Original subtitles

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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

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

for their animal empires.

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