Published: April 1986
Gentle Fliers of the African Night
Bat expert Merlin D. Tuttle extolls the beneficial role of endangered flying fox bats.
Article and photographs by Merlin D. Tuttle

This article was originally published in the April 1986 National Geographic.

Hanging in a tree beside a streetlamp in a night-darkened town on Lake Victoria in East Africa, an epauleted bat fluffed his white shoulder fur, puffed out his cheek pouches, fanned his wings, and gave voice to the repeated gonglike calls that would attract a mate.

This handsome little mammal with a 50-centimeter (20-inch) wingspan had already attracted me; for weeks I had been trying to photograph an epauleted bat vocalizing in full courting display. Now I had stumbled onto just such a remarkable demonstration.

Unlike many bats, the epauleted species lack the ability to echolocate. Females apparently need light to see the males' comehither performance. Here on the main street of Kisumu, Kenya, male bat "townies" guarded lighted streetlamps that allowed them to practice their amorous allurements all night long.

Epauleted bats were not in my plans in 1982 when I accidentally became aware of their extraordinary characteristics. They and other species of flying foxes are among Africa's most interesting and important animals. (Indeed, the decline of fruit- and nectar-eating bats here and elsewhere poses a very real threat to the survival of tropical forests—but more of that later.)

On my first adventure in Africa I was mist-netting for other bats on the Sengwa River in Zimbabwe. Alone in the dark at 2 a.m., knee-deep and shivering in the cold water, I was more than a little nervous about the many unidentifiable sounds. Lions and hyenas called, and a herd of Cape buffalo rustled the tall grass nearby. One sound, particularly, was memorable and tantalizing—a continuous singsong honking. What creature spoke with this voice? In the next few nights I netted several epauleted bats, but weeks passed before I discovered that the haunting call was the courtship song of this member of the flying fox group.

I set out to capture on film a courting epauleted bat. Yet my many attempts invariably failed. The animals were extremely shy and alert; they simply wouldn't permit intrusion into their private lives. So my 1982 African journey ended without my seeing even one courting epauleted bat.

My next encounter with this intriguing creature came in 1984, during research on frog-eating bats in Kenya. Dr. Michael J. Ryan, a frog behaviorist from the University of Texas at Austin, was recording evening frog calls beside Lake Victoria when he summoned me to come quickly.

Mike had spotted an epauleted bat performing in a nearby tree. We watched from a few yards away one of the most fascinating of mammalian displays. The bat was simultaneously singing, beating half-closed wings, and flashing the long tufts of white shoulder fur from which it takes its name. Except during courtship, this fur is withdrawn into shoulder pouches. Glands in the pouches are believed to secrete attractive odors, which the long epaulet hairs and beating wings help waft to cruising females.

Distinctive, too, are pouches in the cheeks of the males, inflatable sacs that act as resonance chambers to enhance their calls, rhythmic honking audible for 200 meters or more, with a frequency sometimes exceeding one per second.

I made up my mind to photograph this amazing behavior. Canceling homeward plane reservations, I returned with my camera equipment and Kenyan assistant Paul Kabochi to our previous observation site in the Kaloka Veterinary Research Station.

That evening I was ecstatic when epauleted bats resumed their courtship. The next day we spent seven hours rigging and concealing flashes, remote tripping devices, and other photographic equipment. Our bat returned at dusk, as we had hoped, but before a single picture could be taken, a sudden tropical storm terminated his display and nearly wiped out our gear. A change in weather foiled further attempts.

I had noticed that epauleted bats called every night from perches beside the streetlights in Kisumu, a town we regularly passed through on the way back to our hotel in Kakamega. Inspection revealed that only one "streetlight" bat held forth where I could photograph him. He guarded several trees beside a light at the edge of a shopping center parking lot. I hired a second helper to hold flashes on six-meter (20-foot) poles, while Paul climbed 12 meters into the trees with a light meter to practice getting our exposures right. At night I ran from tree to tree, shaking them and yelling, trying to move the bat to the best perch. In the end I got fewer than half a dozen quality photographs from hundreds of tries. Many of the townspeople must have wondered about my sanity!

Prolonged attempts to photograph the courtship of epauleted bats taught me much about the species' behavior. My subject typically came at dusk to his courting territory and immediately began calling. The early hours of evening seemed to be devoted chiefly to defense of his territory. When another male began calling nearby, my bat responded by speeding up his call rate, apparently to outdo his competitor. When other males attempted to take the site by force, none seemed successful.

Females arrived, one at a time, fashionably late—few before 11 p.m. Each time, the male's excitement was immediately apparent: His song rose to a staccato pitch, and his wing "dance" blurred. As he did his best to impress her, the female would hover a foot or two in front of her suitor. Females were in no hurry; they appeared to move about checking on several males before making a choice. Male voices clearly varied, and I suspected that the high-pitched squeaky ones belonged to young beginners. The culmination of wooing, the actual mating, took place in trees nearby.

Suitors often continued their performances until past 3 a.m., when exhaustion likely forced them to find food and return to their roost. I calculated that an eight-hour courting period cost each male bat more than 26,000 calls and 100,000 wingbeats, a demanding endeavor. I can only speculate on the fate of the unfortunate, or perhaps lucky, males who may never know the thrill, or the price, of "owning" a streetlight!

In the end I had to work with captive bats to get many of the behavior pictures I wanted. From a hotel room northeast of Lake Victoria, I removed furniture, then laid heavy plastic on the floor and installed a screened enclosure and camera gear. In mist nets I caught a dozen epauleted bats as they came to drink nectar from flowers of nearby banana trees. My captive bats proved gentle and inquisitive, yet even in a controlled setting, success always came hard. For nearly a month I virtually lived with my bats, sometimes working for six hours preparing for a single shot, then frequently waiting all night— often in vain—for my subjects to perform.

It was observation of wild bats that taught me most about their habits. By day epauleted bats roost alone or in small groups, usually in trees, sometimes inside well-lit cave entrances. Colonies may include 150 or more bats, spaced at regular intervals, often only a few centimeters apart. Males of at least one species seem to jockey for positions close to females. When disagreements arise, the bats use their wrists to box each other in harmless tests of strength.

Mother epauleted bats give birth to a single baby once or twice a year. In some areas these births are closely synchronized with the onset of the long and short rains, but in others, births seem to occur throughout the year. During the day nursing young are cradled beneath their mothers' wings, invisible except when they occasionally peek out. At dusk mothers carry their babies with them when they fly out to feed, even though, amazingly, some young are two-thirds the weight of their mothers and quite capable of flying on their own. The young bat rides clinging to its mother's breast with its mouth and to her side with its feet. At feeding sites a baby may fly alongside its mother and even compete with her for food. That same baby may then suckle as it is carried home.

These bats depend on a wide variety of native fruits and flowers. With an excellent sense of smell, they may detect food at distances of a mile or more, but young bats need to learn which odors to follow. Mother bats often bring food in their mouths, teaching babies the scents of acceptable fare.

Epauleted bats inhabit most of sub-Saharan Africa. Four genera include more than a dozen species, most of them quite commonly heard but seldom seen.

During earlier investigations on the Mombasa coast of Kenya, Mike Ryan and I learned that these and other flying foxes are considered serious pests in mango plantations. By association, people tend to dislike all bats, killing them at random. Many caves had been eliminated as bat habitat by blocking the entrances. Of the 14 caves we learned about, half already were permanently sealed. In another, the bats had been intentionally killed.

Disturbed by this destruction, I decided to seek the truth. Visiting 15 farms over an area of 2,500 square kilometers (965 square miles), I learned to identify the tooth marks of a variety of animals and examined nearly 7,500 mangoes for damage. When harvestable mangoes were harmed, the culprits nearly always were monkeys, not bats. Bats apparently do not like unripe fruit any more than people do.

On the M'Sangani Estate south of Mombasa, where Mr. and Mrs. Akberkhan Khan own one of Kenya's largest mango farms, they explained that mangoes for export must be picked five to seven days prior to ripening. Even those sold locally were harvested at least two to four days early. The Khans were aware that bats weren't a threat to their crops, but because many of their neighbors thought otherwise, I decided to experiment with captive bats.

Using nets baited with ripe mangoes, I caught 31 flying foxes of six species, including three kinds of epauleted bats. For my tests in a rented beach cottage, the bats were placed in a three-meter-square mosquito net enclosure and for 18 hours were deprived of any food except fruits purchased in local markets. These included mangoes, avocados, bananas, papayas, and guavas; none would be ripe for two to four days. The bats refused these fruits, even though they were very hungry, but immediately ate ripe fruits at the end of each of the five trials.

I was able to demonstrate an important point: Fruits that are ripe enough to attract these bats are too ripe for harvest and worthless to farmers anyway. In fact, bats may well perform a service by removing ripe fruits that otherwise might become food for the larvae of the dread Mediterranean fruit fly.

Recent research clearly shows that the seed dispersal and pollination activities of epauleted bats and other flying foxes are vital to the survival of tropical rain forests and dependent economies. In West Africa, for example, Dr. Don Thomas, biology professor at the University of Sherbrooke in Quebec, concluded that flying foxes, mostly epauleted bats, are critically important to forest regeneration in savannas, abandoned farmlands, and clear-cut areas.

He found in these environments that epauleted bats eat as much as two and a half times their body weight in a single night, digest meals in as little as 15 minutes, defecate in flight, and account for up to 95 percent of aerial seed dispersal. In patches of cleared land each square meter received at least one and sometimes hundreds of seeds a year from bats, and Dr. Thomas concluded that "the steady influx of bat-dispersed seeds can potentially give rise to a massive regeneration." Birds, on the other hand, tend to drop seeds beneath accustomed perches in standing tree groves, where seed predators easily find and eat them.

In East Africa I watched epauleted bats pollinate the baobab tree. This famous giant of Africa's bush, with its large-petaled flowers that open after sundown and drop off the next morning, depends on bats for pollination and supports and shelters a whole community of birds and other animals.

In West African forests flying foxes are the only known seed dispersers for the iroko tree, whose timber is worth millions of dollars annually. The most important bat in this tree's regeneration is the straw-colored flying fox. Single colonies feed on the fruits and nectar of thousands of native trees each night and cover vast areas in annual migrations.

For several months each year, straw-colored flying foxes congregate in colonies that may contain up to a million bats. They roost in dense clusters on tree branches, where each mother rears her single infant. The whole of West Africa may count only a dozen or so such colonies, conspicuous and extremely vulnerable to human persecution.

In many areas the meat of the straw-colored flying fox is considered a delicacy. A shotgun blast can kill 20 to 60 roosting bats. Many more die of wounds. In the Ivory Coast, short of other meat protein, market hunting of bats is lucrative and on the increase. Complicating the problem, misunderstandings have led some countries to consider mass eradication of bats. Wiping out a single straw-colored bat colony could affect forest regeneration over hundreds of thousands of square kilometers. With large areas of Africa being deforested each year, such losses pose serious threats to the continent's ecology.

Misperceptions by fruit growers have brought massive, sometimes government-sponsored, bat eradication programs—in the Middle East, even of bats in nature reserves. And in Queensland, Australia, in response to unstudied fruit-grower complaints, recent legislation places flying foxes on the same list of pests as introduced rats, mice, and pigs. Thousands of Queensland's flying foxes, the prime agents for pollination of many Australian hardwood forests, are now being shot at their nursery roosts. Biologists fear that the results may prove ecologically disastrous.

The rate of decline of flying foxes throughout much of Asia and on islands of the Pacific and Indian Oceans is truly alarming. They are overharvested by hunters, both for their own consumption and as a lucrative market item. On Guam, people pay $10, $25, or even more for a bat, and tens of thousands of slaughtered flying foxes are imported by air.

Several species are already extinct, and once vast populations now survive as mere remnants. A Samoan flying fox with a wingspan of more than a meter is one of the world's last diurnal bats. Soaring on midday thermals, it is an important pollinator of rain forest flowers. But, exported to Guam and Saipan for food, it is rapidly disappearing. Legislation to protect it may be the only way to save this Samoan bat from extinction.

Dr. Norman Myers, consultant for the BBC "Living Planet" series, recently referred to bats such as those that pollinate the baobab as "keystone species." Were such pollinators eliminated, he said, "the loss could trigger a cascade of linked extinctions. "Actually, the most important consideration often may not be bat extinction but the effect of bat numbers becoming insufficient to service rain forest ecosystems and associated economies. This requires large populations, not mere remnants.

The contribution of bats to a healthy ecology has gone largely unnoticed or misunderstood for far too long, even among biologists and conservation planners. Major land-use studies have failed to acknowledge that bats even exist, making it easy for special interest groups to push eradication programs with potentially disastrous consequences. So it is my fervent hope that this brief introduction to the lives and values of epauleted bats and other flying foxes will serve to focus attention on these important mammals.