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20,000 years ago, this cave in Wales
was home for human beings.

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We know because their bones
have been found here.

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And it's a pretty good home, too.

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Here you're out of the wind and the rain,
you can make a fire to keep warm,

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and you can defend yourself against enemies,

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whether they're other human beings
or wild animals like bears and wolves.

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In short, here you've got some
control over your surroundings,

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and you can make yourself comfortable.

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Animals, of course, find homes for themselves
for very much the same sort of reasons.

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Some use ready-made ones
like this cave. Bats, for example.

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0thers build the most ingenious
and elaborate structures

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to shield themselves from a world
that can be so very hostile.

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A rocky coast is one of the most
difficult of all places in which to live.

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Continuously pounded by waves,
submerged twice every 24 hours,

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and twice exposed to the air.

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To survive, small molluscs secrete
stout, almost unbreakable shells.

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And when they're dead and gone,
their vacated homes are much sought-after.

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And in this pool, cut off by the falling tide,

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there's a large housing market
full of anxious tenants.

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This could be just what they're waiting for.

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Hermit crabs have found
the easiest solution to the housing problem -

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using somebody else's.

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There is a major difficulty -

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as a householder grows,
he needs a bigger house. This might be one.

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A check has to be made on the dimensions.

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Too big is almost as bad as too small,

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because then
enemies could pull the occupier out.

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It's just the thing.

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Now a slightly smaller home is on the market.

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And another one, smaller still.

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And another hopeful tenant.

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Nobody wants to vacate a perfect residence,

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but they can be forced to leave
by strong-arm tactics.

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Instead of stealing a hole for yourself,
you could dig one.

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Rosy bee-eaters,
like all their family, do just that.

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They're troubled, not with a shortage of houses,
but of building sites.

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It's the dry season and this entire flock
has chosen one sandbank

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in the middle of the Niger river.
It is, indeed, a very desirable site.

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For one thing, insects hatching from the river
provide a lot of food.

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And, being surrounded by water,
it's protected from land predators.

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Most importantly, its sand,
recently exposed by the fall in water,

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is free of vegetation and loose -
much easier to dig in

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than the vertical river banks and cliffs
that most other kinds of bee-eaters use.

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So rosy bee-eaters come
from many miles around to nest here.

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That means there is great overcrowding.

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0ne benefit from such numbers is that those
who haven't got their heads down digging

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can keep an eye out for danger.

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There are, inevitably, quarrels.

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A half-dug hole represents a lot of work
and a bird will steal another's if it can.

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They work in pairs - one does the digging,

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the other chases away strangers
who might get in the way.

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It's hot work, too,

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but with the river close by
it's easy to take a cool, refreshing dip.

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In a month or so,
the breeding season will be over,

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the river will rise again
and the holes will be flooded,

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but by then the birds will have flown
and won't need a home for another year.

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But some animals need a hole
as a refuge throughout their lives.

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The open grasslands of the American west
are very exposed places to live.

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A small animal sitting here is very vulnerable.

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So prairie dogs dig for protection.

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And the prairie dog community, like
the bee-eater colony, has its alarm system.

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(CHIRPING)

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Below, there's a warm, safe refuge.

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The animals are so successful
that they can proliferate in huge numbers

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and form great settlements
with hundreds of tunnels and entrances.

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I'm in the middle of one of these towns,

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and there are a couple of dozen
burrows within a few yards of me.

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Why does the prairie dog build so many elaborate
burrows, when digging is very hard work?

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Well, there's one way to get a clue.

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This is a candle
which produces a perfectly harmless smoke.

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If I light it...

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..and put it in the burrow,
we can see what happens.

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The smoke doesn't all just blow away, but
a wisp of it gets carried down along the tunnel

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and eventually emerges
at another entrance mound 20 yards away.

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So these two holes are connected.

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It's obviously useful to have an escape hole
if you're pursued by, say, a wild ferret.

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But there's more to it than that.

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0ne of the problems
about having a long burrow like this

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is that it can get very stuffy.

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The prairie dog deals with that problem

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by building two differently-shaped entrances.

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0ne is low to the surface of the prairie,

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and the other has
this mud tower built around it.

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Wind blowing over the prairie
moves faster a foot above ground

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than it does at ground level.

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So a breeze moving across this entrance
will suck out the stale air from the burrow.

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The prairie dog, in fact,
has a home with air-conditioning!

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So no matter how long
the prairie dog remains underground,

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the air of its home remains fresh.

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This refuge was not dug.

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It was woven from silk.

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0nly spiders and insects
have the ability to produce silk.

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This strange insect, a web-spinner,

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has spinnerets on the end
of its forelegs like boxing gloves.

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Caterpillars have spinnerets
just inside the mouth.

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The silk comes out in one continuous filament

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and a single moth caterpillar
can produce a thread 3,000 feet long.

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This marvellous substance
still provides human beings

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with one of the most luxurious
of all their fabrics. The caterpillar uses it

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to build the protective cocoon
within which it will transform itself

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into an adult winged moth.

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Tent caterpillars build co-operatively.

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Their mother laid a batch of 300 or so eggs

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and now all the hatchlings
are erecting a communal shelter.

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As the caterpillars grow in size,
they need more space.

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They continually add new floors
to their dwelling.

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Each tent acts rather like a greenhouse.

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The air trapped inside is quickly warmed
by the sun so that, early in the morning,

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the caterpillars are ready to set out
to look for leaves a little bit earlier

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than other species
that might be competing with them.

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Silk is such a useful building material

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that others who can't make it...steal it.

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A hermit hummingbird uses sticky spider silk

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to bind her nest to the edge of a leaf.

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Flying round as only a hummingbird can,
with a strand in her beak,

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she creates a suspended nest, sheltered
from the rain beneath the roof of the leaf

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and far more difficult for predators to find

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than one placed on a branch or on the ground.

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The Indian tailor bird also uses silk,

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not to bind but to stitch.

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She searches all the bushes around
for her silk threads.

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With this spectacular feat of craftsmanship,

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she converts two floppy leaves
into a single firm cup.

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It may not look strong,

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but it's quite secure enough
to hold a lining of fibre and hair,

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and mother and chicks sitting on top.

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Leaves form excellent protection from the rain.

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There's nowhere you need it more
than the tropical rainforest.

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Many animals that live here feed on fruit.

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If their shelters are permanent ones,
like a cave or a hollow tree,

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they may have to travel long distances
every day in order to find a fruiting tree.

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It's much more convenient
to have temporary encampments,

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and no creature uses leaves
more elegantly for that purpose

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than those living under this leaf.

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They've cut through these side ribs
so that the leaf flops down

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and forms a perfect watertight tent.

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And there they are.

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Tent-making bats -
the size of golf balls and pure white,

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though the light filtering through the leaf
makes them look green.

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They'll only use this shelter for a few nights,

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then they'll be off to another leaf
near another fruiting tree.

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But you can use leaves in a much
more radical way than this to build a home.

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Weaver birds are the great experts.

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It's the males who do the building.

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The first step
is to tie a leaf strip onto a twig.

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It's not easy, for the fibre is very springy.

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The trick is to keep
a firm hold on it with one foot.

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Then you can tie the knot with your beak.

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It's a simple half hitch but a firm one,

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and all subsequent work
will, literally, depend on it.

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Knotting takes practice,
and this young bird is having a little trouble.

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The next step is to weave a ring.

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But you can't do that
until you've got the first knot right.

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The ring has got to be big enough
to allow its maker to slip through

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and not so big that it will allow
larger animals to do so.

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But it certainly mustn't be too small.

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The strips must be fresh and supple,

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and the birds get supplies
from a patch of grass nearby.

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They tear off the strips by gripping
the side of the grass blade close to the ground

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and then simply flying straight up.

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0ver a thousand of these strips
are needed for a single nest.

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0nce the ring is complete and firm,
work starts on the roof.

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The novice still has his problems.

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Their technique, in essence,
is the same as that of human weavers.

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A strip is threaded alternately above and below
other strips that run at right angles to it.

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In the beak of a master craftsman,
this produces neat and beautiful results.

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In less skilful beaks...

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Well, not so good. But he's learning.

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Very critical eyes are watching progress.

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A female selects her mate
largely on his ability as a weaver,

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and he calls attention to it
with his fluttering wings.

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But others have the same idea.

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She flies over to have a look.

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The novice is being a little optimistic.

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No one is taking any notice.

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And eventually she makes her choice.

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This looks neat enough,
but it's not yet won him a mate.

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But this bird, luckier or more skilful, has,

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and now he can get on with finishing the job.

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The whole construction is completed
by adding with a looser weave

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a long, downward-pointing entrance tube.

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This will deter unwelcome visitors.

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If, after a few days,
a weaver hasn't managed to attract a partner,

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all his work is wasted.

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For a female never chooses a nest
that's so old it's turned brown.

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There's only one thing to be done.

187
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He'll have to start all over again.

188
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That means dismantling his first attempt.

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This is the only place he can build,
as all the rest of the sites are occupied,

190
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and dismantling it is almost
as hard work as weaving it.

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0n rocky cliffs like this, the problem
is not so much shortage of sites for a nest

192
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but of material with which to build it.

193
00:22:17,886 --> 00:22:23,085
Shags like to cushion their breakable eggs
to stop them rolling about.

194
00:22:23,246 --> 00:22:28,843
But there's only what the sea washes up,
and that's a very mixed bag indeed.

195
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There's an easier way of getting stuff
than carrying it all the way from the seashore.

196
00:23:26,926 --> 00:23:30,396
But if you're caught red-handed,
there's big trouble.

197
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When material is in such short supply,
almost anything will do.

198
00:24:05,006 --> 00:24:08,396
Even the beak and bones of another bird, a tern,

199
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or the dried corpse of a rabbit.

200
00:24:19,006 --> 00:24:21,804
There's no shortage of building material here...

201
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..particularly if you build in wood,

202
00:24:32,686 --> 00:24:36,281
which is the lifelong preoccupation
of this animal.

203
00:24:36,446 --> 00:24:38,641
It's a beaver.

204
00:25:19,526 --> 00:25:23,678
This is one of the most massive
of all animal constructions.

205
00:25:23,846 --> 00:25:28,920
It's a dam that's blocked this valley
and built up behind it a sizeable lake.

206
00:25:29,086 --> 00:25:34,797
Its foundations are sticks that have been
rammed vertically into the bed of the stream.

207
00:25:34,966 --> 00:25:41,314
Horizontal poles have been laid across those,
then boulders are dumped on it to give weight.

208
00:25:41,486 --> 00:25:46,241
The downstream side slopes gently
and is buttressed with poles.

209
00:25:46,406 --> 00:25:49,716
The upstream is more vertical
and faced with mud.

210
00:25:49,886 --> 00:25:55,563
It was designed, built and maintained
by a family of beavers over decades,

211
00:25:55,726 --> 00:25:58,479
and handed down through the generations.

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00:25:58,646 --> 00:26:02,685
If ever there was an ancestral pile, this is it!

213
00:26:04,366 --> 00:26:08,678
Such large properties
need constant care and attention.

214
00:26:09,326 --> 00:26:14,525
Every dam has to have a spillway
to carry away the flow of the stream.

215
00:26:14,686 --> 00:26:16,995
After heavy rains, it has to be enlarged

216
00:26:17,166 --> 00:26:21,045
to allow the rising water to escape
before it bursts the dam.

217
00:26:21,206 --> 00:26:25,199
When the flood subsides,
the dam has to be built up again.

218
00:26:42,206 --> 00:26:47,121
The beavers have very clear ideas
about the exact position for any one piece

219
00:26:47,286 --> 00:26:49,880
and labour away until they get it just right.

220
00:26:53,606 --> 00:26:56,882
Large beams are needed for structural strength.

221
00:27:11,046 --> 00:27:16,040
Small twigs, leaves and mud
are essential to plug the gaps.

222
00:27:30,326 --> 00:27:33,602
The purpose of all this labour
is to create a lake.

223
00:27:33,766 --> 00:27:36,041
In summer, they sink branches in it.

224
00:27:36,206 --> 00:27:40,085
In winter, when the lake is frozen over,
they dive beneath the ice

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to retrieve the still green leaves
from cold storage.

226
00:27:43,766 --> 00:27:48,601
But it has another purpose, too:
it makes their home virtually impregnable.

227
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This...is the lodge,

228
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the family residence.

229
00:28:10,046 --> 00:28:12,719
There seems to be no way into it.

230
00:28:12,886 --> 00:28:17,164
That's because the entrance, in fact,
is underwater, just about here.

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00:28:17,326 --> 00:28:22,116
So you have to be a skilled swimmer
and underwater diver to get into the residence.

232
00:28:22,286 --> 00:28:25,756
In fact, it's a pretty well burglar-proof home.

233
00:28:25,926 --> 00:28:30,761
Impressive though it is, and ingenious
though the beavers are in utilising wood,

234
00:28:30,926 --> 00:28:34,680
they do little more
than cut it up into convenient lengths.

235
00:28:34,846 --> 00:28:39,158
However, there are some animals
that can process wood

236
00:28:39,326 --> 00:28:43,399
and turn it into
an altogether more malleable material.

237
00:28:47,086 --> 00:28:49,316
Wasps chew up wood,

238
00:28:49,486 --> 00:28:52,717
mix it with their saliva
and make it into a fine paste,

239
00:28:52,886 --> 00:28:58,438
which dries into a material that is
both lightweight and strong - paper.

240
00:28:59,686 --> 00:29:04,396
The common European wasp
produces a very high-quality paper,

241
00:29:04,566 --> 00:29:07,126
and with it builds nests of great perfection.

242
00:29:07,286 --> 00:29:09,925
Within these identical hexagonal cells,

243
00:29:10,086 --> 00:29:15,080
a huge workforce is raised to serve
the queen and maintain the nest.

244
00:29:22,286 --> 00:29:27,121
This tiny Malaysian hover wasp is
one of the least ambitious wasp builders.

245
00:29:27,286 --> 00:29:32,041
Her nest of rather crumbly paper
is just a few open cells on a stem.

246
00:29:34,406 --> 00:29:38,115
These are clearly vulnerable
to the elements and predators,

247
00:29:38,286 --> 00:29:43,440
but she protects them from their main enemies,
ants, by smearing the egg in each cell

248
00:29:43,606 --> 00:29:48,202
and ringing the stem with a sticky repellent
that blocks access all round.

249
00:29:53,006 --> 00:29:58,205
This nest is suspended from the ceiling
of a cave by a narrow paper stalk.

250
00:29:58,366 --> 00:30:00,755
It's well protected from the weather,

251
00:30:00,926 --> 00:30:05,716
but the females guarding the open cells
must be ever-watchful for raiders.

252
00:30:18,606 --> 00:30:23,600
0ther species protect their young
by building a paper wall around the cells.

253
00:30:23,766 --> 00:30:28,237
They often pattern it by using different
coloured materials for camouflage.

254
00:30:28,406 --> 00:30:33,002
With only a single entrance,
the nest is readily defendable.

255
00:30:35,766 --> 00:30:38,155
But some predators are unstoppable.

256
00:30:38,326 --> 00:30:43,116
This nest has been wrecked and its young stolen
by another member of the wasp family,

257
00:30:43,286 --> 00:30:48,121
a giant hornet. This bandit is a merciless eater
of the larvae of other species

258
00:30:48,286 --> 00:30:50,675
and few nests are safe from it.

259
00:30:52,606 --> 00:30:58,363
Bees construct their defences with
a substance no other animal produces - wax.

260
00:30:58,526 --> 00:31:01,120
They secrete it from abdomen glands

261
00:31:01,286 --> 00:31:04,278
and derive it from honey combined with fat.

262
00:31:04,446 --> 00:31:07,483
Tropical stingless bees mix it with resin

263
00:31:07,646 --> 00:31:11,764
and build entrance tubes
to their nests within tree trunks.

264
00:31:11,926 --> 00:31:14,679
These tubes often take bizarre shapes.

265
00:31:17,366 --> 00:31:21,325
But they all have a narrow entrance,
often flared into a landing platform,

266
00:31:21,486 --> 00:31:26,276
which is heavily guarded
by platoons of sentries who vet every arrival.

267
00:31:32,406 --> 00:31:37,799
Inside, the workers labour, building a maze
of interconnecting struts and plates

268
00:31:37,966 --> 00:31:40,560
to support the brood combs.

269
00:31:50,206 --> 00:31:52,959
The resin stiffens the waxy structures

270
00:31:53,126 --> 00:31:57,916
and antibiotic chemicals within it
reduce the risks of infection.

271
00:32:03,646 --> 00:32:08,436
Those cells that will contain young
are first three-quarters filled with pollen.

272
00:32:08,606 --> 00:32:11,916
Then the huge queen comes over to inspect them.

273
00:32:19,406 --> 00:32:24,434
As soon as a cell's provisioning is complete,
the queen drops an egg into it.

274
00:32:24,606 --> 00:32:28,599
Immediately, one of the workers
seals off the top with wax.

275
00:32:51,606 --> 00:32:56,999
In a separate part of the nest,
there are special pots for storing honey.

276
00:32:57,166 --> 00:33:01,637
This is why they must use wax.
Paper cells couldn't hold liquid.

277
00:33:02,646 --> 00:33:06,639
They will be filled to the brim,
for they are the reserves for times

278
00:33:06,806 --> 00:33:10,242
when there's little or no food
to be found outside.

279
00:33:11,446 --> 00:33:14,518
Wax is certainly a superb building material,

280
00:33:14,686 --> 00:33:17,996
malleable, strong
and capable of holding liquids,

281
00:33:18,166 --> 00:33:20,760
but it's very expensive to produce.

282
00:33:21,926 --> 00:33:24,599
Mud is much cheaper.

283
00:33:37,846 --> 00:33:42,636
These pea-sized vessels
are the work of another kind of wasp -

284
00:33:42,806 --> 00:33:44,797
a potter wasp.

285
00:33:52,766 --> 00:33:55,678
0nce again, saliva is an important ingredient.

286
00:33:55,846 --> 00:33:59,361
It prevents the mud from crumbling
when it dries.

287
00:33:59,526 --> 00:34:04,680
With jaws scissoring away on the inside
to keep the mud properly mixed and fluid,

288
00:34:04,846 --> 00:34:07,360
and front legs checking the wall's thickness,

289
00:34:07,526 --> 00:34:10,040
she lays the mud round and round in a strip,

290
00:34:10,206 --> 00:34:13,278
using a technique human potters call coiling.

291
00:34:20,646 --> 00:34:22,955
When the main body of the pot is finished,

292
00:34:23,126 --> 00:34:26,721
this greatly accomplished potter
brings another ball of mud

293
00:34:26,886 --> 00:34:29,480
and adds a final and most elegant flourish.

294
00:35:15,526 --> 00:35:18,279
In goes an egg.

295
00:35:20,966 --> 00:35:23,355
Now the cells must be provisioned.

296
00:35:23,526 --> 00:35:27,280
A potter wasp doesn't feed her larvae
on chewed bodies or honey.

297
00:35:27,446 --> 00:35:29,914
She gives it living food -

298
00:35:30,086 --> 00:35:32,475
a caterpillar, paralysed by her sting.

299
00:35:33,846 --> 00:35:37,998
The lip, built so carefully around the entrance,
helps to guide it in.

300
00:35:49,806 --> 00:35:54,402
The mouth of the pot will be sealed
with a clay pellet and the lip removed.

301
00:35:54,566 --> 00:35:57,603
The larva eats its caterpillar,
turns into an adult,

302
00:35:57,766 --> 00:36:01,042
and emerges
by breaking through the side of the pot.

303
00:36:01,206 --> 00:36:05,802
Although abandoned,
the tough pots survive for several years.

304
00:36:08,806 --> 00:36:13,675
These much bigger mud constructions were built
by cliff swallows in the American mid-west.

305
00:36:13,846 --> 00:36:19,239
Protected from winter rain,
they too may last for several years.

306
00:36:21,246 --> 00:36:23,635
Each spring, the birds fly up from Argentina.

307
00:36:23,806 --> 00:36:28,197
They arrive in a flock and together, as a flock,
inspect the old tenements

308
00:36:28,366 --> 00:36:30,675
they occupied last year.

309
00:36:47,966 --> 00:36:53,086
Their favoured building sites
are beneath natural overhangs.

310
00:36:53,246 --> 00:36:55,635
The trouble is, there's not many of them,

311
00:36:55,806 --> 00:36:59,037
so they readily take advantage
of a man-made one.

312
00:36:59,206 --> 00:37:03,961
But, of course, old buildings
do have their disadvantages.

313
00:37:04,126 --> 00:37:06,799
They can be infested with vermin,

314
00:37:06,966 --> 00:37:11,084
optimistically waiting
to parasitize the new occupants.

315
00:37:11,246 --> 00:37:16,274
The decision on whether to re-occupy a site
is taken by the flock as a whole.

316
00:37:16,446 --> 00:37:21,725
0nce they've made it, each pair claims a nest
and starts smartening it up.

317
00:37:41,006 --> 00:37:43,395
(CH0RUS 0F BIRD CALLS)

318
00:37:55,366 --> 00:37:57,755
To get the mud as it wants it,

319
00:37:57,926 --> 00:38:01,839
a bird may have to gather some really wet
material from the water's edge

320
00:38:02,006 --> 00:38:06,397
and then mix it in its mouth
with drier mud from farther back.

321
00:38:50,246 --> 00:38:52,635
The consistency of the mud is crucial.

322
00:38:52,806 --> 00:38:58,278
If it's too dry, it won't stick, but if
it's too sloppy, it's very difficult to handle.

323
00:39:00,486 --> 00:39:05,480
And working upside down with it
can be a real problem.

324
00:39:19,806 --> 00:39:24,596
When the chicks hatch, the price
of using old buildings may have to be paid.

325
00:39:24,766 --> 00:39:29,237
These, whose parents chose their home wisely,
are fit enough...

326
00:39:32,486 --> 00:39:37,002
..but in other nests the parasites
have had a feast and are proliferating.

327
00:39:37,806 --> 00:39:40,604
These young swallows will probably not survive.

328
00:39:49,126 --> 00:39:53,119
But most do.
Their parents succeeded in raising them

329
00:39:53,286 --> 00:39:58,565
while spending the minimum of their energy
and time on the labour of building.

330
00:40:05,006 --> 00:40:10,205
The most impressive of all animal homes
are built by the smallest of all labourers.

331
00:40:10,366 --> 00:40:15,838
Termites. They have, to perfection,
all the qualities you could want from a home.

332
00:40:16,006 --> 00:40:21,239
Security, heating, air conditioning
and self-contained nurseries, gardens

333
00:40:21,406 --> 00:40:23,761
and sanitation systems.

334
00:40:23,926 --> 00:40:28,761
Termites of many different species
build their fortresses all over the tropics,

335
00:40:28,926 --> 00:40:33,602
but this kind in Northern Australia
builds a particularly strange one.

336
00:40:33,766 --> 00:40:37,759
It has a very broad flank,
but a very narrow edge,

337
00:40:37,926 --> 00:40:42,761
and it's so placed that the flank catches
the full strength of the early morning sun

338
00:40:42,926 --> 00:40:45,486
so that now it's almost painful to touch.

339
00:40:45,646 --> 00:40:47,443
But...

340
00:40:47,606 --> 00:40:50,962
..on the other side,
in the shade, it's quite cool.

341
00:40:51,126 --> 00:40:55,085
What is more,
all the hills here are placed in this way,

342
00:40:55,246 --> 00:40:58,841
with their narrow edges
pointing north and south,

343
00:40:59,006 --> 00:41:01,566
which is why they are called magnetic termites.

344
00:41:01,726 --> 00:41:05,958
But, in fact, this orientation
has got nothing to do with magnetism

345
00:41:06,126 --> 00:41:08,515
and everything to do with heat.

346
00:41:09,526 --> 00:41:13,644
Termites don't like the cold
and are easily overheated.

347
00:41:13,806 --> 00:41:20,041
And by building their hills in this way,
they manage to avoid both those disasters.

348
00:41:20,206 --> 00:41:25,439
In the morning, the termites move to the eastern
side, which is warmed by the rising sun.

349
00:41:25,606 --> 00:41:28,359
By midday, the danger is overheating,

350
00:41:28,526 --> 00:41:32,519
but now only the knife edge along the top
catches the sun.

351
00:41:34,126 --> 00:41:37,118
(THUNDER)

352
00:41:38,086 --> 00:41:42,876
Most termites deal with temperature extremes
by retreating below ground

353
00:41:43,046 --> 00:41:47,915
where conditions are very stable, but these ones
live in places that are flooded each year

354
00:41:48,086 --> 00:41:50,475
so they have to remain high in their mansions,

355
00:41:50,646 --> 00:41:55,276
and unless they build homes of this particular
shape, they would either overheat,

356
00:41:55,446 --> 00:41:57,835
be chilled or drown.

357
00:41:59,646 --> 00:42:02,114
But it's to West Africa you must go

358
00:42:02,286 --> 00:42:06,199
if you want to see
the ultimate in termite architecture,

359
00:42:06,366 --> 00:42:10,245
the biggest, the most complex
and most subtly sophisticated

360
00:42:10,406 --> 00:42:12,601
of all their buildings.

361
00:42:13,966 --> 00:42:18,403
This immense fortress,
towering 15 feet above me,

362
00:42:18,566 --> 00:42:21,364
is the work of a Nigerian termite.

363
00:42:21,526 --> 00:42:26,554
But what could be in these towers?
They sound hollow...

364
00:42:26,726 --> 00:42:29,399
There's an easy way to find out.

365
00:42:33,686 --> 00:42:38,282
Very little.
This long chimney is virtually empty.

366
00:42:40,526 --> 00:42:45,520
To find the inhabitants, you have to
penetrate much further into the nest.

367
00:43:12,646 --> 00:43:17,436
The workers are continually building,
constructing magnificent arches,

368
00:43:17,606 --> 00:43:20,245
vaults and corridors.

369
00:43:28,686 --> 00:43:31,678
Among them are the bigger soldiers,

370
00:43:31,846 --> 00:43:36,317
their huge heads filled with the muscles needed
to power their great jaws.

371
00:43:41,526 --> 00:43:46,759
Each worker places its pellet of mud
in a position demanded by a master plan.

372
00:43:46,926 --> 00:43:50,965
How they're able to do so,
we don't begin to understand.

373
00:43:51,126 --> 00:43:57,201
They store their food - dead wood -
in special chambers throughout the nest.

374
00:43:57,366 --> 00:44:01,245
Wood is very hard to digest,
but they extract the most from it

375
00:44:01,406 --> 00:44:05,524
by first eating it and then
cultivating a fungus on their dung,

376
00:44:05,686 --> 00:44:08,405
which extracts more of the nutriment.

377
00:44:08,566 --> 00:44:10,761
They then eat the fungus.

378
00:44:10,926 --> 00:44:14,441
This fungus grows nowhere else
but inside termite hills,

379
00:44:14,606 --> 00:44:18,281
where the temperature is exactly right for it.

380
00:44:21,166 --> 00:44:25,159
In the very heart of the fortress
lives the queen.

381
00:44:33,246 --> 00:44:35,806
She produces a thousand eggs a day,

382
00:44:35,966 --> 00:44:40,084
to provide fresh recruits
for the teams of gardeners and masons

383
00:44:40,246 --> 00:44:42,680
and the ranks of the army.

384
00:44:47,886 --> 00:44:52,516
She resides in a special chamber
which the workers renovate and adapt

385
00:44:52,686 --> 00:44:55,200
to accommodate her growing bulk.

386
00:44:55,366 --> 00:44:58,244
After a year or two she is, in effect, a prisoner,

387
00:44:58,406 --> 00:45:02,843
for she's far too big to squeeze
through the corridors of her residence.

388
00:45:03,006 --> 00:45:05,236
But that is of no consequence.

389
00:45:05,406 --> 00:45:10,196
She's so bloated with egg-producing
that she couldn't move even if she wanted to.

390
00:45:10,366 --> 00:45:12,880
And her eggs, as she produces them,

391
00:45:13,046 --> 00:45:18,040
are carried away to the nurseries
by the attentive, indefatigable workers.

392
00:45:19,286 --> 00:45:23,325
There are a million and a half insects
in this one colony.

393
00:45:23,486 --> 00:45:26,444
They and their gardens generate a lot of heat.

394
00:45:26,606 --> 00:45:31,475
Within this enclosed building
the air could easily become foul and hot.

395
00:45:31,646 --> 00:45:35,002
The fungus and therefore
the colony itself would die

396
00:45:35,166 --> 00:45:40,194
if the temperature varies more
than two degrees from 31 degrees centigrade.

397
00:45:40,366 --> 00:45:45,201
But the colony has a solution,
and it's an architectural one.

398
00:45:50,006 --> 00:45:54,443
This...six feet beneath the surface
of the earth,

399
00:45:54,606 --> 00:45:56,915
is the cellar of the colony.

400
00:45:58,086 --> 00:46:02,557
Its floor is studded with shafts
that go down 12-14 feet,

401
00:46:02,726 --> 00:46:09,438
down to the water table, where worker termites
can gather moist mud to carry on their building.

402
00:46:09,606 --> 00:46:12,325
And its ceiling is a great plate

403
00:46:12,486 --> 00:46:15,319
which carries the entire weight of the colony.

404
00:46:15,486 --> 00:46:18,558
But on its underside is what I think is

405
00:46:18,726 --> 00:46:22,560
really the most remarkable
animal structure I've ever seen.

406
00:46:22,726 --> 00:46:25,684
Lines of concentric veins.

407
00:46:25,846 --> 00:46:30,397
They are made of mud
and absorb moisture from the colony above,

408
00:46:30,566 --> 00:46:36,084
and, as it evaporates, it leaves
this encrustation of white salts on them.

409
00:46:36,246 --> 00:46:41,001
But more important than that,
as it evaporates, it cools,

410
00:46:41,166 --> 00:46:45,762
so that this, the cellar,
is much the coolest part of the colony.

411
00:46:50,406 --> 00:46:53,921
And it's this that drives the air-conditioning.

412
00:46:54,086 --> 00:46:58,204
The air, heated by all the activity
in the middle of the building,

413
00:46:58,366 --> 00:47:01,278
rises up into the upper storeys.

414
00:47:01,446 --> 00:47:05,405
But this basement,
thanks to these veins, is many degrees colder.

415
00:47:05,566 --> 00:47:09,639
It draws down the stale warm air
from the colony above,

416
00:47:09,806 --> 00:47:15,324
down long chimneys
which go right round the edge of the cellar.

417
00:47:15,486 --> 00:47:18,080
As it does so, there's a seepage of gas

418
00:47:18,246 --> 00:47:20,635
through porous dimples in the walls.

419
00:47:20,806 --> 00:47:23,878
0xygen flows in and carbon dioxide out,

420
00:47:24,046 --> 00:47:27,755
so that the mixture approximates to fresh air.

421
00:47:30,206 --> 00:47:34,245
So these spires and turrets are key elements

422
00:47:34,406 --> 00:47:37,637
in an air-conditioning system
of a near-perfect mansion

423
00:47:37,806 --> 00:47:43,005
that has stout walls to protect its inhabitants
from the elements and from their enemies,

424
00:47:43,166 --> 00:47:45,726
deep dungeons where they can gather moisture,

425
00:47:45,886 --> 00:47:49,242
space inside for barns to store their food,

426
00:47:49,406 --> 00:47:51,874
and gardens where they grow their crops.

427
00:47:52,046 --> 00:47:56,961
And yet all this was built
by tiny insects with minute brains,

428
00:47:57,126 --> 00:48:01,722
working in total cooperation
in the complete darkness.

429
00:48:01,886 --> 00:48:06,880
We might like to think that we are
the most accomplished architects in the world,

430
00:48:07,046 --> 00:48:12,757
but if this was built in human terms
with every worker termite the size of me,

431
00:48:12,926 --> 00:48:15,998
then it would stand a mile high.

432
00:48:16,166 --> 00:48:18,634
And we haven't done that yet!