Silver-haired bats are found throughout the United States (with Florida as a possible exception), northward into southern Canada up to the treeline, and reach their northern limits in Alaska . The range may also include extreme northeastern Mexico (due to similar habitat conditions), although there have been no confirmed sightings of the bat.

Biogeographic Regions: nearctic (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: Range extends from southeastern Alaska and much of western Canada south of the Northwest Territories south to central California, northern Mexico, and east through Georgia (Yates et al. 1976, Hall 1981). The species is known also from Bermuda. It winters in the Pacific Northwest, in scattered areas of the southwestern United States, and at middle latitudes of the eastern United States approximately south of Michigan and east of the Mississippi (Cryan 2003). Males seem to stay farther south in spring and summer than do females, except for populations in British Columbia that do not appear to migrate (Cryan 2003).

Silver-haired bats are medium sized bats, weighing 8 to 12 grams. Measurements of these bats include: total length, 90 to 115 mm; tail length, 35 to 50 mm; wingspread, 270 to 310 mm; forearm, 37 to 44 mm; head size, 60 mm long; and a hind foot length of 6 to 12 mm. Silver-haired bats receive their name from their dark, silver-tipped fur. The fur is usually black in color, however some individuals may be dark brown with yellow-tipped fur. The ears of these bats are relatively short (15 to 17 mm in height), round, and naked. The dorsal surface of the interfemoral membrane is lightly furred, with 50 to 75% of the tail being naked.

Range mass: 8 to 12 g.

Range length: 90 to 115 mm.

Range wingspan: 270 to 310 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Length: 11 cm

Weight: 15 grams

• Terrestrial

Silver-haired bats prefer temperate, northern hardwoods with ponds or streams nearby. The typical day roost for the bat is behind loose tree bark. Silver-haired bats appear to be particularly fond of willow, maple and ash trees (most likely due to the deeply fissured bark). Hollow snags and bird nests also provide daytime roosting areas for silver-haired bats. Less common daytime roosts include buildings, such as open sheds and garages; however, due to their solitary nature and adaptation to woodland roosts, these bats rarely invade buildings in large enough numbers to cause alarm. During the winter months, silver-haired bats that hibernate find shelter in northern areas inside trees, buildings, rock crevices, and similar protected structures.

Habitat Regions: temperate

Terrestrial Biomes: forest

Comments: Prefers forested (frequently coniferous) areas adjacent to lakes, ponds, and streams. During migration, sometimes occurs in xeric areas. Summer roosts and nursery sites are in tree foliage, cavities, or under loose bark, sometimes in buildings. In Manitoba, migrants roosted typically in narrow crevices in tree trunks (Barclay et al. 1988). See Vonhof and Barclay (1996) for information on characterisitcs of roost trees in British Columbia. See Campbell et al. (1996) for roost characteristics in Washington. Rarely hibernates in caves. Relatively cold tolerant. Young are born and reared in tree cavities or similar situations. In South Dakota, maternity aggregations primarily were in woodpecker-created cavities in ponderosa pines (Mattson et al. 1996).

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: No. No populations of this species make annual migrations of over 200 km.

Generally migrates south for winter; see Cryan (2003) for monthly distribution based on museum records. Found only during spring and fall migration over major part of range. Migrates along southern shore of Lake Manitoba in waves in May and early June (Barclay et al. 1988).

Silver-haired bats are insectivorous. Their diet mainly consists of flies, beetles, and moths. However, these bats feed opportunistically on any concentration of insects they come across. They have a short-range foraging strategy, traveling over woodland ponds and streams. Silver-haired bats do not always feed in mid-flight; they have been caught in mouse traps, suggesting ground foraging, and they have been reported to consume larvae on trees.

Animal Foods: insects

Primary Diet: carnivore (Insectivore )

Comments: Forages for small to medium-size flying insects over small water bodies within forested areas.

Silver-haired bats have an important role in the food chain as consumers of vast quantities of insects.

Predators of silver-haired bats include striped skunks and great horned owls.

Known Predators:

• striped skunks
• great horned owls
• striped skunks (Mephitis mephitis)
• great horned owls (Bubo virginianus)

100,000 to >1,000,000 individuals

Comments: Total adult population size is unknown but presumably exceeds 100,000. This bat is locally common in some areas.

Densities probably low. Usually roosts singly, but occasionally in groups of up to 3-6 (Barclay et al. 1988).

Silver-haired bats use echolocation to find their prey. They have acute hearing, and communicate with one another using sound. Baby bats give high-pitched chirps when they become separated from their mothers.

Communication Channels: acoustic

Perception Channels: acoustic ; echolocation

Comments: Leaves roost and begins to forage relatively late. Migrants in Manitoba emerged from roosts typically 30 minutes after sunset in spring (Barclay et al. 1988). Major activity peaks 3 hours after sunset and later at 7-8 hours after sunset. May be active at low air temperatures. Roosting migrants in Manitoba became torpid at air temperatures below 20 C (Barclay et al. 1988). Active throughout the year in southeastern Virginia and northeastern North Carolina; winter activity occurred on evenings when air temperature was 13 C or more (Padgett and Rose 1991).

Tooth wear of silver-haired bats suggests that these bats can live up to 12 years.

Typical lifespan

Status: wild: 12 (high) years.

Average lifespan

Status: wild: 12 years.

Courtship and mating of silver-haired bats occurs in autumn when both sexes congregate for migration. Fertilization is delayed until the next spring. Births occur after a gestation period of 50 to 60 days. At parturition, the female roosts with her head facing upward. The tail membrane is bent forward to form a basket, in which the young are caught as they leave the birth canal. Two young are produced, usually between late June and early July.

Breeding season: Courtship and mating of silver-haired bats occurs in autumn.

Range number of offspring: 1 to 2.

Average number of offspring: 2.

Range gestation period: 50 to 60 days.

Average weaning age: 36 days.

Range time to independence: 21 to 36 days.

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

Average birth mass: 1.67 g.

Average number of offspring: 2.

Average age at sexual or reproductive maturity (male)

Sex: male: 152 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 152 days.

Newborns weigh about 2g. The litter weight equals 36% of the mother's body weight. Young are born with their eyes closed, ears folded over, and most of their 22 deciduous teeth in place. Within a period of 21 to 36 days, young are able to forage for themselves.

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

Breeds in late September. Fertilization is delayed until spring. Gestation lasts 50-60 days. Litter of 1-2 young is born in June-July, sometimes later in north. Sexually mature in first summer. Able to fly at about 3 weeks. Maternity colonies are small (Parsons et al. 1986).

Silver-haired bats have no special endangered or threatened status; however, activities such as logging and deforestation may pose a threat for the bat in the future.

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 Lasionycteris noctivagans 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

Reasons: Presumed to be stable and relatively widespread.

Comments: Habitat loss and fragmentation as a result of clearcutting and other causes of deforestation constitute one of the greatest concerns to these "tree bats" (Parker 1996, Parker et al. 1996).

Management Requirements: "Recruitment and retention of snags and the maintenance of structural complexity in upland as well as riparian areas are important...in managed forests" (Campbell et al. 1996).

Biological Research Needs: Although widely distributed, little information is available on migratory patterns. Further research into relationships between western and eastern groups may facilitate interpretation of seasonal movements (Cryan 2003).

Silver-haired bats are occasionally implicated in the transmission of rabies to humans.

Negative Impacts: injures humans (carries human disease)

Silver-haired bats help with insect control, consuming large numbers of insects each night.

Positive Impacts: controls pest population

Comments: No subspecies are recognized.