Missouri has two species of big-eared bats (in genus Corynorhinus): Rafinesque’s big-eared bat (Corynorhinus rafinesquii), and our subspecies of Townsend’s big-eared bat (Corynorhinus townsendii), which is called the Ozark big-eared bat (C. townsendii ingens).
Both are species of conservation concern in Missouri:
- Rafinesque’s big-eared bat is critically imperiled and occurs only in the Bootheel;
- The Ozark big-eared bat is considered extirpated from the state and was formerly found only in a few southwestern counties; it is a federally endangered species.
Compared to our other species of bats, the two big-eared bats are easily distinguished by their long ears, which are more than 1 inch (25 mm) in length. All other bats in Missouri have ears that are shorter. Also, our big-eared bats have a lump on each side of the nose (hence the alternate common name “lump-nosed bat”).
Rafinesque’s big-eared bat (Corynorhinus rafinesquii) is critically imperiled in Missouri; vulnerable/apparently secure globally. Missouri’s Bootheel is on the northwestern edge of this species’ overall range, and in our state, this species has only been recorded from the southeastern (Bootheel) corner.
- Of our two big-eared bats, it is distinguished by its gray back and white belly (not brown and tan); the strong (not weak) contrast between the base and tips of the fur; and its occurrence in Missouri’s southeastern counties.
Townsend’s big-eared bat (Corynorhinus townsendii) is mostly found in western North America; one of its subspecies, the Ozark big-eared bat (C. townsendii ingens), is a federally endangered subspecies that used to occur in Missouri, but there have been no official sightings here since the early 1970s. It is currently considered extirpated from the state but is still found in Arkansas and Oklahoma. If it is once again discovered in our state, it will likely be in southwestern Missouri.
- Of our two big-eared bats, it is distinguished by its brown back and tan belly (not gray and white); the weak (not sharp) color contrast between the base and tips of the fur; and by its (most probable) occurrence in southwest Missouri.
For your safety and the safety of bats, do not handle bats. Biologists who study bats receive special training and pre-exposure rabies vaccinations. Bats are not aggressive toward people but will bite in self-defense if handled. If you absolutely must handle a bat, wear heavy leather gloves. For more information about bats, see the bats group page.
Similar species: In Missouri, the northern long-eared myotis (Myotis septentrionalis) is much more common and widespread and also has longish ears, but its ears are short compared to our two big-eared bat species, which are in a different genus.
- The ears of the northern long-eared myotis are only long when compared to its sister species in genus Myotis, reaching only about ¾ inch long (while the ears of big-eared bats range from about 1 to 1½ inches long).
To avoid confusion, some bat specialists have started calling the northern long-eared myotis simply the “northern bat” or “northern myotis.”
Rafinesque’s: Total length: 80–107 mm (3⅛–4¼ inches); tail length: 47–50 mm (1⅞–2 inches); weight: 5–14 g (about 0.2–0.5 ounce); ear length: 31 mm (1¼ inches); wingspan: 25–30 cm (3–4 inches).
Ozark: Total length: 79–88 mm (3⅛–3½ inches); tail length: 34–44 mm (1⅜–1¾ inches); weight: 3–8 g (0.1–0.3 ounce); ear length: 30–39 mm (1¼–1½ inches).
Rafinesque’s big-eared bat has been recorded from five counties in southeastern Missouri (Cape Girardeau, Scott, Stoddard, Mississippi, and New Madrid), and it probably also occurs in the rest of the Bootheel, too.
The Ozark subspecies of Townsend’s big-eared bat used to occur in Barry and Stone counties, in southwest Missouri. Currently it is known from only a few locations in Arkansas and Oklahoma. If it is again found in Missouri, it would probably be in the southwestern corner.
Habitat and Conservation
Rafinesque’s big-eared bat is associated with forested areas, bottomland forests, and streamside habitats throughout its range. Because of this species’ overall rarity, its winter and summer homes are relatively little known. In other parts of its range, it uses caves and mines for winter hibernation, and in Missouri, it probably hibernates in those habitats as well. In summer, nursery colonies have been reported in tree cavities and in buildings, but only rarely in caves. In summer, males tend to roost in buildings or behind the loose bark of trees and in hollow trees.
Being associated with the Mississippi River alluvial basin, Rafinesque’s big-eared bats especially prefer large wetlands with bald cypress, water tupelo, and black gum.
The Ozark big-eared bat subspecies is strongly associated with caves. Year-round, they live in caves and rocky crevices (though other subspecies of Townsend’s big-eared bats can live in a variety of other sheltered places).
During hibernation, they hang singly or in clusters of up to 30 individuals. They generally select rather exposed and cold places in caves, such as near the entrance in the “twilight zone.” But if temperatures become too severe, they move to areas of the cave where the temperatures are more stable. Indeed, they awaken periodically, fly about their hibernating quarters briefly, then return to their torpor. They may even fly from one cave to another.
In summer, male Ozark big-eared bats are solitary, while the females establish nursery colonies that may contain several hundred individuals. They ordinarily use the same site year after year.
- When big-eared bats hibernate, they hang by their hind feet with the head downward. Individuals that hang singly or in small groups coil their large ears and flatten them against the neck. When the bats awaken, the ears straighten out again. There is a tendency for bats in larger clusters to keep their ears erect.
- Both species of big-eared bats have declined and disappeared from former parts of their ranges due to habitat loss, especially with destruction of suitable cave habitats and disturbance by people. Big-eared bats, with the types and locations of roosts, make them highly susceptible to disturbance.
Food
Both of our big-eared bats feed on flying insects, especially moths, which they capture on the wing. They usually eat at their roost, picking the wings from the moth before consuming the body. Other prey include beetles, leafhoppers, and small flies. They usually have two foraging periods: one soon after sunset, and another before sunrise.
Ozark big-eared bats prefer to forage in the edges between open and wooded areas. Apparently, Rafinesque’s big-eared bat prefers to hunt in forested bottomland areas along streams.
Status
Rafinesque’s big-eared bat is a species of conservation concern in Missouri, ranked as critically imperiled. Throughout its entire range, it is nowhere abundant. Other states that have ranked it as a species of conservation concern include West Virginia, Illinois, and Mississippi.
The Ozark subspecies of Townsend’s big-eared bat is also a Missouri species of conservation concern, ranked as endangered both federally and statewide. In our state, it is considered extirpated, since it has not been seen within our borders since the 1970s. The entire global population of this subspecies is only a few thousand individuals, all living within a tiny range.
A number of factors contribute to big-eared bats' decline:
- In addition to being highly sensitive to disturbances in their caves, big-eared bats have a relatively low reproductive rate, bearing at most one pup per year, making it difficult for a population to rebound if reproduction is repeatedly unsuccessful.
- More concerning, it appears that female Ozark big-eared bats are extremely loyal to their nursery caves, and once a maternity colony has been extirpated from its cave, no new females will repopulate it and reestablish it as a nursery cave. This means that each of the few known nursery caves must be protected.
Life Cycle
Rafinesque’s big-eared bats do not migrate but stay in the same general area throughout their lives. Not much is known about their reproduction, though apparently fertilization is delayed as in other bat species, with mating probably occurring in winter and spring, and the sperm stored in the female’s body until spring, when the eggs are fertilized. Only one pup is born, at the end of May or in early June, and after about three weeks, it is able to fly.
The Ozark big-eared bat is similarly little-studied. Like Rafinesque’s big-eared bat, they do not migrate long distances. They mate in fall and winter, with delayed fertilization, so gestation does not begin until spring. Only one pup is born, in May or June; it is able to fly after about three weeks.
Control
Human Connections
The decline of big-eared bats is mainly due to destruction or disturbance of their roosting and nursery sites. These bats seem especially vulnerable to interruptions during hibernation; when something causes them to arouse from hibernation, they burn through too much of their bodies’ fat reserves and may not survive the winter. This is why the hibernation caves of these species are being gated, to prevent people from inadvertently harming them.
The genus name for big-eared bats, Corynorhinus, means “club-nosed.”
The species name for Rafinesque’s big-eared bat, rafinesquii, honors Constantine Rafinesque (1783–1840), a self-taught French zoologist, botanist, anthropologist, geologist, and linguist who spent much of his career as a professor of botany at Transylvania University in Lexington, Kentucky. He contributed greatly to our knowledge of the natural world and human prehistory, though many of his ideas seemed eccentric and, because he was self-educated, he was generally spurned by the scientific establishment during his lifetime. But dozens of species and even genera were named in his honor.
The species name for Townsend’s big-eared bat, townsendii, honors John K. Townsend (1809–1851), a Philadelphia-born MD, naturalist, and contemporary of John James Audubon who collected many scientific specimens during his travels. In addition to a species of big-eared bat, several other animals were named in his honor, including Townsend’s warbler and Townsend’s solitaire, the whitetail jackrabbit, and a chipmunk, ground squirrel, mole, vole, and pocket gopher.
The name of our subspecies of Townsend’s big-eared bat, ingens, means “large” or “remarkable.”
Ecosystem Connections
Protecting cave-dwelling bats also includes protecting their underground habitats from pollution. This improves the stability and quality of interconnected karst features such as groundwater, springs, sinkholes, and cave systems.
The predator-prey relationship between bats and moths has led moths to evolve many fascinating ways to avoid being captured by bats. Several types of moths, upon sensing the sonar clicks of bats, will immediately, reflexively, engage in erratic flight patterns, or produce sounds that can confuse or jam the bats’ echolocation abilities.
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, feed many small organisms that are then eaten by other forms of cave live.
Bat conservation is one of the main reasons why most caves are now closed to the public, at least seasonally. These closures not only help bats to survive and reproduce successfully, but also protect many other sensitive organisms that live in caves.
There are five subspecies of Townsend’s big-eared bat. In addition to the federally endangered Ozark subspecies, C. townsendii ingens, there are:
—C. t. australis, the southern Townsend’s big-eared bat, occurs in western Texas south to the mountains of central Mexico.
—C. t. pallescens, the western big-eared bat or pale Townsend’s big-eared bat; has a relatively small range, occurring from New Mexico to northern Colorado and southern Wyoming.
—C. t. townsendii, the nominate subspecies, thus called Townsend’s big-eared bat, but also called the Pacific Townsend’s big-eared bat; ranges along the Pacific coast from British Columbia south to Mexico, and east to the Colorado Plateau and the Black Hills.
—C. t. virginianus, the Virginia big-eared bat, whose numbers are declining; federally endangered; the official state bat of Virginia; this is the Appalachian subspecies, ranging from Virginia through West Virginia, North Carolina, to eastern Kentucky.
