the hottest part of the day. Among microbats, The Yuma myotis, The Mexican free-tailed bat, And the pallid bat cope with Temperature up to 45 degrees Celsius 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 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 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 and oversized ears for the same purpose. Torpor, A state of decreased activity where the body temperature and metabolism decreases, Is especially useful for bats as it allows them to control the temperature of their As they use a large amount of energy while active, Depending on an unreliable food source, And have a limited ability to store fat. They generally drop their body temperature in this State to 6 to 30 degrees Celsius and may reduce their energy expenditure by 50 to 99 percent. 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 50 grams have been known to use torpor. The common blossom bat, The long-tongued nectar bat, And the eastern tube-nosed bat. Torpid states last longer in the summer for megabats than in the winter. During hibernation, 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 traveling 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. The smallest bat is kitty's hog-nosed bat which is 29 to 34 Millimeters long with a 150 millimeter wingspan and weighs 2 to 2. 6 grams. It is also arguably The smallest extant species of mammal next to the Etruscan shrew. The largest bats are a few species Of pteropus megabats and the giant golden-crowned flying fox which can weigh 1. 6 kilograms with a Wingspan of 1. 7 meters. 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.

Reviews

I love bats. Wish I could've learned more but I was out like a light 😴 💤