This is the largest family of bats, with over 318 species. Vesper bats are found throughout the world except in the polar regions and some remote islands. Although vesper bats are found throughout temperate and tropical regions, vesper bats are the only kinds of bats that are found in colder, temperate areas, such as northern North America. The 8 species of bats found in Michigan are all vesper bats.
Vesper bats are mainly small, insectivorous bats. They range in size from about 4 grams to 50 grams. They have small eyes, relatively simple faces (no facial appendages, as in some bats), and long tails with well-developed tail membranes. Their fur is generally brownish or black, though some have bright red fur or white markings.
Vesper bats that are found in temperate regions either migrate to more hospitable wintering areas where they can find food or hibernate. Hibernating bats gather in safe hibernation areas, such as caves, other natural structures, or man-made structures, where air temperatures usually remain above freezing. They then allow their body temperatures to drop to that of their surroundings.
Vesper bats are found in many kinds of habitats, from deserts to cold temperate forests.