Seventy-four species of bats flourish on one small Panamanian island, carving out distinct niches for habitat and forage.
By Jennifer S. Holland
National Geographic staff
Photograph by Christian Ziegler
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.
|panama bats interactive|
|Equipped with echolocation and gaffing claws, the greater bulldog bat can detect the hair-thin fin of a fish breaking the water's surface, a useful skill in a forest full of competitors.|
|With claws that knife through water, the greater bulldog bat, Noctilio leporinus, is able to trawl for prey.|
|A keen sense of smell and a "nose leaf," which tilts to direct the animal's echolocation call, help the chestnut short-tailed bat pinpoint pepper plants in the forest understory.|
|With a firm but gentle grip, bat researcher Sergio Estrada-Villegas feeds a little fruit-eating bat, Artibeus watsonii, an energizing mixture of sugar and water prior to releasing it.|
|Spix's disk-winged bats have suction cups that enable them to grip the inside of a smooth furled leaf and scuttle in and out of its protective confines.|
|Extravagant blossoms rich in nectar invite long-tongued bats to bury their faces in hundreds of flowers a night, pollinating one after another in the process.Glossophaga sp|
|Strobes capture a greater bulldog bat's success on Lake Gatún. The behavior likely originated when insect-eaters snagged fish by mistake. Trick became tradition, and another specialist took its place in Panama's night skies.|