Poorly known. Probably found statewide, except for southern tier of counties. Little known of distribution and habits in Alabama. MODERATE CONSERVATION CONCERN.
Silver haired bats are forest-dwelling and are very distinctive in appearance from other bats. They have dark, blackish-brown fur which is tinged or “frosted” with silver, hence their descriptive common name “silver-haired.” Their wingspan is 27-33 cm (11-13 inches) and they weigh 8-15 grams (0.3-0.5 ounce). Their ears are short and rounded.
Silver haired bats are found from southern Canada southward through most of the continental United States and into northeastern Mexico. Silver-haired Bats are rare in Alabama during most of the year, but are relatively common during their mid-spring and autumn migrations. They are most often encountered in Alabama during the extended fall migration which lasts from October through November.
Silver-haired bats are considered forest-dwelling bats, and use deciduous, coniferous, and mixed woodlands. Some evidence indicates that they may have a preference for “old forest” systems. They roost under loose tree bark, in cavities in living trees, in dead trees, and in bird nests. They are found occasionally in open artificial structures such as sheds, garages, and outbuildings, but they almost never use caves, enclosed buildings, or artificial bat houses. During migration, they also may be found in piles of logs, rocks, or brush.
They are insectivorous, eating a wide variety of night flying insects including moths, beetles, mosquitoes, night midges, flies, and termites.
LIFE HISTORY AND ECOLOGY:
Silver-haired bats roost and sleep during the day, and are active at night. Insects may be caught in the wing or tail membrane during flight and eaten “on the wing.” Silver-haired bats are very slow flyers and, accordingly, are easily recognized in flight. They usually fly fairly high and relatively straight while foraging along stream corridors and over woodland ponds. Mating occurs in the fall, but implantation of the embryo in the uterous is delayed until spring. Young (usually twins) are born during early summer in the northern portion of their range. They are not known to breed in Alabama.
Though their distribution is widespread, silver-haired bats are strongly migratory and are relatively uncommon in the southeastern United States. They usually are solitary, but may migrate in small groups.
When caught or handled, silver-haired bats can be very aggressive. As with most wild mammals, they can and do contract and transmit rabies. Indeed, most rabies contracted by humans is associated with a variant of th virus found in Silver-haired Bats. Though the incidence of rabies in any bat is very low, any bat that appears sick or cannot fly should be avoided. The silver-haired bat is a very beneficial species and, like all of Alabama’s bats, help to naturally control insect populations.
M. Keith Hudson, Wildlife Biologist, Alabama Wildlife and Freshwater Fisheries.