All language subtitles for The Life of Mammals 4of9 Chisellers 720p HDTV x264 AAC MVGroup org_Subtitles01.ENG

Morning in the rainforest of Panama.

Capuchin monkeys are having
a rather wasteful breakfast.

Inside these nuts, there is a kernel
that is very, very good eating.

But the tree has protected them
with such a hard shell

it's almost impossible
to get at the kernel inside,

even if I hit it with a stone.

Unbroken!

So it is hard to believe,
but nonetheless true,

that there's an animal in these
Central American forests that can
open these nuts with its bare teeth.

But it's certainly NOT
these monkeys.

The best they can do is to scrape
off the thin, fleshy coating.

The nut itself,
they simply throw away.

But another animal is
listening for that tell-tale sound.

GENTLE THUD AND RUSTLE

It's an agouti.

(The agouti is certainly
no bigger or stronger than a monkey,

(but it has the right tools
to deal with ANY nut...)

..a pair of extremely strong
and sharp front teeth that can
cut through even the toughest casing.

Agoutis belong to a large and
highly successful group of mammals,
the rodents.

And rodents specialise
in being able to chisel their way
through almost anything.

But what is so special
about an agouti's front teeth

that enables them to cut a hole
in the toughest of nuts?

They have a layer of strong enamel,
but only on the front surface.

Behind it, the body of the tooth is
made of a softer material - dentine.

Gnawing something hard wears down
the dentine faster than the enamel,

leaving an edge
as sharp as a carpenter's chisel.

And unlike the front teeth
of many other mammals,
a rodent's grow continuously,

replacing what gets worn away.

Armed with these formidable teeth,

the rodents have become
the most successful and numerous
of all mammals.

The largest group of them
are the rats and mice.

There are 1,300 species of those
and they are ALL
accomplished stealers of seeds.

Other rodents use their teeth
to cut up vegetation.

Some even tackle wood.

The rodent body is very versatile

and has evolved into an astonishing
variety of shapes and sizes

to suit many different lifestyles.

Some are amazingly nimble
tree-climbers - the squirrels.

They use their teeth
to open cones and collect seeds
that few other mammals can reach.

Abert squirrels use their teeth,
not only to cut into cones,

but to nip off the tips
of the branches of ponderosa pines,

where the underlying bark
is particularly nutritious.

This is a valuable food reserve
if the pine cones run out
during the long northern winters.

Abert squirrels
are now such specialised feeders

that they can only survive where
there are plenty of ponderosa pines.

Most squirrels, however,
have more general tastes and
high on their menus are often acorns.

Oak trees usually produce
a heavy crop of acorns each autumn.

This is good news
for squirrels like these greys,

because they must eat a great deal
to fatten themselves up for winter.

They must also bury some
to eat later on when times get hard.

But for squirrels here
in the woodlands of the eastern
United States, in Virginia,

things are not quite so simple.

Here there are two kinds of oaks -
red oaks and white oaks -

and their acorns are very similar.

This is the acorn of a white oak.

And this, a red oak.
This one is just slightly darker.

But the acorns of the white oak
germinate almost immediately,
using up their food supply.

The red oaks, on the other hand,
don't germinate until next spring.

The squirrels recognise
the difference between the two
and treat them differently.

When a squirrel finds a white acorn,
it always eats it immediately,

because otherwise
it would soon germinate.

On the other hand, red acorns,
like this one, are almost always
buried as a store for winter.

Squirrels are colour blind, so
they can't recognise the difference
between the two acorns by sight.

It's the smell that tells them
which should be eaten straightaway
and which should be buried for later.

Some years, the white oaks produce
their usual bonanza of acorns,

while the red oaks
provide hardly any at all.

When this happens - as now -
the squirrels change their tactics.

You might think this one is
tucking into a white acorn as usual,

but after only a quick nibble,
it takes it away and buries it.

What's it up to?

It has neatly cut away the tip,
beneath which lies
the embryo of the seed.

And once that has gone,
the acorn will never germinate.

But its food store will remain fresh
throughout winter for the squirrel.

So, with dexterous paws
to hold the acorn

and sharp front teeth
to cut out the embryo
with the precision of a surgeon,

the squirrels get
the best possible value out of
these apparently well-protected nuts.

Seed-producing plants
grow pretty well everywhere,

so, potentially, seed-eating rodents
can live everywhere, too.

But there is one problem.

Although all seeds are full of
nutriment, most of them are small,
like these from these desert plants.

You'd need about 500 of these
to make the food equivalent
of a typical nut like an acorn.

Any rodent wanting to store the tiny
seeds produced by plants like these
faces a transport problem.

It would be hopelessly impractical
to carry them away one by one,
as squirrels carry acorns.

Here in California's Mojave Desert,
there is a little rodent
that has solved that problem,

and its burrows are all around me.

Like most desert animals,

the creature that owns this hole
usually doesn't come out
until after dark, when it's cooler.

But if I scatter a few seeds
around its entrance,

maybe that will tempt him
to come out a little earlier.

Well, as it happens, it didn't.

It wasn't until much later, when
the moon was up, that the burrow's
owner eventually showed itself.

A kangaroo rat.

It can carry hundreds of seeds
at one time because it has
expandable cheek pouches.

The pink toes,
poking out from the fur,

are those of its back legs, which
are huge and support its whole body.

That's why it is called
a kangaroo rat.

Its front legs,
hidden beneath its chin, are
shovelling the seeds into its mouth.

Normally a kangaroo rat would have
to travel quite a long way to find
enough seeds to fill its pouches.

But because of what I have supplied,

this one's shopping bags are soon
full enough to take to its burrow.

There we are!

And it covers them over with sand,
just to keep them safe.

Its deep burrow
is a relatively safe place

and the kangaroo rat sleeps here
throughout the day
and much of the night.

Even so, the slightest suspicious
sound from outside will wake it.

WHISHING

A gopher snake
is crawling towards the burrow.

It might find its way inside.
It had better be seen off.

Foot stamping is the first warning.

That seems to have no effect.

Perhaps kicking sand in its face
will do the trick.

The snake doesn't like that at all.

Victory to the kangaroo rat.

Seeds, of course, are not the only
part of a plant that is edible.

Some rodents, like these marmots
that live in the European Alps,
eat the entire thing.

And they fight over grazing rights.

When Alpine marmots come out
of their burrows in late spring,
after their winter sleep,

they immediately set about
re-establishing
their territorial boundaries.

Calling and tail-flagging
are only the preliminaries.
WHISTLING CALL

If that doesn't work, there is
nothing for it but to go to battle.

The senior males
do most of the fighting,

while their female partners
guard the family burrow and watch.
CALLING

When a male wins a territorial scrap,

he marks the boundaries
just established with scent
from a gland on his cheek.

Marmots form strong pair bonds,
and the females usually only mate
with their one permanent partner.

By late spring, a marmot family
consists of the adult pair together
with a few of last years' offspring,

all of them females.

Last year's males
have already been chased away.

Although daughters are allowed
to stay, their mothers constantly
beat them up, particularly in spring.

They persecute them so severely
that, if any of the youngsters
have become pregnant, they abort.

The reason for this strange and
merciless behaviour doesn't become
apparent until later in the year.

By midsummer, relative peace
has come to the mountainside.

This season's babies are about
to emerge from the maternity burrow
for the first time.

There are usually between four
and six babies in a litter

and they immediately get down
to the important business of grazing.

Alpine summers are short,

so marmots have to feed
as fast as they can, while they can.

Their incisors slice with ease
through the tough stalks
of flowers and grasses.

The babies put on weight rapidly,
but even so,

by the end of the summer,
they still do not have fat reserves
to match those of their parents.

In the autumn, the family
start on their final harvest -

hay to line their deep burrow,
in which they will sleep
through the winter.

By October,
the weather has turned really cold.

Down in the burrow,
the marmots' body temperature
has dropped to 2 degrees centigrade

and their hearts are beating
only two or three times a minute.
They are hibernating.

They are sustained only by their fat
reserves which will have to last
them until the following April.

They snuggle together
to minimise the loss of heat.

The youngsters are always
in the middle of the pile.

With less body weight, they can't
afford to let their temperatures
drop as low as the adults.

The thermal-imaging camera

shows that a baby, glowing orange,
is several degrees warmer
than the adults, which show green.

The burrow, which registers blue,
is well below freezing point.

The adults couldn't keep
more than one litter of youngsters
warm enough throughout the winter.

THAT is why the dominant female
made quite sure that none of her
youngsters produced any babies.

But hibernating isn't the only way
to survive the winter
in the mountains.

Here in North America,
the winters can be just as severe
as they are in the high Alps.

Yet here there is a rodent
that manages to find food
throughout the winter months,

and it does so with an extremely
ingenious device - a refrigerator -

a pool of deep, cold water like this.

And over there,
is its builder and owner...

..a beaver, one of a family that
lives here in this lake at the foot
of the Teton Mountains in Wyoming.

While beavers can get around
perfectly well on land,
they are most at home in the water,

where their webbed hind feet and
paddle-like tail make them powerful
swimmers above and below the surface.

Like marmots, beavers feed
on all kinds of vegetation,

and eat wood as well as leaves.

And they are accomplished
engineers - this great pond
is entirely their own creation.

Only a few years ago,
this shallow, pebbly stream
flowed straight down the valley.

Then a family of beavers moved in
and built a dam.

The main body of it
is built of boulders.

On the downstream side,
it has been lined with logs,
some of them big and quite heavy.

And on this side, it has been
packed with mud and vegetation.

It has been built so accurately
that it is, to within a few inches,

horizontal across its entire length
of about 150 yards
from one side to the other.

And the lake it has created
stretches upstream for almost a mile.

So important is their dam to them,

that if they detect the slightest
leak - usually by hearing
the sound of trickling water -

they start repair work immediately.

Mud is needed as well as logs.

The repair team will labour away
until the leak is fully repaired.

Maintaining the water
at a high level brings
the beavers several advantages,

one of which is that it floods
the surrounding woodlands

and so enables them to swim in
safety to their main source of food.

They increase the distance they can
swim by digging channels that lead
into the very heart of the woodland.

Here they can use their sharp
incisor teeth to strip off the bark
from a fallen tree trunk,

while still being close enough
to water to slip away should
a bear or a mountain lion turn up.

Their network of channels
also enables them to ferry
whole branches back to their pond.

And there,
where the water is deepest,

they dive down and push each branch
firmly into the mud at the bottom.

This is the beavers' fridge,

where the vegetation will keep fresh
through the long winter
when the pond is covered with ice.

Stocking the fridge
takes a lot of work

and the beavers are at their busiest
in autumn.

At one side of the lake,
stands their lodge -

a fortress built of branches
and boulders that is so strong that
not even a bear could break into it.

The only entrance is through tunnels
that open underwater

and the beavers take refuge here
whenever they are alarmed.

That was a warning signal to say
that danger was around - that is me.

And now I may not see the beavers
for some time.

They can stay underwater
for five minutes at a time -
up to 15, if they need to.

They can get back to the safety
of their lodge without putting their
head above water for a single second.

Most lodges have
at least two different entrances.

By October, winter is well under way,
but whereas marmots
would now be hibernating,

the beavers are still active
and will remain that way
throughout the winter.

Even when the pond
ices over completely,

they are still able
to swim under the ice
to get back and forth to their lodge.

No-one knew exactly what went on
inside the lodge during winter,

so when the beavers were away,
we installed a couple of infrared
cameras in order to find out.

A branch from the fridge
is being brought back to the lodge
for the whole family to feed on.

And another.

No wonder they don't need to
hibernate, with this ingenious setup.

The lodge is warm and safe,
even in midwinter,

and the only sign of activity in the
snug home beneath the snow is hot
air rising from the vent at the top.

Inside, our cameras catch a glimpse
of what, at first sight,
looks like a very small beaver.

It's a muskrat.
There are a pair of them in here.

This is a new observation.

Do the beavers actually know,
in the pitch blackness,
that there are strangers among them?

We noticed that the muskrats
regularly left the lodge
to forage under the ice.

And on several occasions,
they returned a few minutes later
with a load of fresh reeds.

Perhaps the muskrats are paying rent
by regularly providing fresh bedding
for the lodge.

Maybe that is why the beavers
accept them, and even allow them
to share their food.

Our infrared lights, however,
are no longer welcome, it seems.

A lodge makes a very safe home
for a beaver.

Other rodents take more active steps
to defend themselves,
and one is positively dangerous.

Darkness provides
one of the best forms of defence

and it is very dark right now.

The only reason you can see me in
the middle of the African night is
that we are using a starlight camera.

So, many rodents don't come out
except under cover of darkness -

and that applies
even to one of the most ferocious
and well-armed of all rodents.

I think
there could be one around here.

(There it is.

(And what a formidable sight!

(An African crested porcupine.

(It seems to have found something
to eat underneath that spiny bush.

(Most of the time,
those quills would be lying flat.

(The fact that they are half erect
is a sign that it's not too happy
to have me so close.

(Those long quills are VERY sharp.

(And I'm quite sure
it knows how to use them.

(It is turning its back on me -
but don't be fooled. That's
not because it is about to run away.

(If it gets really angry,
it will attack
by suddenly sprinting backwards.

(And it's off.)

That's not the sort of thing
you want to stumble into
in the middle of the African night.

Porcupines feed mainly on roots
and tubers, but they are big animals

and to find enough to eat,
they must travel long distances
every night across open savannah.

That means that they have to be
prepared to take on all comers.

This young leopard
has probably never been
close to a porcupine before,

so it doesn't realise how dangerous
it would be to interfere with it.

The porcupine, on the other hand,
seems to have total confidence
in its armoury.

If it's not very careful,
that naive young leopard will
end up with a face full of quills.

And the porcupine
goes back to digging for food.

There's confidence for you!

Belding's ground squirrels
don't have that kind of nerve.

They live in the hills of California
and make their burrows
close to one another

so there are plenty of watchers to
give warning of the slightest danger.

This is particularly important in
summer when there are babies about.

There are always at least one or two
adults on watch nearby so that the
young can feed in relative safety.

Only the females care for the young.
They are nearly all related -
mothers, sisters and daughters -

and each looks after
her nephews and nieces as carefully
as she does her own offspring.

When one of the guards spots a
potential predator, such as an eagle,
she sounds a preliminary warning.

Those trills mean, "Danger seen
but evasive action not needed".

A bobcat - and once again a warning.

HIGH-PITCHED SQUEAK

Each female is trying to keep the
enemy in view to ensure it doesn't
sneak up and catch them by surprise.

But the bobcat is getting closer.
Now the warning will change.

LOUD CHIRRUP
That means, "Run for it!"

Another small rodent that would make
a tasty meal for a predator lives
here in the arid north of Kenya.

There are dozens
within a few yards of me.

But this one has adopted the safest
strategy of all - to spend
nearly all of its time below ground.

And this is all that most people
will ever see of it.

A naked mole rat.

They use their teeth for digging.

Uniquely, their lips close
behind the teeth. That stops earth
getting into their mouth.

With this superb burrowing equipment,
they dig a great network of tunnels

radiating from a central chamber,
where the colony gathers
and the babies are kept.

All the babies
are produced by one big female,
the founder of the colony.

All the rest of them - and
there may be as many as a hundred -
are the founder's children,

and none of them will breed here
as long as their mother is alive.

Their job is to tunnel away,
searching for tubers and roots,

creating a vast network of tunnels
that stretches for hundreds of yards
under the African plains.

Above ground,
you have to look very hard

to find any sign of a plant
that might provide mole rats
with an underground meal.

Mostly, there is just dry grass
and the odd acacia seedling.

When mole rats meet, they assess
one another's status with a sniff,

and the junior one has to pass
underneath the senior one.

They are blind, and in the darkness
they are just as happy
travelling backwards as forwards.

I've now come
about a quarter of a mile from
where I saw those mole rats digging,

and this is the plant
I have been looking for.

Now, in the dry season, it's
nothing more than a curly stem
and a few withered leaves.

But beneath the ground,
there's treasure.

And here it is.

Tubers like this
are few and far between here

and it is a matter of pure chance as
to whether the mole rats, burrowing
underground blindly, bump into one,

which is why mole rat colonies
have to have several dozen workers.

But if they do find one like this,
it could sustain the colony
for two or three weeks.

Their sharp incisors
cut into the tough tuber.

Some of it, the lucky finders
will eat on the spot.

They also drag back lumps
to the central chamber to be shared
by the rest of the colony.

This colonial arrangement, where
all the workers are sterile and
labour away to support their mother,

is also the basis
for the colonies of bees and ants.

But naked mole rats
are the only mammals of any kind
that have adopted it.

Although those long, chisel
front teeth are rodent hallmarks,

rodents are also famous
for reproducing
with extraordinary rapidity.

Mole rats certainly do that.

But the most prolific members
of the whole family are the mice.

Tiny harvest mice produce their
babies in a carefully woven nest

among the stems of reeds
or tall grasses.

Litters of up to eight babies,
fed on their mother's rich milk,
mature in only a few weeks.

Each pair can produce three litters,

that is up to nearly 30 young,
in a single season,

provided that the adults
can find enough seeds to feed on.

The young leave the nest when they
are only two weeks old and start
searching for food by themselves.

To begin with, they are not nearly
as agile as their parents.

In fact, sometimes they seem
quite unsure about just where
they can safely tread.

These little creatures
have been living in our cornfields,

taking a small proportion of
our crops ever since farming began.

Usually they only became visible
when the crops are gathered, which
is why they were called harvest mice.

Even after harvesting, there is
still the spilt grain to feed on.

But in the vast wheat belt
of Australia,

a different mouse takes advantage
of this plentiful supply of food,

digging their burrows
along the edge of the sandy fields.

These are common house mice, the
most prolific breeders of them all.

Each female is capable of becoming
pregnant at only five weeks old,

and if there is
a good supply of grain,
she will breed every month or so.

In some years, if all the grain
out in the fields gets eaten,

the mice head for the nearest
farm buildings to look for food.

As they leave the stripped fields,
it becomes clear just how many
have been feasting out there.

Once they do find their way into
a grain store, they become a plague.

But eventually, when they finish
the grain, their numbers
will fall as quickly as they rose.

On the flat, windswept plains
of Patagonia,

lives a much larger rodent with
a more measured system of breeding -
the Patagonian cavies or maras.

Although this litter may appear
to be very large, all the young
are of slightly different ages.

That is because
they belong to different parents.

Only one pair is on guard.
The others are away grazing.

This, in fact, is a communal creche.

It is based around a hole
that was often dug initially
by burrowing owls.

The maras have simply enlarged it.

Although the adults guard each
others' offspring, each female only
gives her milk to her own babies.

The others will have to wait
until their own mother arrives
to take her turn as guard.

Here comes the next pair.

The adults
are not necessarily related,

so the changing of the guard
can be a somewhat tense business.

The mara couples behave as though
they were rivals rather than friends.

Galloping around,
grazing out on the plains,

the maras have evolved long legs,
so that they look
more like antelopes than rodents.

That may be the reason that they are
not particularly good at digging

and prefer to steal holes
from the burrowing owls.

A plover warns of approaching danger.

The babies, thanks to the owls,
have a hole to go to.

But it's not big enough for the
adults. All THEY can do is run.

There is yet another kind of rodent
that gather together in vast numbers
to graze.

They really do remind one
of the huge herds that you see
on the savannahs of East Africa.

But we are in South America,
and these are not wildebeeste
or antelope.

These are the biggest rodents
in the world - capybara.

Capybara are, like the mara,
related to guinea pigs,

but these are real giants.

And they use their rodent teeth
to crop grass - lots of it.

BARKS

When they want to, they can gallop
as fast as a small horse.

Although they are very agile on land,
they are equally at home in water.

Within these herds,
each family sticks together,
in groups of 20 or so.

There are mothers and daughters,
children and grandchildren.

And just one large dominant male.

That's him at the back.

He marks his territory with scent
from a gland on the top of his nose.

And he will vigorously
chase off any rival males

that venture too close to his family,
and particularly to his females.

Capybara will graze
out on the dry savannahs, but
they're most at home in the water.

They have oily water-resistant fur,
partially webbed feet

and their eyes and nostrils
are on the top of their heads

so that they can remain
almost completely submerged

but able to hear, see and smell
what is happening on dry land nearby.

Even the male's scent gland, which
most other rodents carry on their
cheeks, is on the top of his nose.

During the rainy seasons,
the plains flood and the capybara
are truly in their element.

If the maras are the South American
equivalent of antelope,

then these surely are
the rodents' version of hippopotamus.

Rodents truly are
the most adaptable of mammals.