In Washington, some individual bats 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. Males and non-reproductive females roost solitarily in cavities or under the loose bark of large, decaying trees. Young are able to fly at about three weeks old.
Silver-haired bats forage on a variety of small to medium-sized flying insects, especially moths and flies, over water bodies within forested areas. They winter alone or in small groups, and 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.
Description and Range
The silver-haired bat is a medium-sized bat with very dark fur tipped with silver or white.
Silver-haired bats occur broadly across North America, from southeastern Alaska to northeastern Mexico. They are documented throughout Washington, predominantly where forest and riparian habitats occur. Surveys indicate the species is relatively common in a number of areas in the state, but population trends are unknown.
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 roost trees, and a multi-layered canopy structure is favorable to flying and foraging. The species is sometimes found in man-made structures, especially during migration or hibernation.