Big brown bat mating season is in the fall. The little brown bat lacks a vomeronasal organ. The little brown bat likely has few predators. The big brown bat has few natural predators. It is a small brown bat; its forearm length is . For the little brown bat, this occurs about eighteen days after birth. The little brown bat lives throughout much of North America. The cave is populated by both the brown bat and northern long ear bat. The big brown bat has been documented from above sea level. The big brown bat is encountered widely throughout North America in present times. The big brown bat was described in 1796 by French naturalist Palisot de Beauvois. The big brown bat is nocturnal, roosting in sheltered places during the day. Like most species of bat, the big brown bat only has two nipples. An alien brown bat superhero who is a character from Michelangelo's comic book. Humans frequently encounter the little brown bat due to its habit of roosting in buildings.