Of the estimated 430 species of mammals that make their home in the forests of the Amazon basin, the vast majority are either bats or rodents.
Forming the order Chiroptera (from the Greek for “hand” and “wing”), bats are the world’s only flying mammals. As key players in the stability of the ecosystems in which they live, in the forests of South America, as in other parts of the world, bats act as important controllers of nocturnal insects, while serving as major pollinators of many plants, and assisting in seed dispersion.
More than 1300 species of bat have been identified throughout the world; however, this number continues to grow rapidly, as previously unknown species are discovered and new genetic techniques improve the classification of known species.
Scientists divide bats into seventeen families, of which nine are present in the Amazon. The world’s bats vary in size from some of the smallest known mammals, weighing between 1.5 and 2.0 grams (0.05 to 0.07 ounces) to the so-called “flying fox” species, which can weigh more than 1 kilogram (35 ounces) and possess a wingspan of up to 1.5 meters (59 inches).
Only one species of bat, the common vampire (Desmodus rotundus), can be described as potentially harmful to humans or livestock. Nevertheless, widespread prejudice has meant that other bat species are often targeted by people, in the mistaken belief that they are all somehow dangerous to humans.
A total of 160 species of bat have been identified in the Amazon basin. However, in spite of their importance to the ecosystems they inhabit, and due in part to the difficulties inherent in studying them, relatively little is known about most bat species.
Bats have been around for at least fifty million years. What makes them such a successful group of species (found in the night skies of practically every life zone with the exception of the Arctic and Antarctic and certain remote islands) is the way they combine two particular skills: powered flight and echolocation. Their unique talent for nocturnal aerial hunting means that no other group of mammals can rival bats for the variety of food sources they are able to exploit.
More than half the world’s bats use echolocation to detect obstacles in flight and identify their prey. Echolocation is the use of sonar (Sound Navigation and Ranging). Bats can produce sounds at ultrasonic levels by contracting their larynx or clicking their tongues. The echoes created by the sounds they produce are picked up by the highly sensitive receptor cells bats possess in their inner ears, enabling them to “see” sound and navigate by detecting infinitesimal variations in frequency.
While many bat species have evolved to be hunters of aerial insects, some species hunt for vertebrates (including reptiles, amphibians, fish, birds, and even other bats). Others specialize in the gathering of plant matter (including fruit, nectar, pollen, seeds and leaves). Some bat species have highly specialized diets; one species (Anoura fistulata, the tube-lipped nectar bat) is believed to be the only pollinator of the South American plant species Centropogon nigricans, thanks to what scientists have identified as the longest tongue possessed by any mammal relative to body size.