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NARRATOR: Donkeys stranded on a desert island
conquer the arid wilderness.
Pigs in paradise
sunbathe on a Caribbean beach.
And off the east coast of the United States
two herds of horses share one island.
Animals gone wild
must adjust to life on their own.
That means unusual adaptations
and surprising behaviors.
But their very success
could be their downfall.
NARRATOR: Inside the different realms
of the wild kingdom
members of a single species
assemble in droves.
One flock,
herd
or troop
reigns supreme.
These are the world's great
NARRATOR: The small Dutch island of Bonaire
lies off the northwest coast of Venezuela.
Just over 100 square miles in total area
this tiny island of dry land
and sparse bush, is the adopted home
of one the world's most iconic beasts of burden,
the donkey.
Donkeys have been living wild on Bonaire
for over 500 years.
Most of them have distinctive stripes
that form a cross down their back.
This has led to a long association
between the donkeys and Christianity.
Other than snakes, donkeys are the only animals
that speak in the Bible.
The cross is actually a trait
inherited from the Nubian wild ass,
one of two sub-species from which
all domestic donkeys are descended.
The donkey's ancestors made their home
in the desert land of Northeast Africa,
between Egypt and Somalia.
Then over 5,000 years ago
humans domesticated them,
and brought them across the far reaches of Asia
and into Europe.
In the 16th century,
it was the Spanish conquistadors
that brought donkeys to Bonaire.
For centuries, donkeys were used in Bonaire's salt trade,
alongside enslaved African people.
When slavery was abolished on the island in 1862,
the salt business industrialized.
The donkeys were set free.
Today, they are a reminder of the island's history.
The feral donkeys quickly adapted to Bonaire.
They are naturally suited to desert environments like these.
In the 1950s, their population exceeded 1,200.
There were 10 donkeys for every square mile.
Their diet here consists of grass,
shrubs and desert plants.
The plants also give the donkeys
most of the water they need.
The thick hooves protecting donkey's feet
actually benefit from the rough and rocky ground.
Their hooves are the same material as human fingernails,
and never stop growing.
Trekking across the hard terrain files them down
protecting from painful overgrowth.
To keep cool, the donkeys kick up the desert dust
and cover their bodies.
This insulates them from the hot sun.
Male donkeys are called jacks.
The dominant jack will lead a herd
of around 20 individuals.
The herd includes a harem of up to eight females,
their foals, and often
a few subordinate males too.
These days, the donkey's desert home is changing.
Development on the island and a growing tourism industry
have intensified competition for territory
between jacks.
And, as humans move in on the donkey's turf,
conflicts with their new neighbors are inevitable.
NARRATOR: In the Bahamas,
the Exumas are an island chain
about the length of Long Island, New York.
This is Big Major Cay.
One of the 365 sandy isles
that make up the chain.
It's home to some surprising castaways.
Stranded here,
pigs in paradise.
These are the same species of swine
that can be found on farmer's fields across the globe.
But these ones are feral.
Domesticated pigs are descended from wild boars.
These pigs may live in the Bahamas now,
but their ancestors hail from Asia.
More than ten thousand years ago,
people there started capturing and breeding
wild boars for food.
Today domesticated pigs are found
on every continent except Antarctica.
About one billion domestic pigs
are alive at any given time,
making them among the most numerous
large animals in the world.
But here, domestic pigs have gone wild,
and live feral lives.
Whether it's a nursery rhyme about pigs going to market,
a folk tale featuring three little pigs
hiding from the big bad wolf,
or a classic novel
where a well-meaning spider named Charlotte,
tries to save her barnyard buddy.
Stories about pigs
have been igniting the imagination of children
for centuries.
Big Major Cay is no exception.
The origin of these pigs has become a local legend.
Some speculate that they swam to shore
following a 16th century shipwreck.
The truth is they were actually brought here
as livestock from the Bahamian capital, Nassau
in the 1990s.
At first, there were only five juvenile pigs
and they were fed and fenced in.
But when they grew larger, they escaped.
The pigs survived on the island for seven generations.
Now, the population has grown to over 30.
They may technically be domestic pigs,
but these boars and sows
haven't lost their innate ability to find food.
This behavior is called rooting.
Pigs see the world
through a heightened sense of smell.
Digging with their elongated snouts,
they can sniff out edible roots
as far as three feet underground.
Most of their diet comes from roots,
but they also eat wild cabbage and berries.
They get their water
from the island's three inland springs.
By nature pigs are social, gregarious creatures.
They travel in groups, called sounders.
This one consists of three mature sows,
one boar, and their offspring.
A curious disposition and a broad diet
means pigs can find food in just about any range,
making them one of the world's most adaptable animals.
But there's a downside to their success.
With no predators, the number of pigs here
will continue to grow
until there's not enough food and water for everyone.
Potentially devastating the island's native ecosystem
in the process.
NARRATOR: Assateague is a barrier island
running parallel to the East Coast
of the United States,
from Maryland to Virginia.
It's a narrow strip of sand and sediment
almost 37 miles long.
Another island, with another species gone wild.
Horses.
Assateague's horses have free rein
over the island's open meadows.
Worldwide the population of domestic and feral horses
is estimated to be 58 million,
with over nine million in the United States alone.
There are so many horses in the U.S.,
that if they were to form their own state,
it'd be the eleventh most populous in the country.
Prior to their domestication,
horses roamed the open plains
and grasslands of the Eurasian steppes,
from Ukraine to Mongolia.
First domesticated as a food source,
humans eventually realized that tame horses
made great workers.
Over thousands of years,
people brought horses with them across the globe,
just like pigs and donkeys.
Assateague Island's horses have been here
since before the American Revolution.
But how they got here, is a mystery.
Some say that the horses arrived
when two Spanish galleons crashed into the island
during the 1500s.
Others believed that early colonizers
stashed the horses on the island
to avoid paying livestock taxes.
Regardless of how they arrived,
they've been roaming free for over three centuries.
Today 300 horses live on Assateague.
Horses instinctively form herds like this one
to protect one another and act as lookouts.
Feral horse herds are often called bands.
The bands are led by a dominant stallion.
He's the herd's protector
and enforcer of the band's rigid hierarchy,
leading a harem of up to eight mares.
In addition to a dominant stallion,
every band has a lead-mare, like this white horse.
She decides where to graze and when to go find water.
Horses are prey animals.
They grow anxious and flighty when alone,
even here where there are no predators.
The company and hierarchy of the band
keep everyone feeling secure.
With winter on its way,
this horse has begun shedding dead hair
and growing in a thicker coat.
The horse's pituitary gland
recognizes the shift in daylight hours,
and produces a hormone
that triggers the increased hair growth.
It's an itchy process for the horse.
Horses need to keep their coat well groomed all year.
It regulates body temperature
and protects against the elements.
Horses also produce pheromones
that make it possible to identify other herd members
from as far as 400 feet away.
Of course, there's always an itch
that you just can't reach without a little help.
When animals clean each other
its called "allo-grooming."
It's a sign of an intense bond between horses.
The more horses an individual grooms,
the higher her social status is within the herd.
Scientists have even found that mares,
who are the most gregarious groomers,
also produce the most offspring.
Horses spend between 15 and 17 hours a day grazing.
Horses here eat the grasses that grow in the salt-marsh
or on the beach.
This diet is high in salt content,
so the horses drink twice as much water
as other wild horses.
All that water makes them bloated.
The grasses are also low in nutrients,
so the Assateague horses are shorter and stockier
than other breeds.
Adult horses eat 21,000 calories each day.
Grazing the grass and trampling the field
takes an enormous toll on the island,
and increases erosion.
With no natural predators to control the population,
these horses could eat themselves
out of house and home.
NARRATOR: In the 1950s,
there were 5500 people living on Bonaire.
At the time, that meant that for every five people
on the island, there was one donkey.
But as the world changes around them,
the donkeys are starting to disappear.
These days it's tourism, not salt,
that drives Bonaire's economy.
70,000 people visit annually,
most of them coming to dive the clear blue water
and explore the coral reef that surrounds the island.
16,000 human residents
now also call the island home.
Development has encroached on the donkey's former range,
meaning there's less area to graze
and less food to go around.
Many also believe,
the donkeys are throwing the ecosystem out of balance
killing plants and, like the Assateague horses,
eroding the island with their non-stop grazing.
The donkey's brave new world
is full of unknown threats,
And their ancient instincts never prepared them
for dangers like these.
Unlike horses, who instinctively flee nearby threats,
these frightened donkeys freeze in the face of danger,
stopping to investigate threats.
It's an impractical defense
when your range extends across roadways.
Donkeys stay close to the road for a reason.
It's quite resourceful and efficient for grazing.
The asphalt repels water,
which means that during the rainy season,
runoff from the road
spills over onto the curbside,
cultivating some of the island's most luscious greens.
In recent years, up to 60 donkeys annually
have been killed in motor vehicle accidents.
Even though their numbers are declining,
there are still too many donkeys
and not enough space.
So measures have been put in place to control
Bonaire's remaining population of wild donkeys.
Jacks have been gelded,
and then released back into the wild.
Meanwhile mares are being relocated to a protected area,
safe from the island's development.
Limiting the number of free roaming donkeys on the island
means fewer car accidents,
and more space for the donkeys to graze.
But population control may just be the straw
that finally breaks the donkey's back.
It might mean the long history of the donkeys'
wild life on Bonaire
could be coming to an end.
NARRATOR: The wild pigs' colonization
of the Bahamas' Big Major Cay
has been so successful
that the locals now refer to this spot
as Pig Beach.
To avoid the hot sun, the island pigs
spend the hottest hours of the day
in the shade.
They save their foraging for the early morning
and late afternoon.
Pigs don't have sweat glands to help them keep cool.
They're susceptible to heat exhaustion,
sunburns and even skin cancer.
Wallowing in sand,
while not as effective as a mud bath,
cools them, and also helps the pigs
by shielding them from harmful UV rays.
And when things get really hot,
these pigs have another trick up their snouts.
Out on the ocean, a commotion sounds.
The pigs storm the sea.
And then, an even more curious behavior,
they piggy paddle out to the waiting boats.
They weigh between 100 and 200 pounds each,
and they're not exactly hydrodynamic.
But what these pigs lack in speed
they make up for in determination.
In the last 10 years, the legend of Pig Beach
has spread far beyond the Bahamas.
They've become the biggest single attraction
in the Exuma Cays.
The sight, sounds and smells of boats and humans
draw the pigs out of the bush,
and into the water.
This isn't the first time stories of swimming pigs
have amazed humans.
During a World War I naval battle,
an attacking British vessel rescued a pig
swimming away from a sinking German ship.
He was nicknamed Tirpitz, and became the official mascot
of the HMS Glasgow.
In 1946, 200 pigs were brought to the Marshall Islands
to test the effect of nuclear fallout
from an atomic bomb detonation.
After the explosion, they found Pig Number 311
swimming safe and sound in the Pacific Ocean.
She lived out her remaining days at Smithsonian's
National Zoological Park in Washington, D.C.
Swimming is actually instinctual in pigs,
and can be traced back to their ancient ancestors.
Wild boars are exceptional swimmers.
In 2013, a wild boar swam seven miles
into the English Channel,
and was found on an island off the coast of France.
So if pigs have always been able to swim,
why is it such a rare sight?
For the most part,
domestic pigs just have no reason to swim.
So what makes Big Major Cay's pigs
take to the sea?
Food naturally!
From the same humans who come to see them swim.
Widely considered amongst the smartest animals
on the planet, pigs have similar brainpower
as elephants, dolphins and chimpanzees.
Pigs have excellent long-term memories
and exhibit extraordinary problem-solving skills.
Both qualities help them exploit
what's become a dependable supplementary food source.
Locals were the first to discover
Big Major Cay's swimming pigs.
But in the age of social media,
word spreads quickly.
By the mid-2000s, photos of the pigs
began popping up online.
Before long, the pigs went viral.
They've made international headlines,
partied with pop stars,
been photographed with swimsuit models,
and even appeared on reality television shows.
Hashtag pigs in paradise?
Not so fast.
The daily visits and supplemental feeding
are beginning to blur the line
between wild and domesticated once again.
Although the pigs here are being fed,
there's no one directly responsible
for their well being.
If left unchecked, feral pig populations grow rapidly.
One sow can birth over 20 piglets annually.
The number of feral pigs in the United States
has tripled in the last 25 years,
from two million to six million pigs.
An island like this one could quickly become overrun,
devastating the local flora and fauna.
In the past, population control for swine
meant the slaughterhouse.
Nobody seems keen to take these little piggies to market.
But If left alone,
the number of pigs living in this hog heaven
could go hog wild.
NARRATOR: The sand that makes up Assateague Island's beaches
comes from the ancient eroded rock
of the nearby Appalachian Mountains.
Waves pounding against the shore, move the sand,
and keep this barrier island
in a state of constant flux.
But man-made barriers also shape life on this island,
for both people, and horses.
A state border runs across the island,
separating it into two parks.
The northern section of the island
is Maryland's
Assateague Island National Seashore.
The southern part is in Virginia,
where the horses live
on the Chincoteague National Wildlife Refuge.
A fence separates the two parks
and divides the island's horses
into two distinct herds.
This is one of the Maryland horses.
Now in his fourth year,
he's just beginning to reach sexual maturity.
He's on his own.
The leader of his band, probably his own father,
chased him away when he got old enough
to become a threat to the stallion's dominance.
For horses, this is an instinctual prevention
against inbreeding.
Stallions form their own band
by drawing in females that have also been cast out,
Or by attracting a mare
that's left her band to give birth.
The Assateague Island horses are one of the few
wild roaming herds in the United States.
They're the subjects of ongoing studies by scientists
striving to understand
the secrets of wild horse herds.
They've found that individual horses
form close bonds with each other,
but these relationships are so prone to fall-outs,
that researchers have compared life in the herd
to a soap opera.
The horse's reign on Assateague Island
faces a similar set of threats
as the donkey's empire on Bonaire.
The horses are drawn to the rich grasses
on the side of the road;
humans are drawn to the majestic horses.
It's a dangerous and potentially deadly combination.
Since 1982,
traffic accidents have killed 29 horses on the island.
But the horses themselves
may be their own worst enemy.
By pulling up the grass,
the hungry horses are weakening the island's foundation.
This salt marsh is regularly flooded by the tides.
Assateague is a barrier island
and, like all barrier islands, it's made from sand.
The grass is the glue that keeps the island
from washing away.
When this area was made a National Park in the 1960s,
there were only 28 horses
living on the Maryland side of the island.
A nor'easter had decimated their numbers,
and the park sought to protect the small herd.
By 1997, the herd's numbers had risen to 165,
and the park faced the opposite problem.
The horse population was too high.
To protect the horses and their home,
the United States National Park Service
put in place a plan to control the population.
Most of the female horses
on the Maryland side of the island
are now on birth control.
Mares who have given birth at least once
are shot with a dart gun
containing a state-of-the-art equine contraceptive.
For the first few years of the program,
the population continued to grow.
But officials were patient
and in 2014 the Maryland horse population
dropped to a sustainable 100 horses,
with no cull or relocation necessary.
The female horses that receive the contraceptive
even live longer because they're spared the stress
of pregnancy and nursing.
The future of the Maryland horses has been secured.
On the Virginia side of the island,
the horses' appetite poses the same threat
to the Island's foundation.
But officials there
are trying a different solution
to manage the population.
NARRATOR: Worldwide, 95% of donkeys
are still domesticated workers.
In places like Latin America, the Middle East,
India and Sub-Saharan Africa,
they remain a valuable beast of burden.
There are an estimated 44 million donkeys
around the globe, and their numbers are growing.
In industrialized countries it's a different story;
donkeys are in steep decline.
Affordable cars and trucks mean donkeys get left behind.
Donkey Sanctuary Bonaire exists to ensure the future
of the next generation of the island's donkeys.
It was established in 1993 to help care for
the island's sick and injured donkeys.
Displaced by development, and killed by cars,
before the sanctuary, the donkeys' island empire
was on the road to extinction.
The donkeys here are fed three times a day,
a diet of horse pellets, vegetables
and as much hay as they can eat.
These days its far safer for Bonaire's donkeys
to live in the sanctuary
than it is to try and survive in the wild.
This foal was brought to the sanctuary
when she was just two weeks old.
She was hit by a car
and was found with a broken leg.
Without Donkey Sanctuary Bonaire
she would have died.
Here on-site veterinarians provide regular check-ups.
The foal's two months old now, and still healing.
They line her legs with wooden stints
to keep the bone straight.
Donkeys' bones grow until they're 3 years old.
This is a critical time. If her bone doesn't set right,
she'll face a life of constant pain,
and will need to be euthanized.
But so far the young foal is doing well,
and if she continues to recover,
she could live to be 40.
Today close to half of the island's donkeys
live in the safety of the sanctuary.
That means 600 donkeys
don't have to worry about car accidents.
The jacks are more aggressive,
so they still roam free on the outside.
Most are tagged, chipped and gelded
to limit population growth.
Meanwhile, the island is still looking for ways
to make the wild safer for donkeys.
Like these street signs
that have been placed across the island,
warning motorists to look out for crossing donkeys.
The next step is a scientific study to determine
the number of donkeys the island can support.
When the carrying capacity of the island is determined,
and measures are put in place to keep wild donkeys
away from human development,
Bonaire will be safe for donkeys once again.
Until then, the Sanctuary will continue providing
the highest quality of life possible.
That includes plans to deepen the island's gene pool
by artificially inseminating mares.
So when the time comes for the donkeys to live free again,
Bonaire's donkeys will have
the best possible chance of survival.
The donkey's long reigning empire
may soon be ready to rise again.
NARRATOR: On a second sandy and deserted island
in the Bahamas,
the burgeoning empire of Bahamian pigs
is growing.
These pigs were born on Pig Beach,
about 55 miles away from Big Major Cay.
They were relocated here
because its closer to the Exuma's capital,
and therefore more accessible to tourists.
This sounder is comprised of three separate litters,
each with about 4-7 piglets.
Like all piglets, they were born highly developed;
they could see and hear at birth,
and walk within minutes.
The youngest pigs are just six weeks old,
but a life-long "pecking order" already exists among siblings.
It was established the day they were born,
as the piglets competed to suckle from teats.
The piglets will nurse for up to five months,
but even after they've weaned
they'll remain close to their mother and siblings.
Unlike the pigs on Big Major Cay,
these pigs can't survive without human help.
Because there's no freshwater spring on this island,
their drinking water is shipped here daily.
The pigs here have been domesticated once again.
Their new fence is the Caribbean sea.
It's an odd combination of agriculture and tourism.
The spread of this pig empire
could spell disaster for both pigs
and their adopted lands.
Across the Bahamas other introduced species
like cats and mice, have decimated island ecosystems.
Left free the highly adaptable pigs
could eventually outcompete native species,
and wipeout local plant life in the process.
The unregulated nature of this bizarre phenomenon
means there's currently
no population management plan.
But for the pigs, life in the Bahamas
beats life on the farm.
Most of those pigs don't make it to their first birthday.
As long as they have food, shelter and water they need,
these pigs could live for another 20 years.
NARRATOR: The Chincoteague National Wildlife Refuge
in Virginia, is on the southern side
of Assateague Island.
Though these horses are left to roam free,
each one is branded with the year of their birth
so the herd's numbers can be monitored over time.
There are a few differences between the northern
and southern Assateague horses.
One difference is their name.
Down here people call them Chincoteague ponies.
Genetically a horse and a pony are the same.
The difference is in the height.
Horses are taller;
island life has made these short and stocky over time,
so by equestrian standards, the Assateague horses
are, in fact, also ponies.
The Chincoteague ponies' relentless grazing
poses the same threat to the island
as their northern cousins.
When unmanaged, feral horse populations
can double every four years.
But even though 70 new foals are born each year,
the effect on the ecosystem here
hasn't been as severe.
To prevent overpopulation
this herd has been managed for nearly a century.
But it's done differently
than it is for their northern cousins.
Each spring, once foals are weaned,
they're rounded up and auctioned off,
sent to new homes off the island.
Today there are over a thousand Chincoteague ponies
living on the mainland.
The breed is highly valued for their calm demeanor
and a hardy nature.
Every year, a few foals are kept back
to make sure the wild population stays strong.
There are now a manageable 150 horses
on this side of the island.
That number falls firmly in line
with the ecologist's recommendations.
The two herds are both considered
conservation success stories.
With proper population control
the hope is the sun will never set on the empire
of the Assateague Island horses.
NARRATOR: Thousands of years ago
animals like donkeys, pigs and horses
became reliant on their owners.
Likewise, humans came to rely on them,
bringing them with us as we traveled the globe.
But when animals are abandoned in strange new lands,
the consequences are unpredictable.
Controlling the population of feral species
remains an ongoing challenge
for conservationists around the globe.
These empires gone wild
struggle with depleted ecosystems
and new relationships with humans.
As these herds,
bands
and sounders
continue to try to find harmony
for their
animal empires.
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