II.

Range and Habitat

Bats are found in all habitable regions of the earth, from the cold, treeless plains of northern Canada to the rich tropical rain forests of Borneo. The majority of species occupy tropical habitats. Their long-range flying abilities have enabled some species to colonize remote islands in the Indian and Pacific Oceans, including Hawaii.

Bats favor habitats that provide ample food and adequate roosts. The majority of bat species are insectivorous (insect eaters), and sizeable bat populations (often estimated in the millions) are usually found in tropical regions, where insect populations are abundant year-round. The quantities of insects consumed by bats in these regions are astonishing: as many as 250 tons of insects may be devoured by a colony of Mexican free-tailed bats in a single night. Bats that thrive on fruit are nearly as demanding. To meet its nightly juice-drinking needs, the dwarf epaulletted bat of tropical Africa, which weighs about 170 g (6 oz), must eat 500 g (18 oz) of food—approximately three times its body weight in fresh fruit.

During the daytime, bats sleep in caves, crevices, tree cavities, and human-made structures. Some choose exposed sites on trunks, limbs, and branches of trees. Nearly all bats rest and sleep, or roost, hanging upside down by their hind feet. Bats do not need to expend energy to maintain this position—as a bat hangs, its own weight causes the foot tendons to automatically grasp, firmly holding the animal in place.

Most species are colonial, roosting in dense clusters, often comprising several thousand individuals. Wherever large numbers of bats roost, huge piles of bat droppings, or guano, accumulates. In many countries, guano is collected and applied as a high-quality fertilizer for agricultural crops. In the past, the nitrogen and phosphorus in guano was extracted and used in the manufacture of explosives.