At dawn or dusk, you may see bats entering or leaving a home or building. It is This is to see them at dawn, because bats swarm and fly around the entrance hole a few times before entering the roost.  Bats can see, but they use ultrasonic pulses to guide their flight and locate insects. Roosting bats may squeak or scurry when disturbed.  Piles of black, dry, guano usually found under the main exit hole in the attic. Can be found scattered throughout an area, particularly in roosts where bats enter and fly about, but roost in a specific area such as a wall void or the intersection of the beams and rafters. May also see scat on the side of the house, usually below a hole or crack. Bat droppings look like mouse droppings, but mouse scat isn't found in large piles, and is also a little smaller. Also, bat droppings will crumble into powdery dust but mouse droppings won't. You may see pieces of insect wings, or their reflections, in bat scat. Rub marks along the edges of exit holes: Slight brown discoloration that's a mix of body oils and dirt. During the summer, they'll use different roosts during the day and night. The daytime roost is usually in an attic, barn, garage, soffit, cave, underneath shutters or roof shingles, in wall voids, or behind siding or chimneys. At night, they'll rest in a breezeway, under an awning, or in a garage or similar areas. In the winter, both species hibernate in colonies in caves, mines, and deep rock crevices. Big brown bats are more likely to hibernate in buildings, often in the attic or in wall voids.

A colony of 100 little brown bats can eat hundreds of thousands of insects each summer. They eat many insects that damage crops and ornamental plants, such as moths and flies. Females of both species are colonial, while the males are usually solitary or found in small bachelor groups. Females roost together to raise their young. Pregnant females look for a hot niche within the roost that will serve as an incubator. These maternity colonies are often found in attics, soffits, wall voids, behind chimneys, in barns, tree cavities, rock crevices, and caves. Bats are Nocturnal, with peak feeding at dusk and dawn. After feeding in the early morning, they'll return to the daytime roost and hang out, in a slightly dormant state. After their evening feeding, they'll usually rest. Females return to the roost often to nurse their young. Both bats hibernate in colonies in caves, mines, and deep rock crevices. Big browns will also hibernate in buildings. The body temperatures of both species drops to within several degrees of the "room temperature." Big brown bats can tolerate below-freezing temperatures for short periods, which is why they are often found roosting in buildings. Both species will migrate locally. Their hiberancula are usually within several hundred miles of their summer roost, but some big brown bats will hibernate in their summer roost.

​Breeding dates: Bats have an unusual habit. They mate during the fall, but the females store the sperm in their bodies for months. Fertilization doesn't take place until the late winter or early spring, when the bats emerge from hibernation or return from the south. Gestation: 50–60 days.Birthing period: Late May through early July (births are typically staggered over a 2–3 week period).Litter size: Little brown: 1 pup; big brown: 2 pups.