Tri-coloured Bat

The tricolored bat has blond fur that is distinctly tricolored on its back. Individual hairs tricolored: dark gray at the base, buffy (yellowish brown) in the middle, and brown or reddish brown at the tip. It is the smallest bat species found in the eastern and midwestern US. Individuals have a forearm length of 31.4–34.1 mm (1.24–1.34 in) and weigh 4.6–7.9 g (0.16–0.28 oz). Its forearms are reddish, contrasting sharply with the black membranes of its wings. Its wingspan is 21–26 cm (8.3–10.2 in). It has a dental formula of 2.1.2.33.1.2.3 for a total of 34 teeth.

The tricolored bat is common throughout eastern North America, with the southern extent of its range in Central America and the northern extent in southern Canada. Its range has expanded since the 1980s, with westward expansion reaching the US states of Colorado, New Mexico, South Dakota, and Wyoming. Additionally, its range started to include the Great Lakes Basin.

The tricolored bat is a seasonal breeder, with copulation (mating) occurring in the fall before hibernation. Ovulation does not occur until the spring, however, and females store the males' sperm in their uteruses through the winter. Gestation (pregnancy) length is about forty-four days, with females giving birth in June or July. The litter size is typically two individuals. As newborns, the combined mass of twin pups can be as great as 58% of the mother's postpartum mass. At birth, the young lack fur and their eyes are closed. The mother leaves the offspring behind at the roost while she forages at night. Offspring develop rapidly, beginning to fly at three weeks old. By four weeks old, they are foraging for themselves. Young do not reach sexual maturity in their first fall; they do not breed until their second fall. Individuals can live at least 14.8 years in the wild; juveniles have higher mortality rates than adults, and females have higher mortality rates than males.