You might not think of Idaho as bat country, but the Gem State hosts an impressive diversity of these nocturnal mammals. All 14 species are insectivorous, meaning they feast on mosquitoes, beetles, moths, and other flying insects.
A single bat can consume up to its body weight in insects each night, providing natural pest control worth millions of dollars to Idaho’s agriculture industry.
Idaho’s varied landscapes—from the lava caves of the Eastern Snake River Plain to the coniferous forests of the panhandle—create ideal habitats for both resident and migratory bat species.
Twelve of these species hibernate in Idaho’s caves and mines during winter, while two migrate south to warmer climates. Understanding these remarkable creatures helps us appreciate their ecological importance and the conservation challenges they face, particularly from threats like white-nose syndrome.
1. Big Brown Bat
The Big Brown Bat (Eptesicus fuscus) is one of the most commonly encountered bats throughout Idaho and North America. This medium-to-large species has earned its widespread presence through remarkable adaptability to human structures and diverse habitats.
You can identify this bat by its rich brown fur on the back with lighter, buff-colored underparts. The ears and snout are black and relatively short, giving it a compact and robust appearance. With a wingspan of approximately 13 to 16 inches and weighing around 14 to 25 grams, it’s the largest bat species you’ll regularly encounter in Idaho.
This species commonly roosts in attics, barns, bridges, and even behind window shutters during summer months. During summer, females form maternity colonies while males tend to roost alone. In winter, they hibernate in caves, mines, and buildings, often remaining relatively close to their summer roosting sites.
Identification Tip: Big Brown Bats emerge shortly after sunset and fly with strong, steady wingbeats. Their ability to tolerate a wide range of temperatures helps them survive Idaho’s varied climate better than many other bat species.
You’ll find Big Brown Bats across forest edges, agricultural lands, river corridors, and residential zones throughout Idaho. They play a vital role in natural pest control by consuming large quantities of beetles, flies, and other insects.
2. Little Brown Bat
The Little Brown Bat (Myotis lucifugus) is about the size of a human thumb, yet this tiny species is incredibly important for pest and disease control. Despite being historically abundant, it’s now experiencing severe population decline.
This small species has a wingspan of about 9 to 11 inches and weighs just 5 to 14 grams. Its fur is shiny and dark brown with a lighter underside. The relatively short snout and rounded ears make it easy to distinguish from other Myotis species. Reaching a weight of 7 to 14 grams, the Little Brown Bat isn’t actually that little for a bat species.
You can attract Little Brown Bats to your property by installing bat houses. They prefer to roost in buildings, tree hollows, and bat boxes during warmer months. Harriman State Park offers the best viewing opportunity for Little Brown Bats in Idaho, where they’ve congregated since the early 1900s. These bats arrive around mid-to-late May to the same roosting places, where mothers rear their offspring that arrive in June. You can see them leaving their roosts at dusk in large numbers when they hunt for food.
In winter, they hibernate in caves and mines, sometimes traveling long distances to reach suitable hibernation sites. A single Little Brown Bat can eat up to 1,200 insects in an hour, including mosquitoes that carry malaria and West Nile virus. Preferring to feed over sources of water, these bats use their wings and tail membrane to scoop insects into their mouth in mid-flight.
Conservation Note: White-nose syndrome has had a devastating impact on Little Brown Bat populations. The species is currently under review by the U.S. Fish and Wildlife Service for listing on the Endangered Species Act.
Little Brown Bats are strong fliers with rapid, fluttering wingbeats. They use echolocation to navigate and find prey in the dark. In Idaho, you’ll find them near rivers, lakes, wetlands, and forests, especially common in riparian corridors.
3. Silver-Haired Bat
The Silver-Haired Bat (Lasionycteris noctivagans) gets its name from the distinctive frosted appearance of its dark fur tipped with silver. This migratory species is one of Idaho’s most fascinating bats.
Female Silver-Haired Bats usually give birth to twins, which is an exception to the rule as most other bat species give birth to only one pup per year. These large, furry bats live in forests and roost in trees—you’ll be hard-pressed to find them in a cave. They’re widespread throughout North America and up to the mid-regions of Canada, and remarkably, they’re the only species of bat in Hawaii.
As relatively slow flyers, Silver-Haired Bats forage 20 to 25 feet above the ground over woodland ponds and streams. They’re one of the slowest flying bats in North America. They emerge earlier in the evening than many other species to consume insects. This species migrates into the northern United States and Canada to raise their pups in the summer and heads south for the winter.
Migration Pattern: Silver-Haired Bats are still making their way through Idaho on their southward migration in fall. As one of Idaho’s two migratory species, they don’t hibernate but instead travel to warmer climates.
You’ll find Silver-Haired Bats in forested habitats throughout Idaho, particularly near water sources. They’re one of the two bat species in Idaho that need conservation attention, making their protection particularly important.
4. Hoary Bat
The Hoary Bat (Lasiurus cinereus) is Idaho’s largest bat species, and its thick, frosted silver-tipped fur gives it a distinctive appearance that’s easy to recognize.
With a wingspan of up to 15.5 inches and a body weight between 20 and 35 grams, the Hoary Bat is an impressive sight. Its name comes from the frosted, silver-tipped appearance of its fur, which is thick and dark brown underneath. This coloring provides excellent camouflage against tree bark.
Hoary Bats usually roost at the edge of clearings, preferring foliage of both coniferous and deciduous trees. Less common roost sites include cavities or, in unusual situations, caves or human structures. They roost individually in trees, usually at the end of branches where they often choose sites not visible from above. The area below the roost is open and likely along the edge of a clearing.
| Characteristic | Hoary Bat | Silver-Haired Bat |
|---|---|---|
| Size | Largest in Idaho (15.5″ wingspan) | Medium (slower flyer) |
| Migration | Migrates south for winter | Migrates south for winter |
| Roosting | Individual tree roosts | Tree roosts in forests |
| Young | Average 2 pups (1-4 possible) | Usually twins |
These bats eat grasshoppers, dragonflies, wasps, beetles, flies, and moths—with moths being their preferred food. They have a swift flight pattern and usually fly high and direct to feeding areas along watercourses and meadows. Hoary Bats typically emerge after dark, with feeding activity peaking 4-5 hours after sunset and a secondary peak occurring several hours before dawn.
Hoary Bats may fly in waves from northern forests to southern latitudes, usually in late fall. The species breeds from September to November in North America, with fertilization delayed. Gestation lasts 90 days, and females produce one litter of 1-4 young (averaging 2) in mid-May to early July. Young are able to fly at 4 weeks and probably become sexually mature in their first summer.
You’ll find Hoary Bats most commonly in southwestern Idaho. They enter torpor during cold periods and may feed in cold weather, making them more active than many bat species during transitional seasons.
5. Western Small-Footed Myotis
The Western Small-Footed Myotis (Myotis ciliolabrum) lives up to its name with unusually small feet that are about half the length of the tibia. This tiny bat is among Idaho’s smallest species.
You can identify this species by its yellowish-brown fur with paler, sometimes white, underparts. The muzzle and chin are black, as are the 11 to 16 mm long ears. With a total length of 8 to 10 cm and a wingspan of about 24 cm (9.4 inches), they weigh just 4 to 5 grams. Females are slightly larger than males.
The fur color can vary from golden brown to reddish-brown. The face, wings, ears, and legs are black. The tail is 3 to 5 cm in length but is almost entirely enclosed within the tail membrane, with only the tip extending beyond it.
Unique Behavior: Pregnant Long-eared Myotis (a related species) often roost at ground level in rock crevices, fallen logs, and cracks of sawed-off stumps. Only one other western forest bat has been found regularly roosting at ground level: the Western Small-Footed Myotis.
You’ll find Western Small-Footed Myotis in Idaho in rocky areas near water, like canyons, cliffs, under loose rocks, and caves. They have relatively low wing aspect ratio and wing loading values for bats, which gives them excellent maneuverability in tight spaces.
Since this bat is small, its most common predators are owls. Unfortunately, these little guys also sometimes have to worry about predation from other larger bat species. They hibernate in caves and mines during winter months.
6. Long-Eared Myotis
The Long-Eared Myotis (Myotis evotis) has the longest ears of any North American Myotis species, making it one of the most distinctive bats you’ll encounter in Idaho.
The relatively long black ears are dramatic in contrast with the bat’s paler body fur. These ears range between 19 and 22 mm in length and are essential for helping them distinguish between ambient noise and sounds of prey or predators. The species is dull to pale brown or straw-colored with black ears and membranes. The tragus is long and slender, and total length ranges from 87 to 100 mm.
Long-Eared Myotis exhibit very little sexual dimorphism, with females being slightly larger than males. They’re found predominantly in coniferous forests throughout Idaho, typically only at higher elevations in southern areas between 7,000 and 8,500 feet.
From British Columbia to northern Arizona, they roost in tree cavities and beneath exfoliating bark in both living trees and dead snags. In southern British Columbia, Long-Eared Myotis roost in tree cavities in dense forests. They’ve recently adapted to forest management by roosting in the stumps of clear-cut stands, preferring stumps of ponderosa pine and lodgepole pine.
- Summer Roosts: Tree cavities, dead snags reaching into forest canopy, and occasionally abandoned buildings
- Winter Hibernation: Caves, mines, and protected rock crevices
- Feeding Strategy: Forages in and around forest canopy, eating moths, beetles, and other flying insects
- Social Structure: Males and females inhabit different roosting sites during summer, forming separate colonies
This species is known as a “whisper bat” because it echolocates at much lower frequencies than other bats. Long-Eared Myotis are endemic to the west, ranging from southwestern Canada south through California into Baja, eastward through Arizona and New Mexico, and north into the Dakotas.
7. Long-Legged Myotis
The Long-Legged Myotis (Myotis volans) gets a head start over other Idaho bats by leaving their roost early and beginning to forage before sunset, then continuing to eat throughout the entire night.
This smaller bat has fur varying from dark brown to grayish, with dull and pale underside fur. The feet are large and wide compared to other Myotis species. The ears are long, straight, and thin, with a short head and broad snout. The wingspan is approximately 9.4 inches (24 cm).
These bats are found in many different lowland habitats in Idaho, including coniferous forests and dry scrub forests. However, they’re typically always near water. You’ll often see them in huge groups in caves, buildings, mines, or other structures.
Like other bats in Idaho, Long-Legged Myotis primarily eat moths using echolocation. However, they differ from other species because they get a head start by leaving their roost early, foraging before sunset, and then eating throughout the entire night. This early emergence gives them access to insects that other bat species miss.
Long-Legged Myotis look for roosting sites in Idaho in forested habitats at lower elevations. They roost in rock crevices, dead or hollowed trees, under loose bark, and buildings in summer. In winter, you’ll find them in caves or mines. The females and males roost in separate places during summer but then reunite during hibernation.
8. Fringed Myotis
The Fringed Myotis (Myotis thysanodes) gets its name from the distinct fringe of short, wire-like hairs found on the membrane between its hind legs. This unique feature sets it apart from all other bat species.
This species has the shortest ears of the long-eared myotis group. The dorsal upper fur is often reddish-brown, the rounded ears are long (16-20 mm), and the tragus is long and pointed. With a lifespan that can reach upwards of 18 years, this species has an average total body length of roughly 85 millimeters and an average weight of 8.8 grams. They possess a pelage that is full and tends to be light yellow-brown or olive on the back with an off-white color on its underside.
Fringed Myotis are a small species, only weighing 5 to 7 grams. Their diet consists of beetles (60 to 73%) and moths (36-40%), which appear later in the evening, as well as arachnids and orthopterans found in tree canopies. It has been suggested that the wire-like hairs along the interfemoral membrane help trap the insects it catches in flight.
Flight Characteristics: With short, broad wings, this species is built to fly at low speeds but is capable of high maneuverability. Their flight is slow, which gives them better agility when hunting near vegetation.
This species occurs in a large number of roosting conditions including snags, hollows in trees, buildings, mines, rock crevices, and bridges. Fringed Myotis are particularly sensitive to temperature and will relocate roost sites to adjust for excessive heat or cold. It’s known that they migrate, but to where and how far is yet to be discovered.
You’ll find Fringed Myotis in desert, oak and pinon-juniper woodlands (where most common), and coniferous or mixed deciduous forest, usually at mid elevations. In Idaho, they’ve been found with many other species, including Long-Eared Myotis, Long-Legged Myotis, and California Myotis. They’re known to roost communally but never closer than 3 meters to other bat species.
Newborn pups are placed together in a group separate from adults and will only be joined by the parent to feed. The months of October through March are spent hibernating.
9. Yuma Myotis
The Yuma Myotis (Myotis yumanensis) is an opportunistic hunter that isn’t picky about what it eats. This adaptable species is commonly found near water throughout Idaho.
Yuma Myotis are very similar in appearance to Little Brown Bats and are often only distinguishable by their echolocation calls. This smaller bat has fur varying from dark brown to grayish, with dull and pale underside fur. The feet are large and wide, and the ears are long, straight, and thin, with a short head and broad snout. The wingspan is approximately 9.4 inches (24 cm).
These bats are found in many different lowland habitats in Idaho, including coniferous forests and dry scrub forests. However, they’re typically always near water. You will often see them in huge groups in caves, buildings, mines, or other structures.
The Yuma Myotis is an opportunistic hunter and isn’t picky about what it eats. They prefer to feed over sources of water, using echolocation to detect insects flying just above the surface. Females and males separate during summer pup rearing, with females forming maternity colonies.
- Often confused with Little Brown Bats due to similar appearance
- Distinguishable primarily by echolocation call patterns
- Forms large roosting colonies in caves and buildings
- Active hunters over water sources throughout the night
- May roost among Pallid Bats in some locations
10. Pallid Bat
The Pallid Bat (Antrozous pallidus) is a terrestrial forager with a unique appearance and fascinating feeding behavior. This species has pale, cream-colored fur that makes it stand out among Idaho’s bat species.
Pallid Bats have a head and body length of approximately 2.75 inches, forearm length of approximately 2.1 inches, a tail of approximately 1.75 inches, and a wingspan of 15-16 inches. They weigh 14-25 grams. These bats are large, with long forward-pointing ears (over 2.5 cm). The fur has a woolly feel with a cream-yellow to light brown color on their back and very pale to white color underneath. They have a blunt, pig-like snout.
The face has small wart-like glands that produce a skunk-like odor, which is thought to be used as a defense mechanism. This species usually feeds on ground-dwelling arthropods, gleaning scorpions, Jerusalem crickets, cicadas, beetles, or smaller insects associated with flowers and cacti. Remarkably, Pallid Bats can eat Arizona bark scorpions—the most venomous scorpions in North America whose stings can be fatal to humans. They’re immune to the scorpion’s venom due to missense mutations in their voltage-gated sodium channels.
Unique Foraging: Pallid Bats are gleaners, capturing prey from the ground and transporting it to their night roost for consumption. When foraging, they typically fly at low heights of 1-2 meters off the ground.
Pallid Bats frequent arid or semi-arid shrub steppe, grasslands, and to a lesser extent, higher elevation coniferous forests. They roost in rock crevices, mines, hollow cavities in trees, and occupied or vacant buildings. They may also roost in objects placed on the ground.
This species is gregarious and usually forms clusters in diurnal roosts. Yuma Myotis may roost among Pallid Bats. They may also gather in night roosts that are frequently near but separate from day roosts. The species emerges from day roosts relatively late, and foraging peaks at the beginning and end of their nocturnal activity cycle.
Pallid Bats are largely inactive in winter and are believed to hibernate, though in Idaho, the species is considered migratory. Breeding occurs between October and February, and sperm is stored until spring ovulation. Females usually give birth to 2 pups from late May to early June.
11. Canyon Bat
The Canyon Bat (Parastrellus hesperus) is Idaho’s smallest bat species. Known as the smallest North American bat, this tiny species weighs less than a penny.
This smaller bat has fur color that can vary from golden brown to reddish-brown. The face, wings, ears, and legs are black. The wingspan is approximately 8 inches (20 cm), making it the smallest wingspan among Idaho’s bats, ranging between 7.5 and 8.5 inches.
The Canyon Bat is mainly found in Idaho in rocky areas near water, like canyons, cliffs, under loose rocks, and caves. Day and night roosts in southwestern Idaho deserts and canyons include rock crevices, under rocks, in burrows, and sometimes in buildings or mines. Since this bat is small, its most common predators are owls. Unfortunately, these little guys also sometimes have to worry about predation from other larger bat species.
| Feature | Canyon Bat | Western Small-Footed Myotis |
|---|---|---|
| Size | Smallest in Idaho (8″ wingspan) | Very small (9.4″ wingspan) |
| Weight | Less than a penny | 4-5 grams |
| Coloring | Golden to reddish-brown | Yellowish-brown |
| Habitat | Rocky canyons, deserts | Rocky areas near water |
They fly erratically, much like a butterfly, and they eat small swarming insects. They emerge well before dark, drink and eat, and remain out later in the morning than other bats. Maternity colonies of no more than 12 give birth to twins in June or July. Pups fly at about one month.
Interestingly, the Canyon Bat has been known to occupy rodent burrows in the ground if their habitat doesn’t provide sufficient shelter. This species ranges from southeastern Washington south to Mexico. This is a species of special concern in Idaho.
12. Townsend’s Big-Eared Bat
Townsend’s Big-Eared Bat (Corynorhinus townsendii) is easily recognized by its extraordinarily long and thin ears. With ears reaching 1.5 inches in length and a wingspan of 12 inches, they’re among the largest of western bat species.
This medium-sized bat has extraordinarily long and thin ears with lumps on each side of the nose. Dense fur covers them all over, and colors vary from grayish brown to brown. Their wingspan is approximately 12 inches (30 cm). It’s pretty easy to see how these bats got their name—their large ears are essential for helping them distinguish between ambient noise and sounds of prey or predators.
Townsend’s Big-Eared Bats will use a variety of habitats, almost always near caves or other roosting areas. They can be found in pine forests and arid desert scrub habitats. Big-eared bats occupy both forest and desert/sage habitats within Idaho. When roosting, they do not tuck themselves into cracks and crevices like many bat species do but prefer large open areas.
During summer, males and females inhabit different roosting sites. Males live alone, while females form colonies where they raise their pups. Summer maternity colonies range in size from a few dozen to hundreds of individuals. These colonies form between March and June, with pups born between May and July. Maternity colonies choose sites that have warm, stable temperatures for pup rearing.
“Whisper Bat” Characteristic: This species is known as a “whisper bat” because it echolocates much lower than other bats, making their calls harder for both prey and predators to detect.
These bats specialize in eating moths and other insects such as beetles, flies, and wasps. Townsend’s Big-Eared Bat is usually a late flier and will forage along the edge of vegetation. They can be found throughout the western United States from British Columbia to central Mexico.
Natural predators include snakes, owls, cats, raccoons, and hawks. The ears of Townsend’s Big-Eared Bat are rolled up around its head when resting, which is a distinctive feature you can use for identification.
13. Spotted Bat
The Spotted Bat (Euderma maculatum) is one of Idaho’s rarest and most distinctive bats. This species has dramatic white spots on black fur and is one of the few bats whose echolocation sound is low enough to be heard by humans.
Spotted Bats are insectivores that eat a variety of insects, with moths being their food of choice. Unlike many other species, they are solitary and territorial, residing in arid environments. The spotted bat prefers arid regions, desert scrub, and open forests in rugged landscapes. They roost on vertical cliffs and in open canyons.
Their habitat always seems to be associated with a water source such as a spring, creek, river, or lake. The habitats include undisturbed roosts on cliffs along canyons, as well as open and dense deciduous and coniferous forests, hay fields, deserts, marshes, and dry shrub grasslands.
This bat can be found from British Columbia, Canada, southward through the western United States and into Mexico. The spotted bat’s mating season is in autumn, with the female giving birth in a maternity colony in June to usually only one pup. The pup does not have the distinctive color pattern of adults at birth.
Not much is known about the life span of the Spotted Bat, but it is assumed to live in the wild for more than 20 years. The ears of the Spotted Bat are rolled up around its head when resting. Natural predators include owls, raccoons, and skunks.
Audible Echolocation: This is one of the few bats whose echolocation sound is low enough to be heard by humans, producing distinctive clicking sounds that can help with identification.
14. Brazilian Free-Tailed Bat
The Brazilian Free-Tailed Bat (Tadarida brasiliensis) is known for its impressive migratory patterns and distinctive free tail that extends beyond the tail membrane. This medium-sized bat is an accomplished flyer capable of long-distance migration.
Brazilian Free-Tailed Bats are medium-sized, with a wingspan of 12-16 inches. They’re brown or reddish-brown with lighter fur on their undersides. Their most distinctive feature is their tail, which extends noticeably beyond the tail membrane—hence the name “free-tailed.”
These bats primarily eat insects like beetles and moths. They’re able to eat up to half their body weight in a single night, providing substantial pest control benefits. Known for their impressive migratory patterns, each year they migrate long distances between their wintering and breeding grounds.
Brazilian Free-Tailed Bats are known to roost with other bat species, principally Myotis species and Pallid Bats. They form large colonies, sometimes numbering in the thousands or even millions in other parts of their range.
While this species is less common in Idaho compared to states further south, they do occur in the southern portions of the state. They prefer roosting in caves, buildings, and under bridges. These fast-flying bats emerge in the evening to forage for insects at various heights.
Conservation and White-Nose Syndrome
Idaho’s bats face several significant threats, with white-nose syndrome being the most pressing concern. This deadly fungal disease has killed more than six million bats in the United States and Canada since its discovery in 2006. In 2022, white-nose syndrome was detected for the first time in three Idaho bat species at Minnetonka Cave.
White-nose syndrome is caused by the cold-loving fungus Pseudogymnoascus destructans, which grows on the nose, ears, and wings of hibernating bats. The disease rouses bats from hibernation, causing them to consume their winter fat stores and starve before spring. Some areas have seen bat declines of up to 90 to 100 percent due to this disease.
Idaho Fish and Game, along with partner agencies, is conducting vital research and monitoring efforts before the disease becomes more widespread.
In October 2024, in collaboration with the National Wildlife Health Center and Caribou-Targhee National Forest, Idaho Fish and Game conducted a round of white-nose syndrome vaccination at Minnetonka Cave.
How You Can Help Idaho’s Bats
There are many ways you can support bat conservation in Idaho:
- Plant native gardens: Create habitats that attract insects for bats to eat by planting native flowers and avoiding pesticides
- Install bat houses: Provide safe roosting sites where natural roosts are limited
- Add water features: Install birdbaths or small ponds to provide drinking water for bats
- Reduce light pollution: Turn off unnecessary outdoor lights at night to protect insect populations
- Practice cave etiquette: Decontaminate gear before and after visiting caves to prevent spreading white-nose syndrome
- Participate in citizen science: Join monitoring projects to help track bat populations
- Respect hibernating bats: Never disturb bats during hibernation, as even minimal disturbance can be fatal
By state law, it’s illegal to harass, harm, or kill any species of bat in Idaho. Two of the 14 species—the Silver-Haired Bat and the Hoary Bat—need special conservation attention within the state.
Final Thoughts
Idaho’s 14 bat species represent a vital component of the state’s ecosystems. From the common Big Brown Bat roosting in your barn to the rare Spotted Bat clicking in desert canyons, each species plays an irreplaceable role in controlling insect populations and maintaining ecological balance.
These remarkable mammals have adapted to Idaho’s diverse habitats over thousands of years, developing unique characteristics and behaviors that allow them to thrive in environments ranging from lava caves to mountain forests.
A single bat can live for decades and consume millions of insects during its lifetime, providing pest control services worth billions of dollars nationwide.
As you explore Idaho’s wild places, take a moment to appreciate these nocturnal neighbors. Watch for them emerging at dusk from caves, bridges, and trees.
Listen for the distinctive clicks of echolocating bats on summer evenings. By understanding and protecting Idaho’s bats, you’re helping preserve an essential part of the state’s natural heritage for future generations.
