- today
Category
📺
TVTranscript
00:00To be continued...
00:30To be continued...
01:00Rajasthan, central India.
01:13It's the middle of the morning, the day is beginning to warm up, and the animal community is in a relaxed mood.
01:21The sambar deer are cooling themselves in the shallows of the lake, looking for a bit of greenery to nibble here and there, and tolerantly taking the egrets for a ride.
01:31The egrets, too, are finding a little to eat, an insect perhaps picked out of the deer's coat.
01:39Nature isn't always red in tooth and claw.
01:42Different kinds of animals are often regular companions and get on well with one another.
01:47In the trees, lango monkeys are finishing their morning meal of leaves.
02:16They're fussy, untidy feeders, and drop a lot of the leaves, either by accident or because they don't fancy those particular ones.
02:31And that suits the spotted deer.
02:36At this time of the dry season, the ground is parched and greenery worth eating very scarce.
02:42So even the smallest fragment of vegetation fallen from above is worth having.
02:47And the deer follow the monkeys from tree to tree, picking up leaves that, by themselves, they couldn't reach.
02:54The monkeys also benefit from the presence of the deer.
03:19They sometimes come down to forage on the ground, and there, of course, they're vulnerable.
03:25The deer, however, have a keener sense of smell than the monkeys, and may detect dangers that the monkeys can't see.
03:31And if they do, they will stamp a warning.
03:34We ourselves have very few such relationships, voluntarily, with other species of animals.
03:56Except, of course, with those animals that we have domesticated and enslaved.
04:01But back in our evolutionary past, we doubtless had many.
04:05Today, maybe, we think they're so powerful, or have become so detached from nature, that we think we no longer need them.
04:13But in the natural world at large, those relationships are widespread.
04:18Sometimes they've been in existence for so long that they have transformed the bodies of the animals concerned.
04:24Sometimes they are only just forming.
04:26This species of goby, for example, that lives around coral reefs, has, probably quite recently, struck up a relationship with a shrimp.
04:37The two regularly live together, sharing the same hull.
04:43But the goby plays no part in making it.
04:46It's dug entirely by the shrimp.
04:48The shrimp, in fact, seems to be a compulsive excavator, never content with its home as it is, always carrying out improvements and digging extensions.
05:07And the goby doesn't help.
05:09In fact, if anything, it gets in the way.
05:14But it's an essential companion for the shrimp, for this species of shrimp is virtually blind.
05:20The goby, on the other hand, has excellent eyesight, and is always on the alert.
05:32The shrimp, as it works, keeps in touch, literally, by continually flicking one of its long antennae over the fish to make sure that it's still there.
05:42As long as the goby is out of the burrow, then the shrimp knows that it's safe to carry on working.
05:47The goby, naturally, is always on the lookout for something to eat, and may have to make little excursions to get it.
06:04A tiny edible morsel that floated by.
06:07But even while it's feeding, the shrimp's antennae is still in touch with it.
06:23Danger.
06:24And when the watchman retreats to safety, so does the shrimp.
06:27The goby, having fed, seems quite content to remain in the hole.
06:38Why expose yourself to danger unnecessarily?
06:41But the shrimp is perpetually keen to work, and often appears to be hustling the goby, as though to persuade it to go out again.
06:48The shrimp collects its food from a little patch of alga that grows beside the burrow entrance.
07:08It knows just where that is, so it can nip across quickly and snatch a few clawfuls with the minimum of risk.
07:14All is well, as long as the shrimp keeps in touch with the goby.
07:34But if it ventures away, then there can be trouble.
07:37That was an anemone it blundered into, and it beats a swift retreat.
07:43For a moment, it seems lost.
07:50Then the goby comes over, and contact is re-established.
07:55The partners are together again, and all is well.
07:58So, two very different animals operate a partnership.
08:15The blind landlord provides the accommodation, and the tenant provides a guidance service.
08:24Hermit crabs live in a different kind of home.
08:27Instead of a hole, they use an empty shell, but they, too, confine themselves with lodgers.
08:44This one's companion is a ragworm.
08:47For the worm, this is a good place to be.
09:09It has an excellent home, where it's safe from predators, curled up inside the shell alongside the crab's abdomen.
09:15And on its very doorstep, there's a regular supply of food brought there by the crab.
09:23Nonetheless, collecting a share of that food seems a fairly risky business.
09:28The crab's mandibles could easily chop the worm's head off, but the worm has had a lot of practice at this sort of thing.
09:39Whether the crab gets any benefit at all from the arrangement is rather doubtful,
09:43but there's not much it can do to get rid of its lodger, anyway.
09:47A small octopus.
10:03Hermit crabs are one of its favorite foods.
10:05It's a very famous rod board.
10:08A small octopus.
10:22Thiago and the tip of crab worm.
10:24A small octopus.
10:25In the center of those writhing arms, it has a powerful beak with which it can drag the crab from its shell.
10:42And that's the end of both the hermit crab and its lodger.
10:55But this species of hermit crab recruits a bodyguard.
11:00Anemones have stings in their tentacles, stings that are quite strong enough to repel an octopus.
11:08Since the crab wanders about a great deal, its bodyguard, to be any good, has to travel with it.
11:14It's not easy to unstick an anemone from a rock, but the crab knows the trick.
11:29You have to tickle it around the edge of its bottom.
11:44It's a première to be removed.
11:45You can see the anemone is almost alive.
11:47It's just fuzzy.
11:48It's stillゴム with eggs, but it's not veryぜ.
11:49It's just fuzzy.
11:50And it's it.
11:51But this is used by anemones.
11:52It's always been pushed.
11:53It's very strong.
11:54It's hard to do without any elements.
11:55And it's still the same.
11:56It's the second time it's only doing an anemone.
11:57It's just too hard to be able to do an anemone.
11:58You can tell that anemone is not just as strong as a being.
12:00The only thing that has been broken than an anemone is not just as strong as an enemy.
12:02It's very strong as an enemy.
12:06It's nothing too hard to be able to do with these scars.
12:08You can tell that the anemone.
12:11You can tell that the anemone isn't particularly alarmed by this procedure
12:16because it hasn't closed up and is still confidently waving its tentacles.
12:41That makes three guardian anemones on the crab's shell.
12:47But is that enough to give it protection?
13:11The octopus is not sure.
13:41No, it's not worth it.
13:54So the crab has its bodyguards, and its bodyguards, for wages,
13:59are likely to get little bits and pieces that float by
14:02when the crab chews up its meals.
14:04It's not always easy to decide in these partnerships which is exploiting which.
14:14The balance of advantage is often very delicate.
14:18Take, for example, these ants in Australia.
14:21They are extremely ferocious, and normally they'll rip apart any caterpillar.
14:26But see how they're treating this one.
14:29This one.
14:33The caterpillar has on its back a number of little nipples
14:37which apparently fascinate the ants.
14:48One near its back end, when stimulated by an ant,
14:52produces a drop of liquid, honeydew, which the ant drinks.
14:59As the caterpillar grazes on leaves, the ants keep continuous guard over it,
15:10threatening anything that comes near it so that even birds don't attack it.
15:29The caterpillar has to make sure that the ants don't forget what kind of caterpillar they're dealing with.
15:38If they think it's any other kind, they will tear it apart and eat it.
15:41So the caterpillar, every now and then, makes a characteristic buzzing vibration.
15:46Not only that, but on either side of the honeydew nipple there are two others,
15:52and from these sprout little tentacles, which apparently release a pheromone,
15:57a kind of perfume that keeps the ants happy and unaggressive.
16:03The tree ants build nests almost as big as footballs from the growing leaves of the tree.
16:08And they feed on any small creature that happens to land in the tree.
16:17This grasshopper stood little chance.
16:20As soon as it landed, they set upon it.
16:22Now they are butchering it and carrying it back piece by piece to their nest.
16:27As well as this nest, the workers also construct small shelters.
16:37First, a team bridges two leaves and slowly pulls them together.
16:41Others arrive carrying grubs, which they gently squeeze,
16:45so that the grubs are stimulated to produce a sticky silk.
16:49By passing the grubs back and forth, they weave a fabric that holds the two leaves together.
16:54They're making a shelter for their precious caterpillar.
17:00When it's complete, they guide the caterpillar into it.
17:11Once in its shed, it'll be safe for the night.
17:15The ants look after it like farmers looking after a dairy cow.
17:19And their cow, in return, provides them with nourishing food.
17:24When it comes to the nest, it'll be safe for them.
17:26When it comes to the nest.
17:27When it comes to the nest.
17:28When it comes to the nest.
17:29When it comes to the nest.
17:34So, at this stage in the history of their relationship,
17:38neither ant nor caterpillar seems to have the advantage.
17:41But this same species of ferocious, stinging ant
17:45has also got a partnership with a slightly different species of caterpillar.
17:49And there the result seems to be very different.
17:55This one has a glossy, horny shield on its back.
17:59And it, entirely of its own accord, marches right into the ants' nest.
18:05It is in no way deterred by the ants' threatening postures and sprays of formic acid.
18:11No matter what the ants do, they can't stop it.
18:15Deeper and deeper it goes through the corridors of sown leaves,
18:19right into the heart of the nest.
18:21It reaches the queen.
18:22If she is killed, the whole colony will die.
18:23If she is killed, the whole colony will die.
18:24But she is not left.
18:25If she is killed, the whole colony will die.
18:26If she is not what the intruder is looking for.
18:37If she is not what the intruder is looking for.
18:41If she is killed, the whole colony will die.
18:45This wasn't all!
18:46It reaches the queen.
18:47If she is killed, the whole colony will die.
18:51But she is not what the intruder is looking for.
18:54The soldiers attack valiantly,
18:56but their jaws make little impression on the caterpillar's armour.
19:00Neither can they get underneath it and reach the soft, vulnerable body.
19:05On it goes, until at last it reaches the nursery chambers
19:09where the developing grubs lie.
19:16Try as they might, they can't lift up the shield sufficiently
19:19to enable other defenders to get beneath.
19:24With the intruder actually within the nursery,
19:34the workers become totally confused.
19:37Some try to carry off the grubs to safety elsewhere.
19:51But they can't do it quickly enough.
19:54The caterpillar snatches a grub, pulls it under the shield
19:57and then, secure beneath its armour, slowly eats it.
20:01As the season progresses, several of these armoured intruders make their way into the nest,
20:07and there, gorge themselves on ant grubs.
20:15As the season progresses, several of these armoured intruders make their way into the nest,
20:20and there, gorge themselves on ant grubs.
20:24their lens splurved 있을, and ex Lifetime看er?
20:25It's still doing awesome.
20:26It's a частムorn there remains.
20:27Do its power with death on the internet.
20:28I've reached the ceiling in front of the이를
20:31The Caterpillar
21:01and all the grubs they need to grow to their full size.
21:05Now, deep in the heart of the nest,
21:07they're ready to shed their armour and turn into butterflies.
21:11But how can a butterfly get through the ranks of the ant soldiers?
21:15Now, surely, they'll have a chance to get their revenge.
21:20Slowly, the insect hauls itself out of its horny armour.
21:31But it's a strange sort of butterfly that emerges.
21:50It's covered in scales that are so slippery
21:53that the ants can't get a proper grip on them.
22:01Those that do manage to bite
22:05get their jaws covered with a sort of fluff
22:08that they clearly find intensely irritating.
22:15So, at last, the murderous lodger goes free.
22:19Ants and caterpillars, like crabs and anemones,
22:31are about the same size.
22:33But if a lodger is very much smaller than its landlord,
22:36then it tends to live not so much with it as on it.
22:42Those monkeys over there, for example,
22:44they've got a number of tiny passengers.
22:49Like most mammals with hairy coats, they've got fleas.
23:04And when fleas bite and start sucking blood, they itch.
23:13It may be necessary to get a friend
23:16to help pick them out from parts that you yourself can't reach.
23:19This, however, is not fur.
23:26This is the fabric of a bird's nest.
23:28And fleas live here too.
23:33A young starling, within two days of hatching,
23:36is likely to have several dozen fleas.
23:42Fleas have six legs, just like any other insects,
23:45but they've lost their wings.
23:47Those would be a real encumbrance to an animal crawling around among fur and feathers.
23:52Instead, they have powerful hind legs that enable them to jump onto their host.
23:57Their jaws have become specialised for sucking blood,
23:59and they feed on nothing else.
24:01They have to live on another animal, and they contribute nothing to its welfare.
24:06This is not a partnership.
24:08It's parasitism.
24:12Nor are fleas the only parasites in a bird's nest.
24:15Lice are there, eating feathers.
24:19They too are insects, and any one bird may have up to a dozen different kinds,
24:24each living on and eating a different kind of feather, on the neck, the wings, or the head.
24:29Insects seem to have a particular flair for parasitism.
24:38Every one of their main families has some members who've taken it up.
24:43But insects themselves can also be parasitised.
24:47This nest of bumblebees has been invaded by mites, diminutive cousins of spiders.
24:53They're so tiny that several hundred of them can sit on the leg of a bee.
25:01And they too itch.
25:12They get everywhere, and once they've found their way into a colony,
25:16they spread to every member of it.
25:23Mites are just as specialised as feather lice.
25:35These bee mites live nowhere else but on this particular species of bumblebee.
25:41And this flower, milkweed, is a staging post for one of the most specialised mites of all.
25:47Moths come to feed on the milkweed at night, dipping their long thread-like tongues deep into the heart of the flowers to sip the nectar.
26:02But this moth is already infested with mites.
26:08Its ear, a tiny hole in the side of its head, has become the home of a whole colony of them.
26:17And a new colonist awaits on the flower itself.
26:30While the moth drinks, the mite crawls up its tongue.
26:47And then, its blood and a little brother of the moth,
26:48but in the middle of the night of the moth,
26:48it knows mysteriously that the moth has shot out of a stone and a little bit.
26:53Once on the moth's head, it knows mysteriously just which direction it must take
27:19through the jungle of fir to reach the ear.
27:23There is one great danger in all this.
27:26Blocking up an ear inevitably makes it useless to the moth.
27:29And if the moth can't hear, it can't avoid the bats that hunt it.
27:33That would be as disastrous for the mites as for the moth.
27:37So the mites obligingly occupy only one ear and always leave the other free.
27:44Here they live and breed, using one part of the ear tube for stacking their droppings,
27:49another for laying their eggs, and yet another for rearing their grubs.
27:54And how do their offspring find another of these highly specialised homes?
27:59Why, of course, by clambering down their host's tongue as it drinks,
28:04and waiting on the flower for another moth of the same species to turn up?
28:19But panocytes are themselves preyed on.
28:22This little mouse that lives in Central America
28:24regularly carries a dozen or so passengers wriggling around in its fur.
28:29They're beetles, and they were once thought to be parasites that suck the mouse's blood,
28:43for they have large and powerful jaws.
28:46But oddly, the mice that carried the most beetles
28:49are not by any means the most anemic and wretched, as you might expect.
28:53On the contrary, they seem to be the most healthy.
28:55It turns out that the mouse's most serious parasites
29:00are, in fact, here, in the lining of the nest.
29:04Fleas and ticks that do suck its blood.
29:13Each mouse has several holes in the forest,
29:17and all are likely to be infested with these fleas.
29:20When a mouse settles down to rest in one,
29:24the beetles drop off and go hunting for the fleas in the nest lining.
29:28So the beetles, far from injuring a mouse, actually aid it.
29:42Got one.
29:43Got one.
29:50As far as a beetle is concerned,
29:53the mouse is a convenient transport system
29:56for getting from one rich hunting ground to another.
29:59And the mouse that carries the most beetle passengers
30:02has the most comfortable and flea-free life.
30:07These birds, too, are hunters of parasites.
30:10They're finches that live in the Galapagos Islands.
30:12And the creatures they help, the giant tortoises.
30:24You can hardly scratch yourself if you have legs like these.
30:31Yet tortoises, like so many other animals,
30:34are pestered by skin parasites, especially ticks.
30:38The finches eat mainly seeds,
30:42but ticks apparently make a welcome change.
30:51When there's a tortoise nearby,
30:53and the finches want a meal with a difference,
30:55they signal to the tortoise
30:57by jumping up and down in front of it.
31:01The tortoise reacts to the finches' advances
31:04in a remarkable way.
31:06It stiffens its legs
31:08so that its huge body is lifted clear of the ground
31:10and cranes up its neck.
31:16The invitation is an unmistakable one.
31:26There's no way that the tortoise
31:28could pick off parasites
31:29from the places that these attendants
31:31managed to reach.
31:36A few minutes servicing by the finches
31:53is quite enough to clear the tortoise
31:55of most of its pests.
31:57Another satisfied customer.
31:59Fish have the same sort of problem
32:05and the same sort of solution.
32:08The huge manta ray
32:10is troubled by sea lice
32:11and parasitic barnacles
32:13that burrow into its skin.
32:14But it has other company,
32:20an attendant fleet of small fish
32:22that travel with it.
32:24And when the opportunity arises,
32:26they swim over their host's body,
32:28even inside its gaping mouth,
32:31picking off the passengers.
32:32Like the giant tortoises,
32:52fish with skin problems
32:54patronise regular cleaning establishments.
32:57This grouper hangs in the water
33:02at this special place on the reef
33:04and small wrasse that have been waiting
33:06amongst the coral
33:07swim out and start fussing around it,
33:10even daring to swim inside the huge jaws.
33:13It's not only fish that work as cleaners.
33:26This Murray eel is being tended by a shrimp.
33:32Open wide, please.
33:33Amazingly, the cleaners are never harmed,
33:56even though they tickle.
33:58These shrimps are really quite large,
34:10big enough anyway to make a reasonable meal,
34:12but they're never injured either.
34:23Regular customers come back
34:25to these cleaning stations every few days.
34:28And although the resident staff of wrasse and shrimps
34:31can deal with as many as 50 an hour,
34:33they're often queues of itchy fish waiting their turn.
34:43Some fish, however, have their own personal valets.
34:51Suckerfish or remoras have got a fin on their back
34:54that has been modified into a sucker so powerful
34:57that it's almost impossible to pull off a remora
34:59if it wants to stay on.
35:02They travel with their host wherever it goes
35:04and slip around its body,
35:06picking off the parasites
35:07whenever there's an opportunity to do so.
35:09Giraffe, like many other big-game animals in Africa,
35:18also have their own personal staff.
35:22Giraffe, like many other big-game animals in Africa,
35:27also have their own personal staff.
35:29Giraffe, like many other big-game animals in Africa,
35:32also have their own personal staff.
35:34Oxpeckers live almost permanently on the bodies of their hosts,
35:46scuttling about all over it.
35:56On this spacious pattern stage, they act out almost all their lives.
36:01Here they argue and court.
36:03Here, too, they feed their newly-fledged young.
36:06They can't its true nest here, they do that in holes in trees,
36:10but they do line those holes with hair that they pluck from their host's body,
36:15so that, presumably, they'll still feel at home.
36:23Their claws are so long that they're able to cling in almost any position
36:27and move in any direction.
36:29Their beak is flattened so that it slips easily between the long hairs of the giraffe's coat
36:35as they scissor through it, searching for ticks.
36:38And they get everywhere, on young and on old.
36:52Even when the animal moves off,
36:54they will hang on with the skill, and unconcern, of accomplished jockeys.
37:08But oxpeckers are a mixed blessing.
37:11The ticks they eat are full of the giraffe's blood,
37:14but sometimes they take that blood directly, from an open wound.
37:19And by doing that, they're not improving their host's health,
37:22but damaging it,
37:24keeping the wound open long after it would otherwise have healed.
37:27Even so, without them,
37:33giraffes would be much more seriously troubled
37:35by their skin parasites than they are.
37:44We ourselves, of course,
37:45can also get infested with ticks and fleas if we're not careful.
37:49They're everywhere, particularly in the rainforest.
37:51One has a reasonable chance
38:02of getting rid of animals that settle on your outside,
38:06like and flick off these ticks.
38:09And if you can't do it for yourself,
38:11well, then maybe you can get an oxpecker
38:13or a cleaner fish to do it for you.
38:15But if the parasite settles,
38:17not on the outside of your body,
38:19but manages to get actually inside it,
38:21that's a very different matter.
38:27The corridors and chambers of an animal's digestive system
38:31offer great advantages to any creature that can dwell in them.
38:36Inside here, they're secure from enemies
38:38and washed continuously by a nutritious soup
38:41that their host has already chewed,
38:44mashed and partially digested for itself.
38:47All they have to do is to absorb it through their skin.
38:50They don't even need a mouth.
38:55The animals that are best suited to this interior life
38:59are those long, spineless, legless creatures
39:02we call collectively worms.
39:05Flat, ribbon-shaped tapeworms
39:07hang onto the walls of the gut
39:09with a crown of hooks that encircle their head.
39:11In the long corridors of the intestines,
39:21roundworms proliferate.
39:23Every backbone animal that has been thoroughly examined,
39:26whether fish or amphibian, reptile, bird or mammal,
39:30has proved to be the host of a roundworm of some kind.
39:33These living in a gut merely rob the host of some of its food,
39:38but they may spread to cause severe damage to the liver and the lungs.
39:44Other roundworms, too, cause serious problems.
39:49There are some as thin as threads of cotton
39:51that swim along the blood vessels
39:53and collect in the valves of the heart,
39:56blocking them so seriously that their host dies.
40:03The young of such threadworms,
40:05swimming around in the bloodstream,
40:07depend on biting insects
40:09to transfer them to another host.
40:12During the day,
40:12they swim in blood vessels deep within the body,
40:15but at night,
40:16when mosquitoes are biting,
40:18they move up into the capillaries just beneath the skin
40:20so that when a mosquito does start to suck their host's blood,
40:24they are taken up.
40:26They continue to grow inside the mosquito
40:28and when, in due course,
40:30it bites some other animal,
40:32they are transferred into a new host,
40:35a new home.
40:37Others, smaller still,
40:39that wriggle among the blood corpuscles,
40:41belong to the most ancient of all animal groups,
40:43the protozoans.
40:45They first got inside animals so long ago
40:48that most of their hosts
40:49have developed an immunity to them.
40:52But human beings,
40:53those most recent of mammals,
40:55have not yet done so,
40:56and in them,
40:57they cause sleeping sickness and death.
41:01The problem that faces all these internal parasites
41:04is how to get their offspring into another host.
41:07Tiny ones, like the protozoans,
41:09may be transferred by biting insects.
41:11Bigger ones, like this round worm,
41:14have to use other methods.
41:16The first stage,
41:18getting their eggs to the outside world,
41:20is easy.
41:27This round worm, full of eggs,
41:30simply sheds them into its host's gut
41:32so that they fall out with its droppings.
41:34Once in the soil,
41:38they may lie dormant for some considerable time.
41:42But eventually,
41:43when the conditions are suitable,
41:44the temperature just right,
41:45and a reasonable amount of moisture around,
41:48they begin to hatch.
41:49The tiny worms crawl up leaves of grass,
42:12and there await the moment
42:13when a hungry mouth will crop the grass,
42:16and they will get carried into another stomach.
42:19But such transfers are not always so straightforward,
42:22and sometimes the complexities of the route they follow
42:25are almost beyond imagining.
42:30Denmark.
42:31A morning in summer.
42:32There has been a shower of rain,
42:37and the meadows and woodlands are drenched.
42:49Snails are slowly crawling around through the wet leaves,
42:53grazing.
42:54They are feeding on algae
42:56and rotting vegetable matter of one kind and another.
43:00Early morning is the best time for them.
43:03The sun is not yet hot enough to dry them out,
43:06and they can explore parts of the vegetation
43:08they can't reach at other times.
43:10But this one is different from the others.
43:35Its left tentacle is swollen and pulsating.
43:40It has a parasite.
43:44A few months ago,
43:46the snail took in, along with its normal food,
43:48some bird droppings.
43:50Within them were the tiny eggs of a fluke
43:52that was living within the bird's gut.
43:55Those hatched,
43:56and the parasite developed enormously,
43:58taking over much of the snail's body.
44:01As the sun shines brighter,
44:03the parasite extends a striped muscular bag
44:06packed with tiny larvae
44:07into the snail's tentacle.
44:10If it has the choice,
44:11it nearly always picks the left one.
44:13Birds rarely eat whole snails.
44:16They're far too big,
44:17and few can extract them from their shells.
44:20Nonetheless,
44:21the larvae must reach the body of another bird
44:24to develop further.
44:25For some reason,
44:28the presence of the parasite
44:29changes the snail's behaviour.
44:31As the day wears on,
44:33it does not,
44:34like uninfected snails,
44:35crawl back into the cool undergrowth
44:37out of harm's way.
44:39Instead,
44:40it remains exposed
44:41out in the open,
44:43dangerously so.
44:44now there is a parasite
44:52in each tentacle.
45:03Perhaps they look like caterpillars
45:05or tasty worms.
45:07Maybe they just look odd,
45:09but certainly the flycatcher
45:11finds them interesting.
45:13The connection has been made.
45:33The circle is complete.
45:36Another bird has become infected.
45:38Inside the bird,
45:42the striped bag
45:43releases its multitudes of larvae.
45:46They soon move through the bird's body
45:48and take up residence in its gut,
45:50and the whole cycle starts all over again.
45:58Flukes are related to the flatworms
46:00that live independent lives
46:02in ponds and swamps.
46:03But they found their greatest success
46:06as internal parasites.
46:08Some reside in the liver.
46:11Other kinds anchor themselves
46:12in the bladder
46:13or the lungs
46:14or the gut.
46:15And most are capable
46:16of causing serious disease.
46:19All internal parasites, however,
46:21do not necessarily injure their hosts.
46:24Some indeed actually help them.
46:26These microscopic organisms,
46:30undoubtedly alive
46:31and arguably animals,
46:32since they don't have chlorophyll-like plants
46:34with which to manufacture their food,
46:37live in the stomachs
46:38of most large animals.
46:40They are able chemically
46:42to break down the cellulose
46:43which forms the substance
46:44of most plant tissues,
46:46something the digestive juices
46:48of most large plant-eating animals
46:50can't do.
46:50Their free-living ancestors
46:54swam in ponds
46:55as some of their relatives
46:56still do today.
46:58These are members of the family
46:59that have simply found
47:01a warmer, darker pond
47:03and one that is extraordinarily rich
47:05in edible material,
47:07a stomach.
47:13So a buffalo,
47:15like most wild animals,
47:16is not, as it might appear,
47:19a single individual.
47:20It's a walking zoo.
47:23Its oxpecker companions
47:24are obvious enough,
47:26but if we looked closer
47:27we would find ticks
47:29boring into its skin.
47:31In its mouth,
47:32leeches that it picked up
47:33when it drank from the river.
47:35Tapeworms are trading
47:37through its guts,
47:38flukes are moored
47:39in the veins of its liver
47:40and protozoans are swimming
47:43in its blood
47:43and swilling around
47:44in its stomach.
47:46It's a whole community
47:47of different kinds of animals
47:49that have been committed
47:50by evolution
47:51for better or for worse,
47:54in sickness and in health
47:56to live together.
47:57even if you think of it,
48:01then you can walk us
48:02through there.
48:04So if you think of it
48:06and also don't forget
48:07what you sont us
48:07to get into it,
48:08because if you think of it
48:08you'll find out
48:09and help you figure it out.
48:11Hook to mission
48:1233ld
48:13huh-
48:17we did.
48:18Yellow
48:19should go
48:23through and
48:23run
Recommended
48:46
|
Up next
49:28
58:34
1:06
1:06
49:05
29:08
29:15
29:16
41:16
37:32
49:51
49:23
1:54:53
51:11
1:23:24
40:40
50:58
51:11
1:08:58
42:04
1:22:18