Big Free Tailed Bats

Big Free Tailed Bats (Nyctinomops macrotis) is the largest bat in Colorado. The dorsal surface is pale reddish to dark brown; the ventral surface is slightly paler. The hair is bicolored with the bases nearly white. The ears are united at their bases and when laid forward extend well beyond the nose. Measurements are: total length 125-140 mm; length of tail 48-54 mm; length of hindfoot 14-16 mm; length of ear 9-11mm; length of forearm 58-64 mm; weight 12-18 g; wingspan 417-436 mm.

Bats feed on beetles, bugs, flying ants, various flies, and moths. Natural predators include owls, hawks, Raccoons, Black Rat Snakes and feral cats. The reported lifespan in this species is about five years, but is probably longer. Evening Bats are known to share roosts with other species of bats, like the Big Brown Bat and the Brazilian Free-tailed Bat.

Diet: They forage mostly on large moths.

Food: This bat forages late at night, but sometimes is seen on the wing early in the afternoon. Its flight is straight and rapid, and the noise of its wings is sometimes audible as it flies overhead. It often emits a sharp, piercing call while foraging.

The northern part of the distributional range of the species, individuals are present from the latter one-half of May to mid-September, but none are present in winter. This bat is a fast and powerful flier, and after the young are weaned, individuals may appear hundreds of kilometers beyond what seems to be the usual range. Records of accidental occurrence are widespread in Northern united states.

Life Cycle: Breeding occurs on the winter range in February and March, and female free-tailed bats thus are already pregnant when they arrive at their roosts in the spring. They form large maternity roosts consisting of almost all pregnant females plus a few barren females and young males born the previous year.

A single, relatively large, young is born in June after a gestation period of 77 to 100 days. For about 6 weeks, the females roost separately from the pups but visit the pups to nurse 2 or 3 times per day. Mothers find their pups by location, vocalization, and olfaction. The young grow rapidly and are capable of migrating long distances by September.

Habits: The big free-tailed bat is a migratory species in Kansas, and spends its winters in warmer parts of the continent. Only three specimens have been reported from southern Kansas, but this bat may be found in other parts of the state, and it is also known from Iowa. Elsewhere, it usually inhabits rocky country.