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Culture Express
  • 6/20/2025

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02:32To survive on the rocks, small mollusks secrete stout, almost unbreakable shells, and when they're dead and gone, their vacated homes are much sought after.
02:43And in this pool, cut off by the falling tide, there's a large housing market, full of anxious tenants.
02:59This could be just what they're waiting for.
03:02Permit crabs have found the easiest of all solutions to the housing problem, using somebody else's.
03:20There is, of course, a major difficulty.
03:23As a householder grows, he needs a bigger house.
03:26This might be one.
03:27A careful check has to be made on the dimensions.
03:33Too big would be almost as bad as too small, because then enemies could pull the occupier out.
03:39It's just a thing.
03:40Now a slightly smaller home is on the market.
03:48And another one, smaller still.
04:16And another hopeful tenant.
04:25Nobody wants to vacate a perfect residence, but they can be forced to leave by strong-arm tactics.
04:32Instead of stealing a hole for yourself, you can dig one.
04:53They're troubled, not with a shortage of houses, but with building sites.
05:02It's the dry season, and this entire flock has chosen one sandbank in the middle of the Niger River.
05:22It is indeed a very desirable site.
05:25For one thing, insects hatching from the river provide a lot of food.
05:29For another, being surrounded by water, it's protected from land predators.
05:34And most importantly, it's sand, recently exposed by the falling water, is free of vegetation and loose.
05:41Much easier to dig in than the vertical riverbanks and cliffs that most other kinds of bee eaters use.
05:48So, rosy bee eaters come from many miles around to nest here.
06:00That means there is great overcrowding.
06:14One benefit from such numbers is that those who haven't got their heads down digging can keep an eye out for danger.
06:29There are, inevitably, quarrels.
06:47A half-dug hole represents a lot of work, and a bird will steal another's if it can.
06:56They work in pairs.
07:04One does the digging, the other chases away strangers who might get in the way.
07:07It's hot work too, but with the river close by, it's easy to take a cool, refreshing dip.
07:23In a month or so, the breeding season will be over, the river will rise again, and the holes will be flooded.
07:38But by then, the young and their parents will have flown, and won't need a home for another year.
07:45But some animals need a hole as a refuge throughout their lives.
07:52The open grasslands of the American West are very exposed places to live.
07:57A small animal sitting around here is very vulnerable, so prairie dogs dig for protection.
08:10And the prairie dog community, like the Beater Colony, has its alarm system.
08:17Below, there's a warm, safe refuge.
08:20The animals are so successful that they can proliferate in huge numbers and form great settlements with hundreds of tunnels and entrances.
08:28I'm in the middle of one of these towns, and there are a couple of dozen burrows within a few yards of me.
08:36But why does the prairie dog build so many elaborately shaped burrows when digging is very hard work?
08:42Well, there's one way to get a clue.
08:44This is a candle which produces a perfectly harmless smoke.
08:48If I light it and put it in the burrow, we can see what happens.
08:56The smoke doesn't all just blow away, but a wisp of it gets carried down along the tunnel
09:01and eventually emerges at another entrance mound 20 yards away.
09:07So, these two holes are connected.
09:11It's obviously useful to have an escape hole if you're pursued into your burrow by, say, a wild ferret,
09:16but there's more to it than that.
09:19One of the problems about having a long burrow like this is that it can get very stuffy.
09:25And the prairie dog deals with that problem by building two differently shaped entrances.
09:32One is low to the surface of the prairie like that, and the other has this mud tower built around it.
09:39Wind blowing over the prairie moves faster a foot above ground than it does at ground level.
09:45So, a breeze moving across this entrance will suck out the stale air from the burrow.
09:52The prairie dog, in fact, has a home with air conditioning.
09:57So, no matter how long the prairie dog remains underground, the air of its home remains fresh.
10:10This refuge was not dug, it was woven from silk.
10:25Only spiders and insects have the ability to produce silk,
10:29and this strange insect, a web spinner, has spinnerets on the end of its forelegs, like boxing gloves.
10:36This is a long-term pattern of all the prairie can see on the other side of the desert.
10:47You can see as the dragon and a cloud of the prairie can see on the other side.
10:54Caterpillars have spinnerets just inside the mouth.
11:09The silk comes out in one continuous filament,
11:12and a single moth caterpillar can produce a thread 3,000 feet long.
11:16This marvellous substance still provides human beings
11:20with one of the most luxurious of all their fabrics.
11:22The caterpillar uses it to build the protective cocoon
11:26within which it will transform itself into an adult winged moth.
11:45Tent caterpillars build cooperatively.
11:48Their mother laid a batch of 300 or so eggs,
11:54and now all the hatchlings are erecting a communal shelter.
12:06As the caterpillars grow in size, they need more space,
12:09and they continually add new floors to their dwelling.
12:12Each tent acts rather like a greenhouse.
12:23The air trapped inside is quickly warmed by the sun
12:26so that early in the morning the caterpillars are ready to set out
12:29to look for leaves just that little bit earlier
12:32than other species that might be competing with them.
12:34Silk is such a useful building material
12:59that others who can't make it steal it.
13:02A hermit hummingbird uses sticky spider silk
13:10to bind her nest to the edge of a leaf.
13:13Flying round and round as only a hummingbird can with a strand in her beak,
13:25she creates a suspended nest sheltered from the rain beneath the roof of the leaf
13:30and far more difficult for predators to reach or even find than one placed on a branch or on the ground.
13:46The Indian tailor bird also uses silk, not to bind, but to stitch.
13:53The Indian tailor bird also uses silk, not to bind but to stitch.
13:58She searches all the bushes around for her silk threads.
14:20With this spectacular feat of craftsmanship, she converts two floppy leaves into a single firm cup.
14:49It 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.
15:11The leaves form excellent protection from the rain, and there's nowhere you need it more than here in the tropical rainforest.
15:17Many of the animals that live here feed on fruit, and if their shelters are permanent ones, like a cave or a hollow tree,
15:24they may have to travel long distances back and forth every day in order to find a fruiting tree.
15:29It's much more convenient to have temporary encampments.
15:31And no creature uses leaves more elegantly for that purpose than those that are living under this leaf.
15:38They've cut through these side ribs so that the leaf flops so that the leaf flops down and forms a perfect watertight temperament.
15:45And there they are.
15:47Tent-making bats, the size of golf balls and pure white, that the light filtering through the leaf makes them look green.
15:54They'll only use this shelter for a few nights, and then they'll be off to another leaf near another fruiting tree.
16:01But you can use leaves in a much more radical way than this to build a home.
16:09Weaver birds are the great experts.
16:14They'll be off to another leaf near another fruiting tree.
16:19But you can use leaves in a much more radical way than this to build a home.
16:24Weaver birds are the great experts.
16:27It's the males who do the building.
16:37The first step is to tie a leaf strip onto a twig.
16:41It's not easy, for the fibre is very springy.
16:44The trick is to keep a firm hold on it with one foot.
16:59Then you can tie the knot with your beak.
17:02It's a simple half hitch, but a firm one, and all subsequent work will literally depend on it.
17:20Notting takes practice, and this young bird is having a little trouble.
17:25The next step is to weave a ring.
17:37But you can't do that until you've got the first knot right.
17:43The ring has got to be big enough to allow its maker to slip through,
18:03and not so big that it will allow larger animals to do so.
18:07But it certainly mustn't be too small.
18:19The strips have to be fresh and supple, and the birds get supplies from a patch of grass nearby.
18:24They tear off the strips by gripping the side of the grass blade close to the ground,
18:29and then simply flying straight up.
18:36Over a thousand of these strips are needed for a single nest.
18:43Once the ring is complete and firm, work starts on the roof.
18:47The novice still has his problems.
19:07Their technique, in essence, is the same as that used by human weavers.
19:11A strip is threaded alternately above and below a series of strips that run at right angles to it.
19:16In the beak of a master craftsman, this produces neat and beautiful results.
19:32In less skilful beaks, well, not so good, but he's learning.
19:37Very critical eyes are watching progress.
19:53A female selects her mate largely on his ability as a weaver,
19:57and he calls attention to it with his fluttering wings.
20:09But others have the same idea.
20:11She flies over to have a look.
20:27The novice is clearly being a little optimistic.
20:30No one is taking any notice.
20:32She flies over to a thornswishman,
20:33and she does really think of a bird.
20:36And eventually she makes her choice.
20:38choice.
20:47This looks neat enough, but it's not yet won him a mate.
20:55But this bird, luckier or more skilful, has, and now he can get on with finishing the job.
21:08The whole construction is completed by adding, with a rather looser weave, a long downward
21:14pointing entrance tube.
21:19This will deter unwelcome visitors.
21:27If after a few days a weaver hasn't managed to attract a partner, then all his work is
21:32wasted, for a female never chooses a nest that is so old that it's turned brown.
21:38There's only one thing to be done.
21:43He'll have to start all over again.
21:45And that means dismantling his first attempt.
21:49This is the only place he can build, because all the rest of the sites are occupied.
21:54And dismantling it is almost as hard work as weaving it.
22:08On rocky cliffs like this, the problem is not so much shortage of sites for the nest, but
22:15of material with which to build it.
22:18Shags like to have just something to cushion their breakable eggs and stop them rolling about.
22:23But there's not much around, except for what the sea washes up.
22:26And that's a very mixed bag indeed.
22:30Of course, there's an easier way of getting stuff than carrying it all away from the seashore.
22:37of course, there's an easier way of getting stuff than carrying it all away from the seashore.
22:56of course, there's an easier way of getting stuff than carrying it all away from the seashore.
23:03But if you're caught red-handed, there's big trouble.
23:28When material is in such short supply, almost anything will do.
23:58Even the beak and bones of another bird, a tern, or the dried corpse of a rabbit.
24:19There's no shortage of building material here.
24:25Particularly if you build in wood, which is the life-long preoccupation of this animal.
24:36It's a beaver.
24:37It's a beaver.
24:38It's a beaver.
24:41×™×›elen ruffinet
24:45It's a beaver.
24:49You can feel more at all.
24:52MUSIC PLAYS
25:22all animal constructions. It's a dam that's blocked this valley and built up behind it
25:27a sizeable lake. Its foundations are sticks that have been rammed vertically into the
25:33bed of the stream. Horizontal poles have been laid across those and then boulders dumped
25:39on it to give the whole thing weight. The downstream side slopes gently and is buttressed
25:45with poles. The upstream is more vertical and faced with mud. It was designed, built
25:51and maintained by a family of beavers over decades and handed down from one generation
25:57to the other. If ever there was an ancestral pile, this is it. Such large properties need
26:06constant care and attention. Every dam has to have a spillway to carry away the continual
26:12flow of the stream. After heavy rains, it has to be enlarged to allow the rising water to
26:18escape before it bursts the dam. And when the flood subsides, the dam has to be built
26:23up again.
26:41The beavers have very clear ideas about the exact position for any one piece and labour
26:47away until they get it just right. Large beams are needed for structural strength.
27:10Small twigs, leaves and mud are essential to plug the gaps.
27:30The purpose of all this labour is to create a lake. During the summer they sink branches
27:35in it. When winter comes and the lake is frozen over, they will dive beneath the ice to retrieve
27:41the still green leaves from cold storage. But it has another purpose too. It makes their
27:46home virtually impregnable.
27:56This is the lodge. The family residence. There seems to be no way into it. That's because
28:13the entrance in fact is underwater, just about here. So you have to be a skilled swimmer and
28:19underwater diver to get into the residence. In fact, it's a pretty well burglar-proof home.
28:25But impressive though it is, and ingenious though the beavers are, in utilising wood, they
28:30do little more than cut it up into convenient lengths. However, there are some animals that
28:36have discovered how to process wood and turn it into an altogether more malleable material.
28:46Wasps chew up wood, mix it with their saliva, and make it into a fine paste which dries into a material that
28:53is both lightweight and strong. Paper.
28:58The common European wasp produces a very high quality paper, and with it builds nests of great
29:05perfection. Within these identical hexagonal cells, a huge workforce is raised to serve the
29:11queen and maintain the nest.
29:13This tiny Malaysian hover wasp is one of the least ambitious wasp builders. Her nest of rather crumbly paper
29:28is just a few open cells on a stem.
29:31These are clearly vulnerable to the elements and predators, but she protects them from their main
29:39enemies, ants, by smearing the egg in each cell and wringing the stem with a sticky repellent
29:45that blocks access all round.
29:48This nest is suspended from the ceiling of a cave by a narrow paper stalk. It's well protected from the
29:59weather, but the females guarding the open cells must be ever watchful for raiders.
30:18Other species protect their young by building a paper wall around the cells.
30:23They often pattern it by using different coloured materials to give some degree of camouflage,
30:27and with only a single entrance, the nest is readily defendable.
30:34But some predators are unstoppable.
30:37This nest has been wrecked and its young stolen by another member of the wasp family, a giant hornet.
30:43This bandit is a merciless eater of the larvae of other species, and few nests are safe from it.
30:51Bees construct their defences with a substance that no other animal produces, wax.
30:57The workers secrete it from glands on their abdomen and derive it from honey combined with fat.
31:03Tropical stingless bees mix it with resin and build entrance tubes to their nest within the trunk of the tree.
31:10These tubes often take bizarre shapes.
31:16But they all have a narrow entrance, often flared into a landing platform,
31:20which is heavily guarded by platoons of sentries who vet every arrival.
31:31Inside, the workers' labour, building a maze of interconnecting struts and plates to support the brood combs.
31:38The resin stiffens the waxy structures and antibiotic chemicals within it reduce the risks of infection.
31:56Those cells that will contain young are first three quarters filled with pollen, then the huge queen comes over to inspect them.
32:10As soon as the cell's provisioning is complete, the queen drops an egg into it, and immediately one of the workers seals off the top with wax.
32:26In a separate part of the nest, there are special pots for storing honey.
32:29In a separate part of the nest, there are special pots for storing honey.
32:30This is why they must use wax.
32:33Paper cells couldn't hold.
32:34In a separate part of the nest, there are special pots for storing honey.
32:39This is why they must use wax. Paper cells couldn't hold liquid.
32:46They will be filled to the brim, for their contents are the reserves for times when there's little or no food to be found outside.
32:51In a separate part of the nest, there are special pots for storing honey.
32:55Wax is certainly a superb building material, malleable, strong and capable of holding liquids, but it's very expensive to produce.
33:20Mud is much cheaper.
33:37These pea-sized vessels are the work of another kind of wasp, a potter wasp.
33:49Once again, saliva is an important ingredient.
33:55It prevents the mud from crumbling when it dries.
33:58With jaws scissoring away on the inside to keep the mud properly mixed and fluid,
34:03and front legs checking the thickness of the wall on the other,
34:06she lays the mud round and round in a strip, using a technique that human potters call coiling.
34:12When 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.
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34:53In goes an egg.
35:20Now the cells must be provisioned.
35:22A potter wasp doesn't feed her larvae on chewed bodies, nor does she supply honey.
35:27She gives it living food, a caterpillar paralyzed by her sting.
35:32The lip, built so carefully around the entrance, helps to guide it in.
35:37The mouth of the pot will then be sealed with a clay pellet and the lip removed.
35:53The larvae, having eaten its caterpillar and turned into an adult, emerges by breaking through the side of the pot.
36:00But although abandoned, the tough pots survive for several years.
36:04These much bigger mud constructions were built by cliff swallows in the American Midwest.
36:13Protected from winter rain, they too may last for several years.
36:17Each spring the birds fly up from Argentina.
36:23They arrive in a flock and together, as a flock, inspect the old tenements they occupied last year.
36:28Their favoured building sites are beneath natural overhangs.
36:47The trouble is, there are not many of them, so they readily take advantage of a man-made one, if they can find it.
36:58But of course, old buildings do have their disadvantages.
37:02They can be infested with vermin, optimistically waiting to parasitize the new occupants.
37:11The decision of whether to reoccupy a particular site is taken by the flock as a whole.
37:15Once they've made it, then each pair claims a nest and starts smartening it up.
37:28And they notice a bird may have to get the mud as it wants it,
37:54To get the mud as it wants it,
37:56a bird may have to gather some really wet material from the water's edge
38:00and then mix it in its mouth with drier mud from farther back.
38:24.
38:49The consistency of the mud is crucial.
38:52If it's too dry, it won't stick.
38:54But if it's too sloppy, it's very difficult to handle.
39:00And working upside down with it can be a real problem.
39:04When the chicks hatch, the price of using old buildings may have to be paid.
39:16These, whose parents chose their home wisely, are fit enough.
39:28But in other nests, the parasites have had a feast and are proliferating.
39:32These young swallows will probably not survive.
39:44But most do.
39:49Their parents succeeded in raising them, while at the same time,
39:53spending the minimum of their energy and time on the labour of building.
39:57The most impressive of all animal homes are built by the smallest of all labourers.
40:09Termites.
40:10They have, to perfection, all the qualities you could want from a home.
40:15Security, heating, air conditioning, and self-contained nurseries, gardens, and sanitation systems.
40:21Termites, of many different species, build their fortresses all over the tropics.
40:27But this kind, in northern Australia, builds a particularly strange one.
40:32It has a very broad flank, but a very narrow edge.
40:36And it's so placed that the flank catches the full strength of the early morning sun,
40:41so that now, it's almost painful to touch.
40:45But, on the other side, in the shade, it's quite cool.
40:50What is more, all the hills here are placed in this way,
40:54with their narrow edges pointing north and south,
40:58which is why they're called magnetic termites.
41:01But in fact, this orientation has got nothing to do with magnetism,
41:05and everything to do with heat.
41:08Termites don't like the cold, and are easily overheated.
41:13And by building their hills in this way,
41:16they manage to avoid both those disasters.
41:19In the morning, the termites move to the eastern side,
41:22which is warmed by the rising sun.
41:25By midday, the danger is overheating.
41:28But now, only the knife edge along the top catches the sun.
41:38Most termites deal with temperature extremes by retreating below ground,
41:42where conditions are very stable.
41:44But these termites live in places that are flooded each year.
41:47So they have to remain high in their mansions,
41:50and unless they build homes of this particular shape,
41:53they would either overheat, be chilled, or drown.
41:57But it's to West Africa you must go,
42:01if you want to see the ultimate in termite architecture.
42:04The biggest, the most complex,
42:06and the most subtly sophisticated of all their buildings.
42:13This immense fortress towering 15 feet above me
42:17is the work of a Nigerian termite.
42:20But what could be in these towers?
42:23They sound hollow.
42:26Well, there's an easy way to find out.
42:33Very little.
42:34This long chimney is virtually empty.
42:40To find the inhabitants,
42:41you have to penetrate much further into the nest.
42:50The workers are continually building,
43:14constructing magnificent arches, vaults, and corridors.
43:18Among them are the bigger soldiers,
43:30their huge heads filled with the muscles needed
43:33to power their great jaws.
43:40Each worker places its pellet of mud
43:43in a position demanded by a master plan.
43:45Though how they're able to do so,
43:47we don't begin to understand.
43:50They store their food, dead wood,
43:52in special chambers throughout the nest.
43:56Wood is very hard to digest,
43:58but they extract the most from it
44:00by first eating it,
44:01and then cultivating a fungus on their dung,
44:04which extracts more of the nutriment.
44:07They then eat the fungus.
44:09This fungus grows nowhere else but inside termite hills,
44:13where the temperature is exactly right for it.
44:20In the very heart of the fortress lives the queen.
44:23She produces a thousand eggs a day to provide fresh recruits
44:36for the teams of gardeners and masons and the ranks of the army.
44:40She resides in a special chamber,
44:49which the workers renovate and adapt to accommodate her growing bulk.
44:53After a year or two she is in effect a prisoner,
44:57for she's far too big to squeeze through the corridors that lead to her residence.
45:01But that is of no consequence.
45:03She's so bloated with egg-producing machinery
45:06that she couldn't move even if she wanted to.
45:09And her eggs, as she produces them,
45:11are carried away to the nurseries by the attentive and indefatigable workers.
45:18There are a million and a half insects in this one colony.
45:22They and their gardens generate a lot of heat.
45:25Within this enclosed building the air could easily become foul and hot.
45:30The fungus, and therefore the colony itself,
45:33would die if the temperature varies by more than two degrees from 31 degrees centigrade.
45:39But the colony has a solution and it's an architectural one.
45:43This, six feet beneath the surface of the earth,
45:53is the cellar of the colony.
45:56Its floor is studded with shafts that go down 12, 14 feet,
46:01down to the water table,
46:03where the worker termites can gather moist mud to carry on their building.
46:08And its ceiling is a drape plate
46:11which carries the entire weight of the colony.
46:14But on its underside,
46:16is what I think is really the most remarkable animal structure I've ever seen.
46:21Lines of concentric veins.
46:24They are made of mud and they absorb moisture from the colony above.
46:29And as it evaporates, it leaves this encrustation of white salts on them.
46:35But more important than that,
46:37as it evaporates, it cools.
46:40So that this, the cellar, is much the coolest part of the colony.
46:49And it's this that drives the air conditioning.
46:52The air, continuously heated by all the activity in the middle of the building,
46:57rises up into the upper stories.
46:59But this basement, thanks to these veins, is many degrees colder.
47:03And it draws down the stale warm air from the colony above,
47:08down long chimneys which go right round the edge of the cellar.
47:14As it does so, there's a seepage of gas through porous dimples in the walls.
47:19Oxygen flows in and carbon dioxide out,
47:22so that the mixture approximates to fresh air.
47:25So these spires and turrets are key elements in an air conditioning system of a near-perfect mansion,
47:36that has stout walls to protect its inhabitants from the elements and from their enemies,
47:41deep dungeons where they can gather moisture,
47:44space inside for barns where they can store their food,
47:48and gardens where they can grow their crops.
47:50And yet all this was built by tiny insects with minute brains,
47:55working in total cooperation in the complete darkness.
48:00We might like to think that we are the most accomplished architects that the world has ever seen,
48:05but if this was built in human terms with every worker termite the size of me,
48:11then it would stand a mile high.
48:14And we haven't done that yet.
48:20THE END
48:24THE END
48:43THE END