Northern Prairie Wildlife Research Center
Return of little brown bats to North Dakota occurs in late April to May. They are hibernators and seek out suitable underground areas in the fall which will remain above freezing throughout the winter. North Dakota lacks a significant amount of this type of habitat and, therefore, bats will move southward into areas such as the Black Hills of South Dakota during September or October each year.
After returning to North Dakota in the spring, females bearing young gather in maternity colonies within buildings, hollow trees, rock crevices, or similar warm areas. Since bats are insect eaters, these colonies are usually found near a body of water where ample food will be found after insects hatch. Males and nonfertilized females will be located singly and roost in stacks of lumber, behind shutters, under shingles or loose bark of trees, in rock outcroppings, or the eaves of buildings.
Each pregnant female has been bred in the fall or winter and has stored spermatozoa until she emerges in the spring. At this time, fertilization takes place. The gestation period is about three months, upon which time a single young is born. The young bat grows quickly and can fly in about three weeks.
Bats begin foraging for food after sunset. It is believed many follow a set flight pattern night after night. They fly 10-20 feet above ground in open areas and among trees searching for flying insects. Their flight is guided by echo location which is thought to be one of the most sophisticated systems ever developed. Knowing this, it is a rare occasion when a bat ever strikes any object, including a person. Bats may eat hundreds of insects each night and flights of up to 50 miles have been recorded.
During the day, bats spend considerable time within their warm, moist roosts grooming themselves. Bats have been known to have rabies but only ten people in all the United States and Canada have developed rabies from bats in the past four decades. More people die each year from dog attacks.
Many people become alarmed when bats are found in a neighborhood. Other folks welcome the insect-eating guests. They are harmless and beneficial but may become a nuisance if they take up residence in your home. The best way to prevent bats from entering a man-made structure is to shut the bats out. This is done by sealing with weatherstripping, caulking, or screen any opening which they can enter. This includes cracks around window frames, chimneys, or other structures which vent warm air and attract bats. Other methods such as live-trapping, high frequency sounds, or moth balls may remove bats. Finally, providing a nest box or artificial roosting site may entice bats to use that structure instead of your house.