Roosts – Roosts are the places where bats sleep, rest and hibernate, and they often use different roosts for each. Roosts, food and water are key to where a bat may live (like all animals, they need water, and often look for a drink when they wake up to go hunting at night).
People often think that caves and bats go together. While many bat species do use caves, not all do. You can even separate bats into groups such as cave roosting and tree roosting. Each of those groups tend to roost just in those locations (or something similar).
Different species use caves, trees, tree hollows, rock crevices, bridges, buildings, and almost anywhere a bat can fit. Bridges, for example, are a great substitute for caves for bats that roost in caves.
Bats choose roosts for many reasons, including temperature control (e.g., caves maintain usually maintain a constant temperature, concrete bridges moderate temperature), protection from predators, a place to raise young, a place to sleep, and a place to rest while actively feeding at night.
Some bats prefer their roosts to be very close to feeding areas, while others will travel some distance to find the best feeding for the time. Social bats that live in large colonies are more limited in where they can live, so often they have to fly some distance to eat (e.g., Mexican free-tailed bats). Solitary bats that live alone can often stay quite close to their hunting grounds (e.g., red bats). Regardless, temperature is critical for a roost.
Day roosts tend to be more protected, for bats are more vulnerable then. Night roosts are typically in a place where something is overhead, open below and it may be open to the sides. Bats are known to use porches, open garages, carports and such for night roosts.