What are bats?
Bats are from the order Chiroptera (Greek; “hand-wing”) and make up over 20% of the mammal species worldwide. They are the only group of mammals capable of true flight. There are more than 1,300 recognized species of bats in the world, 46 species in the United States, and 14 species in Missouri. The wing of a bat is made up of the same bones present in the human arm and hand but in different proportions. The order Chiroptera can be broken up into two groups (suborders): The Microchiroptera (micro-bat) and the Megachiroptera (mega-bats). About 90% of bat species belong to the Microchiroptera suborder and are typically smaller than the other suborder and use echolocation to hunt. Megachiropterans, also known as fruit bats or flying foxes, use their large eyes to forage and are found in Africa, India, Australia, and Asia.
Bats are found on every continent besides Antarctica and come in a large range of sizes, from a 6.5-inch wingspan (bumblebee bat) to a 6-foot wingspan (giant golden-crowned flying fox). In Missouri, the tri-colored bat is the smallest species (4 grams) while the hoary bat is the largest (35 grams). Bats also have relatively long lifespans for their size, the oldest recorded bat living over 41 years in the wild.
Biology of Bats
Diet: Microbats use their echolocation to find and catch insects, including flies, mosquitoes, beetles, and roaches. A young bat can eat 600 mosquitoes in an hour. Other bats feed on fish, frogs, lizards, rodents, and even other bats. Out of the 1200 species of bats, only three actually feed on blood (the common vampire bat, the hairy-legged vampire bat, and the white-winged vampire bat). Other bats eat fruit, flowers, or nectar, a diet typical of megabats. There is a correlation between the shape of the bat’s head and their diet. Bats with broad faces typically eat rounded fruit, while bats with longer faces typically eat the nectar from flowers. (The University of Edinburgh, “What do Bats Eat”)
Habitat: Bats can live almost everywhere, except in polar regions and deserts. They usually live in large groups or clusters in caves, trees, and bridges. In Missouri, the gray bat uses the caves year round, but most bat species hibernate in caves in the winter and roost in tree cavities during the summer. (San Diego Zoo, “Bat”, 2016)
Reproduction: Since bats live in large groups, it is not difficult for them to find mates, however, the two genders usually stay segregated until they are ready to mate, usually in the spring. Even though a female can have multiple litters, only one young will typically be born at a time. Some species of bats can have multiple litters in a single season because some of the young can become fully independent starting at six weeks! Female bats can also control when fertilization takes place, delaying the process until there is more food available. This delayed fertilization process is present in all bat species of Missouri. Gestation of most Missouri bats is about 45 days. (BatWorlds, “Bat Reproduction”, 2013)
Echolocation: Similar to sonar, echolocation is the process of locating an object using the reflection of sound and is most commonly done by bats and dolphins. Bats send out “calls” as they fly and listen to the returning echoes to build a sonic map of their surroundings. The bat is able to determine the distance to any object by the time it takes for the sound to return to them. These calls are very high pitched, up to 110 kHz, whereas humans can typically hear up to 20 kHz. Bats echolocate at different frequencies so it is possible to identify them by listening to their calls. (Bat Conservation Trust, “Echolocation”)
Dr. Donald Griffin has conducted a large amount of research on echolocation in the 1930’s. Research shows that even species with “insensitive” echolocation capabilities can easily distinguish between different textures on an object. We also know that bats use different frequencies and call rates (the amount of signals sent out at a time) depending on their habitat and prey. For example, species in uncluttered habitats and eat large prey have lower pitched frequency pulses that allow the bat to detect objects at longer distances with less resolution, while species living in cluttered areas or eat small prey have higher frequency pulses that allow for better resolution. Research on echolocation is not only aimed at the ecology and behavior of bats, but how it can be applied for the military in solar technology.
Click here to listen to a Pipistrellus bat approaching its prey. (AvsoftBioAcoustics, “Pipistrellus Echolocation”, 2010)
Hibernation and Migration: When the cold weather drives insects away, bats must either hibernate or migrate to warmer areas with more food sources. Hibernation requires a large reduction in metabolic rate, heart rate, and respiratory rate so that bats can survive without food. A bat’s heart rate is usually at 200 or 300 beats per minute, but must drop to 10 beats per minute to successfully hibernate. The internal temperature of bats may also drop to near freezing, depending on the environment. In this state or torpor, bats can reduce their energy expenditure by about 98%! During hibernation, bats cycle through periods of torpor followed by brief period of arousal. Some bats may enter torpor for just a few hours to save energy during a cold day, or they can hibernate for more than six months, like the little brown bat. The places where bats hibernate are called hibernacula, and may include caves, mines, or rock crevices. Many species of bats also migrate south during the winter time. In Missouri, there are several species that spend their summers there, remaining active in the warmer areas of southern Missouri. (National Park Service, “Hibernate or Migrate”)
Predators and Parasites: There are not many predators of bats, but the most common ones in Missouri are the black rat snakes and raccoons. Hawks and owls are not known to eat many bats and domestic house cats may occasionally kill bats if the opportunity arises. It is illegal for humans to kill bats in Missouri unless they are damaging property. Bats in Missouri can carry a variety of parasites, including fleas, a bat bug (closely related to the bed bug), ticks, and mites, which are the most common. These parasites rarely effect humans.
Interactions with Humans
Benefits: There are many benefits of bats, mainly because bats act as pollinators and pest controllers. Bats also act as indicator species in some areas, meaning that changed in these bat populations can indicate changes in the biodiversity of the environment. Over 500 species of plants rely on bats to pollinate their flowers, including species of mango, banana, cocoa, and guava. Chiropterophily is the pollination of plants by bats. The plants that are pollinated by bats often have pale flowers, compared to the bright flowers that attract bees. These flowers are also large and bell-shaped. Bats are also useful pest controllers, such as the Brazilian free-tailed bat that is especially important for cotton farming. Bats can also spread the seeds of trees and plants. An example of this are some tropical fruit bats, which carry seeds inside them as they digest the fruit, then drop to the ground in their own fertilizer. (Bat Conservation Trust, “Why Bats Matter”)
Threats to Bats: The greatest threat to bats is people, mainly due to habitat destruction and climate change. Habitat destruction due to development work is a major concern for bats roosting in older buildings. Bats that roost in forests are also affected by deforestation and development. In Missouri, fire suppression has transitioned many open forests into closed forests, making it difficult for bats to navigate if they are not used to the excessive vegetation. Caves that bats roost in are also under duress from human vandalism and river flooding. During hibernation, bats are susceptible to disturbances and will burn a lot of their stored fat when woken from hibernation, causing them to starve to death if repeated too often. You should avoid entering caves or mines where large numbers of bats may be hibernating between the months of October and April.
Two other major threats to bats are wind turbines and White-nose Syndrome. Wind energy has become increasingly popular due to the rising costs of fossil fuels. However, large amounts of bats are being killed at these wind energy facilities, mostly because the wind turbines form a pressure vacuum behind the blades. The change in pressure causes the lungs to expand forcing capillaries to burst. White-nose Syndrome (WNS) was discovered in New York in winter 2007 and has killed hundreds of thousands of bats. The cause of death is starvation before the end of hibernation and is characterized by a white fungus (Geomyces destructans) growing on the muzzle and wing membranes, extreme weight loss, and odd behaviors. As of 2009, WNS has not been found in Missouri. Researching Bats: Bats are very difficult to study because they are volant and most are nocturnal. The first step in most studies is to capture the bat. To capture bats in flight, researchers use mist nets and harp traps. Mist nets are large nets stretched between two poles to cover an area where bats normally fly, such as over streams. The netting is made of monofilament or nylon that tangles the bat when it hits the net. Bats are able to detect this net with echolocation, but some are not able to avoid it in time. Harp traps consist of two rectangular frames with monofilament lines strung vertically about one inch apart and an open plastic bag under the frame. Bats attempt to fly between the lines but usually hit one of them and fall into the bag. This method is most effective at entrances to caves and can capture hundreds of bats an hour. After a bat is captured, researchers will record its species, age, gender, and measurements, and will mark it with a band on their forearms. Some researchers have begun using passive integrated transponder tags (PIT tags), which are small electronic devices encased in glass tubes that are injected under the skin of bats. When scanned, they return a unique number to identify an individual. Fecal pellets are also collected and provides useful data about its genetics. Recently, researchers have begun collecting small tissue samples and hair. Field ecologists use radiotransmitters and bat detectors to study bats in the wild. Radiotransmitters are small electronic devices that can be attached to the back of a bat with glue and emit a “beep” with a certain frequency that can be detected by researchers allowing them to find the trees where bats roost. The transmitter then falls off after a few weeks. Bat detectors are small recording devices that allow researchers to listen to bats’ echolocation calls by creating sonograms.
Species of Missouri
All information comes from Bats of Missouri, by Boyles, Timpone, and Robbins
*Click on an image to view a larger version.*
Big Brown Bat, Eptesicus fuscus
The big brown bat is relatively large compared to other bat species in Missouri. The dorsal (back) fur is usually light brown, but can also appear a shiny reddish color on some bats. The ventral (belly) fur is typically lighter than the dorsal fur. The ears and wings are black and they have no tails. This bat is fond in every county in Missouri and actually benefits from humans, as they roost in manmade structures. During the summer, these bats naturally live in dead trees, but now can be found in manmade structures, such as old brick buildings. During the winter, these bats hibernate in small clusters (about 100 individuals) at relatively low temperatures compared to other bats in Missouri, sometimes even below freezing. Big brown bats mate during the fall and females give birth after a 60 day gestation period. Most females in Missouri give birth to two young, while individuals west of the Rocky Mountains give birth to one. The diet consists of agricultural pests, such as beetles, stinkbugs, moths, and leafhoppers.
Evening Bat, Nycticeius humeralis
The Evening bat has a dull brown dorsal and ventral fur. The ears, wings, and tails are furless and black. These bats have a distinct musky smell that serves as a useful identifying feature, especially from the big brown bat, which has similar colored fur, albeit larger in size. These bats are found throughout the eastern United States, and are common in the Gulf Coast region. In Missouri, this bat is commonly found in the southern part of the state. Evening bats are relatively weak flyers and do not undergo long migrations. In the summer, these bats also roost in the cavities of dead trees, usually oaks or hickories. In the fall, these bats can put on a lot of weight to prepare for the winter. Little is known about the mating in evening bats, but in Missouri, females tend to be pregnant in mid-May and the young are born around mid-June. Within a few weeks, a mother will feel any young in the colony, not just her own. A study in Indiana found that the most common food item was the spotted cucumber beetle.
Tri-colored Bat, Perimyotis subflavus
The common name of this bat used to be the Eastern pipistrelle, however, it is no longer appropriate since genetic evidence does not support a linkage with the Pipistrelles genus. Although these bats appear to be yellowish/reddish, close examination of their fur reveals a tri-coloration of each hair – black at the base, yellow in the middle, and brown on the tips. The ears are light brown and are long and rounded at the tips. The tails are covered by the fur. The eastern small-footed bat is most likely to be confused with this bat, but that species is rare in Missouri. The tri-colored bat is mostly found in the eastern United States, but there is evidence that their range is expanding west. In Missouri, these bats are found in most counties. These bats can also be identified by their small size and slow and erratic flight. Mating season begins in late August and continues into October. Adults of both genders mate at staging areas – usually the entrance to a cave – and participate in “swarming”. After swarming, the bats hibernate and the sperm is stored until the following spring. These bats are usually the only species hibernating in the small caves of Missouri. They prefer a warmer and stable temperature. Their diet consists of tiny flies, moths, beetles, and ichneumon wasps.
Northern Bat, Myotis septentrionalis
Myotis is from the Greek roots meaning mouse (mys) and ear (otis). The dorsal fur is medium brown and the ventral fur is a lighter yellowish color. This bat is most commonly confused with other members of the Myotis genus but can be distinguished by their longer ears. They also have a dagger-shaped tragus. The northern bat is widely distributed across the eastern United States and southern Canada. In Missouri, these backs are common and can be found in forested areas. Mating takes place in caves and mines and consists of males mounting the females from behind and maintaining this position by grasping the furs on the females’ neck with their teeth. Like many other species, sperm is stored in the uterus until spring. Northern bats in Missouri hibernate from mid-October to early April and often do so individually in crevices or cracks. Their diets consist of flies, moths, and beetles.
Indiana Bat, Myotis sodalis
Sodalis is Latin for “companion,” which refers to the tendency of this species to cluster together during hibernation. The dorsal and ventral fur are gray or dull brown, but the ventral fur is lighter. The ears and wings are black and the nose is light gray. The winter distribution used to just be in the karst regions from Missouri to Alabama, but now includes states farther north such as Vermont and New Hampshire. They hibernate in approximately 25 caves and mines in southern Missouri. They are most common north of the Missouri River during the summer. They are federally and state endangered, with less than 14 thousand individuals in Missouri. The decline in populations is partly due to a decline in the quality of Missouri caves. They begin entering caves in October and November and cluster in groups of up to tens of thousands to hibernate in temperatures from 36-45 degrees Fahrenheit. Indiana bats begin leaving hibernation sites in April and migrate to summering areas. Most males, however, tend to remain near the hibernacula year round. Females usually roost in larger trees, while males roost in smaller trees. They probably mate in the fall and delay fertilization until spring. Their diet consists of flies, beetles, and moths.
Little Brown Bat, Myotis lucifugus
The dorsal fur is light brown and shiny while the ventral fur is tan or beige. The base of each hair is dark black and the tragus is blunt rather than pointed. The little brown bat is one of the most widespread species in North America and can be found in every county of Missouri. Populations, however, are declining due to white-nose syndrome. This species of bats migrates between summer and winter habitats on a regional scale, rather than continental scale. Maternity colonies in buildings can be large, some reaching over 2000 individuals. Research on the migratory patterns is greater for this species than any other species of bats. During the fall, their body weight increased by 30% in preparation for hibernation. Most little brown bats mate during the fall, but some also mate during the winter. The gestation period is approximately 60 days and the young are born in July. This species often forages over open water and their diet consists of moths, beetles, and flies.
Gray Bat, Myotis grisescens
Grisescens comes from the Latin word, griseus, which means “becoming gray.” The gray bat is the largest member of the genus Myotis in the eastern United States, and may weigh up to 16 grams before hibernation. What distinguishes them from other Myotis species is that their individual hairs on the back are uniformly colored. This species can be found as far south as Florida, up to central Illinois, and as far west as Kansas. They are federally and state endangered. Since 1976, populations in Missouri have decreased by over 70%. Research on these bats in Missouri dates back to 1933. Populations in the state have stabilized over recent years. This species is one of the few true “cave bats,” meaning that maternity, hibernation, and bachelor are found in caves throughout the year. They are highly selective, only using caves that have narrow temperature and humidity levels necessary. They do migrate to different caves during the winter time, usually within 200 kilometers, and hibernate in large colonies. A University of Missouri zoologist, Mary Jane Guthrie, studied several bat species and was the first to document seasonal movements in gray bats in the 1930’s. Gray bats forage over streams and rivers and eat large numbers of beetles, moths, and flies.
Southeastern Bat, Myotis austroriparius
Austroriparius is from Latin roots meaning southern (austro) and edges of streams (riparius). The dorsal fur is thick, short, and woolly and the color is typically gray. The ventral fur is white. Their foot lengths are larger than other Myotis specials in Missouri (0.4 inches) and their toes have hairs extending beyond the claws. The range of the southeastern bat in the United States is much of the southeastern part, westwards to Texas and north to southern Illinois. In Missouri, this bat is listed at a species of special concern and are not known to hibernate in the state. These bats prefer warmer temperatures and avoid long periods of hibernation. They typically migrate from 5 to 15 miles (8 to 24 kilometers). Females usually give birth to twins in mid-May. These bats breed in the spring, which is unusual as most bats breed in the fall and delay fertilization. These bats also fly low over the water and feed mostly on moths, flies, and beetles.
Eastern Small-footed Bat, Myotis leibii
This bat is also called Leib’s bat in honor of Dr. George C Leib, who collected the initial specimen. It is the smallest bat species in Missouri and in the eastern United States. They have thick glossy dorsal fur that is yellowish-goldish in color. The ventral fur is white-gray. The face, ears, and muzzle all form a black “mask” that contrasts with the rest of the fur. This species weighs between 3 and 7 grams. This species also looks similar to other species of Myotis in Missouri but can be easily identified by its small size and black facial mask. It one of the rarest species of bat in North America, and is most common in the mountains of New York, Pennsylvania, West Virginia, and Virginia. They are only found in the Ozarks region in Missouri. Little is known about the ecology of this species because it is so rare. In Canada, they were found to migrate less than 13 miles between winter and summer habitats. The males roost in different areas than the females during the summer. This species was first recorded in Missouri in October 1949, found under a rock in Iron County. This bat hibernates in caves or mines, and are more tolerant to the cold temperatures than other bats. Their flight patterns are weak and erratic, often foraging above ponds and streams. They commonly eat moths, flies, and beetles.
Eastern Red Bat, Lasiurus borealis
Lasiurus comes from the Greek roots meaning hairy (lasios) tail (oura). This is the only strongly sexually dimorphic species found in Missouri. Adult males are bright red with a white collar and females are duller orange or yellow. The ears are small and rounded and the tragus is very short. The muzzle and ears are usually pink and blend in well with the fur. No other common species resemble this bat, however, the Seminole bat can be similar in some ways (darker color). This species is widespread in eastern United States and is found in every state east of Wyoming. They are common in the state of Missouri and are considered litter conservation concern. During the summer, the red bat roosts in the foliage of large deciduous trees, where they are able to blend in and receive protection. They are also highly migratory, flying all the way to Mexico, and even some ships and islands in Bermuda. Mating is likely to occur in the autumn while flying. Research in Taney and Carter Counties showed that red bats roost in the dead foliage of oak trees on warm winter days, but seek shelter beneath leaf litter on the forest floor when it’s cold. They can even insulate themselves with their furred tails on very cold days. They also do not enter caves unless by accident. Their diet mainly consists of moths.
Hoary Bat, Lasiurus cinereus
Cinereus is related to cinerosus, which is Latin for ash, referring to the color of the bat. Hoary comes from the term hoar frost, referring to the white tipped hairs. It is the largest species in Missouri, with brown fur that is tipped in white. Their face is yellow and they have rounded yellow ears. The feet and tail membrane are fully furred. Big brown bats are the only species in Missouri that come close in size to the Hoary bat, however, they can be distinguished by the uniformly brown fur and lack of white tips. It is one of the most widely spread species in North America, spanning south to Southern Mexico and north into northern Canada. They are found in every state. They have a large migration range, making it hard to determine the number of individuals in an area. During the summer, these bats roost in deciduous trees, as well as some evergreens. They have thick fur, providing insulation against the cold temperatures in the north. They are also more prone to enter torpor when prey is scarce. Hoary bats feed almost exclusively on moths and forage in open areas and above the canopy.
Seminole Bat, Lasiurus seminolus
The common name of this species, Seminole, refers to the Seminole Indian tribe and their homelands, where these bats were first described. Their fur is dark red and males have a distinct white “collar” around their neck. The ears ae small with a short tragus. The two most similar species are the more common eastern red bat, which is a lighter orange color and the hoary bat, which is larger. The Seminole bats are mostly limited to the Carolinas and Gulf Coast states but have also been found in Wayne County and Reynolds County. These bats commonly roost in evergreen trees and make use of hanging Spanish moss. They are not known to migrate and do not enter long bouts of hibernation. They feed mostly on moths, beetles, and flying ants.
Silver-haired Bat, Lasionycteris noctivagans
Lasionycteris is Greek and means hairy bat. Noctivagans is Latin and means wondering at night. Their fur is black with white or silver tips, although the amount can vary between individuals. The fur on the tail sometimes lacks the white tips. The silver-haired bat is similar to the hoary bat, but is much smaller. This species of bat is widespread in North America and is found in most counties of Missouri during the fall and spring migration periods, but not during the rest of the year. This species is one of the most commonly killed by wind turbines. During the winter, they are usually solitary and roost in caves, mines, and under rocks. During the summer, they roost in the cavities in dead trees in mature forests. Mating occurs in autumn and the females store the sperm until spring. The gestation period is 50 to 60 days and the young are born in June/July. They feed heavily on moths, but also eat beetles, flies, and leafhoppers. They have relatively short lifespans compared to many other bat species.
Rafinesque’s Big-eared Bat, Corynorhinus rafinesquii
These bats have unusually long ears, up to one and a half inches. Their dorsal fur is gray and their ventral fur is white. The only species that can be confused with this bat is the Ozark Big-eared bat, which has tan fur compared to the white ventral fur of the Rafinesque’s Big-eared bat. Also, this bat is found almost exclusively in the southeastern part of Missouri, while the Ozark Big-eared bat is found almost exclusively in the southwest region. Because of the rarity of this species, few studies have been conducted on it and none in the state of Missouri. They are non-migratory and prefer mature bottomland forest. During the summer, their use of manmade structures increases. Like many other North American bats, delayed fertilization is assumed to occur in this species. They are considered to be a moth specialist species, eating only the nutritious body of the moths and not their wings.
Ozark Big-eared Bat, Corynorhinus townsendii ingens
Corynorhinus comes from the Greek roots meaning “club-nosed” and townsendii is named in honor of C. H. Townsend. They have unusually long ears, which makes them easy to identify. They often appear reddish brown with a tan underside. Another unique feature is the two lumps found on either side of their snout. The only similar looking species is the Rafinesque’s big-eared bat, which has equally long ears but is gray rather than red. The Ozark Big-eared bat was historically found in southwestern Missouri, northwestern Arkansas, and northeastern Oklahoma. The species has since contracted to less than 2,000 species. As of 1979, the species is classified as endangered. These bats are extremely sedentary, with little migration. Colonies are small and cluster in caves. Hibernation occurs from October to April and mating occurs in the fall and winter, but gestation does not start until spring. Their diet consists mostly of moths and small flies.
Brazilian Free-tailed Bat, Tadarida brasiliensis
The common name, “free-tailed bat,” refers to the fact that the lower half of the tail is not connected to the uropatagium. It is the only member of the family Molossidae recorded from Missouri. It is easily distinguished from other bats because of its tail. This bat is found in much of the southern half of the United States, throughout Central America, and South America. This species is considered accidental in the state of Missouri. It is known for its larger maternity colonies, which can reach up to millions of individuals, making this species little conservation concern. Most colonies are found in caves, buildings, or bridges. The western subspecies is considered migratory, migrating up to 1100 miles, while the eastern subspecies is not. Gestation lasts approximately 11 weeks and females give birth in June. The young are capable of strong flight by week 6. They are known for fast, straight, efficient flight. They generally eat moths and beetles.
Nubuo Suga is a professor of biology at Washington University in St. Louis and a famous bat researcher who has been studying the auditory system in bats for the past 30 years. He conducts research on echolocation and the plasticity (ability to change) of the hearing systems. He believes that the changes in the auditory system in response to stimuli can help researchers develop therapies of those with brain damage. Suga has been a member of the Washington University faculty since 1969 and concentrates his focus on the neurophysiology of hearing in bats and porpoises. His findings on echolocation has implications because there is a relationship between the auditory signals the brain receives and how it interprets the sounds. He has studied all over the world, including Tokyo, Harvard, and St. Louis. While at Washington University, Suga was able to create a map of the bat brain and identified the areas where “different kinds of biosonar information are processed” (Fitzpatrick, 2001). He showed that “the bat auditory system was remarkably similar to the mammalian visual system, in which form is processed in one part, motion, for instance, in another.” Suga was elected to the US national Academy of Sciences, which is one of the highest recognitions for a scientist.
This page was created and written by Seth Adler
“I do not claim to have taken, produced, or created any of the artwork and images displayed on this webpage. All photographs are citied to their rightful owners.” – Seth Adler, March 28, 2018
- Chiropterophily – The pollination of plants by bats.
- Hibernacula – The place where a creature seeks shelter during the winter.
- Roost – A place where birds usually rest at night.
- Sonogram – A graph representing a sound.
- Torpor – A state of physical or mental inactivity.
- Tragus – The prominence in front of the external opening on the outer ear.
- Uropatagium – The membrane that extends between the thighs of a bat and includes the tail.
- Volant – Able to fly.
- White-nose Syndrome – A disease affecting hibernating bats.
Unless otherwise stated, the information came from the Bats of Missouri Field Guide, written by Justin Boyles, John Timpone, and Lynn Robbins. Full citation included in Resources, Further Reading, and References.
Bat. (2016). Retrieved November 21, 2016, from http://animals.sandiegozoo.org/animals/bat
Bat Reproduction. (2013, November 5). Retrieved November 25, 2016, from http://www.batworlds.com/bat-reproduction/
Echolocation. (n.d.). Retrieved November 26, 2016, from http://www.bats.org.uk/pages/echolocation.html
Fitzpatrick, T. (2001, Fall). Of Bats and Men. Retrieved December 13, 2016, from http://magazine-archives.wustl.edu/fall01/nobuosuga.html
Hibernate or Migrate. (n.d.). Retrieved November 26, 2016, from https://www.nps.gov/subjects/bats/hibernate-or-migrate.htm
Pipistrellus Echolocation. (2010). Retrieved November 25, 2016, from https://en.wikipedia.org/wiki/File:Pipistrellus.ogg
What do Bats Eat. (n.d.). Retrieved November 21, 2016, from http://www.nhc.ed.ac.uk/index.php?page=493.169.180
Why Bats Matter. (n.d.). Retrieved November 26, 2016, from http://www.bats.org.uk/pages/why_bats_matter.html