The population size of silver-haired bats in Washington is unknown and the trend is unknown. Although relatively common in much of Washington, silver-haired bats experience extensive mortality at wind turbines. Loss of large roost trees and snags locally and along migration routes is another important concern.
White-nose syndrome is a deadly fungal disease that has been confirmed in some Washington bat species; it has been detected in silver-haired bats. This disease does not affect humans, livestock, or other wildlife.
If you find sick or dead bats or notice bats acting strangely, such as flying outside in the day or in freezing weather, please report your sighting online or call WDFW at 360-902-2515. Do not handle bats that appear sick or injured.
Description and Range
The silver-haired bat is a medium-sized bat with very dark fur tipped with silver or white. The wings and tail membrane are black. Ears are short and round with a short, blunt-tipped tragus. The dorsal surface of the tail membrane is partially furred and the calcar (spur from the ankle that runs along the membrane of the leg) lacks a keel (flap of skin on the tail).
Ecology and life history
Silver-haired bats occupy forests and riparian areas. They prefer uneven-aged forests with large dead and dying trees that offer structural complexity rather than intensively managed, even-aged stands. Large snags provide suitable roosts trees and a multi-layered canopy structure is favorable to flying and foraging. They are also sometimes found in man-made structures, especially during migration or hibernation.
In Washington, some individuals migrate while others hibernate. Males and females occupy separate summer ranges throughout much of their range, but in Washington, the trend towards summer habitat separation may be less pronounced.
Silver-haired bats probably breed in fall and winter, with fertilization delayed until spring. One or two pups are born in June or July. Lactating females roost in small colonies of typically 5 to 25 individuals in the cavities of large dead or dying trees. Young are able to fly at about three weeks.
Males and non-reproductive females roost solitarily in cavities or under loose bark of large decaying trees.
Silver-haired bats forage on a variety of small to medium-sized flying insects, especially moths and flies, over water bodies within forested areas.
The bats winter alone or in small groups; both sexes may be found together. Non-migrating individuals may hibernate in trees as well as man-made structures. Wintering silver-haired bats may rouse from torpor and forage in western Washington when conditions are sufficiently warm.
Silver-haired bats range broadly across North America from southeastern Alaska across the southern half of Canada south through most of the contiguous U.S. and into northeastern Mexico. The species is present throughout Washington.
For a map of range-wide distribution and conservation status of this species, check out NatureServe Explorer.
Sensitivity to climate change
*NOTE: In general the CCVA methodology does not include human responses to climate change in sensitivity rankings. However because wind energy development is a direct and expanding response, and has an outsized impact on this species, it is included here. Without wind energy development as a factor, sensitivity would be LOW. A significant portion of the siliver-haired bat population in Washington is highly migratory. Collisions with wind turbines are a major mortality source for migrating individuals, thus the expansion of wind energy facilities in response to climate change will likely have a strongly negative impact on this species. Additionally, silver-haired bats have a broad geographic distribution throughout North America and display a preference for old-growth forests and riparian areas between 0 to 1,830 m in elevation, although a variety of other habitats are used, including younger forests and human developed areas. Roosting occurs mainly in trees, especially in the warmer months; buildings, abandoned mines, and caves (rarely) are also used. Silver-haired bats are probably sensitive to the structural changes in forests caused by logging and fire, which would reduce roosting and possibly foraging opportunities. Thus, altered forest fire regimes associated with climate change could degrade or eliminate roosting habitat on a local scale. However, increased insect outbreaks in forests could benefit this species by providing more snags for roosting, unless management responses result in extensive salvage logging or clearcutting. Warmer, drier conditions could affect insect availability and reduce drinking sources for this species, which could impact survival and reproductive output. Hotter, drier conditions in the Columbia Basin could also negatively affect the migration behavior of a significant portion of the population passing through Washington.
Exposure to climate change
- Wind energy development
- Altered fire regimes
- Changes in precipitation
- Increased forest insect outbreaks
Conservation Threats and Actions Needed
- Energy development and distribution
- Threat: The species is highly susceptible to mortality from wind energy facilities.
- Action Needed: Monitor wind farms for mortality, avoid siting wind farms in areas of high bat activity, and encourage power companies to curtail wind turbine use during periods of low wind speeds.
- Fish and wildlife habitat loss or degradation
- Threat: Logging and conversion to younger even-aged forest stands probably reduces the quality of roosting habitat.
- Action Needed: Encourage logging techniques that maintain complex forest structure and large trees and snags.
- Resource information collection needs
- Threat: Better information is needed on migration behavior and routes, and the extent that individuals winter in Washington.
- Action Needed: Conduct research on migration patterns.
- Management decision needs
- Threat: Better information is needed on habitat requirements and population status.
- Action Needed: Conduct research on habitat requirements and population status.
See the Climate vulnerability section for information about the threats posed by climate change to this species.
For some people bats don't present a problem. For others, bats can be a worry, especially when they become unwanted guests in an attic, inside a wall of a home, or inside the home itself.
Unlike rodents, bats only have small teeth for eating insects, so they do not gnaw holes in walls, shred material for nests, chew electrical wiring, or cause structural damage to buildings. Damage caused by bats is usually minimal, but they can be noisy and alarming, and the smell of bats and their droppings can be offensive. It is possible to learn to coexist with bats, and to benefit from their presence. Learn more on our Living with Wildlife: Bats webpage.
Hayes, G. and G. J. Wiles. 2013. Washington bat conservation plan. Washington Department of Fish and Wildlife, Olympia, Washington.
Nagorsen, D. W. and R. M. Brigham. 1993. The bats of British Columbia. UBC Press, Vancouver, British Columbia.