Iowa’s night sky hosts more mammalian diversity than most residents realize. Nine species make up the types of bats in Iowa, ranging from a common house guest that roosts in barn rafters to a solitary giant that migrates as far south as Panama each winter. Two of these species are federally endangered, and several more are sliding toward that same status because of a fungal disease that has reshaped bat conservation across North America.
Whether you found a bat in your attic, spotted one skimming a pond at dusk, or simply want to know what is flying over your backyard, this guide breaks down every species that calls Iowa home. Each one plays a role in controlling insect populations, and one study estimated that bats save corn farmers an estimated $1 billion annually through pest control alone.
1. Big brown bat
The big brown bat (Eptesicus fuscus) is the bat most Iowans are likely to encounter, whether they realize it or not. According to Iowa State University Extension research, the big brown bat is not only the most widely distributed species in Iowa, but also roosts in the greatest variety of places, both natural and human-made. State wildlife data confirms this pattern statewide, noting that the big brown species of bat, followed by the eastern red species, are most common throughout the state.
This species has brown fur with a blackish, hairless patagium, and it is genuinely tough by bat standards. Big brown bats are widely distributed in Iowa and will hibernate in human structures as well as caves, and they prefer beetles in terms of diet, and are quite hardy. That cold tolerance also means big brown bats are the last species to enter hibernation in fall and the first to re-emerge in spring, and Iowa researchers note that the only species known to overwinter in buildings in Iowa is the big brown bat.
Pro Tip: If you find a single bat roosting in a gap above a door frame or in a chimney during winter, it is almost certainly a big brown bat riding out the cold in your home rather than a cave.
Females form maternity colonies of anywhere from a few dozen to well over a thousand individuals each summer, tucked into attics, bridges, and hollow trees alike. Unlike several of its cave-dwelling relatives, the big brown bat has held relatively steady against white-nose syndrome, largely because it tolerates the near-freezing hibernation temperatures that keep the deadly fungus from thriving. Readers comparing regional bat populations may also want to look at how the same species behaves in the bats found in New York, where big brown bats show a similar pattern of living alongside people.
2. Little brown bat
The little brown bat (Myotis lucifugus) was once considered Iowa’s most familiar house bat, and in many ways it still is during the warmer months. Insects of Iowa researchers describe it plainly: the little brown myotis is one of Iowa’s most common bats, frequently using man-made structures in summer, but not in winter. That summer familiarity is exactly why so many people assume the species is doing fine, even though state and regional data tell a more troubling story.
Females gather in nursery colonies that can hold up to 1,000 adults inside buildings, bridges, and hollow trees before switching entirely to natural hibernation sites once cold weather sets in. Come winter, both sexes retreat to eastern Iowa’s caves and mines rather than sticking around buildings, often bunking down alongside other cave-hibernating species. That shared hibernation habit has proven costly: white-nose syndrome spreads efficiently between species packed into the same humid, above-freezing caverns that little brown bats prefer.
| Species | Roosting Group | Winter Strategy |
|---|---|---|
| Big Brown Bat | Cave/building hibernator | Hibernates in caves and structures statewide |
| Little Brown Bat | Cave hibernator | Hibernates in eastern Iowa caves and mines |
| Northern Long-Eared Bat | Cave hibernator | Hibernates solitary or in small groups |
| Indiana Bat | Cave hibernator | Very limited hibernation sites in Iowa |
| Tri-Colored Bat | Cave hibernator | Hibernates in caves, mines, rock crevices |
| Silver-Haired Bat | Tree-roosting migrant | Migrates south; occasionally overwinters in buildings |
| Evening Bat | Tree/building roost, migrant | Migrates south for winter |
| Eastern Red Bat | Tree-roosting migrant | Migrates south, sometimes in groups |
| Hoary Bat | Tree-roosting migrant | Migrates as far south as Panama |
This species remains widespread across the state in summer, though research notes it is statewide in summer and most common in the eastern half of Iowa. Anyone curious how a related myotis species fares in a different climate can compare notes with the bats native to Montana, another state where little brown bats hibernate in cave systems.
3. Northern long-eared bat
The northern long-eared bat (Myotis septentrionalis) is one of the two Iowa species carrying federal endangered status, a steep fall for an animal that was once a relatively common bat in the eastern U.S. before their population began to decline after introduction of WNS. Iowa DNR acoustic monitoring paints a grim but telling picture: despite steep losses, the data show the myotis is present in all Iowa regions even while being described as the state’s most imperiled bat.
Telling this species apart from the little brown bat takes practice, since they both have wingspans of 9-11 inches and both can have dark brown fur. The giveaway is in the ears: the ears of the northern long-eared bat are much longer than those of a little brown bat. Behavior differs too, since the northern long-eared bat is much more solitary in its habits, and is generally found singly or in small groups containing up to 100 individuals, unlike the little brown bat’s dense winter clusters.
Important Note: Because the northern long-eared bat and little brown bat look so similar in flight, most field identifications in Iowa are considered tentative unless the bat is examined up close by a trained biologist.
The species’ Midwestern relative shares a name with a neighboring state’s guide; readers researching regional variation may find it useful to compare with the bats documented in Indiana, where the same white-nose syndrome pressures have hit myotis populations hard.
4. Indiana bat
The Indiana bat (Myotis sodalis) is Iowa’s other federally endangered species, and its foothold in the state is genuinely narrow. Entomologists at Insects of Iowa note that a fifth species, the Indiana myotis, has been found hibernating in only two places in Dubuque County, making it by far the rarest hibernating bat documented statewide.
Iowa State University researchers describe a species already under pressure long before white-nose syndrome arrived: the Indiana bat has been on the decline throughout its Midwestern range due to habitat loss for many years, and is increasingly threatened by the exotic fungal disease. The Iowa DNR lists it alongside four other species affected by the fungus, confirming that of the bat species affected by WNS in North America, to date five are native to Iowa, including the big brown bat, little brown bat, and tri-colored bat, as well as the endangered northern long-eared bat and Indiana bat.
Because so few hibernation sites exist within Iowa’s borders, most of the state’s Indiana bats likely spend winter in larger cave systems just across the border. Anyone tracking how this species fares elsewhere in its range can look at the bats found in Arkansas or the bat species recorded in South Carolina, both of which host Indiana bat populations with their own conservation challenges.
5. Tri-colored bat (eastern pipistrelle)
The tri-colored bat (Perimyotis subflavus), formerly classified as the eastern pipistrelle, holds a memorable title: the tri-colored bat is the smallest bat found in Iowa. Its flight style matches its size, since observers describe how this bat flies somewhat like a giant moth, and has a wingspan of only 8-10 inches.
Fur color is a useful field mark here too, as its fur is yellowish or greyish brown and can be found foraging for insects over waterways and water edges. Come winter, this species retreats underground, since the tri-colored bat overwinters in caves, mines, and rock crevices, and in summer both males and females inhabit waterways bordered by woods and usually roost in trees.
This species has taken one of the hardest hits from white-nose syndrome of any bat in the state. Iowa DNR’s acoustic survey data confirms that the tri-colored bat and the myotis, or northern long-eared bat, populations have declined in eastern Iowa because of the deadly disease. Because of that decline, the species is currently under consideration for federal Endangered Species Act listing alongside the little brown bat.
6. Silver-haired bat
The silver-haired bat (Lasionycteris noctivagans) is one of Iowa’s true forest bats, easy to identify by the frosted, silvery tips on otherwise dark fur. According to Wikipedia’s summary of its natural history, they often roost in tree cavities or in bark crevices on tree trunks, especially during migration, and their coloring helps them blend into that bark almost perfectly.
Diet-wise, this species leans heavily on soft-bodied prey, since silver-haired bats consume primarily soft-bodied insects, such as moths, but will also take spiders and harvestmen, and they typically hunt low over still or slow-moving water. Most silver-haired bats migrate south for winter, though some individuals seem to overwinter in buildings, which may allow them to spend the winter in places that would otherwise be too cold for them.
Unfortunately, this species pays a steep price for its migratory habits. Bat Conservation International reports that the silver-haired bat, along with the hoary bat and eastern red bat, is among the three bat species most commonly killed by the turning blades at windmill facilities, making up over 75 percent of the mortalities recorded at wind energy sites nationwide. Anyone comparing tree-roosting bat behavior across borders might find the bat species documented in Canada useful, since silver-haired bats range well into that country during the warmer months.
7. Evening bat
The evening bat (Nycticeius humeralis) sits at the northern edge of its range in Iowa, and it is easily one of the least frequently reported bats in the state. It closely resembles a small version of the big brown bat, which sometimes leads to misidentification unless a wildlife biologist examines a specimen directly.
Like its larger cousin, the evening bat roosts in tree cavities, loose bark, and occasionally buildings during the summer breeding season, where females form small maternity colonies. Winter behavior sets it apart from Iowa’s cave-hibernating species, since the evening bat is one of the state’s migratory species that leaves entirely rather than overwintering underground.
Pro Tip: If you spot a small brown bat foraging in southern Iowa in midsummer that seems slightly smaller than a typical big brown bat, take a photo before assuming it is the same species. It may be the far less common evening bat.
Because sightings are relatively rare and research specific to Iowa’s evening bat population is limited, much of what biologists know about the species locally comes from broader regional studies rather than dedicated Iowa surveys. This data gap is common for range-edge species, and it is one reason state wildlife agencies continue to expand acoustic monitoring routes across the state.
8. Eastern red bat
The eastern red bat (Lasiurus borealis) ranks as one of the two most frequently encountered bats in Iowa, trailing only the big brown bat in overall sightings statewide. Its long, narrow wings and short, rounded ears make it fairly distinctive, and red bats have long, narrow wings, short rounded ears, and white markings on their shoulders and wrists.
This species is a master of disguise during daylight hours. Observers note that during the day, red bats hang by one foot from the branch of a tree or more commonly, a shrub such as sumac, with their tails wrapped around them, looking like dead leaves. Solitary by nature, red bats live solitary lives, only coming together to mate and migrate, and researchers have documented groups of up to 100 on these journeys during peak migration.
Reproduction sets this species apart from nearly every other Iowa bat, since the eastern red bat will give birth to up to four youngsters at a time, rather than a single or two pups. Diet skews heavily toward moths, and the species is often spotted circling streetlights on warm summer evenings. Many of Iowa’s red bats winter far south of the state; anyone curious how far this migration can stretch might look at the bat species found in Costa Rica, a region within the broader winter range used by several North American tree bats.
9. Hoary bat
The hoary bat (Lasiurus cinereus) closes out the list as Iowa’s largest bat by a comfortable margin. Marion County Conservation describes it plainly: the hoary bat is Iowa’s largest bat, with a wingspan of 13-16 inches, dwarfing every other species covered here.
Its name comes directly from its appearance, since it has yellowish or brownish fur with a frosty appearance due to the white tips on the hairs, paired with white patches at the elbow and wrist on an otherwise dark wing membrane. This species is also a serious traveler. Marion County notes these bats undertake long seasonal migrations, sometimes traveling as far south as Panama to spend the winter before returning to Iowa in the spring, and Bat Conservation International adds that hoary bats fly enormous distances along the way, since they can cover 24 miles in a single night.
Roosting habits set the hoary bat apart from its red and silver-haired relatives, since hoary bats often roost in evergreen trees rather than oak, maple, or other deciduous trees. Because people seldom encounter hoary bats as they don’t use human structures for roosting or as nurseries for their young, most Iowans who see one catch only a brief glimpse at dusk. Readers interested in how this same wide-ranging species behaves further west can check the bat species native to California or the bats found in New Mexico, both within the hoary bat’s expansive winter range.
Nine species, three survival strategies. Iowa’s bats either tough out winter in caves and mines, hole up in buildings alongside people, or abandon the state entirely for warmer climates until spring. Understanding which strategy each species uses explains almost everything else about where to look for them, why some are declining faster than others, and what backyard habitat changes actually help.
White-nose syndrome remains the biggest threat facing the state’s cave-hibernating species, while wind energy mortality increasingly threatens the migratory tree bats. Anyone interested in broader regional bat diversity can browse the full overview of bat species found across North America, or compare notes with neighboring states like the bats recorded in North Dakota. For readers curious about the rest of Iowa’s nocturnal wildlife, guides to the state’s snakes, frogs, and spiders round out the picture of what shares the night with Iowa’s bats.