Home Making The Trials of Life

Twenty thousand years ago, this cave in Wales was home for human beings.

We know because their bones have been found here.

It's good. You're out of the wind and the rain. You can make a fire,

and you've got a reasonable chance of defending yourself against your enemies, whether human or animal.

In short, here, you've got some control over your surroundings and you can make yourself comfortable.

Animals find homes for themselves for the same sort of reasons.

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

But others build ingenious and elaborate structures to shield themselves from a hostile world.

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

Continuously pounded by waves, submerged twice every 24 hours

and twice exposed to the air.

To survive on the rocks,

small molluscs secrete almost unbreakable shells.

When they're gone their homes are sought-after.

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

there's a large housing market, full of anxious tenants. This could be what they want.

Hermit crabs have found the easiest of all solutions to the housing problem using somebody else's.

There is, of course, a major difficulty.

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

Dimensions are carefully checked. Too big is as bad as too small.

Enemies could pull an occupier out.

It's just the thing!

Now a slightly smaller home is on the market.

And another one, smaller still.

And another hopeful tenant.

Nobody wants to vacate a perfect residence,

but they can be forced to leave by strongarm tactics.

Instead of stealing a hole for yourself,

you could dig one.

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

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

It's the dry season. This entire flock has chosen one sandbank in the middle of the Niger River.

The site's desirable. Insects hatch from the river and provide food.

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

Above all, its sand, recently exposed by the falling water, is free of vegetation, and loose.

Much easier to dig in than the vertical river-banks and cliffs most other kinds of bee-eaters use.

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

That means there is great overcrowding.

One benefit from such numbers

is that those who haven't got their heads down digging can keep an eye out for danger.

There are, inevitably, quarrels.

A half-dug hole represents a lot of work,

and a bird will steal another's if it can.

They work in pairs.

One does the digging, the other chases away strangers who might get in the way.

It's hot work, too!

But, with the river close by,

it's easy to take a cool, refreshing dip.

In a month, the breeding season will be over, the river will rise again and holes will be flooded.

But by then, the young and their parents will have flown and won't need a home for another year.

Some need a refuge throughout life.

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

A small animal sitting around here is very vulnerable.

So prairie-dogs dig for protection.

And the prairie-dog community also has its alarm system.

Below, there's a warm, safe refuge.

The animals are so successful they can proliferate in huge numbers

and form great settlements with hundreds of tunnels and entrances.

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

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

But why build so many elaborately shaped burrows when digging's hard?

There's one way to get a clue. This candle produces a perfectly harmless smoke.

If lit and placed in the burrow

the smoke doesn't just blow away,

but a wisp of it gets carried down along the tunnel, emerging at an entrance mound twenty yards away.

So these two holes are connected.

It's obviously useful to have an escape hole if you're pursued into your burrow by a wild ferret.

But there's more to it than that.

One problem about having a long burrow like this is that it can get very stuffy.

The prairie-dog deals with that problem by building two differently-shaped entrances.

One is low to the surface of the prairie

and the other has this mud tower built around it.

Wind blowing over the prairie moves faster a foot above ground

than it does at ground level.

So a breeze moving across here sucks stale air from the burrow.

It's a home with air-conditioning.

No matter how long the prairie-dog remains underground,

the air of its home remains fresh.

This refuge was not dug, it was woven.

From silk.

Only spiders and insects have the ability to produce silk,

and this strange insect a web-spinner

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

Caterpillars have spinnerets just inside the mouth.

The silk comes out in one continuous filament

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

This substance provides us with one of the most luxurious fabrics.

The caterpillar uses it to build the protected cocoon

within which it will transform itself into an adult winged moth.

Tent caterpillars build co-operatively.

Their mother laid a batch of three hundred or so eggs

and now all the hatchlings are erecting a communal shelter.

As the caterpillars grow in size, they need more space

and they continually add new floors to their dwelling.

Each tent acts rather like a greenhouse.

The air trapped inside is quickly warmed by the sun

so that early in the morning, the caterpillars are ready to set out to look for leaves

just that little bit earlier than other species that might be competing with them.

Silk is such a useful building material that others who can't make it steal it.

A hermit humming-bird uses sticky spider silk to bind her nest to the edge of a leaf.

Flying round and round, as only a humming-bird can,

with a strand in her beak,

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

and more difficult for predators to reach than one on a branch.

The Indian tailor-bird also uses silk,

not to bind, but to stitch.

She searches all the bushes around for her silk threads.

With this spectacular feat of craftsmanship,

she converts two floppy leaves into a single, firm cup.

It may not LOOK strong,

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

and mother and chicks sitting on top.

Leaves form excellent protection from the rain.

You need it nowhere more than here in a tropical rain forest.

Many animals living here feed on fruit.

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

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

Temporary encampments are helpful.

The creatures living under this leaf use it elegantly to this end.

They cut through these side ribs so the leaf flops down to form a watertight tent. There they are!

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

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

They'll only use this shelter for a few nights, then off to another leaf near another fruiting tree.

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

Weaver-birds are the great experts. It's the males who do the building.

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

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

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

then you can tie the knot with your beak.

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

and all subsequent work will literally depend on it.

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

The next step is to weave a ring.

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

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

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

But it certainly mustn't be too small!

The strips have to be fresh and supple, and the birds get supplies from a patch of grass nearby.

They tear off strips by gripping the side of the grass blade close to the ground and then flying up.

Over a thousand of these strips are needed for a single nest.

Once the ring is complete and firm,

work starts on the roof.

The novice still has his problems.

Their technique, in essence, is like that used by human weavers.

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

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

In less skilful beaks,

well...not so good, but he's learning.

Very critical eyes are watching progress.

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

And he calls attention to it with his fluttering wings.

But others have the same idea.

She flies over to have a look.

The novice is clearly being a little optimistic.

No-one is taking any notice.

Eventually, she makes her choice.

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

But this bird, luckier or more skilful, has.

And now he can get on with finishing the job.

Th whole construction is completed by adding, with a looser weave,

a long, downward-pointing entrance.

This will deter unwelcome visitors.

If, after a few days, the weaver hasn't attracted a mate,

then all his work is wasted.

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

There's only one thing to be done.

He'll have to start all over again, dismantling his first attempt.

This is the only place he can build

because all the rest of the sites are occupied,

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

On rocky cliffs like this,

the problem is not so much shortage of sites for the nest, but of material with which to build it.

Shags like to have something to cushion their eggs and stop them rolling about.

But there's not much around, except for what the sea washes up. That's a very mixed bag indeed.

Of course, there's an easier way of getting stuff than carrying it all the way from the seashore.

But if you're caught redhanded there's big trouble!

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

Even the beak and bones of another bird, a tern, or the dried corpse of a rabbit.

There's no shortage of building material here.

Particularly if you build in wood,

which is the life-long preoccupation of this animal.

It's a beaver.

This is one of the most massive of all animal constructions.

It's a dam that's blocked this valley and built up behind it a sizable lake.

Its foundations are sticks that have been rammed vertically into the bed of the stream.

Horizontal poles have been laid across those and then boulders dumped on to give the thing weight.

The downstream side slopes gently, buttressed with poles. Upstream is more vertical, faced with mud.

It was designed, built, maintained by a beaver family over decades.

Passed from one generation to another.

Such large properties need constant care and attention.

Dams need a spillway to carry away the continual flow of the stream.

After heavy rains, it has to be enlarged to allow rising water to escape before it bursts the dam.

And when the flood subsides, the dam has to be built up again.

The beavers have very clear ideas about the exact position for any one piece,

and labour away until they get it just right.

Large beams are needed for structural strength.

Small twigs, leaves and mud are essential to plug the gaps.

The purpose of all this labour is to create a lake.

During the summer, they sink branches in it.

In winter when the lake is frozen over,

they will dive beneath the ice to retrieve the still-green leaves from cold storage.

It has another purpose. It makes their home virtually impregnable.

This is the lodge the family residence.

There seems to be no way into it.

That's because the entrance, in fact, is underwater, about here.

So you have to be a skilled swimmer and an underwater diver to get into the residence.

It's a pretty well burglar-proof home.

Ingenious though the beavers are, they do little more than cut wood up into convenient lengths.

Some animals have discovered how to process wood and turn it into an altogether more malleable material.

Wasps chew up wood,

mix it with their saliva, make it into a fine paste that dries into a light, strong material PAPER.

The common European wasp produces a very high-quality paper,

and, with it, builds nests of great perfection.

Within these identical hexagonal cells, a huge workforce is raised

to serve the queen and maintain the nest.

This tiny Malaysian hover-wasp is one of the least ambitious wasp builders.

Her nest of rather crumbly paper is just a few open cells on a stem.

These are clearly vulnerable to the elements and predators,

but she protects them from their main enemies ants

by smearing the egg in each cell and ringing the stem with a sticky repellent that blocks access.

This nest is suspended from the ceiling of a cave by a narrow paper stalk.

It's well-protected from weather

but the females guarding the open cells must be ever-watchful for raiders.

Other species protect their young by building a paper wall around the cells.

They often pattern it by using different coloured materials to give some degree of camouflage.

With only a single entrance, the nest is readily defendable.

But some predators are unstoppable.

This nest has been wrecked and its young stolen by a giant hornet.

It's a merciless eater of larvae of other species. Few nests are safe.

Bees construct their defences with a substance no other animal produces wax.

Workers secrete it from abdominal glands. It is honey, combined with fat.

Tropical stingless bees mix it with resin and build entrance tubes to their nest within the tree-trunk.

These tubes often take bizarre shapes.

All have a narrow entrance, often flared into a landing platform,

which is heavily guarded by platoons of sentries

who vet every arrival.

Inside, the workers labour,

building a maze of interconnecting struts and plates to support the brood cones.

The resin stiffens the waxy structures

and antibiotic chemicals within it

reduce the risks of infection.

Those cells that will contain young

are first three-quarters filled with pollen.

Then the huge queen comes over to inspect them.

As soon as the cell's provisioning is complete, the queen drops an egg into it.

Immediately, one of the workers seals off the top with wax.

In a separate part of the nest, there are special pots for storing honey.

This is why they must use wax.

Paper cells couldn't hold liquid.

They will be filled to the brim,

for their contents are the reserves for the times when there's little or no food to be found outside.

Wax IS a superb building material, but very expensive to produce.

MUD is much cheaper!

These pea-sized vessels are the work of another kind of wasp.

A potter wasp.

Once again, saliva is an important ingredient.

It prevents the mud from crumbling when it dries.

With jaws scissoring away on the inside, to keep the mud properly mixed and fluid,

and front legs checking the thickness of the wall on the other,

she lays the mud round in a strip, using a technique potters call coiling.

When the main body of the pot is finished, this greatly-accomplished potter brings another ball of mud

and adds a final and most elegant flourish.

In goes an egg.

Now the cells must be provisioned.

A potter wasp doesn't feed her larvae on chewed bodies,

nor does she supply honey.

She gives it living food a caterpillar, paralysed by her sting.

The lip, built so carefully around the entrance, helps to guide it in.

The pot mouth is then sealed with a clay pellet, and the lip removed.

The larva, having eaten its caterpillar, and become an adult,

emerges by breaking through the pot's side. The pots survive for several years.

These much bigger mud constructions

were built by cliff swallows in the American Midwest.

Protected from winter rain, they too may last for several years.

Each spring, the birds fly up from Argentina.

They arrive in a flock and, as a flock, inspect the old tenements they occupied last year.

Their favourite building sites are beneath natural overhangs.

The trouble is, there are not many of them,

so they readily take advantage of a man-made one, if they can find it.

Old buildings have disadvantages.

They can be infested with vermin, optimistically waiting to parasitise the new occupants.

The flock as a whole decide whether to reoccupy a particular site.

Once they've decided, each pair claims a nest and smartens it up.

To get the mud as it wants it,

a bird may have to gather some wet material from the water's edge

and then mix it in its mouth with drier mud from farther back.

The consistency of the mud is crucial.

If it's too dry, it won't stick.

If too sloppy, it's hard to handle.

And working upside-down with it can be a real problem!

When the chicks hatch, the price of using old buildings may have to be paid.

These, whose parents chose their home wisely, are fit enough.

But in other nests the parasites have had a feast and are proliferating.

These young swallows will probably not survive.

But most do. Their parents succeeded in raising them,

while, at the same time, spending the minimum of their energy and time on the labour of building.

The most impressive of all animal homes are built by the smallest of all labourers.

Termites.

They have, to perfection, ALL the qualities you'd want from a home.

Security, heating, air-conditioning and self-contained nurseries, gardens and sanitation systems.

Termites of many different species build their fortresses all over the Tropics.

This kind, in northern Australia, builds a particularly strange one.

It has a broad flank, a narrow edge and is placed so the flank catches the full strength of morning sun,

so it's almost painful to touch.

But, on the other side, it's cool.

What is more, all the hills here are placed in this way,

with their narrow edges pointing north and south,

which is why they're called magnetic termites.

This orientation has nothing to do with magnetism,

and everything to do with heat.

Termites don't like the cold and are easily overheated.

Here, they avoid both disasters.

Morning finds them on the eastern side, warmed by the rising sun.

By midday, the danger is overheating.

But now, only the knife edge along the top catches the sun.

Most termites deal with temperature extremes by retreating below ground where conditions are very stable.

But these termites live in places that are flooded each year

and unless they build homes of this particular shape they'd overheat, be chilled or drown.

But it's to West Africa that you must go if you want to see the ultimate in termite architecture.

The biggest, the most complex and the most subtly sophisticated of all their buildings.

This immense fortress, towering fifteen feet above me,

is the work of a Nigerian termite.

But what could be in those towers?

They sound...hollow. There's an easy way to find out.

Very little.

This long chimney is virtually empty.

To find the inhabitants, you have to penetrate much further into the nest.

The workers are continually building,

constructing magnificent arches, vaults and corridors.

Among them are the bigger soldiers,

their huge heads filled with the muscles needed to power their great jaws.

Each worker positions a mud pellet as demanded by a master plan,

though how they are able to do so we don't begin to understand.

They store their food, dead wood, in special chambers throughout the nest.

Wood is very hard to digest but they extract the most from it by first eating it

and then cultivating a fungus on their dung which extracts more of the nutrient.

They then eat the fungus. It grows only inside termite hills, where the temperature is exactly right.

In the very heart of the fortress,

lives the queen.

She produces a thousand eggs a day

to provide fresh recruits for the teams of gardeners and masons

and the ranks of the army.

She resides in a special chamber

which the workers renovate and adapt to accommodate her growing bulk.

After a year or two, she is, in effect, a prisoner as she is too big to squeeze through corridors.

But that is of no consequence.

She's so bloated with egg-producing machinery that she couldn't move, even if she wanted to.

Her eggs, as she produces them, are carried away to nurseries by the attentive, indefatigable workers.

There are 1.5 million insects in this one colony.

They and their gardens generate a lot of heat. Within this enclosed building the air could become foul.

The fungus and colony will die if the temperature varies by over 2 degrees from 31 degrees Centigrade.

But the colony has a solution, and it's an architectural one.

This, six feet beneath the surface of the earth,

is the cellar of the colony.

Its floor is studded with shafts that go down 12, 14 feet,

down to the water table, where the worker termites can gather moist mud to carry on their building.

And its ceiling is a great plate which carries the entire weight of the colony.

But on its underside is what I think is the most remarkable animal structure I've ever seen.

Lines of concentric veins.

They are made of mud and absorb moisture from the colony above.

As it evaporates, it leaves this incrustation of white salts.

But, more important than that, as it evaporates, it cools

so that this, the cellar, is much the coolest part of the colony.

And it's this that drives the air-conditioning.

The air, continuously heated by all the activity in the middle of the building,

rises into the upper storeys.

This basement, many degrees colder, draws down the stale, warm air from the colony above,

down long chimneys which go right round the edge of the cellar.

As it does so, there's a seepage of gas through porous dimples in the walls.

Oxygen flows in, carbon dioxide out.

So these spires and turrets are key elements in an air-conditioning system of a near-perfect mansion

that has stout walls to protect its inhabitants from the elements and their enemies,

deep dungeons where they can gather moisture, space inside for barns where they can store their food,

gardens where they can grow crops.

And yet all this was built by tiny insects with minute brains, working in total co-operation, in darkness.

We might like to think that we are the most accomplished architects that the world has ever seen,

but built in human terms, with each worker termite the size of me, this would stand a mile high.

And we haven't done that yet.

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