Hoary bats are the most widespread of all bats in the United States. Though not yet recorded in Alaska, these bats are thought to occur in all 50 states. They range from the tree limit in Canada down to at least Guatemala in Central America, and throughout South America. They are the only bats found in Hawaii. There are records of migrant hoary bats on Southampton Island off of Northern Canada, and from Iceland, Bermuda, and the Orkney Islands off Scotland. They are rare in most of the eastern United States and northern Rockies and common in the Pacific Northwest and prairie states. They are abundant in California, Arizona, and New Mexico, where they winter. They winter in southern California, southeastern United States, Mexico, and Guatemala, but have also been found in Michigan, New York and Connecticut during December and in Indiana during January. This suggests that some may winter farther north than was previously expected.

Sexes are generally only found together in parts of Nebraska, Montana, and the Badlands of South Dakota. Males and females are usually separated during the warmer months in North America, except during the mating season. Females appear to be more concentrated in the western part of North America. There is evidence for an altitudinal separation of sexes in California, with females concentrated in the lowlands and coastal valleys and males higher up in the foothills and mountains.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Occurs throughout the U.S. north to northern Canada (southern British Columbia, southeastern Mackenzie, Hudson Bay, and southern Quebec), south through Mexico to Guatemala; also in western South America (Colombia and Venezuela to central Chile, Uruguay, and central Argentina), Hawaii, Galapagos, Bermuda, and (accidently) on other islands. Rare or absent in most of the southeastern U.S. and in deserts of the Southwest. The only nonmarine mammalian species native to Hawaii (subspecies SEMOTUS). Wintering areas for northern breeders include the southeastern U.S., southern California, and northern Mexico. In the U.S., adult females bear young in northeastern, midwestern, and prairie states, in small numbers south to Arkansas, Louisiana, and Tennessee; adult males summer in the western states, generally in montane areas; adult males and females both have been found in early summer only in the Black Hills of South Dakota (Layne 1978).

The body of hoary bats is about the size of a fat mouse. Hoary bats weigh 20 to 35 g. The length from the tip of the nose to the end of the tail vertebrae is 13 to 15 cm. The wingspan is 43 cm. These bats have blunt, rounded noses and small, beady eyes. The ears are short, thick, broad, and rounded. When laid forward they do not reach the nostrils. The tragus in the ear is short and blunt. The hindfoot is half as long as the tibia and has thick fur on the dorsal side. The thumbs are long. The calcar is twice as long as the hindfoot and is narrowly keeled on the posterior edge, bearing lobes on the tip. These bats have four mammary glands.

Thick, long, soft hair covers the entire dorsal surface extending to the elbow, the median ventral border of the undersides of the wings, the ventral side of the long bones that make up the upper arm and forearm, and the basal part of the lower surface of the interfemoral tail membrane. The coloring of the dorsal area (including the tail membrane) is a mixed brown-gray with a heavy white tinge, giving these bats a frosty appearance. In fact, these bats' name means "frosty or ash colored hairy tail." The individual silky hairs are basally dark, medially yellowish, and distally black with white tips. The belly of these bats is not heavily frosted. The throat has a distinct yellow patch. The hair on the elbow, at the base of the clawed thumb, and the upper arm is yellowish as well. The ears are yellow with black edges. Brownish fur extends out on the underside of the wing nearly to the wrist.

The skull is large (16 mm long) and broad (13 mm wide), with a large auditory bullae. These bats have large, strong teeth, with the first premolar located at the inner junction of the large canine.

Juveniles appear nearly grayish, but still have a frosty appearance.

Range mass: 20 to 35 g.

Range length: 13 to 15 cm.

Average wingspan: 43 cm.

Average basal metabolic rate: 1.19 cm^3 oxygen/hour.

Length: 15 cm

Weight: 35 grams

Larger than L. BOREALIS and Seminolus, in which adult total length is less than 120 mm. Upper surface of interfemoral membrane is furred to the tip (only the basal half is furred in Intermedius and L. EGA, both of which have 30 teeth (32 in L. CINEREUS) and are pale yellowish brown without white frosting).

• Terrestrial

Authorities disagree as to the bat's preference for coniferous versus broadleaf trees. Hoary bats are thought to prefer trees at the edge of clearings, but have been found in trees in heavy forests, open wooded glades, and shade trees along urban streets and in city parks.

Habitat Regions: temperate ; tropical

Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral ; forest ; rainforest ; scrub forest

Other Habitat Features: urban ; suburban

Comments: Prefers deciduous and coniferous forests and woodlands. Roosts usually in tree foliage 3-5 m above ground, with dense foliage above and open flying room below, often at the edge of a clearing and commonly in hedgerow trees. Sometimes roosts in rock crevices, rarely uses caves in most of range. Hibernating individuals have been found on tree trunks, in a tree cavity, in a squirrel's nest, and in a clump of Spanish-moss. Solitary females with young roost among tree foliage; female may use same site in successive years. In Saskatchewan, reproductive females roosted on the south (especially southeast) side of white spruce trees, where wind speed was reduced (Willis and Brigham 2005).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Migration takes place in waves, with large numbers passing through an area on a few nights in spring and fall (Layne 1978). Females precede males in spring migration. In the north, some may hibernate rather than migrate (Whitaker 1980). Those migrating through the western U.S. in fall go south at least into Mexico (Caire et al. 1989). Basically a spring-fall migrant in Texas, though some may overwinter (Schmidly 1991).

Northward migration in spring appears to stem mainly from wintering areas in California and Mexico; in summer, adult males are distributed mainly in the western half of North America whereas females dominate samples from eastern North America (Cryan 2003).

Moths (Lepidoptera) make up the bulk of the diet of hoary bats. These bats are also known to feed on flies (Diptera), beetles (Coleoptera), small wasps and their relatives (Hymenoptera), grasshoppers (Orthoptera), termites (Isoptera), and dragonflies (Odonata). The bat approaches the insect from behind, taking the abdomen and thorax in its mouth and biting off and swallowing this area of the insect, while dropping the wings and head. In comparison to other bats, hoary bats feed on relatively few orders of insects. On rare occasions, these bats have been observed to feed on leaves, grass, shed snake skin, and eastern pipistrelles.

Animal Foods: mammals; insects

Plant Foods: leaves

Primary Diet: carnivore (Insectivore )

Comments: Feeds chiefly on large moths and to a lesser extent on other insects over clearings. Begins foraging in early evening before it becomes too dark to see them (Layne 1978) (others report that this species emerges late in the evening). May forage around lights in nonurban situations (Furlonger et al. 1987). May forage at considerable distances (a mile or more) from the diurnal roost site; often along streams or lake edges. Hunting area may be defended if food is scarce.

Hoary bats have an important ecosystem role as insect consumers. These bats are often infested with mites (Pteracarus chalinolbus and Chiroptonysus americanus), helminths (Longibucca lasiura, Oochoustica taborensis, and Physocephalus), and protozoa (Distoma).

Commensal/Parasitic Species:

• mites
• worms
• microorganisms
• Pteracarus chalinolbus
• Chiroptonysus americanus
• Longibucca lasiura
• Oochoustica taborensis
• Physocephalus
• protozoa (Distoma)

The main enemies of hoary bats are hawks and owls. American kestrels and rat snakes have on rare occasions been reported to feed on hoary bats. These bats are also known to become entangled in barbed wire fences. Another important source of mortality is females falling out of their roost with attached young, thus becoming easy prey for terrestrial passers by.

Known Predators:

• hawks
• owls
• American kestrels
• rat snakes

Basically solitary, except for mother-young association; however, during migration, groups of up to hundreds of individuals may form. Dispersed population allows little chance to obtain density figures.

Some mother-young groups often change roosts whereas others do not; movements generally are less than 100 m from the previous roost.

Important predators include various birds and snakes.

Like all microbats, hoary bats use echolocation while flying. They make a shrill, hissing sound when disturbed. Lasiurus cinereus is one of the only vespertilionid bats which makes an audible chatter during flight.

Perception Channels: acoustic ; echolocation

Comments: Emerges usually well after dark, though Layne (1978) stated that emergence occurs early in the evening and, at least in Hawaii, diurnal flight is known (Fujioka and Gon 1988). Feeding activity peaks 4-5 hours after sunset, with a secondary peak several hours before dawn. May hibernate in north.

Average lifespan

Sex: male

Status: wild: 2.1 years.

In North America, the breeding range of hoary bats extends across Canada and northcentral and northeastern United States down to at least Kansas and Kentucky, and perhaps to Arkansas, Louisiana, and Georgia. Hoary bats are thought to mate around the time of autumn migration. Researchers are uncertain about whether copulation occurs before, during, or after the southward migration. Courtship is believed to proceed during day flights. Mating may also occur at southern wintering grounds.

Copulation is followed by delayed fertilization, a process in which the sperm is stored in the female reproductive tract all winter and is available to fertilize the egg when ovulation takes place in the spring. Parturition appears to range from the middle of May into early July. Little is known about the bat's gestation time. One study found three females to deliver between 900 and 1300 hours. Litter size is usually two, but can range from one to four.

Breeding interval: Hoary bats breed once per year.

Breeding season: Hoary bats breed in the autumn.

Range number of offspring: 1 to 4.

Average number of offspring: 2.

Average gestation period: 56 days.

Average weaning age: 34 days.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous ; sperm-storing ; delayed fertilization

Average birth mass: 5.5 g.

Average gestation period: 56 days.

Average number of offspring: 2.

Hoary bats give birth to their young while hanging upside down in the leafy shelter of their daytime retreat. The newborn's skin is brown, darker on the body than on the wings, and lighter beneath. The throat and head are much paler and their feet are nearly black. Fine, silver-gray hair covers their dorsal area. The hoary bat's ears and eyes are closed at birth and open on days three and twelve, respectively. Purposeful flight is possible for the infants by the thirty third day. The young cling to the mother in the day, while she sleeps, and hang on a twig or leaf while she hunts at night.

Parental Investment: altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

In North America, breeding occurs September-November, with delayed fertilization. Gestation lasts 90 days. Litter size is 1-4 (average 2), with one litter per year born between mid-May and early July in most areas. Young are able to fly at 4 weeks. Probably becomes sexually mature in first summer. Female sometimes may carry young during feeding flight.

Hoary bats are widespread and secure over much of their range. One subspecies, the Hawaiian hoary bat (Lasiurus cinereus semotus), is listed as endangered by the U.S. Fish and Wildlife Service.

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. While there are currently no reports of Lasiurus cinereus mortalities as a result of white-nose syndrome, the disease continues to expand its range in North America.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Global Short Term Trend: Unknown

Hoary bats occasionally hang out under overhangs of houses and garages, but this is only menacing and they rarely cause any true disturbance to homeowners.

These bats have a relatively high incidence of rabies. In some years, 25% of sick bats collected were found to be rabid.

Negative Impacts: injures humans (carries human disease)

Hoary bats prey on many insect species that are considered to be pests.

Positive Impacts: controls pest population

Comments: New World Lasiurus were placed in the genus Nycteris by Hall (1981), who based the change on nomenclatural (rather than biological) concerns; few if any other authors have followed this change (see Jones et al. 1992; Koopman, in Wilson and Reeder 1993). See Baker et al. (1988) for a genic analysis and information on relationship to other Lasiurus. Subspecies SEMOTUS of Hawaii formerly was regarded by some authors as a distinct species.