As twilight descends over the Mile High City, an extraordinary transformation takes place in the skies above Denver. While most residents wind down their day, a specialized group of aerial acrobats emerges to begin their nightly patrol.
These remarkable creatures—bats—represent some of Colorado’s most valuable yet misunderstood wildlife residents.
Denver’s unique position along Colorado’s Front Range creates an exceptional crossroads where nine distinct bat species thrive in diverse habitats ranging from urban neighborhoods to nearby mountain forests.
Whether you’re standing in City Park at dusk or hiking the foothills just west of town, you have opportunities to witness these incredible flying mammals in action.
Understanding how to identify each species and where they prefer to roost transforms ordinary summer evenings into fascinating wildlife encounters.
Colorado is home to approximately 18-20 bat species statewide, with Denver serving as habitat for roughly half of them. These insect-eating specialists consume hundreds to thousands of mosquitoes, beetles, and moths nightly, providing invaluable natural pest control worth millions of dollars to Colorado’s agricultural economy.
Learning to recognize and appreciate these nocturnal neighbors deepens your connection to Denver’s urban ecosystem while supporting conservation efforts that protect their declining populations.
1. Big Brown Bat
The big brown bat (Eptesicus fuscus) stands as Denver’s most common and adaptable bat species. You’ll recognize these robust flyers by their glossy chocolate-brown fur, relatively large size, and impressive 13-to-16-inch wingspan. As year-round Colorado residents, big brown bats have mastered urban living better than any other local species, making them the bat you’re most likely to encounter in Denver neighborhoods.
These substantial bats measure 4 to 5 inches in body length and weigh between 0.5 to 0.7 ounces—hefty by bat standards. Their fur appears uniformly dark brown on the back with slightly paler undersides, while their broad nose, large head, and short black ears create a distinctive profile. Unlike many bat species that migrate or hibernate in remote caves, big brown bats often spend winter hibernating right in Denver’s buildings, storm sewers, and other urban structures.
Where to find them: Big brown bats thrive throughout metropolitan Denver, from downtown skyscrapers to suburban neighborhoods. You’ll most commonly spot them hunting around streetlights, over parks, and near water features at Washington Park, City Park, and Sloan’s Lake. These adaptable creatures roost in buildings, under bridges (including several South Platte River crossings), behind loose siding, in attics, and within tree cavities throughout the metro area.
Their hunting strategy involves flying in relatively straight, steady patterns at heights of 20 to 30 feet, emerging shortly after sunset to pursue beetles, flying ants, and other larger insects. Big brown bats use powerful echolocation to detect prey, producing calls you can hear with a bat detector at frequencies around 25-30 kHz. During summer, female big brown bats form maternity colonies of 20 to 200 individuals where they collectively raise their young, typically giving birth to one or two pups in late May or early June.
These bats can consume half their body weight in insects each night, making them extraordinary allies in natural pest control. A single big brown bat can eat up to 600 insects per hour during peak feeding times. Their tolerance for cold weather and urban environments ensures you might even spot them flying on mild winter afternoons when temperatures exceed 45°F, making them one of Denver’s most reliable year-round wildlife viewing opportunities.
2. Little Brown Bat
Once considered Colorado’s most abundant bat species, the little brown bat (Myotis lucifugus) has experienced devastating population declines due to white-nose syndrome. Despite these challenges, you can still observe these small, agile flyers in select Denver locations, particularly during their active season from April through October.
Little brown bats are noticeably more petite than their big brown cousins, measuring only 3 to 4 inches in body length with 8-to-9-inch wingspans. They weigh less than half an ounce—about the weight of three pennies. Their fur ranges from pale tan to rich chocolate brown, featuring a distinctive glossy sheen that catches the light beautifully. The belly fur appears significantly lighter, often showing pale gray or buff coloration. These bats possess relatively long, pointed ears and small, delicate facial features that distinguish them from the stockier big brown bat.
Where to find them: Little brown bats prefer habitats near water sources where flying insects congregate abundantly. In the Denver area, look for them hunting over the South Platte River corridor, Cherry Creek Reservoir, and Chatfield Reservoir at dusk. They often roost in buildings, barns, and bat houses during summer months, though you’re less likely to find them in downtown Denver’s urban core compared to suburban and rural areas near the metro periphery.
These bats fly in highly erratic, maneuverable patterns as they pursue small insects like midges, mayflies, caddisflies, and mosquitoes. Their flight speed reaches up to 22 miles per hour, and during peak feeding activity, a single little brown bat can consume more than 150 insects in just 15 minutes. They typically emerge earlier in the evening than big brown bats, sometimes appearing while there’s still considerable daylight.
Little brown bats form large maternity colonies during summer, with females gathering in warm attic spaces or under roofs to raise their young. Each female gives birth to a single pup in late May or early June. Unfortunately, white-nose syndrome has reduced Colorado populations by an estimated 90% or more since the disease’s confirmation in the state in 2022, making every sighting particularly significant for conservation monitoring efforts. These bats hibernate in caves and abandoned mines during winter, though such sites are scarce in the immediate Denver area, causing most local populations to migrate to suitable hibernation sites elsewhere in Colorado.
3. Silver-Haired Bat
The silver-haired bat (Lasionycteris noctivagans) adds striking beauty to Denver’s bat community with its distinctive blackish fur tipped with silver-white hairs that create an almost frosted appearance. These medium-sized migratory bats measure 3.5 to 4.5 inches in body length with 10-to-12-inch wingspans, making them moderately sized among Colorado’s bat species.
You can identify silver-haired bats by their unique coloration—dark brown to black fur with prominent silver-white tips along their backs and shoulders, creating a shimmering effect when light catches their fur at certain angles. This silvery sheen becomes less noticeable on their undersides, which appear more uniformly dark. Their ears are short, rounded, and hairless with a black color that contrasts with their frosted backs. The interfemoral membrane (skin between tail and legs) features dense fur on the upper surface, distinguishing them from many other bat species.
Where to find them: Silver-haired bats show strong preferences for forested habitats and are most commonly encountered in Denver’s more wooded parks and foothills areas. Look for them in Washington Park’s mature tree stands, along the wooded sections of the South Platte River corridor, and in foothills parks like Red Rocks and Mount Falcon. They’re particularly abundant during spring (April-May) and fall (September-October) migration periods when they may temporarily roost on building exteriors or in tree bark for several days while passing through the region.
Their flight pattern is relatively slow and steady compared to smaller bat species, often following regular foraging routes along forest edges, over water, and through open areas adjacent to trees. Silver-haired bats typically emerge late in the evening—well after sunset—to hunt for moths, flies, beetles, and other soft-bodied insects. They demonstrate remarkable site fidelity to roosting locations, often returning to the same trees or structures year after year during migration.
During daylight hours, silver-haired bats roost in tree cavities, beneath loose bark, in rock crevices, and occasionally in buildings. They generally remain solitary or form small groups rather than creating the large colonies seen in some other species. These bats migrate considerable distances between summer and winter ranges, with Denver serving as important stopover habitat during their seasonal movements. Their presence in the metro area peaks during spring and fall migrations, though some individuals may remain through summer months to breed and raise young in suitable forested habitats.
4. Hoary Bat
Colorado’s largest bat species, the hoary bat (Lasiurus cinereus), impresses observers with its substantial size and striking frosted appearance. These impressive flyers boast wingspans reaching 15 to 16 inches—nearly the width of a standard piece of paper—and body lengths of 5 to 6 inches, making them unmistakable when spotted in flight.
The hoary bat’s name derives from the white-tipped or “hoary” guard hairs that create a distinctive frosted effect over their brown or grayish-brown fur. This silvery sheen appears especially prominent on their backs and shoulders, while their undersides show less frosting. They feature striking yellowish fur around their throats and necks that creates a collar-like appearance, and their short, rounded ears display prominent black borders. Males typically appear slightly larger and more colorful than females, though both sexes share the characteristic frosted appearance.
Where to find them: Hoary bats prefer open habitats with scattered trees rather than dense forests. In the Denver area, you’ll have the best chances of spotting them hunting over large open parks like City Park, Washington Park, and Rocky Mountain Arsenal National Wildlife Refuge. They frequently forage around park lights that attract flying insects, and you might see them flying at considerable heights—often 30 to 40 feet or higher above ground level.
These powerful flyers demonstrate strong, direct flight patterns with rapid wingbeats that carry them swiftly through the air. Hoary bats are solitary creatures that rarely form colonies, preferring to roost alone in dense tree foliage where their coloration provides excellent camouflage. They target larger prey items than most Colorado bats, including sizable moths, beetles, and occasionally other smaller bat species. Their hunting strategy involves high-altitude foraging, often pursuing insects well above the heights preferred by other local bat species.
Hoary bats migrate through Denver during spring (April-May) and fall (September-October), with some individuals remaining through summer to breed. Females typically give birth to two pups in June or July, roosting in trees throughout their maternity period. Unlike many bat species, female hoary bats can fly while carrying their young, though they usually leave pups at the roost during feeding flights. These bats emerge late in the evening and may continue foraging throughout the night when insect activity remains high. Their size, distinctive coloring, and high-altitude flight patterns make them one of Denver’s most exciting bat-watching targets, though sightings remain less frequent than the more common big brown and little brown bats.
5. Eastern Red Bat
The eastern red bat (Lasiurus borealis) brings vibrant color to Denver’s bat community with its bright rusty-red to orange-brown fur. While more common in eastern Colorado’s plains regions, this medium-sized migratory species occasionally ventures into the Denver metro area during seasonal movements, creating exciting spotting opportunities for bat enthusiasts.
You can identify eastern red bats by their distinctive coloring—males display brilliant brick-red to rusty-red fur, while females appear more frosted with orange-brown to yellowish-brown coloration. Both sexes feature prominent white shoulder patches that create striking contrast against their colored fur, and their throats show yellowish-white fur. These bats measure 3.5 to 4.5 inches in body length with wingspans of 11 to 13 inches. Their ears are short and rounded with a pinkish color, and unlike cave-dwelling species, their interfemonal membrane (tail membrane) is densely furred.
Where to find them: Eastern red bats prefer wooded habitats with scattered trees rather than dense forests or open plains. In the Denver area, your best chances of encountering them occur in parks with mature deciduous trees like City Park, Washington Park, and along the South Platte River’s riparian corridors. They’re most likely to appear during spring and fall migration periods, though occasional summer sightings occur when individuals remain to breed in the region.
Their flight pattern is faster and more direct than little brown bats, with strong, steady wingbeats. Eastern red bats typically emerge later in the evening compared to big brown bats and hunt primarily for moths, beetles, flies, and other flying insects. They’re solitary tree roosters that hang from branches in dense foliage during daylight hours, where their coloration provides remarkable camouflage—they often resemble dead leaves swaying in the breeze, protecting them from visual predators like hawks and owls.
Unlike colonial species, eastern red bats maintain solitary lifestyles throughout most of the year. Females give birth to one to four pups (typically twins or triplets) in June, representing one of the highest birth rates among North American bat species. Mothers roost with their young in trees, and pups can fly by three to four weeks of age. These bats migrate considerable distances between summer and winter ranges, with Denver serving as peripheral habitat at the western edge of their primary range. While sightings in the metro area remain less frequent than more common species, spotting an eastern red bat’s vibrant coloring against the evening sky creates a memorable wildlife encounter.
6. Brazilian Free-Tailed Bat
The Brazilian free-tailed bat (Tadarida brasiliensis), also called the Mexican free-tailed bat, represents one of Colorado’s most fascinating bat species. Named for its distinctive tail that extends well beyond its tail membrane—hence “free-tailed”—this medium-sized bat brings exceptional speed and agility to Denver’s skies during summer months.
You can identify Brazilian free-tailed bats by several distinctive features: their tail extends about half an inch beyond the uropatagium (tail membrane), their body is compact and streamlined, and their narrow wings are built for speed rather than maneuverability. These bats measure 3.5 to 4 inches in body length with 12-to-14-inch wingspans. Their fur ranges from dark brown to grayish-brown with a velvety texture, and their large ears meet at the midline of their head—a key identification feature. Their wrinkled upper lips and musky odor (detectable near roost sites) further distinguish them from other Colorado species.
Where to find them: Brazilian free-tailed bats occur primarily in southern and western Colorado, with Denver representing the northeastern edge of their typical range. In the metro area, they’re most likely to appear in southern and western suburbs including Littleton, Lakewood, and Golden. These bats show strong preferences for warm roosting sites, often selecting buildings, bridges, and other structures that provide stable thermal conditions. The South Platte River corridor and Chatfield Reservoir provide suitable foraging habitat when they do occur in the area.
These bats demonstrate remarkable high-altitude foraging behavior, often hunting 30 to 50 feet above ground or even higher—well above the altitudes preferred by most other Denver bat species. They’re among the fastest flying mammals, capable of reaching speeds exceeding 60 miles per hour in level flight. Brazilian free-tailed bats emerge well after dark and fly in fast, direct patterns with rapid wingbeats. They target moths primarily, though they also consume beetles, flying ants, and other insects.
While Denver doesn’t host the massive colonies found farther south (Texas caves shelter millions of individuals), smaller groups of dozens to a few hundred may establish summer roosts in suitable structures. Colorado’s largest known Brazilian free-tailed bat colony resides at Orient Mine in the San Luis Valley, approximately 150 miles south of Denver, housing an estimated 100,000 to 250,000 male bats during summer. These bats are highly migratory, arriving in Colorado in May and departing by September to winter in Mexico and Central America. Their economic importance cannot be overstated—Brazilian free-tailed bats consume enormous quantities of agricultural pest insects, providing valuable services to Colorado farmers. Though not common in Denver proper, any sighting of these distinctive free-tailed bats represents a noteworthy observation worth reporting to Colorado Bat Watch for their ongoing monitoring efforts.
7. Long-Legged Myotis
The long-legged myotis (Myotis volans) adds another member to the Myotis genus found in Denver, distinguished by its relatively long tibia (leg bone) and distinctive fur patterns. This medium-small bat measures 3.5 to 4 inches in body length with 9-to-10-inch wingspans, making it similar in size to little brown bats but with unique identifying characteristics.
You can identify long-legged myotis by several key features: their fur color ranges from light brown to dark reddish-brown with a notable glossy sheen, and unlike many other bats, they possess fur on the underside of their wings from elbows to knees—a distinctive identification marker. Their ears are relatively short and rounded, and when laid forward, they barely extend beyond the nose. The tragus (small projection inside the ear opening) is relatively short and blunt. Their keel (ridge of skin along the tail membrane edge) is short and barely noticeable.
Where to find them: Long-legged myotis bats prefer forested habitats, particularly areas with mature trees near water sources. In the Denver metro area and nearby foothills, look for them in ponderosa pine forests, mixed conifer-aspen stands, and riparian corridors. They’re more commonly encountered in foothills parks west of Denver—including Mount Falcon Park, Red Rocks, and Golden Gate Canyon State Park—than in the urban core. These bats roost in tree cavities, rock crevices, buildings, and occasionally under loose bark.
Their flight pattern is relatively slow and highly maneuverable, allowing them to navigate through cluttered forest environments effectively. Long-legged myotis emerge around dusk and forage for small flying insects including moths, beetles, flies, and mosquitoes. They often hunt close to vegetation and water surfaces, sometimes gleaning insects directly from foliage rather than catching them in mid-flight. This foraging strategy requires the exceptional maneuverability their broad wings provide.
During summer, female long-legged myotis form maternity colonies of 20 to 200 individuals, often roosting in buildings, tree cavities, or rock crevices. Males typically roost alone or in small bachelor groups. Females give birth to a single pup in June or July, and young bats begin flying by three to four weeks of age. These bats hibernate during winter months, though their specific hibernation sites in Colorado remain poorly studied. Long-legged myotis populations appear stable currently, though like all Colorado bats, they face threats from habitat loss, white-nose syndrome, and pesticide exposure. While less commonly observed than big brown or little brown bats in Denver proper, their presence in nearby foothills makes them accessible targets for bat watchers willing to venture slightly outside the metro area.
8. Fringed Myotis
The fringed myotis (Myotis thysanodes) ranks among Colorado’s most distinctive bat species, easily identified by the fringe of stiff hairs along the edge of its tail membrane. This medium-sized Myotis species measures 3.5 to 4.5 inches in body length with 10-to-11-inch wingspans, making it slightly larger than little brown bats.
You can identify fringed myotis by their namesake feature—a conspicuous fringe of stiff hairs along the posterior (back) edge of the uropatagium (tail membrane) that’s visible with close observation. Their fur ranges from yellowish-brown to dark brown on the back with paler, often buffy undersides. The ears are notably long—when laid forward, they extend well beyond the nose—and the tragus is long and pointed. Their face appears somewhat lighter in color than their back fur, and they possess relatively large feet compared to other similarly-sized bat species.
Where to find them: Fringed myotis bats primarily inhabit Colorado’s Western Slope, with Denver representing the far eastern edge of their typical range. They prefer lower-elevation habitats including pinyon-juniper woodlands, ponderosa pine forests, semi-desert scrublands, and canyons. In the Denver area, your best chances of encountering them occur in western suburbs near the foothills, particularly in areas with rocky outcrops and semi-arid habitats. These bats roost in caves, mines, rock crevices, buildings, and occasionally in tree cavities.
Fringed myotis demonstrate relatively slow, maneuverable flight patterns well-suited to foraging in cluttered environments. They emerge shortly after dusk to hunt for insects, showing a particular preference for beetles. Remarkably, they’re known to glean insects directly from vegetation and other surfaces rather than exclusively catching prey in flight—a foraging strategy that requires exceptional echolocation abilities to detect stationary targets. Their flight often follows regular routes between roosting and foraging areas.
During summer, female fringed myotis form maternity colonies ranging from about 20 to several hundred individuals, often in warm cave or building roosts. Males typically roost alone or in small groups separate from maternity colonies. Females give birth to a single pup in June or July, and young bats begin flying by approximately four weeks of age. These bats hibernate during winter, showing strong fidelity to specific hibernation sites that they return to year after year.
While fringed myotis sightings in Denver proper remain relatively uncommon due to the city’s position at the eastern limit of their range, these distinctive bats occur more frequently in foothills areas west of the metro area. Their unique fringe makes them one of Colorado’s easiest bat species to identify when seen up close, though observing this feature typically requires captured bats examined during research studies. For Denver-area bat watchers interested in seeking this species, focusing efforts in rocky canyon habitats west of Golden and Morrison offers the best opportunities for encounters.
9. Yuma Myotis
The Yuma myotis (Myotis yumanensis) represents another small member of the Myotis genus found near Denver, closely associated with riparian habitats and water sources. This small bat measures 3 to 3.5 inches in body length with 8.5-to-9.5-inch wingspans, making it one of Colorado’s smaller bat species.
You can identify Yuma myotis by several subtle features that distinguish them from similar-sized relatives: their fur ranges from pale tan to dull brown on the back with slightly paler undersides, lacking the glossy sheen seen in little brown bats. The ears are relatively short and rounded, extending just barely to the nose when laid forward. Their tragus is short and blunt rather than long and pointed. The foot is noticeably small—less than half the length of the tibia (lower leg bone)—which helps distinguish them from long-legged myotis. The calcar (spur from ankle supporting tail membrane) lacks a prominent keel.
Where to find them: Yuma myotis bats show exceptionally strong associations with water, more so than any other Colorado bat species. They occur primarily at lower elevations along rivers, streams, ponds, and reservoirs. In the Denver area, look for them hunting low over the South Platte River, Cherry Creek, and area reservoirs including Cherry Creek Reservoir, Chatfield Reservoir, and Bear Creek Lake Park. These bats typically forage within a few inches of water surfaces, where they capture aquatic insects like mayflies, caddisflies, midges, and mosquitoes.
Their flight pattern is slow and highly maneuverable, perfectly adapted for capturing insects emerging from or flying just above water surfaces. Yuma myotis emerge around dusk and often continue foraging throughout the night when insect activity remains high. They demonstrate remarkable precision in flight, capable of plucking insects from water surfaces without getting wet—a skill that requires exceptional echolocation and motor control.
During daylight hours, Yuma myotis roost in buildings, under bridges, in tree cavities, rock crevices, and mines—almost always near water sources. During summer, females form maternity colonies ranging from a few dozen to several hundred individuals in warm roost sites. Males typically roost separately in smaller groups. Females give birth to a single pup in June or July, and young bats achieve flight capability by about three to four weeks of age.
Yuma myotis faces increasing conservation concerns following the confirmation of white-nose syndrome in Colorado. Tragically, the first documented bat death from white-nose syndrome in Colorado was a Yuma myotis found at Bent’s Old Fort National Historic Site in spring 2023. Colorado Parks and Wildlife continues monitoring this species closely as the disease spreads across the state. While Yuma myotis populations appeared stable historically, the arrival of white-nose syndrome represents a severe emerging threat. Despite these challenges, you can still observe these small, water-loving bats along Denver’s waterways, particularly during summer evenings at prime riparian habitats. Their strong association with water makes them one of the most predictable Colorado bat species for targeted observation efforts—simply position yourself near suitable water bodies at dusk and watch for small bats flying low over the surface.
Best Times and Locations for Bat Watching in Denver
Washington Park ranks among Denver’s premier bat-watching destinations, offering accessible viewing opportunities right in the city. Position yourself near the park’s two lakes just after sunset during May through September for optimal viewing. The combination of open water, mature trees, and abundant insects attracts multiple species including big brown bats, little brown bats, and occasionally silver-haired bats. The park’s well-lit pathways provide safety while maintaining enough darkness for bats to forage naturally.
The South Platte River corridor offers exceptional bat habitat throughout the metro area. Cherry Creek’s confluence with the South Platte, the Confluence Park area, and stretches near Chatfield Reservoir provide diverse foraging opportunities. Water-loving species like Yuma myotis and little brown bats concentrate along the river, while big brown bats hunt in adjacent open areas. The riverside trails offer convenient access points for evening bat watches, with particularly good viewing near bridges where bats often roost.
Rocky Mountain Arsenal National Wildlife Refuge provides outstanding bat watching in a protected setting. The refuge’s combination of wetlands, grasslands, and scattered trees creates ideal habitat for multiple species. Big brown bats and hoary bats commonly hunt over the refuge’s lakes and ponds, while silver-haired bats utilize wooded areas during migration periods. The refuge offers organized bat walks during summer months, providing expert-led opportunities to learn about these remarkable animals.
Foothills parks west of Denver—including Red Rocks Park, Mount Falcon Park, and areas near Golden—expand your species possibilities. These transitional habitats between plains and mountains host species less common in Denver’s urban core, including long-legged myotis, fringed myotis, and additional silver-haired bat populations. The higher elevations and varied topography create diverse microclimates that support different bat communities.
Peak season runs from May through September, with July and August offering the most consistent viewing opportunities. Arrive at your chosen location 15 to 20 minutes before sunset—bats typically emerge when there’s still enough light to see silhouettes against the sky.
Bring binoculars for observing flight patterns and relative sizes that aid identification. Consider purchasing an affordable bat detector app for your smartphone to listen to echolocation calls, as different species produce sounds at distinguishing frequencies.
Join Colorado Bat Watch’s organized bat walks and citizen science programs to learn from experts while contributing valuable data to ongoing monitoring efforts.
The organization conducts acoustic monitoring throughout the metro area and welcomes community participation. Their website provides current information about bat populations, conservation efforts, and upcoming events.
The conservation work happening throughout Colorado demonstrates growing commitment to protecting these valuable urban wildlife populations.
Colorado Parks and Wildlife actively monitors bat populations as part of nationwide efforts to detect and respond to white-nose syndrome, climate change impacts, and habitat loss.
Organizations like the Colorado Bat Society and Colorado Bat Watch are establishing protected habitats and conducting crucial research on species populations and health.
Remember that Colorado law protects all bat species—it’s illegal to harm, kill, or disturb bats unnecessarily. If bats roost in unwanted locations at your property, humane exclusion techniques allow them to leave while preventing re-entry, but such work should only occur outside the maternity season (September through April) to avoid trapping dependent young.
Professional wildlife control services certified in humane bat management can assist with exclusions while ensuring legal compliance.
By learning to identify Denver’s nine bat species and supporting conservation initiatives, you contribute to ensuring these remarkable flying mammals continue thriving in the Mile High City for generations to come.
Every evening spent watching bats hunt over Denver’s parks and waterways deepens your connection to the urban ecosystem while celebrating these underappreciated conservation heroes working tirelessly to control insect populations naturally.
