Tennessee is home to a diverse population of at least 15 bat species documented throughout the state. These flying mammals are a significant part of the natural environment, often occupying forested areas, caves, and human-made structures. Bats provide substantial benefits to the ecosystem, primarily through insect consumption. They naturally control populations of agricultural and nuisance pests, as a single bat can consume hundreds of flying insects, including moths and mosquitoes, in one night.
Common Bat Species and Characteristics
The Big Brown Bat (Eptesicus fuscus) is one of the most frequently encountered species across Tennessee. These bats are medium-sized, measuring four to five inches in length with a wingspan of about 12 inches. They typically weigh between half an ounce to nearly one ounce. Their fur is usually two-toned, ranging from dark to cinnamon brown, and they primarily consume hard-bodied insects like beetles.
Another common species is the Little Brown Bat (Myotis lucifugus). This species is smaller, generally weighing less than half an ounce and measuring about three to four inches long. It has glossy brown fur and is known for its ability to eat numerous insects in an hour.
The Eastern Red Bat (Lasiurus borealis) stands out due to its striking coloration. Its fur is often bright red or yellowish-red with white tips, which provides camouflage in tree foliage. Unlike many colonial bats, this species is typically solitary and primarily roosts in trees. Eastern Red Bats are medium-sized, reaching four to five inches in length, and undertake seasonal migrations.
Habitat and Seasonal Patterns
The environments bats utilize in Tennessee change throughout the year, driven by temperature and reproductive cycles. During the warmer spring and summer months, female bats gather in “maternity colonies” to give birth and raise their young. These summer roosts are found in natural settings like hollow trees or under loose tree bark, or in man-made structures such as attics, barns, and bridges.
These summer sites must provide warmth and protection, which is why structures like attics are frequently chosen by species like the Big Brown Bat. Males typically roost alone or in small bachelor groups in separate locations, often utilizing tree cavities.
As temperatures drop, usually from late October to early April, bats enter a state of deep sleep called hibernation to conserve energy. For many species, this requires moving to underground shelters known as “hibernacula,” which maintain a stable, cool temperature and high humidity. Tennessee’s extensive cave systems and abandoned mines serve as important hibernacula for cave-dwelling species. This includes the endangered Gray Bat, which uses caves year-round, and the Indiana Bat, which prefers the largest, coolest limestone caves.
Conservation Status and Threats
Tennessee’s bat populations face serious threats, primarily from White-Nose Syndrome (WNS), a devastating fungal disease. WNS is caused by the fungus Pseudogymnoascus destructans, which grows on the exposed skin of hibernating bats. This growth irritates the bats, causing them to wake up frequently during hibernation and quickly burn through the limited fat reserves needed to survive the winter.
Since its detection in Tennessee, WNS has spread to at least 52 of the state’s cave-containing counties, causing massive mortality in cave-dwelling species. Species such as the Little Brown Bat, Northern Long-Eared Bat, and Tri-colored Bat have experienced estimated population declines exceeding 90% in some regions.
Several Tennessee bat species are protected under federal law due to WNS and habitat loss. The Gray Bat (Myotis grisescens) and the Indiana Bat (Myotis sodalis) are both listed as Federally Endangered. The Gray Bat is particularly vulnerable because the majority of its population relies on only a handful of specific caves for hibernation. The Northern Long-Eared Bat (Myotis septentrionalis) was also reclassified as Federally Endangered in 2022.
Safe Coexistence with Bats
When bats are found in or around human dwellings, it is important to practice safe and humane coexistence methods. All bats can potentially carry rabies, though the incidence rate is statistically low, so direct contact should always be avoided. Never attempt to touch a bat with bare hands, and if a bat is found in a room with a sleeping person or an unattended child, it should be safely captured and submitted for rabies testing.
If bats are roosting in an attic or other structure, the only legal and appropriate method for removal is “exclusion,” which involves installing specialized one-way devices. These devices allow bats to exit the building at dusk to forage but prevent them from re-entering.
State regulations prohibit the exclusion of maternity colonies during the summer “blackout period,” which runs annually from May 1st to August 1st. This restriction prevents the abandonment and death of non-flying young, or “pups.” Exclusion work must be planned outside of this critical period to ensure compliance with state law.