0:00:03 > 0:00:06The Natural World is full of extraordinary animals
0:00:06 > 0:00:07with amazing life histories.
0:00:09 > 0:00:12Yet, certain stories are more intriguing than most.
0:00:15 > 0:00:18The mysteries of a butterfly's life cycle
0:00:18 > 0:00:21or the strange biology of the emperor penguin.
0:00:22 > 0:00:24Some of these creatures
0:00:24 > 0:00:26were surrounded by myth and misunderstandings
0:00:26 > 0:00:28for a very long time.
0:00:29 > 0:00:33And some have only recently revealed their secrets.
0:00:34 > 0:00:38These are the animals that stand out from the crowd -
0:00:38 > 0:00:42the curiosities I find particularly fascinating.
0:00:51 > 0:00:53In this programme, we meet two animals
0:00:53 > 0:00:58whose extraordinary body shapes are determined by their diet.
0:00:58 > 0:01:00The blue whale grows enormous,
0:01:00 > 0:01:03by feeding on tiny shrimplike creatures,
0:01:03 > 0:01:08while flamingos spend their lives eating with their heads upside down.
0:01:09 > 0:01:12And yet, both ways are curiously similar.
0:01:21 > 0:01:25The blue whale weighs almost 200 tonnes.
0:01:25 > 0:01:28It's the largest animal on Earth and it's rarely seen.
0:01:29 > 0:01:31I didn't glimpse one,
0:01:31 > 0:01:34until I had been filming animals for almost 50 years -
0:01:34 > 0:01:37and when I did, it was one of the greatest thrills of my life.
0:01:45 > 0:01:48I can see its tail, just under my boat here.
0:01:48 > 0:01:51And it's coming up, it's coming up...
0:01:52 > 0:01:53There!
0:01:53 > 0:01:58The blue whale is 100 feet long -
0:01:58 > 0:02:0030 metres.
0:02:00 > 0:02:04Nothing like that can grow on land,
0:02:04 > 0:02:09because no bone is strong enough to support such bulk.
0:02:09 > 0:02:13Only in the sea, can you get such a huge size
0:02:13 > 0:02:16as that magnificent creature.
0:02:34 > 0:02:38The blue whale was a mystery to science for a long time.
0:02:38 > 0:02:40Living out in the deep oceans,
0:02:40 > 0:02:44people rarely caught sight of more than the spout of this giant.
0:02:46 > 0:02:48The first published description
0:02:48 > 0:02:51comes from a physician, Robert Sibbald,
0:02:51 > 0:02:56who found a whale stranded off the coast of Scotland in 1692.
0:02:57 > 0:02:59It was first named after Sibbald,
0:02:59 > 0:03:04but later given the scientific name Balaenoptera musculus.
0:03:04 > 0:03:09The Latin "musculus" means both "muscle" and "little mouse" -
0:03:09 > 0:03:12an ironic double meaning for the largest animal on Earth.
0:03:16 > 0:03:20When the first blue whale specimens were washed up on our shores,
0:03:20 > 0:03:24they must have caused quite a stir and excitement.
0:03:24 > 0:03:27Here was a colossal animal, weighing over 150 tonnes.
0:03:27 > 0:03:29Nothing as big had ever been seen before.
0:03:31 > 0:03:34A giant of this scale must be a predator
0:03:34 > 0:03:36at the top of the food chain.
0:03:36 > 0:03:39But what kind of creature was it?
0:03:39 > 0:03:41And what was it feeding on to make it so big?
0:03:44 > 0:03:47The first blue whale specimens were found at a time
0:03:47 > 0:03:51when scientists were just starting to classify animals
0:03:51 > 0:03:53not only by their external appearance,
0:03:53 > 0:03:55but by their internal structures,
0:03:55 > 0:04:00and few animals proved as problematic as the whales.
0:04:02 > 0:04:05From the outside, they looked and behaved like fish.
0:04:05 > 0:04:09But their internal organs were like those of a large mammal.
0:04:12 > 0:04:14The bones of the whale's front fins
0:04:14 > 0:04:17are very similar to those in our own arms.
0:04:17 > 0:04:21The five digits on the hand are clearly visible,
0:04:21 > 0:04:24but they've been modified into paddles for swimming.
0:04:28 > 0:04:32What kind of creatures were these truly extraordinary animals?
0:04:36 > 0:04:39The controversy as to whether whales were fish or mammals
0:04:39 > 0:04:43came to a head in a New York courtroom in 1818.
0:04:43 > 0:04:46A jury was asked to pass judgment on the question,
0:04:46 > 0:04:49for the purpose of the New York state law.
0:04:49 > 0:04:52The issue had come up because a shrewd merchant,
0:04:52 > 0:04:55who owned three barrels of whale oil,
0:04:55 > 0:04:59had refused to pay tax levied on fish oil.
0:04:59 > 0:05:02He pointed out that, according to the latest scientific opinion,
0:05:02 > 0:05:04whales weren't in fact fish.
0:05:04 > 0:05:07The inspector collecting the tax had scorned the idea.
0:05:07 > 0:05:10"What, whales not fish?!" he said,
0:05:10 > 0:05:12and slapped handcuffs on the merchant.
0:05:13 > 0:05:19The lead witness was a respected scientist called Samuel Mitchill.
0:05:19 > 0:05:21Mitchill entered the courtroom,
0:05:21 > 0:05:25expecting to explain to everybody why whales were mammals not fish,
0:05:25 > 0:05:28but, instead, found himself being attacked
0:05:28 > 0:05:32by the most gifted lawyer in the country, William Sampson.
0:05:34 > 0:05:37Sampson argued that scientists didn't have the right
0:05:37 > 0:05:41to rename God's creatures and force them into absurd groupings.
0:05:43 > 0:05:46The idea that humans and whales should be in the same category
0:05:46 > 0:05:48seemed to him grotesque.
0:05:50 > 0:05:54Mitchill and science never stood a chance.
0:05:54 > 0:05:57After deliberating for 15 minutes,
0:05:57 > 0:06:00the jury announced a verdict in favour of Sampson
0:06:00 > 0:06:02and the fish oil inspector.
0:06:02 > 0:06:04According to New York state law,
0:06:04 > 0:06:08whales were deemed to be fish, not mammals.
0:06:10 > 0:06:14Although the general public still considered whales to be fish,
0:06:14 > 0:06:17scientists were, by now, largely agreed
0:06:17 > 0:06:21that they were, indeed, mammals that had taken to living in the sea.
0:06:23 > 0:06:26But what was the blue whale feeding on
0:06:26 > 0:06:29to allow it to grow to such an extraordinary size?
0:06:30 > 0:06:34The answer can be found by looking inside the mouth,
0:06:34 > 0:06:37which contains some very bizarre-looking structures.
0:06:39 > 0:06:43This is the skeleton of a right whale,
0:06:43 > 0:06:47and its mouthparts are very similar to those of the blue whale.
0:06:47 > 0:06:50Instead of teeth, it has these strange plate-like structures,
0:06:50 > 0:06:52hanging from the upper jaw.
0:06:52 > 0:06:55The plates are aligned alongside each other
0:06:55 > 0:06:57and the inner edges fray
0:06:57 > 0:07:01because the large tongue continually rubs up against them.
0:07:01 > 0:07:04And then the frayed edges entangle
0:07:04 > 0:07:08to form a thick mat that acts like a gigantic sieve.
0:07:10 > 0:07:14And when early naturalists opened up the gigantic gut of these whales,
0:07:14 > 0:07:17they found not fish or other large prey,
0:07:17 > 0:07:20but tiny shrimplike creatures called krill.
0:07:20 > 0:07:23To everyone's astonishment, it turned out
0:07:23 > 0:07:28that these whales feed on some of the smallest prey in the sea,
0:07:28 > 0:07:33and these strange plates serve to filter the krill out of the water.
0:07:35 > 0:07:38The rows of plates are called baleen,
0:07:38 > 0:07:40and we now know that they form
0:07:40 > 0:07:43a highly specialised filter feeding system.
0:07:45 > 0:07:49The giant animal dives deep beneath the surface,
0:07:49 > 0:07:51in search of swarms of krill.
0:07:53 > 0:07:56The pleated skin on the throat and belly expand
0:07:56 > 0:08:00and the mouth balloons outward to four times the size,
0:08:00 > 0:08:03taking in an enormous mouthful of water.
0:08:07 > 0:08:11The tongue then forces the water out through the baleen,
0:08:11 > 0:08:14and thousands of tiny krill are left behind.
0:08:17 > 0:08:21Today, we know a lot more about this unusual feeding structure.
0:08:23 > 0:08:26This is baleen.
0:08:26 > 0:08:28It's often referred to as whalebone,
0:08:28 > 0:08:31but it's not bone at all.
0:08:31 > 0:08:35It's keratin - the same substance as our hair and fingernails,
0:08:35 > 0:08:38and it's both strong and slightly elastic.
0:08:38 > 0:08:42The plates emerge from the whale's jaws instead of teeth,
0:08:42 > 0:08:45and continue to grow throughout the whale's lifetime.
0:08:45 > 0:08:49These bands in it are much like the rings of a tree.
0:08:49 > 0:08:52Several may be laid down in the course of a year,
0:08:52 > 0:08:56so the baleen can give us an indication of the age of a whale.
0:08:56 > 0:08:58We also know, from other evidence,
0:08:58 > 0:09:01that blue whales can live to be over 100 years old.
0:09:03 > 0:09:09Recently discovered fossil whales have both teeth and simple filters,
0:09:09 > 0:09:12which suggest that early filter feeding whales
0:09:12 > 0:09:15may have sucked small animals from the seafloor.
0:09:17 > 0:09:21There is a whale alive today that feeds in just that way -
0:09:21 > 0:09:23the grey whale.
0:09:24 > 0:09:28It stirs up the sediment and scoops it into its mouth
0:09:28 > 0:09:32and then filters out small food particles with its baleen.
0:09:41 > 0:09:44Krill is abundant in the oceans,
0:09:44 > 0:09:47and blue whales can eat enormous quantities of it
0:09:47 > 0:09:49with each mouthful,
0:09:49 > 0:09:53soon swallowing 90 times more than they immediately need.
0:09:53 > 0:09:57The surplus is then stored in the form of blubber,
0:09:57 > 0:10:00and this helps them cope with periods when food is scarce.
0:10:05 > 0:10:08The blue whale was a mystery to us for a long time,
0:10:08 > 0:10:11but we now know that its enormous body
0:10:11 > 0:10:16is fuelled with vast quantities of the tiniest of prey.
0:10:16 > 0:10:18Over the course of its lifetime,
0:10:18 > 0:10:23a blue whale will consume around 50,000 tonnes of krill,
0:10:23 > 0:10:27and, unlike teeth, which fall out with old age,
0:10:27 > 0:10:31the baleen never stops growing and is constantly replaced.
0:10:31 > 0:10:33Maybe this unusual body design
0:10:33 > 0:10:37not only helps the blue whale grow to this enormous size,
0:10:37 > 0:10:41but also to such a formidable old age.
0:10:42 > 0:10:44The blue whale has become a giant
0:10:44 > 0:10:47by filtering tiny creatures out of the ocean.
0:10:49 > 0:10:52Our second curiosity, the flamingo,
0:10:52 > 0:10:56also has an unusual body that has been shaped by its diet.
0:10:59 > 0:11:04For a long time, the flamingos were birds of myth and mystery.
0:11:04 > 0:11:06Travellers in Africa saw them,
0:11:06 > 0:11:11shrouded by the hazy mists rising from volcanic soda lakes,
0:11:11 > 0:11:14and believed that they were firebirds.
0:11:15 > 0:11:17In Egyptian mythology,
0:11:17 > 0:11:21the firebird, or phoenix, was a sacred creature
0:11:21 > 0:11:23with beautiful red plumage,
0:11:23 > 0:11:25that was consumed by magical fire
0:11:25 > 0:11:28and then rose again from its own ashes.
0:11:30 > 0:11:33The flamingo's scientific name, Phoenicopterus,
0:11:33 > 0:11:35reflects some of its legendary past.
0:11:35 > 0:11:38It means "phoenix wing".
0:11:39 > 0:11:42These beautiful and elegant creatures
0:11:42 > 0:11:44are some of the most curious-looking of birds.
0:11:44 > 0:11:48No other bird has a beak shaped quite like this
0:11:48 > 0:11:51or, indeed, such glorious pink colours,
0:11:51 > 0:11:54and yet, we're so familiar with them
0:11:54 > 0:11:57that we rarely think about their strange appearance.
0:11:57 > 0:12:02Why is it that the flamingo is so different from all other birds?
0:12:04 > 0:12:07In that classic children's book, Alice In Wonderland,
0:12:07 > 0:12:11Lewis Carroll has fun with the flamingo's oddity.
0:12:12 > 0:12:15Alice plays croquet with the Red Queen,
0:12:15 > 0:12:20using them as mallets, holding their heads and necks upside down,
0:12:20 > 0:12:23in much the same posture as the birds take when feeding.
0:12:27 > 0:12:30When you look at the skeleton of a flamingo,
0:12:30 > 0:12:32the thing that strikes you most
0:12:32 > 0:12:36is the extraordinary length of the legs and the neck.
0:12:36 > 0:12:39The neck has 17 bones in it -
0:12:39 > 0:12:41which is no more than in other birds -
0:12:41 > 0:12:44but each is greatly elongated,
0:12:44 > 0:12:48giving the flamingo its extra-long neck and flexibility.
0:12:48 > 0:12:53But the flamingo's most curious feature is, surely, its beak,
0:12:53 > 0:12:55and the reason it looks so strange,
0:12:55 > 0:13:00is that it is the only beak adapted for use upside down.
0:13:01 > 0:13:07In most birds, the upper part of the bill is larger than the lower one.
0:13:07 > 0:13:10But in the flamingos, it's the other way round.
0:13:10 > 0:13:13The lower bill is much bigger
0:13:13 > 0:13:17and has a deep central groove in it that holds the flamingo's tongue.
0:13:17 > 0:13:21The upper jaw is thin and moveable,
0:13:21 > 0:13:25so when the bird head is upside down,
0:13:25 > 0:13:30the flamingo's jaws work, as it were, normally.
0:13:34 > 0:13:40When feeding, the flamingo gently sweeps its bill back and forth,
0:13:40 > 0:13:44sucking water in at the front and squirting it out from the sides.
0:13:50 > 0:13:55The water that goes in is murky, while that which flows out is clear,
0:13:55 > 0:13:59and that gives us a clue to what it's feeding on.
0:14:03 > 0:14:06The beak has tiny bristles all along its edges,
0:14:06 > 0:14:08much like the whale's baleen.
0:14:11 > 0:14:16And the tongue has two rows of horny spikes along its length.
0:14:17 > 0:14:21FLAMINGOS SQUAWK
0:14:21 > 0:14:25When feeding, the bristles and spikes form a sieve,
0:14:25 > 0:14:27trapping any particles inside.
0:14:29 > 0:14:33And the large tongue acts as a pump, pushing water in and out.
0:14:37 > 0:14:40It's a unique design for a beak.
0:14:40 > 0:14:42No other bird has one like it.
0:14:42 > 0:14:44FLAMINGOS SQUAWK
0:14:46 > 0:14:49Although at first sight, they may look the same,
0:14:49 > 0:14:54flamingo beaks, in fact, come in two different shapes
0:14:54 > 0:14:57and this is because they eat slightly different food.
0:15:00 > 0:15:04This is the beak of a greater flamingo,
0:15:04 > 0:15:06which feeds on crustaceans,
0:15:06 > 0:15:10which are usually found near the bottom of a lake.
0:15:10 > 0:15:12It's long and shallow,
0:15:12 > 0:15:15so the birds can feed in water only a few millimetres deep.
0:15:17 > 0:15:21This beak, on the other hand, is from a lesser flamingo.
0:15:21 > 0:15:26Its bill is shorter, but more bulbous and deep-keeled.
0:15:26 > 0:15:30The lesser flamingo feeds on microscopic algae,
0:15:30 > 0:15:33which usually float just below the surface of the water
0:15:33 > 0:15:36and the deep keel acts as a buoy,
0:15:36 > 0:15:39bobbing along just at the right depth,
0:15:39 > 0:15:41as the bird moves through the water.
0:15:46 > 0:15:50These different bills allow two species of flamingo
0:15:50 > 0:15:52to live side by side.
0:15:53 > 0:15:55In Africa's Rift Valley,
0:15:55 > 0:15:59greater and lesser flamingos are found on the soda lakes,
0:15:59 > 0:16:03having specialised on food that others can't reach.
0:16:06 > 0:16:08The waters are so hot and toxic,
0:16:08 > 0:16:11that they would strip the flesh off any other animal.
0:16:11 > 0:16:14But flamingos thrive here.
0:16:18 > 0:16:21Their long spindly legs have tough scales
0:16:21 > 0:16:25and their webbed feet prevent them from sinking into the soft mud.
0:16:27 > 0:16:29The birds can even drink the water,
0:16:29 > 0:16:32which is two or three times saltier than the ocean.
0:16:35 > 0:16:39But it's not just the mud and water which are poisonous.
0:16:40 > 0:16:44The blue-green algae, which many of them feed on,
0:16:44 > 0:16:48actually contain nasty, toxic chemicals.
0:16:48 > 0:16:51If that were to accumulate in the internal organs of the bird,
0:16:51 > 0:16:53they could be lethal.
0:16:53 > 0:16:55But the flamingo deals with that,
0:16:55 > 0:16:59by directing these chemicals into the feathers and the skin,
0:16:59 > 0:17:01where they do no damage.
0:17:02 > 0:17:06The feathers of flamingos contain very high concentrations of toxins,
0:17:06 > 0:17:10but they also contain another chemical - carotene.
0:17:12 > 0:17:14Carotene is the reddish pigment
0:17:14 > 0:17:17that gives flamingos their distinctive pink colour,
0:17:17 > 0:17:20and it also comes from their diet.
0:17:20 > 0:17:22But carotene is not harmful.
0:17:22 > 0:17:25On the contrary, it's a source of vitamin A
0:17:25 > 0:17:29and boosts the immune system, protecting against illness.
0:17:29 > 0:17:33So, a pink bird is also a healthy bird.
0:17:37 > 0:17:39This glorious pink colour
0:17:39 > 0:17:43was probably an incidental by-product of their diet.
0:17:43 > 0:17:45Nonetheless, over time,
0:17:45 > 0:17:50it has evolved to play an important role in the flamingo's social life.
0:17:51 > 0:17:56The flashes of colour are an integral part of their courtship display,
0:17:56 > 0:17:59and recent research has shown that the pinkest flamingos
0:17:59 > 0:18:03are the most popular, when it comes to finding a mate.
0:18:08 > 0:18:12When flamingos breed, much of the carotene in their diet
0:18:12 > 0:18:15gets channelled into the developing young.
0:18:15 > 0:18:17Even the eggs receive pigments,
0:18:17 > 0:18:22so much, in fact, that the yolk can be virtually blood-red in colour.
0:18:23 > 0:18:27These eggs are from captive flamingos and are infertile.
0:18:27 > 0:18:29Let's have a look.
0:18:31 > 0:18:32There!
0:18:35 > 0:18:37Well, it's nothing like the colour
0:18:37 > 0:18:40of any other bird yolk that I've ever seen.
0:18:41 > 0:18:45Flamingos are so efficient at collecting their specialised food,
0:18:45 > 0:18:50that the yolk is actually packed full of protein and fat.
0:18:50 > 0:18:53This allows the chick to grow particularly quickly
0:18:53 > 0:18:55and gives it a good start in life.
0:18:58 > 0:19:00FLAMINGOS SQUAWK
0:19:00 > 0:19:02Despite the colour of the yolk,
0:19:02 > 0:19:04the chicks hatch with fluffy grey feathers.
0:19:06 > 0:19:10They are fed on special milk from their parents' crop.
0:19:10 > 0:19:13This is not regurgitated food,
0:19:13 > 0:19:17but a secretion produced by the lining of the digestive tract,
0:19:17 > 0:19:20and it's deep red in colour.
0:19:29 > 0:19:34The flamingo chick relies on this for the first few weeks of its life,
0:19:34 > 0:19:39and it will eventually enable it to grow its glorious pink plumes.
0:19:39 > 0:19:42FLAMINGOS CRY AND SQUAWK
0:19:43 > 0:19:47We now know that much of the flamingo's bizarre appearance
0:19:47 > 0:19:49has been shaped by its diet.
0:19:49 > 0:19:52But one question continues to baffle scientists -
0:19:52 > 0:19:56to which group of birds do the flamingos actually belong?
0:19:56 > 0:19:59Some thought that they must be related to ducks and geese,
0:19:59 > 0:20:03because of their webbed feet and short, duck-like beaks.
0:20:03 > 0:20:06But others were convinced that, with their long legs,
0:20:06 > 0:20:08they are more like waders, such as storks.
0:20:11 > 0:20:15Recent DNA studies contradict both these suggestions.
0:20:16 > 0:20:20They reveal that the flamingo's closest relative
0:20:20 > 0:20:24may, in fact, be a small diving bird that looks nothing like a flamingo...
0:20:26 > 0:20:29..the grebe.
0:20:31 > 0:20:33Further studies found other similarities
0:20:33 > 0:20:36in the structure of the eye
0:20:36 > 0:20:39and the number of feathers on the wing.
0:20:41 > 0:20:44So, it seems that flamingos and grebes
0:20:44 > 0:20:47are, indeed, each other's closest relatives.
0:20:47 > 0:20:50But over time, diet and lifestyle has shaped the flamingo
0:20:50 > 0:20:52into a very different looking bird,
0:20:52 > 0:20:56far removed from its grebe-like ancestor.
0:21:02 > 0:21:06It's fair to say, there's nothing else quite like a flamingo.
0:21:11 > 0:21:15The flamingo and the blue whale are two very different creatures -
0:21:15 > 0:21:19one living on land and one in the deep oceans.
0:21:19 > 0:21:23Yet, their bodies have been shaped in a similar way by their diet,
0:21:23 > 0:21:27making each of them a curiosity within its own group.