All language subtitles for Animal Empires - 01x04 - Infestation Eng

NARRATOR: In the shadows
of London, England,

one of the world
most successful species,

the brown rat,
stakes its claim.

A continent away,

the sea lions of
San Francisco's Pier 39

take a different tack,

hauling out
en masse

in the light of day.

And just outside
Melbourne, Australia,

fruit bats forced from
their native home,

take to the trees
of a city park.

In search of food
and shelter,

these uninvited
guests

use sheer numbers
to secure new territory.

Their very survival

may depend on
infesting a place

where they're not
welcome.

NARRATOR: Inside
the different realms

of the wild kingdom,

Members of
a single species

assemble
in droves.

And one flock,

herd,

or troop

reigns supreme.

These are
the world's great

These are
the world's great

NARRATOR: England
is the most overcrowded

major country
in Europe.

On average,
over 1,000 people

are squeezed into
every square mile.

That's over
50 million residents.

And some say,

there are
just as many rats.

On the outskirts
of London,

a derelict basement
has been overrun

with brown rats.

A group of rats
is called a mischief.

It's a fitting term.

At least 100 of
these large rodents

wreak havoc in the shadows
of this building.

It's a full-blown
infestation.

It was once believed
that there was one rat

for every person
in the UK.

Scientists suggest
that it's more likely

one for every
six people,

but that would
still mean

some 10 million rats.

With the exception of
Alberta, Canada,

where
extermination efforts

have kept the province
rat-free since the 1950s,

rats live everywhere
people do.

After humans, this is
the most successful mammal

on the planet.

Which makes it
one of the world's

greatest
animal empires.

The brown rat
is also referred to

as the Norway rat.

British naturalists of
the 18th century

thought that it had migrated
to England from Norway.

But the species,
in fact,

originated on
the plains of Asia

in Northern China,
and Mongolia.

Some time in
the middle ages,

they began
boarding ships,

traveling
far and wide,

and spread
to the four corners

of the globe.

By that time, black rats
had already spread

to Europe during
the Roman Empire

and had firmly cemented
their reputation

as household pests.

But the larger,
more aggressive brown rats

eventually took over,

displacing
their relatives.

Brown rats eat
a wider variety of food.

The transition
from wooden buildings

to brick and tile
construction

also favored
brown rats.

They're much better
diggers

and can tunnel
under walls,

and left black rats
out in the cold.

They also have
very good hearing,

a highly developed
sense of smell,

and can see
ultraviolet lights

that most animals
cannot.

But while
there's much to admire

about this
super species,

a rat is a very
unwelcome guest.

It was long believed
that rats

were responsible
for the Black Death

that devastated
Europe in the 1300s.

Evidence now suggests they may
have been falsely accused.

However,
the stigma remains.

Rats are known
to transmit diseases,

and they make a mess
of basements and attics.

So as these
rodents multiply,

so too do efforts
to exterminate them.

They are under
near constant threat.

Rats don't live long.
The maximum life span

of a brown rat
is around three years.

Most
barely manage one.

So for this
animal empire,

every day
is truly a rat race.

On the northern coast
of California,

the city of
San Francisco

is known
for its historic icons

like the Golden Gate
Bridge

and Alcatraz Prison.

These landmarks,

along with the region's
moderate climate

and easy-going
pace,

make it a popular place
to live and visit.

But it's not just
an attractive place

for residents and
tourists.

Pier 39, once a popular
mooring spot

on San Francisco Bay,

is now infested with
sea lions.

Sea lions
are part of a group

known as "Pinnipeds",

commonly known
as seals.

In fact, the clich�d
circus seal,

balancing a ball
on its nose

and jumping
through hoops,

is typically
a California sea lion.

Sea lions join
fur seals

to make up the family
"Otariidae",

also known
as eared seals.

Unlike other seals,
they have external ear flaps.

In addition, you can
tell the difference

by the sea lions'
proportionately larger

fore-flippers
and pectoral muscles.

Sea lions also have
a long thin ridge of bone

running along
the skull,

known as
a sagittal crest.

The range of
the California sea lion

stretches from Alaska
in the north,

to the Baja Peninsula,
of Mexico

in the south.

California sea lions
spend the summers

breeding on
the Channel Islands,

just over
350 miles

south of
San Francisco.

Once the breeding
season is over,

females stay close to
the newborns on the islands.

The males set out to the open
ocean in search of food

for as long as
two weeks at a time.

Between fishing trips,
they need to rest,

or "haul up"
on shore.

Many do so
on the beaches

of northern California.

Large colonies are
a fairly common sight

along the coast,

but less expected
in the throng

of a bustling
metropolis.

Pier 39 is
in the heart of the city.

It's smack dab
in the middle

of San Francisco's
busy waterfront,

sandwiched between
restaurants,

shops, and
other attractions.

Since 1989,

sea lions
have taken over

Pier 39's K-Dock.

The exact reason
is unknown.

It may be that it's simply
a convenient rest stop

between the breeding grounds
to the south,

and the foraging waters
to the north.

Whatever the reason,

the arrival of
these boisterous bulls

has become a seasonal
event each winter.

Their presence
shuts down the pier

to boat traffic.

And this hauling out
has become

an inner city
infestation.

an inner city
infestation.

Across the Pacific,

on the south coast
of Australia,

the city
of Geelong

is an hour's drive
southwest of Melbourne.

Located on the waters
of Port Phillips,

Geelong
is considered

the gateway city
for the region.

And it is
rapidly growing.

Home to more than
180,000 people.

This Melbourne suburb
has been called

one of Australia's
most livable cities.

And not
just for humans.

Geelong
is also home

to tens of thousands
of bats!

The grey-headed
flying fox

comes by its name
honestly.

It looks a lot
like its namesake.

But it is indeed
a bat.

And a big bat
at that.

The largest in
Australia

and one of the largest
in the world.

Bats are mammals,

the only mammal capable
of sustained flight.

Bats belong to
the order "Chiroptera",

which literally
means "hand-wing."

There are
two sub-orders.

Most are familiar
with the "micro bats",

popularized by Halloween
haunted houses,

horror stories and
the legend of Dracula

Micro bats
are smaller,

only about the size
of a mouse.

They live in caves,
and eat bugs.

They also use "echolocation"
to find their prey,

calling out
and using the echo

that bounces back
to navigate.

The grey-headed flying fox,
on the other hand,

is a mega bat.

It's not only larger,
but it also has good eyesight

and a superior
sense of smell.

This is their food
of choice, fruit.

In fact, they're commonly
known as fruit bats.

And instead of caves,
they live in trees.

Today, fruit bats only live
in the tropical rainforests

of eastern Australia.

Decades ago,
they were endemic

to all southeastern
Australia's forests.

Numbers were
in the millions.

But as trees
were cut down

to make way for expanding
cities and towns,

factories and farms,

development put added
stress on fruit bat habitat.

It is estimated
that as much as 70%

of some of the flying foxes'
favored foraging sites

have been lost
since European settlement.

As a result, there are
now only between

three and six hundred
thousand in the range.

They've simply run out
of places to live.

So in the late 1980s,
the surviving fruit bats

in the southeastern
state of Victoria,

made a move.

They went from
the wild woods,

to Melbourne,
and other nearby cities.

Now, at least three
permanent colonies

make their home here,

including this site,
in Geelong's Eastern Park.

It's hard
to blame them.

There's food
and water nearby.

It's warm in winter,

and cool
in summer.

And the city's green spaces,
like Eastern Park,

offer protected trees
that are ideal for roosting.

As their forest homes
continue to fall,

more and more
fruit bats

move to the city
looking for a roost.

The Eastern Park
colony

has swelled to
as many as 30,000.

These big bats
are not necessarily

a welcome addition
to the city.

They can be
intimidating and noisy.

They damage
other vegetation,

and they are known to carry
dangerous viruses.

What was once an occasional
stopover in the city

has become
an infestation.

Bats in the belfry
are one thing;

bats on
the golf course

is something else
altogether.

But for the flying foxes
themselves,

the stakes
are even higher.

Their very survival

depends on
a peaceful coexistence

with their
human hosts.

Great Britain's
rat population

doesn't have quite
the same housing problem

as the fruit bats.

While Australia's bat-friendly
forests are scarce,

Britain offers
more than enough

suitable habitats
for rats.

There are plenty of sewers,
garbage-filled alleyways,

and bleak building basements
to choose from.

Rats will live
pretty much anywhere

they can
find food.

And they'll eat
just about anything.

Rats are
true omnivores.

They prefer
grains and meat,

but studies have shown
that rats aren't picky.

Scrambled eggs,
macaroni and cheese,

pet food, and
even leftover fruit.

They'll eat whatever
happens to be around.

Once rats identify
a source of food,

they first need to
gain access.

It doesn't take much
to make an entrance.

With a collapsible rib cage
that's hinged at the spine,

they can squeeze through
cracks half their size.

If a rat can get its head
through a hole,

the rest
will follow.

They can also enter
through plumbing pipes,

either by using
their razor sharp claws

and excellent balance
to climb up the outside.

Or they use their superior
swimming skills

on the inside.

They are
such good swimmers

they can tread water
for hours on end.

And yes, they can even
enter a building

through a toilet.

Once inside, rats start
making their home

by burrowing.

In some cases, this means
digging underground

and making
tunnels.

In others, they collect
nesting materials,

insulation, straw, and
any lightweight material

they can use
to create an enclosure.

Burrows provide
the pack

with shelter
and food storage,

as well as safe,
thermo-regulated nests.

Each burrow has
its own nest chamber.

But rats may also
share a burrow

and raise
their young together

in a "communal nest".

They connect their burrow
to others

made by
their relatives.

It's a system of one
to six little burrows,

not unlike families
that chose to live

in the same
village.

After a few days,

a second entrance,
called a bolt-hole,

is added by digging
from below.

It serves as
an emergency exit

in case the burrow
is invaded.

Once the first burrow
is finished,

rats will continue
to add on,

using
the same pattern,

dig a tunnel,
empty out a cavity,

add
a bolt-hole.

Outside the burrow,

brown rats tend to
confine their movement

to the same routes
every day.

Gradually, trails
form on the surface.

Rats don't like
to go far.

As long as food
is available,

they'll stay within
65 feet

of their nest.

It's a matter
of avoiding risks.

Even though these are incredibly
adaptable creatures,

they're also
very vulnerable,

especially outside
the burrow.

Predators,
interspecies conflict,

and the occasional run-in
with an exterminator,

can result
in a rat colony

having a mortality rate
of 95%.

Most rats don't make it
past their first birthday.

How is it then,
that rats have maintained

such a successful
empire?

In a word,

In a word,
breeding.

Rats reach sexual
maturity at an early age,

at just
five weeks old,

and usually start
breeding at two months.

They can breed
throughout the year.

Mating behavior
depends on the colony's

population density.

When numbers
are low,

one male rat will monopolize
a burrow of females.

It's a polygynous
system

where he mates with a number
of females in his group,

and only the members
of his group.

In this case, the male
will defend his territory

fiercely
from other rats.

He'll chase, bite
and box,

fluff up his hair,
hiss, squeal,

and wag his tail,

anything to keep
other males

away from the females
in the burrow.

At higher population
densities,

males can
no longer defend

a burrow
against rivals.

There are simply
too many.

One alpha male
rules the pack,

but he can't control
all the females.

In this polygyandrous
system,

multiple
males mate

with
multiple females.

A female rat
goes into heat, or estrus,

every 4-5 days.

The gestation period
is only 21 days.

Which means
she can have about

a dozen litters
in one year.

And each of
those litters can have

anywhere between
7 and 14 pups.

Her offspring will start
breeding within two months.

And their offspring

will be able to breed
in another two months.

That means,
one mating couple

can produce as many as
15,000 descendants

in a year, if left
to breed unchecked.

At this rate, a few rats
can quickly become

an infestation.

And an infestation
can spell trouble.

A crowded rat pack
leads to

increased competition
and conflict.

And can draw
the unwanted attention

of the local
exterminator.

Like rats and bats,

California sea lions
are motivated by hunger.

The pod at
San Francisco's Pier 39

has figured out
something

their fellow migratory
sea lions haven't,

that the safe harbor
of the pier

provides them with just about
everything they need.

For one thing, there's
plenty of fish in the sea.

Or in this case,
herring in the bay.

Sea lions
are binge feeders,

eating all they can
when food is plentiful.

They'll eat anywhere between
10 to 40 pounds

of food or more
every day.

In addition to
the herring,

they'll prey on some
50 species of marine life,

including squids,
octopuses,

hake, salmon, and
anchovy.

They are excellent
swimmers

and can spend
15 hours at sea,

diving up to
200 times.

They hold their breath
for up to 20 minutes

and dive to depths
of 1,000 feet.

And they are
speedy swimmers,

clocking in at
22 miles per hour.

While the Pier 39
sea lions

may not have to work
so hard for a meal,

they still need a spot
to haul out and rest.

And the Pier provides
a perfect accommodation.

The docks rise
and lower in the tide,

saving them from having
to move up and down

from rocks
on the shore.

It's not unusual for them
to sleep 8 to 12 hours a day.

And they fast
for several days at a time.

Sea lions are very gregarious,
social animals,

so it's normal for large
groups to haul out together.

California sea lions
can't sweat or pant.

Their normal
body temperature

is about
100 degrees Fahrenheit.

In order to regulate
this temperature,

they must move around
in their environment.

When it's cold,

a sea lion will cozy up
to others to stay warm.

If it gets too hot,

he'll lift a flipper
or fan himself.

Sea lion flippers
have many capillaries

that can be cooled off
by the wind

when sunbathing.

Of course, he can
also take a dip in the bay.

The Pier also is also
a place to haul out,

providing protection,
both from storms and predators,

like sharks and
orcas.

It may seem
like an ideal spot

for these pinnipeds.

But that means
it's a popular one, too.

On average, there can be
up to 600

hauled up
on the pier.

A record 1,700

were counted
in 2009.

And there's
not much room

for a few hundred
sea lions.

These are massive
marine mammals.

A fully-grown male

averages more than
660 pounds

and is about
eight feet long.

This is
a boisterous bunch,

prone
to bickering.

When it comes to
prime real estate,

sea lions
aren't afraid

to fight over
who got there first,

and more importantly,
who gets to stay.

and more importantly,
who gets to stay.

Outside the city
of Melbourne, Australia,

a colony of grey-headed
flying foxes

has taken over
the trees

of Geelong's
Eastern Park.

These fruit bats have
both summer

and winter roosting camps
in the trees.

This summer camp,

from September
through round June,

is their main camp.

During the day, hundreds
hang from the branches

high up
in the trees.

There's a good reason
they hang upside down.

Bats are top heavy.

The biggest bones
and muscles

are those
used for flying.

It's far more
energy efficient to hang

than to defy gravity
and stand upright.

It's during
these long summer days

that they mate.

Males set up
mating territories,

generally three-and-a-half
body-lengths along branches.

Males fight for
these territories.

Those with the best locations,
closer to the center,

have access to more,
and better, females.

Males with
lower-rent spots

may have
only one mate,

or they're stuck
being bachelors.

At the beginning
of the mating season,

adult females move in
towards the male territories

where they become
part of 'harems'.

The harems consist of a male
and up to five females,

who come and go.

It's the females who control
the copulation process.

Mating takes place
during the day

between March
and May.

After about six
and a half months,

babies, known as pups,
are born.

For the first
three weeks,

the pups are heavily
dependent on their moms.

Bat mothers provide milk and
warmth for their babies,

which cling to their moms
for the first few weeks of life.

As the day comes
to a close,

the adult bats ready to leave
in search of food.

Pups that are not yet
three weeks old

will cling to their mothers
when they go foraging.

Older pups
remain in the roost

until they are weaned
at about six months.

Bachelors and
lactating females

leave the roost
first.

Mating males wait
and guard their harem

until
all have left.

It's a catch-22.

Those that leave
earlier,

have more time and
light to work with.

But this also makes them
more vulnerable

to predators,
like hawks and eagles.

For each fruit bat,
it's a decision

that could
very well determine

whether they will survive
the night.

In the dark recesses
of this London basement,

there's tension
in the rat colony.

There may have been
plenty of space

when the infestation
began.

But now, the rapidly
expanding population

is putting pressure on
the over-crowded burrow.

There's just
not enough room.

And now there are
even more mouths to feed.

Even though
most rats

won't live past
the age of two or three,

they're reproducing far faster
than they're dying off.

In just four months,

this colony has grown
by a factor of ten.

Conflict
is inevitable.

Crowded rats
turn aggressive.

The alpha male
goes on the offensive;

he attacks and pushes out
lower ranking males.

It may seem like
an extreme solution

to the overcrowding
problem,

but it's a matter of
maintaining the balance.

If it gets
too crowded,

the strong will drive
weaker members

out of the colony.

If the population
declines,

the remaining rats
simply increase

their reproductive rate
to restore numbers.

But it's not always
one big rat race

to see who stays
and who goes.

Studies have shown
that rats

also have the capacity
to work together.

They'll cooperate
to get food.

It's even suggested
that a rat

that has received
help in the past

is more likely
to help another rat,

even one that is
unknown to him.

In other words,

cooperative rats
don't just return favors,

they also
'pay it forward.'

Scientists call this
"general reciprocation".

It's the first time
this behavior

has been documented
in nonhumans.

And another example
of how intelligent

and adaptable
these rodents are.

And they must be.

Though rats have the respect
of researchers,

and some even find
a happy home as pets,

they generally remain
unwelcome house guests.

Rats are under
constant threat.

And so,
as the day breaks,

the mischief
settles safely

back into
the burrow.

They spend
the daylight hours

hidden away
as best they can.

For some, there's work
to be done storing food

and maintaining
the burrow.

For others,
it's time to sleep.

They huddle together
to conserve heat.

New pups nestle together,
depending on each other,

and the heat
from their mother.

Once the young males
are old enough,

they will leave the nest and
strike out on their own,

setting off in search
of new territory,

and once again beginning
the cycle of infestation,

and expanding
the empire.

It's October in the city
of San Francisco.

There's no vacancy on
Pier 39's K-Dock.

At its busiest,
the pier may be home

for 500-600
sea lions.

It can get awfully noisy
when a few hundred

large marine mammals
haul out of the water.

California sea lions

are among the most vocal
of all mammals.

(sea lions bark)

They bark, growl,
and grunt loudly.

(sea lions growl)

(sea lions bark)

During
the mating season,

males will bark incessantly
at each other

as they clash
over territory.

These fights frequently
turn physical.

Breeding bulls
will do whatever it takes

to establish dominance
and claim a harem.

Here on Pier 39,

during the non-breeding
season,

it's the young
submissive males

that are most
aggressive.

Bulls usually
reach

10 years of age
before they mate.

When that
time comes,

they must be ready,

so they train.

It's every sea lion
for himself.

(sea lions growl and bark)

While some
scuffles at the pier

are over favored spots
on the docks,

most fights are between
these juvenile males,

practicing the skills that
they will need in the future.

(sea lions bark and growl)

They work their way
up the hierarchy,

taking part
in regular bouts

as they try to climb
the social ladder.

Only the strongest
will get the chance to mate.

(sea lions bark and growl)

It's a rowdy affair.

(sea lions bark and growl)

They grapple
and bite each other,

and bump and thump
their necks and chests.

(sea lions bark and growl)

Though injuries are common,
fatalities are rare.

(sea lions bark)

A skirmish usually ends
when one or the other

is physically
pushed away.

Currently, the population of
California sea lions is healthy.

But it's not without
its threats.

Foraging adults can become
entangled in fishing nets

or plastic
packaging materials,

causing injury
or even drowning.

And the planet's changing
climate is a growing concern.

Declines in
sea lion numbers

have been linked to
exceptionally warm currents

that cause fish
populations to shift.

This can lead
to poor nutrition,

especially dangerous
to pregnant and nursing females.

These are
increasing threats

to the survival of
the species.

These young bulls
face an uncertain future

in a changing
world.

When the summer
is over,

they will join the other adults
as they make their way

from Pier 39, back
to the breeding grounds

off the Channel Islands.

On the islands, their training
will be put to the test.

These young bulls will fight
to win breeding rights,

the chance to continue
their lineage,

and ensure a future
for their empire.

and ensure a future
for their empire.

Bat's wing bones
are the same as those

of a human arm
and hand.

But these bones are
proportionately much longer.

They're connected by
a double membrane of skin

that forms the wing.

Different bat species
have different wing shapes

depending on where
and how they eat.

Flying foxes have
an average wingspan

of three feet.

Flying foxes
need their large wings

to travel the relatively
long distances

to fruit-filled forests
and fields.

As day turns
to dusk,

the sky above Geelong's
Eastern Park

comes alive.

The grey-headed
flying foxes

are setting off
in search of food.

When a wave of these
large bats take flight,

it quickly
fills the sky.

Their departure
is an impressive sight.

Most will travel
an average radius

of about 20 miles
from the roost.

Some will even go as far as
60 miles to find food.

They travel at a speed of
about 23 feet per second.

If conditions
are right,

they can ride the wind
and travel twice as fast.

And they
have to hurry

if they're to be back
before sun up.

It's a myth
that bats are blind.

All bats can see,

and see better
than humans at night.

But fruit bats have
the best eyesight of all.

They use
their big eyes,

along with
a keen sense of smell,

to locate food.

Many of their food plants
have blossoms

that bats
can see from above.

They're on the lookout for
the flowers of native trees,

such as the many
species of eucalyptus,

as well as turpentines,
and paperbarks.

And of course,
fruit.

Bananas, mangos,

dates, avocados,

just about any kind
of fruit will do.

Far from
the safety of the roost,

these flying mammals
are vulnerable.

Out in
the open air,

predatory birds
like hawks and eagles

hunt
the night sky.

Weasels, snakes,
and even cats

prey upon fruit bats
when they stop to rest or eat.

But it's humans that present
the greatest danger.

Fruit farms are
an attractive place

for a grey headed flying fox
to find a meal.

Farmers have been known
to trap and shoot bats

to protect
their crops

Recent
conservation efforts

are trying to curb
this trend.

It's part of
an increasing awareness

of the important role
that fruit bats play

in the local
ecosystem.

The seeds
they swallow

move quickly through
their system.

They take only
20 minutes to digest,

and are spread through
the fruit bats' excretion.

Bat guano is good
for the environment.

Increased clearing
in the last two centuries

has isolated scattered
patches of forest.

Flying foxes are able
to move seeds

over longer distances
than insects and birds,

linking these patches of
native vegetation.

In this way,
grey-headed flying foxes

can help rebuild
the habitat

that has been
taken from them.

But for now,
as day breaks,

they must return to
the safety of the roost,

to the Eastern
Park trees

and the city they have claimed
as their home.

NARRATOR: From the basements
of Britain,

to bustling
San Francisco Bay,

to the cities
of southern Australia,

every member
of the wild kingdom

depends on finding
a suitable home.

For rats, sea lions,
and flying foxes,

that means moving in where
they may not be welcome.

But whether
invited or not,

these species are simply
struggling to survive,

using strength
in numbers

to claim
new territory

and continue
the legacy

of their

of their
animal empires.

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