10 Types of Bats in Maryland: A Field Guide to the State’s Native Species
September 26, 2026
Ten types of bats in Maryland lift off from tree bark, attic eaves, and limestone caves each evening to hunt moths, beetles, and mosquitoes until dawn. Unlike the fruit-eating flying foxes found in places such as the bats covered in this guide to Australian bat species, every one of Maryland’s native bats is an insect hunter that relies on echolocation rather than sight to find its next meal.
Wildlife biologists split the state’s bats into two working groups: “cave bats,” which spend winter hibernating underground, and “tree bats,” which either migrate south or shelter in bark and leaf litter instead. All 10 species of bats occurring in Maryland are considered to be Species of Greatest Conservation Need, and two are now listed as endangered at the state or federal level. Below is a closer look at each species, how to tell them apart, and where they’re most likely to turn up around the state.
| Species | Roost Group | Standout Trait |
|---|---|---|
| Little Brown Bat | Cave bat | Maryland-endangered; can live decades in the wild |
| Big Brown Bat | Cave bat | Most frequently found bat inside homes |
| Eastern Small-footed Bat | Cave bat | One of the state’s rarest bats |
| Northern Long-eared Bat | Cave bat | Federally endangered |
| Indiana Bat | Cave bat | Federally endangered; easily confused with little browns |
| Tricolored Bat | Cave bat | Smallest bat in Maryland |
| Eastern Red Bat | Tree bat | Most common tree bat; fast, agile flier |
| Hoary Bat | Tree bat | Largest bat in Maryland |
| Silver-Haired Bat | Tree bat | Slow, unhurried flight style |
| Evening Bat | Tree bat | Known for a strong, pungent odor |
1. Little Brown Bat
The little brown bat (Myotis lucifugus) is one of the species most people picture when they think of a bat colony in an old barn or attic. Little brown bats are small – only two and a half to four inches long as adults, with dark brown, glossy fur on their backs and grayish fur underneath. They belong to Maryland’s colonial cave-bat group, alongside the big brown bat, the northern long-eared bat, and the tricolor bat.
This species carries real conservation weight in Maryland. One of Maryland’s two state-listed endangered bats is the tricolored bat, and the other is a native species called the little brown bat. Despite the grim outlook from disease, individual bats can be remarkably long-lived: banding studies have shown some little brown bats can live up to 30 years in the wild.
White-nose syndrome has hit this species harder than almost any other. A 2021 federal study found the disease had killed roughly 90 percent of little brown, northern long-eared, and tricolored bat populations in less than a decade, according to the Bay Journal. The fungus responsible was first documented well beyond Maryland’s borders — a pattern shared with bat populations described in this overview of New York’s bat species, the state where the disease was first confirmed.
Pro Tip: If you find a little brown bat roosting in a shed or eave, leave it alone during summer. Maryland’s colonial cave bats raise a single pup each year, and disturbing a maternity roost can cause mothers to abandon their young.
2. Big Brown Bat
The big brown bat (Eptesicus fuscus) is the species most Marylanders actually encounter, since it readily moves into human structures. Big brown bats are near twice the size of little brown bats, at four to five inches long, with long, silky fur that appears chocolate brown in color and broader noses than little brown bats. A big brown bat typically measures 4–5 inches long, weighs 3/8–5/8 ounce, and has a 12-inch wingspan.
The most common bats seen in houses and businesses in Maryland are the little brown bat and the big brown bat, and this species tends to fare better than its cave-dwelling relatives. The big brown bat is an insectivore that eats mostly beetles but consumes other flying insects like moths, flies, and wasps. Anyone curious about the sheer variety of beetle species a single colony might work through in a summer can check this guide to Maryland beetles.
Unlike several of its Myotis cousins, the big brown bat has held up relatively well against white-nose syndrome. Red bats and big brown bats appear to be doing well in Maryland, likely because they roost in smaller, more scattered groups than the dense cave colonies favored by little brown and Indiana bats. The species ranges across nearly the entire continental United States, including territory covered in this guide to Texas bat species.
3. Eastern Small-footed Bat
The eastern small-footed bat (Myotis leibii) is one of Maryland’s least-seen residents. It’s a genuinely small animal — the name refers to its tiny feet relative to other Myotis species — and it favors rocky terrain over open woodland. Along the Chesapeake and Ohio Canal, sightings include the rare eastern small-footed bat, the at-risk Indiana bat, and the threatened northern long-eared bat.
This species is one of the six cave-dwelling bats native to the state. The six species of bats designated as “cave bats” undergo hibernation during the winter: the Indiana bat, the little brown bat, the eastern small-footed bat, the northern long-eared bat, the big brown bat, and the tricolored bat. Compared with the others on that list, the small-footed bat tends to tolerate colder hibernation temperatures and often roosts alone or in small clusters in rock crevices and talus slopes rather than dense cave chambers.
Because it’s rarely encountered and roosts in less accessible terrain, population data on this species is thinner than for Maryland’s more common bats. It shares part of its Appalachian range with populations described in this guide to Alabama’s bat species, another state where the small-footed bat clings to rocky ridge habitat.
4. Northern Long-eared Bat
The northern long-eared bat (Myotis septentrionalis) has gone from a routine woodland species to one of the most urgent bat conservation stories in the country. The species is a wide-ranging, federally endangered bat found in 37 states and eight provinces in North America, and it typically overwinters in caves or mines while spending the rest of the year in forested habitats.
Important Note: This species’ federal status changed recently. The U.S. Fish and Wildlife Service announced a final rule to reclassify the northern long-eared bat as endangered under the Endangered Species Act; the bat, listed as threatened in 2015, now faces extinction due to the rangewide impacts of white-nose syndrome. The effective date was ultimately extended to March 31, 2023.
The scale of the decline explains the urgency. Data indicate white-nose syndrome has caused estimated declines of 97 to 100 percent in affected northern long-eared bat populations. In Maryland, this species has been documented along the shared range it holds with North Dakota’s bat populations in the upper Midwest, part of the same 37-state footprint tracked by federal biologists. More detail on the listing itself is available directly from the U.S. Fish and Wildlife Service’s species profile.
5. Indiana Bat
The Indiana bat (Myotis sodalis) is a federally endangered species that looks deceptively similar to its more common relatives. The Indiana bat, an endangered species found in Maryland, can be confused for the little brown bat. Because of its protected status, it cannot be harassed, collected, harmed, or killed without a federal permit.
Like Maryland’s other cave bats, Indiana bats form tight colonies during hibernation and summer. The little brown bat, big brown bat, long-eared bat, and the endangered Indiana bat tend to live in colonies and will roost and hibernate in dead trees, rock outcroppings, and manmade structures. Summer maternity colonies don’t last all season, either — maternity colonies begin to disband shortly after the young are capable of flying, typically in late July.
This species has also been documented at one of Maryland’s key bat corridors: the Chesapeake and Ohio Canal, where sightings include the at-risk Indiana bat. Its range extends south and west into the Ozark cave systems described in this guide to Arkansas bat species, another stronghold for the species.
6. Tricolored Bat
The tricolored bat (Perimyotis subflavus), formerly known as the eastern pipistrelle, holds the title of Maryland’s smallest bat. The tricolored bat is the smallest bat species in the state, with a wingspan of just 8 to 10 inches. It’s also one of the state’s two state-listed endangered bats.
One of the best places to encounter this species is underground. Crabtree Cave is the largest bat hibernaculum in Maryland, and recorded species there include the big brown bat, the northern long-eared bat, the tricolored bat, and the little brown bat. Outside the cave, tricolored bats hunt small moths and other soft-bodied insects at dusk — prey that starts its life as the caterpillars covered in this Maryland caterpillar guide.
The species’ outlook has worsened at the federal level too. The tricolored bat has been proposed to be added to the endangered list, while little brown bats are under review to receive some level of federal protection. Its range overlaps with populations documented in this South Carolina bat guide, another state grappling with steep tricolored bat losses.
7. Eastern Red Bat
The eastern red bat (Lasiurus borealis) is the bat most Marylanders have actually seen without realizing it. The most common bat in Maryland, the eastern red bat generally roosts in south-facing deciduous trees 4-10 feet above the ground during the day, but may crawl beneath leaf litter on the coldest days.
It’s also fast. Eastern red bats, the most common tree bats in Maryland, can fly up to 40 miles per hour. At dusk, they often fly hunting for moths, mosquitos, crickets, cicadas, and other insects — a diet broad enough to include the occasional ant swarm, similar to species covered in this Maryland ants guide.
Winter behavior varies within the species. Some eastern red bats will migrate south for the winter, while others will seek out leaf litter or hollow trees for the colder months, and observers sometimes see them flying on warm winter days. The species’ range extends well beyond Maryland into territory shared with the bats profiled in this New Mexico bat guide. Encouragingly, population trends here look stable: red bats and big brown bats appear to be doing well in Maryland.
8. Hoary Bat
The hoary bat (Lasiurus cinereus) is Maryland’s largest bat by a comfortable margin. The hoary bat is the largest bat in Maryland, with a wingspan that can reach 16 inches. That figure lines up with statewide surveys putting the Hoary Bat’s wingspan at 13 to 16 inches, the widest of any species on this list.
Like the eastern red bat, the hoary bat is a solitary tree-roosting species rather than a cave dweller. The eastern red bat and hoary bat are migratory and only occur in Maryland during the summer. Its range stretches coast to coast, overlapping with populations documented in this California bat guide, where hoary bats are also a familiar summer sight.
Acoustic monitoring has become the main way biologists track this and other tree bats along Maryland’s coast. Stationary acoustic monitoring stations at Assateague use bat detectors and microphones to record echolocation calls, which can later be identified to species. These surveys help biologists distinguish the hoary bat’s calls from the state’s five other bat species with similar hunting habits.
9. Silver-Haired Bat
The silver-haired bat (Lasionycteris noctivagans) is easy to spot once you know what to look for — not by sight, necessarily, but by its unhurried flight pattern. Silver-haired bats live life in the slow lane and fly at unhurried, leisurely speeds, a noticeable contrast to the eastern red bat’s high-speed pursuits.
Physically, this is a compact, dark-colored bat. Its color is typically black but sometimes dark brown, with gray tips to its fur; it measures about 10 cm and weighs 8 to 12 grams. Its diet is broad even by bat standards: this insectivore eats flies, leafhoppers, moths, mosquitoes, beetles, bugs, and ants, which it finds in forest habitats.
Silver-haired bats are wide-ranging migrants. The silver-haired bat is a nocturnal, solitary mammal from the central part of North America with an average lifespan of about 12 years, and it migrates to warmer climates in winter. That range pushes well north into territory shared with the species covered in this guide to Canada’s bat species.
10. Evening Bat
The evening bat (Nycticeius humeralis) rounds out Maryland’s list of ten native species, and it comes with a reputation that has nothing to do with looks. Evening bats win the undesirable award of smelliest bat, thanks to a strong, pungent odor.
Despite roosting in colonies somewhat like the state’s cave bats, the evening bat is classified among Maryland’s tree bats, alongside the eastern red bat, the hoary bat, and the silver-haired bat, because it winters in trees or migrates rather than hibernating underground. Its diet leans heavily on beetles, including species similar to those covered in this Maryland ladybug guide — ladybugs are, after all, beetles too.
Common Mistake: People sometimes assume a smelly bat colony in an attic means the animals are sick. In evening bats, the odor is simply glandular and normal — it doesn’t indicate disease, though a colony inside a home should still be handled by a licensed wildlife control operator rather than removed by hand.
Nationally, the outlook for cave-dependent Microchiroptera remains a concern regardless of species. White-nose syndrome, named for a fungus that grows on hibernating bats, is tracked on a spread map maintained by federal researchers. The evening bat has so far avoided the worst of the disease’s impact since it doesn’t overwinter in caves, but the broader story of white-nose syndrome shapes how all ten of Maryland’s bat species are managed and monitored today.
Maryland’s bat populations tell two very different stories at once — steady tree bats holding their ground and cave bats fighting a fungal disease that has reshaped the state’s night skies since the mid-2000s. Anyone interested in how Maryland’s broader ecosystem fits together can explore related wildlife guides covering the state’s native frogs and native snakes, both of which share habitat with these ten remarkable, insect-hunting mammals. For a broader look at how Maryland’s species compare to bats elsewhere, the full roundup of bat types is a useful next stop.