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The natural world is full of extraordinary animals | 0:00:02 | 0:00:05 | |
with amazing life histories. | 0:00:05 | 0:00:07 | |
Yet, certain stories are more intriguing than others. | 0:00:07 | 0:00:12 | |
The mysteries of a butterfly's life cycle, | 0:00:13 | 0:00:17 | |
or the strange biology of the emperor penguin. | 0:00:17 | 0:00:20 | |
Some of these creatures were surrounded by fantastic myths | 0:00:20 | 0:00:25 | |
and misunderstandings. | 0:00:25 | 0:00:27 | |
Others have only recently revealed their secrets. | 0:00:27 | 0:00:32 | |
These are the creatures that stand out from the crowd, | 0:00:32 | 0:00:37 | |
the curiosities that I find particularly fascinating. | 0:00:37 | 0:00:41 | |
In this programme, | 0:00:51 | 0:00:52 | |
I explore the lives of two mothers | 0:00:52 | 0:00:55 | |
who give birth to unusually sized young. | 0:00:55 | 0:00:59 | |
The giant panda, | 0:00:59 | 0:01:01 | |
which, in relation to its size, | 0:01:01 | 0:01:03 | |
produces one of the smallest babies of any mammal. | 0:01:03 | 0:01:07 | |
And, the kiwi, | 0:01:07 | 0:01:08 | |
which lays one of the biggest eggs in the bird world. | 0:01:08 | 0:01:12 | |
Why do pandas and kiwis have babies of such extreme sizes? | 0:01:13 | 0:01:19 | |
Giant pandas are surely one of the most instantly recognisable | 0:01:26 | 0:01:30 | |
of all mammals. | 0:01:30 | 0:01:31 | |
Yet they're also one of the rarest. | 0:01:31 | 0:01:33 | |
Although they once lived over large parts of Central China, | 0:01:33 | 0:01:37 | |
today they're restricted to just six mountain ranges. | 0:01:37 | 0:01:41 | |
Once lowland creatures, | 0:01:51 | 0:01:52 | |
they now live in higher altitudes, in dense forests. | 0:01:52 | 0:01:56 | |
Very little was known about the wild lives of these elusive animals, | 0:02:01 | 0:02:05 | |
and their reproduction remained a mystery for centuries. | 0:02:05 | 0:02:09 | |
The earliest known ancestors of giant pandas | 0:02:12 | 0:02:16 | |
were small forest-dwelling creatures | 0:02:16 | 0:02:18 | |
that existed just over 11 million years ago. | 0:02:18 | 0:02:21 | |
Larger pandas have been around for about 3 million years. | 0:02:21 | 0:02:26 | |
The giant pandas we know today | 0:02:28 | 0:02:29 | |
evolved when bamboo forests were widespread. | 0:02:29 | 0:02:33 | |
With such an easy, reliable food source, | 0:02:33 | 0:02:36 | |
they abandoned their carnivorous ways, | 0:02:36 | 0:02:39 | |
and took to a plant-based diet. | 0:02:39 | 0:02:41 | |
Today, pandas are a huge attraction in our zoos, | 0:02:43 | 0:02:46 | |
but, persuading them to breed and care for their young in captivity, | 0:02:46 | 0:02:50 | |
has been historically very difficult. | 0:02:50 | 0:02:53 | |
Zookeepers were shocked to discover | 0:02:53 | 0:02:56 | |
that a newborn panda baby is one 900th of the parent's body weight. | 0:02:56 | 0:03:01 | |
The smallest of all percentile mammal babies. | 0:03:01 | 0:03:05 | |
But pandas have been a scientific enigma for a very long time. | 0:03:06 | 0:03:10 | |
In 1869, | 0:03:12 | 0:03:14 | |
a French missionary and naturalist called Abbe Armand David | 0:03:14 | 0:03:19 | |
set off on an expedition to China. | 0:03:19 | 0:03:21 | |
He was an expert horticulturist, | 0:03:22 | 0:03:24 | |
and had been commissioned by the Museum of Paris | 0:03:24 | 0:03:27 | |
to bring back plant specimens. | 0:03:27 | 0:03:29 | |
On the 21st of March, while collecting, | 0:03:30 | 0:03:32 | |
he was invited into a local hunter's house for tea and sweets. | 0:03:32 | 0:03:36 | |
He came across a strange, wiry-haired skin, | 0:03:36 | 0:03:39 | |
rather like this one. | 0:03:39 | 0:03:41 | |
He thought it must have come from an unknown species. | 0:03:43 | 0:03:46 | |
So he asked the hunters to bring him | 0:03:46 | 0:03:48 | |
a specimen of this mysterious creature. | 0:03:48 | 0:03:51 | |
After several days, they brought back one that Armand David described | 0:03:51 | 0:03:56 | |
as "a most excellent black and white bear". | 0:03:56 | 0:03:59 | |
Excitedly, he prepared the skin, and then he sent it off to Paris. | 0:03:59 | 0:04:04 | |
Knowing that it might take time to arrive, | 0:04:06 | 0:04:08 | |
he also wrote a letter to Parisian zoologist Milne-Edwards, | 0:04:08 | 0:04:12 | |
urging him to publish a brief description of the animal | 0:04:12 | 0:04:15 | |
for which David proposed the scientific name | 0:04:15 | 0:04:19 | |
of "Ursus Melanoleucus", | 0:04:19 | 0:04:21 | |
literally meaning "black and white bear". | 0:04:21 | 0:04:24 | |
From the very beginning, this new creature seemed odd for a bear. | 0:04:27 | 0:04:31 | |
It had the carnivorous appearance of other bears, | 0:04:31 | 0:04:34 | |
but it's diet was actually almost entirely vegetarian. | 0:04:34 | 0:04:38 | |
It spent up to ten hours a day | 0:04:39 | 0:04:41 | |
feeding on up to 20kg of bamboo. | 0:04:41 | 0:04:45 | |
And unlike other bears, the panda did not hibernate, | 0:04:53 | 0:04:57 | |
and its babies proved to be far smaller | 0:04:57 | 0:04:59 | |
than those of any other bear. | 0:04:59 | 0:05:01 | |
In fact, the panda was so different | 0:05:03 | 0:05:05 | |
that some doubted that it was a bear at all. | 0:05:05 | 0:05:09 | |
A creature called a "red panda" had been discovered some time before, | 0:05:12 | 0:05:16 | |
and it had striking similarities | 0:05:16 | 0:05:18 | |
to Armand David's new black and white bear. | 0:05:18 | 0:05:21 | |
It, too, fed mainly on plant matter, | 0:05:24 | 0:05:27 | |
about two-thirds of which was bamboo. | 0:05:27 | 0:05:29 | |
But this creature was classified as a relative of weasels, | 0:05:31 | 0:05:35 | |
skunks and raccoons, not bears. | 0:05:35 | 0:05:38 | |
Perhaps the giant panda was not a bear after all. | 0:05:38 | 0:05:43 | |
This could explain why its young was so small, | 0:05:43 | 0:05:46 | |
compared to most other bears. | 0:05:46 | 0:05:48 | |
Milne-Edwards, the Parisian biologist | 0:05:51 | 0:05:53 | |
who received the very first giant panda skin and bones, | 0:05:53 | 0:05:57 | |
compared them to his specimens of red panda. | 0:05:57 | 0:06:00 | |
He believed that the skull structure and the teeth were very similar. | 0:06:01 | 0:06:05 | |
This is the small red panda, and this is the giant panda. | 0:06:05 | 0:06:09 | |
He decided it was a new creature, which deserved a new name, | 0:06:10 | 0:06:15 | |
so he called it "Ailuropoda", meaning "panda foot". | 0:06:15 | 0:06:19 | |
Thus it became known as a panda, and not a bear. | 0:06:19 | 0:06:23 | |
Debate and confusion continued over the panda's identification | 0:06:25 | 0:06:29 | |
for nearly 100 years. | 0:06:29 | 0:06:31 | |
Few people had ever seen more than a fleeting glimpse of one, | 0:06:32 | 0:06:36 | |
and their wild behaviour remained a mystery. | 0:06:36 | 0:06:38 | |
Then, in the 1920s, | 0:06:40 | 0:06:41 | |
exploration became very popular amongst the wealthy. | 0:06:41 | 0:06:45 | |
And the race was on for the first foreigner to hunt and kill a panda. | 0:06:45 | 0:06:50 | |
It's said that Theodore Roosevelt Jr and Kermit Roosevelt | 0:06:52 | 0:06:57 | |
were the first Westerners to shoot a panda. | 0:06:57 | 0:07:00 | |
They persuaded the Field Museum in Chicago to foot the bill | 0:07:00 | 0:07:04 | |
for an expedition, | 0:07:04 | 0:07:06 | |
and were secretive about the "golden fleece" that they were hunting. | 0:07:06 | 0:07:10 | |
After six days of tracking in the same area where Armand David | 0:07:10 | 0:07:15 | |
had first found his panda, they saw nothing. | 0:07:15 | 0:07:18 | |
But after moving further south, | 0:07:18 | 0:07:20 | |
they had a dramatic encounter with a panda that they followed | 0:07:20 | 0:07:23 | |
and shot dead. | 0:07:23 | 0:07:25 | |
Sadly, then, the driving force to collect giant pandas | 0:07:27 | 0:07:31 | |
was money and fame, not biological revelation. | 0:07:31 | 0:07:35 | |
The only way to learn anything more about the giant panda | 0:07:36 | 0:07:40 | |
was to watch one in the wild, or to catch one alive. | 0:07:40 | 0:07:43 | |
In 1936, a baby panda was captured alive. | 0:07:45 | 0:07:49 | |
Named Su Lin, she was the first to be brought into captivity, | 0:07:49 | 0:07:53 | |
but sadly died soon after. | 0:07:53 | 0:07:55 | |
A craze for captive pandas followed. | 0:07:56 | 0:07:59 | |
And in the late 1950s, one arrived in Britain. | 0:08:00 | 0:08:03 | |
This particular individual | 0:08:03 | 0:08:05 | |
would help us to appreciate the complexities | 0:08:05 | 0:08:08 | |
of the giant panda's biology. | 0:08:08 | 0:08:10 | |
Perhaps the most famous and popular of all giant pandas was Chi-Chi, | 0:08:12 | 0:08:17 | |
who came to London Zoo in September 1958. | 0:08:17 | 0:08:21 | |
She was actually on her way to the United States, | 0:08:22 | 0:08:25 | |
but the US Customs refused to admit her | 0:08:25 | 0:08:27 | |
on the grounds that she was a communist, | 0:08:27 | 0:08:30 | |
or, at any rate, came from a communist country. | 0:08:30 | 0:08:33 | |
So, London Zoo was able to buy her for £12,000, | 0:08:33 | 0:08:36 | |
and she was very quickly extremely popular. | 0:08:36 | 0:08:40 | |
Desmond Morris, who was in charge of London Zoo's mammals at the time, | 0:08:41 | 0:08:45 | |
decided, however, that she was alone | 0:08:45 | 0:08:47 | |
and she really ought to be allowed to breed. | 0:08:47 | 0:08:51 | |
Don't you want to go to Moscow? | 0:08:51 | 0:08:52 | |
PANDA SQUEAKS | 0:08:52 | 0:08:55 | |
Here, at last, was a chance to learn more about panda reproduction. | 0:08:58 | 0:09:02 | |
Desmond Morris travelled to Russia with Chi-Chi | 0:09:02 | 0:09:05 | |
to introduce her to a potential mate, a male panda called An-An. | 0:09:05 | 0:09:10 | |
But when they were introduced, all did not go to plan. | 0:09:10 | 0:09:14 | |
Chi-Chi was in no mood to breed, and was sent back home. | 0:09:14 | 0:09:18 | |
Clearly, panda mating was not a simple affair, | 0:09:23 | 0:09:26 | |
and it was a rare sight in the wild, too. | 0:09:26 | 0:09:29 | |
Now we know that successful mating needs very precise timing. | 0:09:29 | 0:09:34 | |
Female pandas live a solitary life, | 0:09:34 | 0:09:37 | |
and are only ready to mate for just one or two days a year. | 0:09:37 | 0:09:41 | |
Even then, there is a window of 12 to 24 hours. | 0:09:41 | 0:09:44 | |
It's little wonder that Chi-Chi did not breed. | 0:09:44 | 0:09:48 | |
Males are attracted to the female's scent, | 0:09:49 | 0:09:52 | |
and will guard them until they're ready to mate. | 0:09:52 | 0:09:55 | |
A female in season is a rare thing, | 0:09:56 | 0:09:59 | |
and competition to mate is worth fighting for. | 0:09:59 | 0:10:02 | |
GROWLING, BARKING SOUND | 0:10:02 | 0:10:06 | |
The panda was gaining a reputation for having unusual and difficult | 0:10:21 | 0:10:25 | |
breeding habits, and its peculiar diet seemed to be responsible. | 0:10:25 | 0:10:30 | |
In the 1960s, biologists took a fresh look at the giant panda. | 0:10:36 | 0:10:41 | |
This time, they studied the panda's digestive system, | 0:10:43 | 0:10:47 | |
and discovered that it was exactly like that of a carnivorous bear. | 0:10:47 | 0:10:51 | |
So, the giant panda was reclassified, | 0:10:52 | 0:10:55 | |
and changed from being a relative of the red panda, to being a true bear. | 0:10:55 | 0:11:00 | |
This also revealed that the giant panda gut was unsuited | 0:11:02 | 0:11:06 | |
to its plant-based diet, | 0:11:06 | 0:11:07 | |
and that this oddity might affect its metabolism and breeding. | 0:11:07 | 0:11:11 | |
But how? | 0:11:11 | 0:11:13 | |
Female bears feed on rich food | 0:11:15 | 0:11:17 | |
to build up fat reserves for motherhood and hibernation. | 0:11:17 | 0:11:21 | |
They then give birth to up to four babies, | 0:11:21 | 0:11:25 | |
and produce enough milk to feed all of them. | 0:11:25 | 0:11:28 | |
The well-grown cubs emerge from the den in early spring. | 0:11:28 | 0:11:33 | |
Panda reproduction has significant differences. | 0:11:33 | 0:11:36 | |
They don't have enough fat reserves to hibernate, | 0:11:36 | 0:11:39 | |
and usually produce only one small baby at a time. | 0:11:39 | 0:11:43 | |
Their poor vegetarian diet | 0:11:43 | 0:11:45 | |
seems to have had an impact on their breeding. | 0:11:45 | 0:11:48 | |
Bamboo presents a lot of problems as a food. | 0:11:49 | 0:11:53 | |
To start with, it's very low in energy. | 0:11:53 | 0:11:56 | |
Secondly, the panda has to sit upright | 0:11:56 | 0:11:59 | |
in order to release its front paws, in order to handle the bamboo. | 0:11:59 | 0:12:03 | |
On top of that, the panda's gut is very short, | 0:12:03 | 0:12:07 | |
like that of a carnivore, | 0:12:07 | 0:12:09 | |
so that the food, when it's eaten, | 0:12:09 | 0:12:12 | |
passes through its body very quickly. | 0:12:12 | 0:12:15 | |
As a consequence of all those difficulties, | 0:12:15 | 0:12:17 | |
the panda only manages to extract about 20% of the little energy | 0:12:17 | 0:12:23 | |
that bamboo does contain. | 0:12:23 | 0:12:24 | |
So, the Panda's ancestors switched from being meat eaters | 0:12:26 | 0:12:30 | |
to plant eaters, and this compromised their digestive systems | 0:12:30 | 0:12:33 | |
and greatly affected their metabolism. | 0:12:33 | 0:12:37 | |
They became slow-moving, | 0:12:37 | 0:12:39 | |
and their breeding changed to cope with such a low-energy diet. | 0:12:39 | 0:12:43 | |
In the late 1960s, | 0:12:46 | 0:12:48 | |
efforts to understand panda reproduction became more crucial | 0:12:48 | 0:12:52 | |
as their numbers in the wild plummeted. | 0:12:52 | 0:12:54 | |
The Worldwide Fund for Nature was formed, | 0:12:54 | 0:12:58 | |
and their famous logo was a panda based on Chi-Chi. | 0:12:58 | 0:13:02 | |
The Chinese built a state-of-the-art reserve in Wolong, | 0:13:05 | 0:13:09 | |
leading to a new era of great progress in panda breeding. | 0:13:09 | 0:13:13 | |
Small babies weighing an average of just 100g | 0:13:16 | 0:13:20 | |
are now regularly born in captivity, and are fed on milk for many months. | 0:13:20 | 0:13:24 | |
On a poor diet of bamboo, | 0:13:27 | 0:13:29 | |
pandas are unable to grow bigger babies in the womb, | 0:13:29 | 0:13:32 | |
so they give birth to small young, and use their limited nutrition | 0:13:32 | 0:13:37 | |
to produce food for them after birth. | 0:13:37 | 0:13:39 | |
As with all mammals, | 0:13:41 | 0:13:42 | |
milk is essential to the baby's development, | 0:13:42 | 0:13:45 | |
and ensures even the tiniest babies grow up to be giants. | 0:13:45 | 0:13:49 | |
So, the giant panda is not a racoon, it's a bear. | 0:13:52 | 0:13:56 | |
A bear that spends nearly all its time eating vegetation, | 0:13:56 | 0:14:01 | |
and that's nearly always bamboo. | 0:14:01 | 0:14:03 | |
Which, although it can occasionally produce twins, | 0:14:03 | 0:14:07 | |
normally gives birth to just one baby at a time. | 0:14:07 | 0:14:11 | |
And that a very small one. | 0:14:11 | 0:14:12 | |
But those are the consequences if you are a bear | 0:14:14 | 0:14:17 | |
that has become adapted to living on a very low-energy diet. | 0:14:17 | 0:14:21 | |
The panda's tiny baby is an oddity, | 0:14:23 | 0:14:26 | |
but the only solution for a bamboo-eating bear. | 0:14:26 | 0:14:30 | |
In New Zealand, | 0:14:32 | 0:14:33 | |
there's a very different creature that has just as curious a story. | 0:14:33 | 0:14:38 | |
The kiwi is one of the strangest of birds. | 0:14:45 | 0:14:48 | |
WARBLING | 0:14:48 | 0:14:51 | |
It sleeps underground, and usually only comes out at night. | 0:14:51 | 0:14:55 | |
It can't fly, and its brown feathers resemble a thick coat of fur. | 0:14:57 | 0:15:02 | |
Its small eyes are virtually useless and it finds its food | 0:15:04 | 0:15:08 | |
with its sensitive beak. | 0:15:08 | 0:15:10 | |
It's a peculiar lifestyle, more like that of a nocturnal mammal. | 0:15:10 | 0:15:15 | |
But most remarkable of all, it lays the biggest egg of any bird | 0:15:16 | 0:15:21 | |
in proportion to its body. | 0:15:21 | 0:15:23 | |
A kiwi is roughly the size of a chicken. | 0:15:25 | 0:15:28 | |
But its egg... | 0:15:28 | 0:15:30 | |
..is more than seven times as large as a chicken's egg. | 0:15:30 | 0:15:33 | |
And it can weigh half a kilo. | 0:15:33 | 0:15:36 | |
It's hard to imagine how this huge egg | 0:15:36 | 0:15:39 | |
could fit into a kiwi's small body. | 0:15:39 | 0:15:42 | |
And, yet, it does. | 0:15:42 | 0:15:43 | |
Just before the egg is laid, | 0:15:44 | 0:15:46 | |
it takes up so much room inside the female | 0:15:46 | 0:15:48 | |
that her belly almost touches the ground. | 0:15:48 | 0:15:50 | |
And when she lays it, it's equivalent, in terms of weight, | 0:15:50 | 0:15:54 | |
to a human mother giving birth to a four-year-old child. | 0:15:54 | 0:15:58 | |
Most birds only take around a day to produce an egg. | 0:16:02 | 0:16:06 | |
But because the kiwi's is so large, it takes almost ten days. | 0:16:06 | 0:16:11 | |
The female's inner organs become so compressed, she can't feed. | 0:16:15 | 0:16:20 | |
Expelling the monster egg is also a huge effort. | 0:16:24 | 0:16:27 | |
Why is the kiwi such a curiosity? | 0:16:37 | 0:16:40 | |
And why does it lay such a gigantic egg? | 0:16:40 | 0:16:43 | |
The kiwi didn't come to the attention of Europeans | 0:16:47 | 0:16:50 | |
until about 200 years ago, when a dried specimen, much like this one, | 0:16:50 | 0:16:54 | |
arrived in England on a merchant vessel. | 0:16:54 | 0:16:58 | |
It puzzled those who saw it. | 0:16:58 | 0:17:00 | |
It was clearly a bird, but it had no wings. | 0:17:00 | 0:17:03 | |
Its feathers were soft and hairy, more like mammalian fur. | 0:17:04 | 0:17:09 | |
And it had these strange, long whiskers | 0:17:09 | 0:17:11 | |
around the base of the beak. | 0:17:11 | 0:17:13 | |
The first specimen was examined and described by a naturalist | 0:17:13 | 0:17:16 | |
at the British Museum, a man called George Shaw, | 0:17:16 | 0:17:19 | |
who gave it the scientific name Apteryx, which, in Greek, | 0:17:19 | 0:17:24 | |
means "wingless creature". | 0:17:24 | 0:17:26 | |
Shaw studied the skin, together with his colleague John Latham, | 0:17:26 | 0:17:30 | |
but the two men disagreed as to what kind of bird it could be. | 0:17:30 | 0:17:34 | |
They knew it had come from New Zealand, | 0:17:34 | 0:17:36 | |
and Shaw thought it was probably related to the ratites, | 0:17:36 | 0:17:40 | |
a group of primitive flightless birds that includes the ostrich. | 0:17:40 | 0:17:44 | |
Latham, on the other hand, | 0:17:45 | 0:17:47 | |
was convinced that it was a kind of penguin. | 0:17:47 | 0:17:50 | |
When Shaw published his description in 1813, | 0:17:51 | 0:17:54 | |
it was accompanied by an artist's impression of the living bird. | 0:17:54 | 0:17:58 | |
This is it. | 0:17:58 | 0:17:59 | |
Clearly, the artist must have been swayed by Latham's argument, | 0:17:59 | 0:18:03 | |
rather than Shaw's. | 0:18:03 | 0:18:05 | |
He shows the kiwi standing bolt upright and very tall, | 0:18:05 | 0:18:08 | |
much like a penguin. | 0:18:08 | 0:18:10 | |
And so the kiwi was introduced to the scientific world. | 0:18:11 | 0:18:15 | |
Shaw's kiwi continued to provoke debate long after his death. | 0:18:17 | 0:18:22 | |
The most eminent zoologists of the time disagreed | 0:18:22 | 0:18:26 | |
over the nature of the strange creature | 0:18:26 | 0:18:28 | |
and, indeed, whether it actually existed. | 0:18:28 | 0:18:31 | |
It's not surprising that many wondered if the kiwi was a hoax. | 0:18:34 | 0:18:38 | |
It was a time when travellers were bringing back all kinds of strange | 0:18:38 | 0:18:41 | |
creatures from far-flung places, and many were frauds, | 0:18:41 | 0:18:45 | |
put together from parts of different animals. | 0:18:45 | 0:18:48 | |
Almost 20 years later, | 0:18:49 | 0:18:51 | |
and with only one specimen on which to make a judgment, | 0:18:51 | 0:18:54 | |
the Zoological Society of London made an appeal for more kiwi skins. | 0:18:54 | 0:19:00 | |
So, other specimens finally began to arrive in Britain. | 0:19:00 | 0:19:04 | |
European naturalists may have been mystified by the kiwi, | 0:19:07 | 0:19:10 | |
but the Maori people of New Zealand | 0:19:10 | 0:19:12 | |
had admired and respected the bird for a very long time. | 0:19:12 | 0:19:16 | |
According to Maori legend, | 0:19:18 | 0:19:20 | |
the kiwi lost its wings at the request of Tane, | 0:19:20 | 0:19:23 | |
the god of the forest. | 0:19:23 | 0:19:24 | |
Tane asked all birds to go down to live on the forest floor | 0:19:24 | 0:19:30 | |
and feed on the insects that were killing the trees. | 0:19:30 | 0:19:32 | |
But only the kiwi agreed, and gave up his wings and beautiful feathers. | 0:19:32 | 0:19:38 | |
So, the kiwi has always been sacred to the Maori. | 0:19:39 | 0:19:43 | |
Back in Europe, others now joined in the debate. | 0:19:48 | 0:19:52 | |
Professor Richard Owen, | 0:19:53 | 0:19:55 | |
the most powerful British zoologist of the time, | 0:19:55 | 0:19:58 | |
studied the anatomy of the kiwi in detail. | 0:19:58 | 0:20:00 | |
Comparing its features to those of other birds, | 0:20:03 | 0:20:07 | |
he concluded that it was most closely related | 0:20:07 | 0:20:10 | |
to that group of flightless birds called the ratites. | 0:20:10 | 0:20:13 | |
The ratites include the largest birds in the world - | 0:20:20 | 0:20:23 | |
the emu, the South American rhea, | 0:20:23 | 0:20:27 | |
the cassowary, and the ostrich. | 0:20:27 | 0:20:30 | |
All of them stand nearly as tall as a human being. | 0:20:30 | 0:20:33 | |
So, could the kiwi's large egg have anything to do | 0:20:36 | 0:20:39 | |
with its possible relationship to these larger birds? | 0:20:39 | 0:20:43 | |
To answer that, we need to look at its close relatives. | 0:20:43 | 0:20:47 | |
The emu lives nearby in Australia. | 0:20:52 | 0:20:55 | |
It has remnants of wings, but it can't fly. | 0:20:57 | 0:21:00 | |
And its feathers are similar to those of the kiwi, | 0:21:01 | 0:21:03 | |
hairy and plume-like. | 0:21:03 | 0:21:05 | |
They simply serve to protect the bird, and keep it warm. | 0:21:07 | 0:21:10 | |
So, how similar are the emu and the kiwi when it comes to their eggs? | 0:21:13 | 0:21:18 | |
This is the egg of a kiwi. | 0:21:19 | 0:21:22 | |
And this is the egg of an emu. | 0:21:22 | 0:21:25 | |
More or less the same size. | 0:21:25 | 0:21:27 | |
And, yet, the kiwi is the size of a chicken, | 0:21:27 | 0:21:30 | |
but an emu is almost as tall as I am. | 0:21:30 | 0:21:33 | |
Why should such a big egg come from such a small bird? | 0:21:33 | 0:21:37 | |
Well, for a long time, | 0:21:37 | 0:21:39 | |
it was argued that that was because the ancestors of the kiwi | 0:21:39 | 0:21:44 | |
were once as big as the emu and, over time, | 0:21:44 | 0:21:47 | |
they got smaller, but the egg remained the same size. | 0:21:47 | 0:21:51 | |
And the originator of that theory was, in fact, Richard Owen himself. | 0:21:51 | 0:21:55 | |
In 1839, Owen acquired the fragment of a strange bone from New Zealand. | 0:21:58 | 0:22:05 | |
After studying it closely, he suggested it came from a gigantic, | 0:22:07 | 0:22:11 | |
flightless bird that was probably extinct. | 0:22:11 | 0:22:14 | |
From this meagre evidence, he reconstructed the entire animal, | 0:22:15 | 0:22:19 | |
a giant moa. | 0:22:19 | 0:22:23 | |
Owen was ridiculed by other scientists at the time, | 0:22:23 | 0:22:26 | |
who considered such a deduction on one bone outrageous. | 0:22:26 | 0:22:30 | |
But in due course, other moa birds were found, | 0:22:30 | 0:22:33 | |
and he was proved to be correct. | 0:22:33 | 0:22:35 | |
Owen's discoveries seemed to confirm the idea | 0:22:37 | 0:22:40 | |
that the kiwi could have evolved from a big bird like the moa, | 0:22:40 | 0:22:44 | |
and that maybe its egg was a relic from a giant ancestor. | 0:22:44 | 0:22:48 | |
Large, flightless birds first appeared | 0:22:51 | 0:22:54 | |
when the dinosaurs became extinct. | 0:22:54 | 0:22:57 | |
This is a southern cassowary. | 0:22:58 | 0:23:01 | |
It's a native of northern Australia and New Guinea. | 0:23:01 | 0:23:05 | |
And the males, like this one, | 0:23:05 | 0:23:07 | |
are extremely territorial and, therefore, dangerous. | 0:23:07 | 0:23:11 | |
They will attack you, as I know to my cost. | 0:23:11 | 0:23:14 | |
So, I'm not going to get in there with him. | 0:23:14 | 0:23:16 | |
Instead, I'll see if I can tempt him | 0:23:16 | 0:23:19 | |
with a few grapes, which are one of his favourite foods. | 0:23:19 | 0:23:22 | |
Like the kiwi, the cassowary evolved | 0:23:24 | 0:23:27 | |
in an area where the adult birds have no ground predators. | 0:23:27 | 0:23:31 | |
As a consequence, they don't fly. | 0:23:31 | 0:23:34 | |
Flying is a very energy-demanding business. | 0:23:35 | 0:23:38 | |
If birds don't need to fly, birds don't fly. | 0:23:38 | 0:23:42 | |
Until recently, it was thought that all the ratites | 0:23:46 | 0:23:50 | |
had one common flightless ancestor. | 0:23:50 | 0:23:52 | |
This seemed possible because the places where they live today | 0:23:54 | 0:23:57 | |
were once part of a supercontinent called Gondwanaland. | 0:23:57 | 0:24:01 | |
When this continent split up around 150 million years ago, | 0:24:02 | 0:24:07 | |
the fragments drifted apart. | 0:24:07 | 0:24:08 | |
Each one might independently have evolved its own flightless species, | 0:24:10 | 0:24:14 | |
including New Zealand. | 0:24:14 | 0:24:16 | |
When Owen came to examine the skeleton of a kiwi, | 0:24:20 | 0:24:22 | |
he noticed something very strange about the skull. | 0:24:22 | 0:24:26 | |
Most bird skulls have two little tiny holes there | 0:24:27 | 0:24:30 | |
at the base of the beak, which accommodates the nostrils, | 0:24:30 | 0:24:33 | |
through which they smell. | 0:24:33 | 0:24:34 | |
But there are no such things here on the kiwi skull. | 0:24:34 | 0:24:38 | |
Instead, the nostrils are right at the tip of the beak. | 0:24:38 | 0:24:43 | |
Not only that, but these big spaces on either side the skull, | 0:24:45 | 0:24:49 | |
which in most birds hold the big eye, | 0:24:49 | 0:24:53 | |
are, in fact, filled by the olfactory organ, the smelling organ. | 0:24:53 | 0:24:58 | |
And Owen deduced from those two facts that this, therefore, | 0:24:59 | 0:25:03 | |
must belong to a bird that was nocturnal. | 0:25:03 | 0:25:07 | |
And he was quite right. | 0:25:07 | 0:25:08 | |
The kiwi is mostly active at night, | 0:25:13 | 0:25:15 | |
and uses both touch and smell to find its food. | 0:25:15 | 0:25:19 | |
The long whiskers allow it to feel its way in the dark, | 0:25:22 | 0:25:26 | |
and special sensory cells in the beak | 0:25:26 | 0:25:28 | |
detect the movement of prey underground. | 0:25:28 | 0:25:30 | |
But why did the kiwi choose this unusual lifestyle? | 0:25:32 | 0:25:35 | |
It's possible that the moas had already taken the role | 0:25:37 | 0:25:41 | |
of giant plant eaters during the day, | 0:25:41 | 0:25:43 | |
so the kiwi may have shrunk down to feed on small insects at night. | 0:25:43 | 0:25:47 | |
Owen had shed light on both the moa and kiwi, | 0:25:49 | 0:25:52 | |
but he was wrong about their true relationship. | 0:25:52 | 0:25:55 | |
Evidence from DNA has now revealed that the kiwi is, in fact, | 0:25:57 | 0:26:01 | |
more closely related to flightless birds of Africa and Australia. | 0:26:01 | 0:26:05 | |
This means that the moa and the kiwi had different ancestors, | 0:26:06 | 0:26:10 | |
and flightlessness must have evolved in New Zealand | 0:26:10 | 0:26:14 | |
on two separate occasions. | 0:26:14 | 0:26:16 | |
It's an extraordinary thought. | 0:26:19 | 0:26:21 | |
But another recent finding supports the idea. | 0:26:21 | 0:26:25 | |
Genetic techniques have shown that the closest relative of the ratites | 0:26:26 | 0:26:30 | |
is, in fact, a small flying bird, the tinamou. | 0:26:30 | 0:26:35 | |
Tinamous are partridge-like birds from South America | 0:26:37 | 0:26:40 | |
that spend much of their time on the ground, | 0:26:40 | 0:26:42 | |
but they can fly perfectly well. | 0:26:42 | 0:26:45 | |
So, it seems that birds like this may have flapped their way | 0:26:46 | 0:26:49 | |
between the continents, giving rise to the different ratites, | 0:26:49 | 0:26:54 | |
including the kiwi. | 0:26:54 | 0:26:55 | |
We've unravelled much of the mystery around the kiwi's curious lifestyle, | 0:27:01 | 0:27:06 | |
but one question remains. | 0:27:06 | 0:27:08 | |
What could be the reason for its huge egg? | 0:27:08 | 0:27:12 | |
Some think that the large egg may give the kiwi a competitive edge, | 0:27:14 | 0:27:18 | |
by allowing it to hatch a chick that is already very well developed. | 0:27:18 | 0:27:22 | |
It's like a miniature adult, | 0:27:23 | 0:27:25 | |
and the large yolk sac provides nourishment | 0:27:25 | 0:27:28 | |
until it becomes fully independent. | 0:27:28 | 0:27:31 | |
So, it seems that the kiwi's gigantic egg may have evolved | 0:27:37 | 0:27:41 | |
to suit its lifestyle and habitat. | 0:27:41 | 0:27:43 | |
Most birds have to lay their eggs as soon as possible | 0:27:43 | 0:27:47 | |
to avoid being weighed down when flying. | 0:27:47 | 0:27:50 | |
But the flightless kiwi has no such problem, and can, therefore, | 0:27:50 | 0:27:54 | |
keep the heavy egg in its body for longer, and let it grow bigger. | 0:27:54 | 0:27:58 | |
And in an environment with few predators, it may make sense to, | 0:27:59 | 0:28:04 | |
as it were, put all your eggs in one basket and raise a single chick | 0:28:04 | 0:28:08 | |
that is big and strong, | 0:28:08 | 0:28:10 | |
and therefore has the better chance of survival. | 0:28:10 | 0:28:13 | |
The kiwi and the panda both produce young that stand out | 0:28:14 | 0:28:18 | |
because of their size, | 0:28:18 | 0:28:19 | |
but are a perfect fit for the life choices of these curious creatures. | 0:28:19 | 0:28:25 |