Sixty million years ago, on a planet crawling with mammals, one tree dweller rose above the crowd on paper-thin wings. So goes the story of ancestral bats, which, equipped with flight and a sixth sense called echolocation, mastered the night sky and flourished.
Having since exploded into more than 1,100 species worldwide, bats are still finding unique ways to evade the masses—and each other. Barro Colorado Island, a Key West–size knob of land in the Panama Canal, is a showplace of bat innovation. This patch of tropical forest is home to at least 74 distinct bat species; the entire United States has only 47, and all of Amazonia, with perhaps the highest bat diversity on Earth, logs about 160. With many thousands of individual bats sharing the island's 3,800 acres (1,500 hectares), it's a wonder their jagged wings don't entangle as they struggle to meet life's basic needs.
How do they all live in peace, skirting competition that would drive some to extinction? By finding their own niches in the forest's many layers. Where they roost, what they eat, when they feed, how they use their senses, where in the forest canopy they fly—each species has its own special how-to list inscribed on its genes, its own ways to exploit the island's endless summer. One bites through the lateral veins of a leaf to fold the sides down—creating a tentlike shelter for up to 15 of its kind to share. Another chews out a home for its harem in the heart of a termite nest, prompting the insects to move over and make room. (These bats choose only occupied nests as roosts; scientists are trying to find out why.) Some species chase down insects in the air, while others lick nectar and pollen from night-blooming flowers. Some use short pulses of sonar-like echolocation to find perched insects amid forest clutter; others send out longer calls to pinpoint airborne bugs, staying high above the tangled canopy.
Physical differences reflect these distinctive habits. Take greater bulldog bats, with their dagger-like claws and cheek pouches, in which they can carry fish they don't eat on the wing. Or herbivorous bats, some equipped with bristled tongues and grooved chins to pick up nectar and pollen as they nuzzle blossoms. Long, thin wings suit the bat that soars on high; broad, compact wings allow quick turns for the one dodging trees down low. Ample ears? Tiny eyes? Flesh-ripping canines? A nose flap? Each feature is a clue to how a species makes its living.
The tropical forest not only supports this immense diversity, it also depends on it. Bats spread seeds and pollen, keep a cap on herbivorous pests that might decimate forest flora, and themselves become meals for other forest animals—monkeys, owls, falcons, other bats, even large spiders. Such a healthy ecosystem can sustain quite a crowd, especially when each species knows its place.