Bats. There are almost a thousand species. Nearly a quarter of all mammals are bats.
They are crucial to the world's ecology, yet they are endangered.
Hello I'm Stacy Keech and I'd like you to meet my friend Zuri. He's a flying fox from
Africa and like most bats he plays a crucial role in maintaining and protecting the world
we live in. Yet for centuries Zuri and his kind have been ruthlessly hunted down and
destroyed by human beings driven by ignorance, superstition, and greed. And only now at the
11th hour are we coming to understand the vital role that bats play in sustaining life on this
planet. And that's due largely to the work of one man. The man is Dr. Merlin Tuttle, a biologist
who has dedicated his life to the study and protection of bats around the world. Merlin
Tuttle has probably observed more kinds of bats in more places than anyone in history. He founded
Bat Conservation International, an organization that has developed programs to protect the bats
still left in the world and to encourage the repopulation everywhere. Bats are a passion
with Tuttle and with good reason. Far from being the nightmare creatures of popular myth,
bats are vitally important to life on earth. In the next hour, with the help of some really
astonishing slow motion photography, we will for the first time experience some of the surprise,
the wonder, the amazing diversity of the secret world of bats.
Let's face it, ever since the days of Count Dracula, bats have had bad press. So let's just
set the record straight. Bats are not aggressive, they're not blind, they don't get tangled up in
people's hair, and they're not all rabid. A few get sick, just like most mammals, but even a sick
bat won't attack. And if you leave it alone, it won't harm you. Bats live almost everywhere. They
are found on every continent except Antarctica. There are over a hundred species in North America
alone. Bracken Cave in Texas contains the single largest colony of bats in the world. Between 20
and 40 million Mexican free-tails, it's the densest concentration of warm-blooded animals on earth.
Bats are primarily active at night, so they need to find their way in the dark. They navigate by
echolocation, sending out ultra-high frequency sound waves and reading the bounce back to locate
prey or avoid obstacles. Echolocation is the reason behind the dazzling variety of facial designs
characteristic of bats. Huge ears and distinctive nose leaves help them hunt prey and avoid
accidents. Mexican free-tailed bats come to Bracken Cave during the summer to give birth and raise
their young. Each square foot of cave wall is covered by up to 500 tiny pink hairless bat pups.
The adults and pups roost separately, forming pink and brown patches on the walls.
Female bats give birth to only one baby a year. Each mother, using both sound and smell,
is able to find and nurse her single offspring several times a day in total darkness in a
600-foot long cave. The young are large when born, about a third of adult size, and within
three to four weeks they're exercising their wings. The floor of the cave is a seething mass
of carnivorous beetles. Their first attempt at flight is crucial. Young bats have to leap
off into the air in complete darkness, having never flown before, and avoid several collisions
a second with other bats. A mistake now could prove fatal. The beetles and their larva make
short work of a bat and within minutes only a few bones remain. Some 70 percent of the world's bats
eat insects. They are by far the most important natural controllers of night-flying insects. One
bat can eat between 500 and a thousand mosquito-sized insects in a single hour. The 20 million or so
occupants of Bracken Cave eat over 250 tons of insects each evening while flying over the
surrounding farmland. The California leaf-nosed bat is a highly specialized hunter. It can actually
detect the footsteps of the cricket. In the deserts of the American Southwest,
bats play a vital role in maintaining the fragile ecosystem. Many familiar desert
plants are dependent on bats for their survival. During the day, hummingbirds and insects feed at
the flowers of the agave or century plant, but these creatures play a negligible role in the
pollination of this plant. By day, the flowers are sexually inactive. The flowers only release
pollen after nightfall, and it's now that nectar is secreted. It's this rich source of energy that
attracts the bats. As each lesser long-nosed bat probes the flowers for food, showers of pollen
cover its face and body. The bats unwittingly pollinate hundreds of flowers in a single evening.
Many cactus plants also depend on bats for pollination. Their flowers open after sundown,
ready for their nocturnal visitors. When organ pipe cactus flowers open,
small groups of bats move from one to the next, taking turns feeding. The familiar saguaro is
also pollinated by bats. The saguaro blossoms don't open until midnight, so they don't compete
with the other cacti. It's a remarkable example of the precision with which nature sometimes
arranges things. The long-nosed bats have muzzles that are perfectly shaped to fit deep inside the
cactus blossoms, like keys in a lock. One by one, the bats dip their heads into the blossoms,
and one by one, the saguaro flowers are pollinated. The bats return to their roost,
their faces covered with pollen. What hasn't rubbed off in other flowers is eagerly licked
off by the bats. Without the bats, many of the desert's most important plants could die
out, threatening an entire ecosystem. Yet it's not just in this harsh environment that the
presence of bats is essential. Around the world in tropical rainforests, such as those in French
Guiana, bats have a crucial role to play. Only recently has it become generally recognized
that tropical rainforests are probably the most important ecosystems on earth. Not only do they
serve as the lungs of the planet, but these rich forests are the home of more than 90% of all the
terrestrial plant and animal species. The fine balance that exists between them, which took
millions of years to develop, can be destroyed in a single afternoon.
It's through the work of scientists like Dr. Scott Mori, a leading rainforest specialist,
that we are only now discovering the immense importance of bats. Scott, you've been studying
tropical rainforests for some 25 years now. How important are bats to regrowth a forest in a
clearing like this? Merlin, bats are vital to the reestablishment of tropical rainforests after
large-scale disturbance. Two and a half years ago we came here and the only plants in this field
were plants whose seeds were brought in by bats. Later on, even today, we can see that the majority
of the plants here are bat disperse plants. It's important to remember that the conditions for other
kinds of plants to come in are first established by these bat disperse plants. It's only then that
plants that are dispersed by birds and later on plants that are dispersed by other mammals, such
as primates, can become established. We must remember that any conservation program in the
tropics must give high priority to the conservation of bats because if we take bats out of this
ecosystem, we cannot have normal regeneration of tropical rainforests. Merlin, look, here we have
three different very excellent examples of bat disperse plants. Here's the classic, the Sacropia.
Here's a Vismi in the background. And here's a Solanum in fruit. Look at this Solanum. It has a
very classic kind of bat fruit. Let's take a look at this fruit. We'll open it up. You can see all
of these very small seeds on the inside. The bats will come in here and they actually know which
plants are going to have ripe fruit on any given night. They'll come in here, swallow the whole
fruit, carry that fruit away and digest it and pass these seeds out within 20 minutes. I think
this is one of the most important things that we have to remember is that bats pass the seeds out
relatively rapidly and in flight. And this is one of the reasons that they're so important in getting
those seeds into large-scale disturbance areas. A second species of Solanum holds its ripening
fruits vertically, making life a little easier for the bats. The fruit of the Sacropia hang down in
bunches. The bats come to feed on the seed-packed fleshy fingers. Birds also feed on these fruits,
but it's primarily bats that carry the seeds into clearings. Many plants seem to have evolved their
seed-laden fruits specifically with bats in mind. The Piper has fruits that grow vertically along
its stems while the leaves hang down, enabling the bats to feed in flight.
It has been estimated that just one Corolia bat can disperse up to 60,000 seeds in a single night.
A female Corolia bat has to continue feeding despite the fact that she's nursing her single
offspring. The youngster, only a few days old, clings onto its mother using its feet and thumbs,
even in flight. Feeding continues as normal, even though she's flying with a payload of almost half
her own body weight. The male has no such encumbrance. She eats the Piper like corn on the
cob and then discards the tough stalk. Within minutes, the undigested seeds pass through her
body and are scattered as she flies over the open patches of land. Within two or three years
of being felled, the scars on the face of the forest are already beginning to disappear. The
start of a healing process begun by fruit-eating bats. Yet despite their vital role, bats continue
to be exterminated throughout the world. Far out in the Pacific, bats face a precarious future.
An enormous B-52 thunders into the air as it leaves the tiny island of Guam. There's been an
American military presence here since the First World War, but the island was home to fruit bats
long before humans ever set foot there. The forests on Guam were originally the habitat
of three species of bats. Two, sadly, are now extinct. The surviving Mariana's fruit bat has
declined in number from many thousands to between four and five hundred and is now an endangered
species. Forty percent of the island's plants rely on the bats for either pollination or seed
dispersal. The bats feed on fruits and flowers. In this case, it's the flowers of a Liana. As it
feeds, the bat inadvertently pollinates the plant. The principal reason for such a catastrophic
decline in bat numbers is due to humans. The bats have been hunted for food. These bats were
illegally killed on neighboring islands and were smuggled in to be eaten on Guam, where they are a
popular delicacy. The holes in the wing show the bats were killed by shotgun pellets. It's a pitiful
sight and one which marks a serious threat to the ecology of the whole island because many species
of plants have lost their key pollinator or seed disperser. Today, tons of fruit and even the fleshy
parts of these Liana flowers go uneaten each night. They become food for fruit flies and,
as a result, the fruit fly population has exploded. During a recent trip to Guam,
Merlin Tuttle investigates the damage with Gary Wiles, a local wildlife biologist. Fruit flies
now breed in such enormous quantities that they seriously threaten commercial fruit growing on
Guam. The remaining colony of bats now lives within the safety of the airbase,
right at the end of the runway, where they are carefully protected. With luck, the Mariana's
fruit bat will be saved from extinction. But bats are seriously threatened throughout the world. As
we shall see, the fight to save these gentle animals must overcome centuries of human ignorance
and greed. In Southeast Asia, as dusk falls over the Buddhist monastery of Khao Changpran in Thailand,
an amazing spectacle sweeps through the air. Millions of bats stream out of their daytime
roost and spread over the surrounding forests and farmland. This was, until recently, quite a common
sight throughout the region. But human disturbance of the caves in which the bats roost has caused a
massive decline in bat numbers. It's a familiar story throughout the world, one born largely out
of ignorance. Fortunately, this area is owned by the local monastery, and on the advice of Merlin
Tuttle and Bat Conservation International, has been protected for nine years. In that time,
the number of bats has steadily increased. There are now over six million of them under the watchful
eye of a warden. Without this last-minute intervention, the colony would have been lost.
Most of the half-dozen species that roost in the cave are insect eaters, devouring more than 35
million pounds of insects each year. They are essential to maintaining the balance of nature.
The others are fruit eaters, and a key factor in the commercial fruit trade of Southeast Asia.
Throughout the world's tropical markets, about 70% of the commercial fruits come from plants that,
in the wild, rely on bats for pollination or seed dispersal. The markets are full of them. They
include guavas, peaches, avocados, bananas, mangoes, and plantain. The most important fruit of
Southeast Asia, in commercial terms, is the durian, which adds $120 million a year to local
economies. The flowers of the durian begin to open as the sun goes down. As night falls,
the flowers produce nectar and pollen, ready for the arrival of the bats. The dawn bat is
a key pollinator of the durian. As it feeds on the flower's nectar, the bat is in fact ensuring
that the plant will bear fruit this season. The loss of the bats poses serious problems for the
future of this important fruit growing industry. In the wild, bananas also rely on bats. Although
commercially grown bananas do not require pollination, wild stocks must be maintained
in order to provide the fresh genetic strains needed to keep cultivated varieties healthy.
The bat's face shows just how effective it is at spreading the bananas' pollen. By daybreak,
the bats are already pouring back into the safety of their cave, but sadly not as many bats will
return as originally left. Although the bats are protected within the cave, poachers have
spread their nets in the surrounding countryside. Once the bats' feet and wings become entangled
within the net, there's little chance of it escaping. Throughout Southeast Asia,
many thousands of bats are caught like this each night. The meager amount of flesh on their bones
is in big demand. It's even considered by some to be an aphrodisiac. Many species of bats are
faced with extinction because of such indiscriminate hunting. For some species,
it's already too late. They simply no longer exist. But bats are worth far more alive than
dead. Among their many valuable contributions, they produce excellent fertilizer. Once a week,
the monks permit local villagers to enter certain parts of the cave where high ceilings
minimize disturbance to the bats. Under the watchful eyes of the Buddhas, they venture deep
into the cave system. These people are not here to collect the bats, but rather their droppings
that fall to the floor of the cave in a constant shower. Though the collection of bat guano is no
longer economically practical in industrialized countries, it continues to be a key resource in
developing economies. It is an extremely rich fertilizer, and six million bats provide an
income of almost $100,000 a year for the monastery. The cost of employing a warden to protect the
cave is almost insignificant. As the number of bats continues to increase, so does the amount
of guano, which in turn increases the income for the monastery. However, this industry is small
change when compared to the potential value of other life that requires bat guano for its
survival. Countless thousands of unique organisms from fish and insects to bacteria and fungi would
die without the energy they derive from bat droppings. Just one spoonful may contain up to
a thousand species of bacteria, many of which are of potentially great value in solving human
problems. Their usefulness is only now being realized by microbiologists like Bernie Steele.
Some bacteria already under study show promise of helping us detoxify industrial waste, improve
detergents, even help in the production of gassahol and antibiotics. Elsewhere, the people of
Australia are realizing, perhaps in the nick of time, just how critical bats are to the survival
of their forests. In New South Wales, these colonies of gray-headed and black-flying foxes
are only a tenth of their former population. The reason for their drastic decline is quite
simple. They were shot, burned with flamethrowers, and even dynamited to the verge of extinction by
local people and farmers who blame them for damaging commercial fruit crops. The fact is
that under normal conditions, the bats only eat fruit that is too ripe for commercial harvesting.
On average, birds do more damage to crops. But because of popular misconceptions and ignorance,
bats got the blame and were massacred. Recently, Merlin Tuttle and Bat Conservation International
were instrumental in obtaining legal protection for the flying foxes of New South Wales. Under
the wing of the Ku Ring Gai Bat Committee, any orphaned or abandoned youngsters are cared for
by a group of women who meet regularly to compare notes.
These flying foxes are not kept as pets. Most will be released back into the wild. The people
of Australia are being re-educated about bats. Visitors are encouraged at the Ku Ring Gai Reserve
to meet the bats at close quarters and see just how gentle, attractive, and intelligent they are.
Seen at this close range, it's easy to understand why some scientists think flying foxes are primates
related to monkeys, apes, and humans. Large numbers of people now gather to watch the bats
leave their treetop roosts at dusk and head off to feed. In doing so, the bats often pass over some
familiar landmarks. The bats may travel many miles in search of food, and once again they
play an important part in the pollination and seed dispersal of many economically valuable
plants, including trees such as the ironwood, an important timber tree. Loss of the bats could
pose a serious threat to the lumber industry. But worldwide, it's not just economics that justifies
the importance of bats. In East Africa, the baobab tree is a familiar part of the landscape. The tree
is home to a large number of birds, mammals, and other animals. So many, in fact, that it's
known as the tree of life. The baobab relies on bats for the pollination of its flowers.
The flowers open after sunset and await their nocturnal visitors. Nectar is produced at the
base of the large white petals as a tasty incentive for the bats to visit the flower.
A female epauleted bat lands on the flower to feed. As it moves from nectare to nectare,
its underside rubs against the mass of anthers hanging below, and the pollen is carried from
flower to flower as the bat feeds. In another tree nearby, a male epauleted bat is performing
his courtship display in the hope of attracting a mate for the moment she continues to feed.
But the male persists. Eventually, the female approaches, an indication of her acceptance
of the male as a mate, and they fly off together. Most of the caves along the coast of Kenya
were once important bat roosts. Sadly, many are now threatened. They are jeopardized by
increasing numbers of people who disturb and even intentionally kill sleeping bats. Dr.
Tuttle keeps his visits to these important roosts to a minimum in order to reduce disturbance
to the bats. The bats are, of course, completely harmless and are persecuted only out of ignorance.
Bats and people can exist side by side in perfect harmony, provided the bats are left
in peace. One little known but very positive effect of the bats' presence is that they
disperse the seeds of a local tree. The leaves of the neem tree are well known along the
Kenya coast as an insect repellent. A few branches placed around exposed food keeps
the flies away and the tourists happy. One place where the future of bats is looking
up is Austin, Texas. Crevices beneath the Congress Avenue Bridge are the daytime roost
of about a million Mexican free-tailed bats. A few years ago, people feared the bats and
petitioned city officials to get rid of them. But at the time, Bat Conservation International
was moving its headquarters to Austin, and through their efforts, public opinion gradually
changed and the bats are now appreciated and regarded as a tourist attraction. Large numbers
of people gather on summer evenings to watch the bats emerge. The bats eat 15 to 30,000
pounds of insects nightly, controlling pests throughout the area. As far as the people
of Austin are concerned, the bats are there to stay. To most people, a bat is a bat, despite
the fact that there are almost a thousand species worldwide. But it's the wide variety
of different kinds of bats that Merlin Tuttle finds endlessly fascinating. Accompanied by
Burt Grances, he finds the deserts of West Texas a rich hunting ground.
A fine mist net strung low over the water is the easiest way to get a close look at
them. Each species of bat makes its own unique ultrasonic sounds, too high for us to hear.
With electronic help, it's possible to identify the species of bats without ever seeing them.
Oh, looks like we got a free-tail here. Why do they call them free-tails? Well, they call
them free-tails because unlike most bats, they have a little bare tail like a mouse.
See the membrane here? Most bats have a membrane that comes all the way to the end of the tail.
Note that Dr. Tuttle is handling the bats with a glove. Like any wild animal, a frightened
bat may bite in self-defense. Oh, this is a big free-tail bat. This is several times
larger than the Mexican free-tail bat that we just caught. In fact, these are quite rarely
seen. In all, there are 8 or 9 species feeding or drinking in this small area. Hey, Bert,
we got a ghost-faced bat here. See, here he has these really strange eyes that appear
to be right back in his ears, and that's part of a very sophisticated navigation system
that this bat has. There's no other bat in the United States that looks quite like him.
Nature has, over millions of years of evolution, produced a sonar system far more accurate
than any yet developed by science. As we shall see, even the very sophisticated navigation
system of the tornado bomber is crude when compared to the capabilities of bats. Bats
are famous for their ability to find their way in the dark, and nowhere has this been
more dramatically demonstrated than in the forests of Central and South America. There
in the warm, humid tropical nights, there lives a bat whose echolocation is so well
developed that it can detect an object as fine as a human hair, protruding a mere millimeter
above the water's surface. It feeds on fish and can detect the slightest ripple. Its
sonic pulses have been slowed down 60 times so that we can hear them. Once a fish has
been detected, the fish-eating bat hones in, and dragging its flattened, razor-sharp claws
through the water scoops up its prey. It seldom misses.
Other species of carnivorous bats live in the same area. The rarely seen crotopterus
has a wingspan of over two feet. It's an efficient predator that catches a wide variety of small
animals. The bat returns to a favorite perch with its prey.
The rainforests of Central America are home to over a hundred kinds of bats. Caves here
are rare, so many species roost in hollow trees. Dr. Tuttle carefully checks the interior
for poisonous snakes before venturing inside. Several species of bats have taken up residence
in the tree, such as the nectar-feeding glossophaga. Nearby hang one or two Corolia bats, a species
we've already seen feeding in the rainforest. And in one corner, a vampire bat, a shy species
that has been responsible for much of the general public's misconceptions about bats.
This bat feeds exclusively on the blood of other mammals and birds, especially domestic
ones on nearby farms. A chicken settles down to roost in a low tree. The bat silently lands
nearby and stealthily creeps along the branch. Heat detectors around its nose tell the bat
where the blood vessels are closest to the surface. Licking softens up the skin while
the chicken continues to sleep. One small bite and the bat can settle down to feed.
An anticoagulant in the bat's saliva helps the blood to flow freely. This is a far more
effective anticoagulant than any currently being used in the treatment of heart patients,
and medical researchers are trying to isolate and synthesize it. Even the vampire bat may
prove of considerable value someday. Vampire bats are one of a kind, a rare exception
that's tainted public opinion about bats in general. There are, however, a large number
of bats that can only be described as endearing. Clustered beneath a leaf in a Costa Rican
forest huddles a group of tiny white tent-making bats. They make a home for themselves by chewing
along the midrib of a heliconia, or similar leaf, so that the two halves hang down, making
a very effective tent that shelters them from the frequent rains. These thumb-sized fruit-eating
bats will use a tent for several weeks before making a new one elsewhere. The adults are
pure white, with yellow nose and ears. The young are gray, and this one is being pestered
by a mosquito. Once one starts to struggle, the whole group is disturbed and begins to
shuffle around, trying to avoid the offending insect. Bats that live in tropical regions
are active year-round, but those that live in temperate zones have to hibernate throughout
the winter. In Hubbard's Cave in Tennessee, bats return each autumn to spend up to six
months in a state of dormancy. Here, the overwintering bats are protected from human disturbance
by an enormous 120-ton grill that was erected as a cooperative venture by Bat Conservation
International, the Nature Conservancy, Concern Cave Explorers, and even the Tennessee National
Guard. The bats come and go through the grill. The public is allowed into the cave during
the summer when the bats are gone. During the winter, no one is allowed in, except once
every two or three years when scientists must check on the bats. Hubbard's Cave is one
of the three most important bat-hibernating sites known in the world, and all seven or
eight species spend the winter here. Thousands of endangered gray bats encrust the ceiling
living on reserves of fat built up prior to hibernation. The bats wake up at the slightest
disturbance, and if this happens too often, they use up their energy supplies. As a result,
by the arrival of spring, the bats simply run out of fuel and die. Dr. Tuttle and his
colleague Bob Curry from the US Fish and Wildlife Service enter the cave only briefly. The cave
provides a range of temperatures from above 50 degrees to below freezing, making it suitable
for an unusually wide variety of species. The body temperature of this big brown bat
falls to that of its surroundings. The bat's heartbeat slows dramatically, and its blood
barely moves through its veins. The probe reads just over 30 degrees Fahrenheit. The
bat is actually surviving below the freezing point. Nearby rests one of North America's
rarest bats. The eastern big-eared bat gets its name for obvious reasons. Throughout the
cave, bats are sleeping on the walls and ceiling. A little brown bat, its fur covered in condensation,
clings to the wall. It's spent every winter of its life in this cave. This species has
been known to live for up to 32 years. The bats are now left in peace to hibernate until
the warmer weather of spring heralds their return to the outside world. Without doubt,
the biggest threat to bats throughout the world comes from humans. Cave-dwelling bats
are especially vulnerable whether they're hibernating in a winter shelter like Hubbard's
Cave or raising young in summer nurseries like Bracken Cave. Bat populations are declining
alarmingly worldwide, sometimes as a result of unintentional disturbance of caves, sometimes
as the result of unfounded fear and deliberate killing. Entire colonies of millions of bats
have been destroyed needlessly. Bats have always had natural enemies such as the coachwhip
snake. The bats start to get active before dusk and circle at the cave entrance. All
the snake has to do is hang over the entrance and wait for the wing to touch its mouth.
The snake may eat three or four bats in an evening, an insignificant toll on the millions
of bats passing by. It may take hours for all the bats to leave. A constant stream pours
out of the cave and disappears over the surrounding countryside. Remember they will eat over 250
tons of insects before morning. Those that are the first to leave do so while it's still
light and so face other natural hazards. Red-tailed hawks patrol above the cave entrance and pick
off the bats as they emerge, but again the effect they have on the population is negligible.
The real problem is the human species. Can we learn to curb our destructive nature in
time? Only in the past few years have we come to understand that our own survival on this
earth is dependent upon the fragile ecosystems in which we live. And in the past hour, we
have seen that the survival of those ecosystems is dependent in no small part upon bats. Not
so long ago, bats filled the night skies almost everywhere on earth. But just in the past
few decades, we've lost huge numbers and several species. And yet it's not too late. We've
seen how, through organizations like Bat Conservation International, even a last-minute act of conservation
can begin to restore bat populations. Their survival depends on us, and our survival may
well depend on them. It's as simple as that.