Silver-Haired Bat: Lasionycteris Noctivagans

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Image of a Silver-Haired Bat being held

Silver-haired bats can be found throughout the United States and northwards into southern Canada. They roost in hollow trees, tree cavities, and cracks beneath peeling bark as roosts. They are a migratory species, with most summers spent in the northern part of its range.

Learn More: List Of Bats

Description Of The Silver-Haired Bat

The common name for silver-haired bats derives from the black fur’s silver with white tips, covering both the animal’s ventral and dorsal sides. The fur almost covers the entire bat except for the wings, snout, and ears.

The young bats, called pups, are born blind, ears folded and deaf at first. They are born with no fur, but they have dark skin in places where their fur will develop later in life. Depending on how many young people they produce, they will weigh 30 to 36 percent of the mother’s body mass, which would be about 2.0 g. ¹

Average Size Of The Silver-Haired Bat

Total length: 9.5-11.5 cm (Average of 10 cm)
Weight: 9-11 g (Average of 9.5g)
Forearm Length: 3.7-4.4 cm (Average of 3.9 cm)
Wingspan: 27-31 cm (Average 29.5 cm)

Silver-Haired Bat Habitat

This species is mainly a forest bat year-round using hollow trees, tree cavities, and cracks beneath peeling bark as roosts. Typically, silver-haired bats roost alone. It is also a migratory species, with most summers spent in the northern part of its range, in forested regions, and hibernating in the southern part.

They use various locations for roosting as the bats migrate, including buildings, lumber piles, fence posts, and bricks. A few individuals can be found in rock fissures and in cave entrances (typically wedged far back into a crevice) during cold winter weather.

For foraging, silver-haired bats primarily use stream corridors and lake/pond margins. ²

Silver-Haired Bat Range

Silver-haired bats can be found throughout the United States and northwards into southern Canada, with Alaska as their northern limit. The species has some Sothern exceptions, including Florida and Mexico. ³

Diet & Foraging Habits Of The Silver-Haired Bat

The silver-haired bats catch most of their prey over bodies of water or within forests. Common prey includes moths, beetles, and aquatic insects.

Before sunset, silver-haired bats may begin to forage, return to their roosts during the night, and then leave before sunrise to feed again. Competition with other large species, such as large brown and hoary bats, may change foraging schedules. ⁴

Silver-Haired Bat Behavior & Migration Patterns

Silver-haired bats migrate to regions with milder climates during winter, then hibernate. For this purpose, they use a wide range of locations, including small tree hollows, loose tree bark, woodpiles, crevices of the cliff face, cave entrances, and buildings. Typically, they roost alone, but they are sometimes found in groups of about a dozen.

Women form small nursery colonies in summer in woodpecker or flicker holes, bole cavities, crevices, and hollow trees under bark, such as basswood, black oak, and ponderosa pine. These roosts can be 13-39 feet above ground level, are usually on the tree’s south side, and are generally located near water.

Colonies may contain 6 to 55 individuals who migrate to other nearby roosts periodically. During migration, under loose bark or in other natural cracks or crevices, males roost alone, also on the southern sides of trees, but often at lower altitudes than nursery colonies. A few solitary bats will roost for two or more consecutive days on the same day. In old-growth forests, silver-haired bat roosts are estimated to be 10 times more abundant than in disturbed habitats.

Silver-haired bats migrate to southern regions in fall, their movements closely linked to cold fronts. They mostly winter in the southern third of North America, returning in the spring to the north.

Silver-haired Bats are slow, highly maneuverable flyers that use echolocation for short-distance detection of small insects.

Typically, they feed in protected areas, along roadsides, over streams, and near mixed coniferous/deciduous forests. Silver-haired bats frequent the same hunting ground (approx. 330 feet in diameter) and travel 1.2-31 miles to reach these locations. This species tends to forage at dusk or dawn. ⁵

Reproduction Cycle Of The Silver-Haired Bat

A hardy and usually solitary species is the silver-haired bat. Before migration, mating occurs primarily in fall. During the winter, females store sperm, waiting for spring to ovulate and become pregnant in late April or May. It takes about 50 to 60 days to gestation, and mothers give birth to one or two young people.

Pups are born hairless and pink, with dark membranes and closed eyes, each weighing about 2 g. Young people appear to be raised mainly in the northern third of the United States and Canada, but pregnant women have been found south as Arizona in the mountains. Typically, birth and maturation cycles do not vary across the bat’s range for more than a few weeks. Silver-haired bats can live up to 12 years.

Threats To The Silver-Haired Bat

Wind turbines frequently kill Silver-haired myotisbines during their migration period. Whether the number of dead bats in turbines during migration is sufficiently high to affect population numbers is unknown.

Bats are sensitive to toxins found in herbicides and pesticides. This species is vulnerable to DDT residue, and in the 1940s, this chemical was commonly used by pest control professionals to control bat infestations in attics. As DDT is highly persistent, with a soil half-life of 2-15 years and an aquatic half-life of approximately 150 years, exposure to trace residues remaining in the environment may pose a threat to bats.

This species assembles in caves and over the winter but have not suffered the same dramatic population declines due to White-Nose Syndrome (WNS) that has devastated other North American bat populations. Silver-haired bats, however, have occasionally been found to roost in WNS-infected caves and mines, and a silver-haired bat has recently been found to have Pseudogymnoascus destructans in Delaware (fungus believed to be responsible for causing WNS). ⁶

Sources:

Bentley, J. 2017. “Lasionycteris noctivagans” (On-line), Animal Diversity Web. Accessed January 08, 2021 at https://animaldiversity.org/accounts/Lasionycteris_noctivagans/
“Kentucky Department of Fish & Wildlife Silver-Haired Bat.” Kentucky Department of Fish & Wildlife, Commonwealth of Kentucky, fw.ky.gov/Wildlife/Pages/Silver-Haired-Bat.aspx. Accessed 8 Jan. 2021.
“Silver-Haired Bat Factsheet.” Arizona-Sonora Desert Museum, www.desertmuseum.org/kids/bats/Silver-haired.php. Accessed 8 Jan. 2021.
ESF Office Of Communications. “Silver-Haired Bat | Adirondack Ecological Center | SUNY ESF | College of Environmental Science and Forestry.” SUNY College Of Environmental Science And Forestry, State University of New York, www.esf.edu/aec/adks/mammals/silverhaired_bat.htm. Accessed 8 Jan. 2021.
Texas Parks And Wildlife, TPWD, tpwd.texas.gov/huntwild/wild/species/silverhair. Accessed 8 Jan. 2021.
New York Natural Heritage Program. 2021. Online Conservation Guide for Lasionycteris noctivagans. Available from: https://guides.nynhp.org/silver-haired-bat/. Accessed January 8, 2021.