Most people know a bat when they see one: It looks something like a mouse with wings. There are about 18 families of bats globally, but only one family of bats predominates in Missouri: the evening bats (Vespertilionidae). The bats in our state are all relatively small, usually with prominent ears.
If you want to be able to identify bats to species, it is good to know some basic bat anatomy.
Each ear generally has a well-developed, membranous or flaplike structure, called the tragus (plural tragi), in front of the ear hole. (Humans have tragi, too.) The tragus in bats functions to enhance sound definition just like the spire in the center of a radar dish. The tragus is often triangular, but its shape varies and can be important for identifying species.
The wings consist of paired extensions of soft and generally naked skin, the wing membranes (or patagia; singular patagium), which connect the sides of the body, the large front limbs, the 4 elongated fingers (digits), and the small hind legs. The clawed thumbs are separate. The patagium of a bat has four distinct parts: the propatagium runs from the neck to the first digit, the dactylopatagia run between digits, the plagiopatagium runs from the last digit to the ankles, and the uropatagium joins the hind legs with the tail.
- The hind legs with their 5 toes are turned outward, directing the knees backward; they serve as supports for the wings. A cartilaginous structure, the calcar, arises from each ankle joint and extends toward the tail, giving partial support to the free edge of the tail membrane. The calcar is not keeled if it lies along the very edge of the tail membrane. It is keeled if an obvious extension of membrane, or keel, occurs between it and the outside edge of the membrane.
Missouri’s 14 species of bats include:
- Little brown myotis (Myotis lucifugus) (vulnerable to extirpation from Missouri and to extinction globally)
- Gray myotis (Myotis grisescens) (Missouri and federally endangered)
- Southeastern myotis (Myotis austroriparius) (critically imperiled in Missouri; vulnerable/apparently secure globally)
- Northern long-eared myotis (Myotis septentrionalis) (endangered in Missouri; threatened federally)
- Indiana myotis (Myotis sodalis) (Missouri and federally endangered)
- Eastern small-footed myotis (Myotis leibii) (imperiled in Missouri; critically imperiled/vulnerable to extinction globally)
- Silver-haired bat (Lasionycteris noctivagans) (vulnerable to extirpation from Missouri; secure globally)
- Tri-colored bat (eastern pipistrelle) (Perimyotis subflavus)
- Big brown bat (Eptesicus fuscus)
- Eastern red bat (Lasiurus borealis)
- Hoary bat (Lasiurus cinereus)
- Evening bat (Nycticeius humeralis)
- Townsend’s big-eared bat (Corynorhinus townsendii)
- Rafinesque’s big-eared bat (Corynorhinus rafinesquii) (critically imperiled in Missouri; vulnerable/apparently secure globally)
Additionally, there are three species of possible occurrence in Missouri:
- The Brazilian free-tailed bat (Tadarida brasiliensis) is highly migratory and apparently occurs only accidentally in Missouri. Its range is mostly in the southern half of the United States and most of Mexico.
- The big free-tailed bat (Nyctinomops macrotis) might occur occasionally in Missouri, especially in the fall. Its range is mostly in the southwestern United States and Mexico.
- The Seminole bat (Lasiurus seminolus) occurs only accidentally in southern Missouri; we are in the northwestern edge of its range and are most likely to see this species in summer.
Length (tip of nose to tip of tail): 2¾ to nearly 6 inches (varies with species). Weight: our heaviest bat, the hoary bat, can reach 1½ ounces. In many bat species, females are slightly larger and heavier than males.
Statewide. Although some species occur everywhere in the state, several of our bat species have different distributions within the state.
Habitat and Conservation
Bats live in a variety of habitats, and different species roost and hibernate in different types of refuges.
Bats are famous for living in caves or mines, but many live in hollow tree trunks or behind loose bark of trees, in attics or behind nooks in siding of homes, in crevices in cliffs, or in large storm sewers, old barns, and bridges.
Several species overwinter in caves but spend the breeding season living in crevices and hollows in trees or in barns.
Some species are generalists, living in many types of shelters, while others can live only in certain sites in certain types of caves.
Bats are usually nocturnal, flying at night hunting flying insects. Their vision is poor, but they are not completely blind. They use echolocation (essentially sonar) for navigation, especially in the complete darkness of caves; this is why most species have large and elaborate ears.
BATS AND COVID-19: There is no evidence that Missouri bats have COVID-19 (SARS-CoV02), the virus that is causing the human pandemic. All viruses that have been identified in U.S. bats are alphacoronaviruses, while COVID-19 is a betacoronavirus. MDC, the U.S. Fish and Wildlife Service, and the Association of Fish and Wildlife Agencies are concerned about the possibility of bats contracting the COVID-19 virus from infected humans. Until more information is available, no activities that result in the direct interaction with live wild bats or with MDC-owned caves are permitted under existing or new 2020 Wildlife Collector Permits at this time. To protect bats, people are advised to not interact with them.
Missouri's bats are insectivores, capturing flying insects on the wing: mayflies, mosquitoes, flying beetles and true bugs, caddisflies, crane flies, lacewings, stoneflies, moths, cicadas, leafhoppers, flying aquatic insects, wasps, dragonflies, crickets, and more. Larger species of bats tend to take larger insects, while smaller bats focus on smaller insects.
Echolocation assists bats not only in locating prey but also in identifying the quarry.
Feeding begins at twilight for most species, 1 to 2 hours after nightfall for others; in many cases, the bats fill their stomachs within 1 or 2 hours. Sometimes there are a few feeding periods during the night. Females with young to nurse feed especially heavily; in big brown bats, a lactating female may eat the equivalent of her body mass each night.
Eight of our 14 types of bats are Missouri Species of Conservation Concern, ranging from vulnerable to extirpation from our state to globally endangered to extinction.
Current threats to bats in North America include habitat loss and degradation, cave disturbance, and the use of pesticides, all of which have been threats to our bat populations for many years; however, two new threats are causing noticeable declines: wind power and white-nose syndrome.
Wind turbines cause mortality to bats and birds. The prominent causes for bat mortality have been identified as direct collision resulting in bone fractures and barotrauma, the damage to body tissue due to the abrupt change in pressure close to wind turbines.
White-nose syndrome is a fungus that appears to be of Eurasian origin. It infects the skin of cave-dwelling bats, disrupting hibernation and often resulting in mortality. The first fully developed case of white-nose syndrome was confirmed in Missouri in March 2012. Seven of our 12 species of bats have been confirmed to have white-nose syndrome, including the federally endangered Indiana and gray bats.
Details of seasonal cycles and reproduction vary by species.
Many bats hibernate colonially in caves in winter, with the females entering hibernation first; then they disperse in spring, with females typically forming small to fairly large nursery colonies that may roost together in caves or in trees or a variety of other sheltered places. Most give birth in late spring to only one pup (some species may give birth to two, three, or even four). Usually, the mothers give birth while hanging by their feet; they curl their tail and wing membranes to catch the newborn pup, which begins nursing soon afterward. Bats are typically born naked or only slightly furred, and with their eyes closed.
Bat mothers are solicitous of their young, as they nurse and groom them, and are careful to relocate their own pups within the colony when they return from foraging excursions. The young usually begin to fly in midsummer.
Mating usually occurs in late summer or fall, as bats swarm near the entrances of their hibernation caves, but it can also occur during brief, active times during the winter and again in the spring. Bats typically undergo delayed fertilization: Females that mated in the fall or winter have the sperm within them go dormant, and the egg also pauses its development within the ovary. In spring when the female bat awakens, the egg is shed and fertilization occurs.
Lifespan varies with species; some can live to be more than 30 years old. This longevity reflects the low reproductive rate combined with low predation pressure.
Some bat species do not hibernate in the southern parts of their range, though they may hibernate in Missouri where winters are colder.
Some species, such as the silver-haired bat, eastern red bat, hoary bat, and evening bat, are migratory, moving south in the fall and north in the spring, sometimes flying great distances and in rather large numbers. These migratory bats may not spend much time in caves at all. In some cases, as in the evening bat, some individuals may migrate in fall to warmer climates while others stay in Missouri and hibernate.
Many bat species show a high fidelity to their home caves, returning to the same hibernating sites year after year, and finding their way back even when transported 180 miles away from the cave in which they were trapped.
Bats have been maligned as disease-causing nuisances. Bats infected with rabies have been found in Missouri, but their numbers are very low. It is impossible to determine if a bat has rabies without laboratory tests. The potential for contracting rabies is slight, but handling bats (or any other wild mammal) is not recommended. Anyone who has been bitten by a bat should try to capture it, wash and disinfect the wound, and contact a physician or local health official immediately.
Bats are important as predators of agricultural pests, as pollinators, and as seed dispersers, and their benefits far outweigh their potential for damage. Many people put up bat houses to attract insect-devouring bats to their neighborhoods.
Bats are some of the few mammals that people can truly enjoy watching. It is fun to observe them fluttering silently among the trees and rooftops as the stars are coming out.
Bats are one of the few animals to regularly move in and out of caves. By eating insects outside of caves, then flying into caves and excreting the digestive remains, they bring organic nutrients into the cave ecosystem. Bat guano, and the decomposing remains of dead bats that fall to the cave floor, feeds many small organisms that are then eaten by other forms of cave live.
Bats are also an important control on insect populations, and they are preyed upon by many kinds of animals, such as owls and snakes that wait for bats as they exit their roots in the evening.
As the only mammals capable of true flight, they are a unique and cherished life form on planet Earth.