Feeding & Roosting Behavior
Most bat species eat insects, while many tropical species feed exclusively on fruit or nectar. A few are carnivorous, hunting such small vertebrates as fish, frogs, mice and birds. Three species of vampire bats, all in Latin America, feed on the blood of birds or mammals. With the exception of three species of nectar-feeding bats that live along the Mexican border of Arizona and Texas and the Jamaican fruit bat in the Florida Keys, all bats in the United States and Canada are insectivorous.
Bats can be found living in almost any conceivable shelter, though they are best known for living in caves. Many species that now live mostly in buildings do so, at least in part, because of shrinking natural habitat. Tropical species occupy a wider range of roost sites than other species. For example, some make tent-like roosts by biting through the midribs of large leaves. Several species have suction discs on their wings and feet that enable them to live in the slick-walled cavities formed by unfurling leaves, such as those of the banana plant. Others live in animal burrows, flowers, termite nests and even in large tropical spider webs. Despite the wide variety of roosts used by bats, many species have adapted to living in roosts of only one or a few types and cannot survive anywhere else.
Courtship, Reproduction & Longevity
Most bats that live in temperate regions, such as the United States and Canada, mate in the fall just before entering hibernation. Some sing, do wing displays or other actions to attract mates, but few details are known. Ovulation and fertilization (through sperm that have been dormant in the female reproductive tract since the previous fall) occur in the spring as females emerge from hibernation. Pregnant females then move from hibernating sites (hibernacula) to warmer roosts, where they form nursery colonies. Birth occurs approximately a month and a half to two months later. The young grow rapidly, often learning to fly within three weeks. While the pups are being reared, males and non-reproductive females often segregate into separate groups called bachelor colonies.
Some tropical bats engage in elaborate courtship displays. For example, male epauleted bats sing and flash large fluffs of white shoulder fur to attract mates, while male crested bats perform a spectacular display by expanding long hairs on top of the head, similar to a peacock spreading its tail. At least a few tropical species are monogamous, sharing hunting and family duties. Vampire bats even adopt orphans, unusual for any wild animal.
Bats are, for their size, the slowest reproducing mammals on earth. On average, mother bats rear only one young per year, and some do not give birth until they are two or more years old. Exceptionally long-lived, there is a record of a bat that survived in the wild for 41 years, and bats of a number of species live 15 to 20 years or more. Field mice, by contrast, rarely live beyond 3 to 4 years.