Bats are a critical element in nature’s delicate web of life. The only major predator of night-flying insects, bats often consume over half their body weight in insects each night, and are important for controlling insects that affect crops, forests and humans.
Northern Virginia area bats are in decline, due primarily to loss of habitat and disturbance by humans. However, Little Brown Bats and Tricolored Bats have suffered substantial additional losses from white-nose syndrome (WNS), and have declined by more than 95% since 2009. WNS is a fungal disease that affects hibernating cave bats.
Bats are nocturnal, and the best time to see them is just after sunset as they leave their roosts to feed. They catch their prey in flight and often feed over fields, open water and around street lights, where insects swarm. Some species also forage in the tree canopy or in corridors through forest. A typical bat may consume over 500 insects in just one hour, nearly 3,000 in a single night.
Bats and Their Life Cycles
Bats are the only mammals able to fly. Compared to other small mammals that produce many young each year but live only 1-2 years, bats typically have a single litter of one or two young per year, and can live in the wild for over 20 years. Their low reproductive rates make it difficult for populations to recover quickly after large declines.
In spring, bats migrate back to Loudoun County from places south, or emerge from hibernation in trees and caves. During their time here, bats live in and around forests, wetlands, fields and buildings.
Pregnant females, who mated the previous fall, seek sheltered roosts in buildings, tree cavities and tree foliage to raise their pups. In some species, females gather in maternal colonies, which can be small to thousands. Males remain solitary throughout the season.
Because insects are few during the winter, area bats either migrate or hibernate. For Little Brown Bats, Big Brown Bats and Northern Myotis, maternity colonies disband in late summer and early fall and the bats travel to the hibernation places. This is the time when males and females join, sometimes in very large groups. For our bats that migrate, the Silver-Haired, Eastern Red, and Hoary bats begin their migration to warmer climates.
Bats can see quite well but rely on their hearing at night. Echolocation enables them to use their well-developed ears to navigate and catch moving prey in darkness. A bat’s echolocation system uses ultrasonic sound pulses and echoes to maneuver and catch insects while avoiding flying into objects.
Bats & Human Contact
Left alone, bats are harmless and avoid contact with humans. Occasionally, single bats enter a house; a maternity colony roosts in a building; or a bat may be found on the ground. All these situations can be safely resolved without killing the bats. Information on the proper techniques for handling these situations can be found at here and here.
Bats are a diverse group with over 1,000 species worldwide; 15 species are native to Virginia, and 7 species are known to reside in Loudoun County, including:
Bats less common in Loudoun County include:
(compiled from sources including Loudoun Wildlife Conservancy’s “Bats of Loudoun” and “A Homeowners Guide to Northeastern Bats and Bat Problems,” Penn State College of Agricultural Sciences)