ATTENBOROUGH: The natural world is full of extraordinary animals
with amazing life histories.
Yet, certain stories are more intriguing than most.
The mysteries of a butterfly's life-cycle,
or the strange biology of the emperor penguin.
some of these creatures were surrounded by myths and misunderstandings
for a very long time.
And some have only recently revealed their secrets.
These are the animals that stand out from the crowd.
The curiosities 1 find most fascinating of all.
some animals have mastered the art of deception.
The cuckoo tricks other birds into raising its young,
while the death's-head hawkmoth infiltrates the nests of bees
to steal their precious honey.
They're cheats and imposters.
(CUCKOO WARBLING)
The call of the cuckoo has long been regarded as a sign of spring,
but, in fact, it's the call of a killer and a cheat.
The cuckoo lays its egg in the nests of other birds
and somehow persuades them to treat it and its chick as if it were their own.
How does it get away with it?
It's a question that has puzzled people for centuries.
1n Britain, the cuckoo arrives at the time
when most birds are nesting and laying eggs.
Early egg collectors notice that the nests of some birds
had a slightly odd-looking egg in them.
These are the eggs laid by a number of different birds.
Marsh warbler, spotted flycatcher, linnet and the whitethroat.
And amongst each of those clutches, there is a fraudster.
A cuckoo egg, which mimics that of its host.
Although cuckoos are long known to lay their eggs in the nests of other birds,
no one had actually described it happening.
And then, in the 1 8th century, an English country doctor,
with an interest in natural history decided to investigate.
Edward jenner lived here in Berkeley, Gloucestershire
and is best known for his work on the smallpox vaccine.
In fact, he's said to be the father of vaccination and that
his work has saved more human lives than that of any other man.
What is less known is that he first achieved scientific distinction
by his observations on the behaviour of the cuckoo.
At the time, it was believed that a cuckoo removes
all of the eggs in a nest and then lays its own.
By doing so, it would ensure its own chick gets all the food brought in
by the unwitting nest owners.
But Edward Jenner's detailed observations were to reveal
a rather darker tale.
jenner's work on cuckoos was published in 1 788
here in the Philosophical Transactions of the Royal society,
the world's first scientific society.
It was entitled simply
Observations on the Natural history of the Cuckoo by Mr Edward jenner.
In it, he reported that it was not the parent cuckoo,
but the newly-hatched chick,
which pushes the eggs and nestlings of the foster parents out of the nest.
As soon as it hatches, the cuckoo chick's instinct
is to kill anything else in the nest.
1t's still blind and naked, but it has a cup-shaped depression on its back,
into which an egg fits perfectly.
But, sometimes, the other eggs hatch earlier.
And Jenner's observations of how the cuckoo chick deals with its nest mates
were quite shocking.
He writes, ''The mode of accomplishing this was very curious.
''The little animal with the assistance of its rump and wings
''contrived to get the bird on its back
''and making a lodgement of the burden by elevating its elbows,
''clambered backwards with it up the side of the nest,
''until it reached the top, where, resting for a moment,
''it threw off its load with a jerk and quite disengaged it from the nest.''
The real villain had been uncovered.
jenner's views were met with incredulity and some disbelief,
but, nonetheless, they earned him the fellowship of the Royal Society.
It was the greatest honour that could be given to a scientist at the time.
Jenner's observations had revealed the true nature
of the cuckoo's deception.
But it still wasn't clear why the cuckoo should opt for this strange way
of raising its young.
1t wasn't until 1 00 years later that Charles Darwin
finally provided an explanation with his theory of evolution.
The cuckoo's behaviour has evolved to increase its own breeding success.
By avoiding the task of raising chicks,
the cuckoo can lay more eggs than any other bird,
as many as 25 in a season.
While it makes evolutionary sense for the cuckoo to lay its eggs
in the nests of others, what about its victims?
Why do they put up with this trickery?
1t seems that they sometimes don't.
And this was revealed in an early natural history film in 1 920.
The Cuckoo's Secret was made by Edgar Chance and Oliver Pike,
an egg collector and a wildlife filmmaker.
Chance was fascinated by cuckoos
and spent a great deal of time following them.
He was the first person known to see a cuckoo lay its egg.
The deception involved stealth and speed.
The female waits until a nest is unattended and then she strikes,
but, if she's spotted, the owners fight back.
1f she's successful, the whole deception takes less than 1 0 seconds.
she removes and eats just one egg and replaces it with her own.
The Chance and Pike film solved one mystery, but there were still others.
How does the cuckoo choose its victim?
And why don't the nest owners reject the alien egg?
Green warblers are one of the cuckoos main targets,
and the pair has a nest just in here.
The female warbler has laid four speckled eggs
and, using a model egg, I can illustrate the cuckoo's trickery.
This is the sort of egg that the cuckoo would lay in the reed warbler's nest.
It matches the reed warbler's actual egg very closely in colour.
Experiments with model eggs have shown
that reed warblers have become very good at recognising an alien egg,
and either throw it out or desert their nest to start afresh.
so the cuckoo has to make sure that it produces an egg
that is a very good match.
The cuckoo and its victims are evolving competitively.
(WARBLING)
With each generation, cuckoos improve their mimicry,
while the nest owners become better at spotting a foreign egg.
While many birds are very good at detecting a strange egg in their nest,
they seem incapable of recognising the monstrous cuckoo chick as an imposter.
But the deception is not complete.
The young cuckoo is much larger than a reed warbler chick,
so it also needs a lot more food.
How does it get enough?
The cuckoo has a solution.
1t now uses vocal deception,
to trick its foster parents into providing more food.
This is a sonogram of the sound waves produced by a single reed warbler chick
begging for food.
And below it is the call of a cuckoo chick.
And as you can see, it looks very different.
In fact, it more closely resembles the calls
of a whole nestful of reed warbler chicks.
so, the cuckoo chick's call is a super stimulus
that sounds like a whole nestful of chicks.
And it appears to work.
The adult birds rush back and forth providing the imposter
with the same amount of food as they would for an entire brood of their own.
At three weeks old, the cuckoo chick has spilled out of the nest.
1t's now almost eight times the size of its foster parent.
1t was over 200 years ago that Edward Jenner first shocked us
with his revelation of the cuckoo's extraordinary lifestyle.
Now we know that its unusual behaviour is due to an extraordinary arms race
that has resulted in one of the most fascinating specialisations in nature.
The cuckoo's success relies on deceiving just two parent birds,
but our second subject is a moth that is able to deceive hundreds of bees.
How does it infiltrate one of the most heavily-guarded nests in nature?
This wonderful creature was once one of the most feared insects in Europe.
It's a death's-head hawkmoth.
And it's easy enough to see how it got its name.
It has this mark on its back that looks just like a human skull.
This gave it a bad reputation that lasted for centuries,
but now there are new ideas about this moth's strange appearance
that may help explain its extraordinary ability to rob hives
without being stung.
Death's-head hawkmoths are a rare sight in Britain,
for they spend most of their lives in Africa and Asia.
But every summer, a small number of migrants arrive in northern Europe,
and, if the weather is warm enough, they breed.
Their caterpillars, unlike the drab adult moths, are beautifully coloured.
After feeding for several weeks,
they can grow to a length of 1 3 centimetres.
Once ready to become adults, they pupate in the soil,
and emerge as the sinister, strangely-patterned moths.
In the early 1 9th century, a region of northern France
was hit by a terrible pestilence.
And, at the same time, a large number of hawkmoths were seen in the area.
The local people linked the deaths to these night-flying insects.
But there was another even more disturbing side to this moth.
It could make an unusual noise.
(SQUEAKING)
There, a strange squeak, and that only added to its chilling reputation.
Moths don't usually squeak.
Tiger moths sometimes produce ultrasonic warning clicks
that tell bats that they're poisonous and not good to eat,
but this is not a noise we can generally hear.
Perhaps the death's-head hawkmoth squeaks to scare predators like birds.
However, other large migratory moths don't make such a sound.
This makes the death's-head hawkmoth's squeak all the more surprising.
And it has intrigued people for centuries.
These moths are more than 200 years old.
We know that because the hand-written label there
tells us they were collected in 1 801 by a Robert Darling Willis,
the personal physician to King George III.
George III is well known
as the king who suffered from bouts of madness.
And on a visit to see the King during one of them,
Dr Willis discovered these large moths in the monarch's bed chamber.
Unable to identify them, the doctor sent them to his grandson,
who was at that time superintendent at the Museum of Zoology in Cambridge.
He confirmed that they were death's-head hawkmoths.
And, unusually for an insect, this moth produces a loud call
that has been likened to the mournful cry of a grief-stricken child.
Did the disturbed king hear the plaintive calls of a hawkmoth?
That, we don't know.
But, certainly, many of the ordinary people of the 1 9th century
were struck with a sense of terror whenever this moth appeared.
The moth's unusual appearance and strange behaviour baffled people.
But in nature, such traits usually have a purpose.
And it may be for the death's-head hawkmoth,
that they enable it to break into beehives and steal their honey.
These are the giant honeybees of southeast Asia.
And they form some of the largest bee colonies in the world.
1 once got up close to one in order to demonstrate
their response to a predator.
1 had a model of a large hornet, which produced a kind of Mexican wave
and that makes it very difficult for an aggressor to land.
This covering of bees looks impossible to penetrate.
But at night, a thief can break through their ranks.
A death's-head hawkmoth lands on the carpet of bees
and pushes its way through without being attacked.
1n just a few seconds, it takes some sips of honey and emerges unharmed.
Getting past the guard bees is quite a feat,
but surviving inside is even more astounding.
Death's-head hawkmoths raid domestic beehives too and can be quite a pest.
somehow the moth slips past the guards and, as if invisible,
walks through the hive heading straight for the honeycomb.
1t then feeds unnoticed.
How does it do this?
One theory proposes that its spooky appearance
may help it avoid being attacked.
Miriam Rothschild, a great entomologist and expert on fleas and butterflies,
suggested that the moth's skull pattern looks like the head of a worker bee
and that this could play a role in the moth's deception.
Well, this is a photograph of a worker bee face
taken through a microscope.
Let's see how it looks next to a close-up photo
of the skull pattern of the moth.
There.
Well, I suppose there's a slight resemblance,
but given the fact that most moths raid beehives and nests during the night,
it's unlikely the bees could see that much detail.
The most likely answer lies in the scent the moth gives off.
1n America, in the 1 950s, a German entomologist called Thomas Eisner
studied chemical ecology, in particular, the chemical defences of insects.
Most famously, he illustrated how bombardier beetles fire hot acid
onto a predator.
He also studied moths,
and showed that the feathery projections on their abdomens
and their large antennae were used to produce and pick up scent.
1t seemed that many insects were using scent in surprising ways.
Tests on the chemical scents produced by hawkmoths
reveal a remarkable similarity to those produced by the worker bees
in the hives that they raid.
Their scent is not identical, but it contains several key chemicals
that exactly match those produced by bees.
so, the death's-head hawkmoth's scent acts as an invisibility cloak
that makes it undetectable to the worker bees in the nest.
With thick scales on its body, clawed feet that grip the honeycomb,
and a short, pointed proboscis to pierce the honey cells,
the moth has evolved into an effective hive robber.
But there is another even more impressive imposter
that can also penetrate the protective defences of an insect colony.
1ts victims are not bees, but ants.
The imposter that invades this ant nest doesn't get in there by flying,
nothing as blatant as that.
Instead, the caterpillars of some species of blue butterfly,
like this one, wait for red ants to collect them.
Remarkably, passing ants don't kill them.
They pick them up and take them back into their nest.
The cuckoo caterpillar will stay inside the nest for up to 1 0 months.
just like the death's-head hawkmoth, it produces a chemical scent
that deceives the ants.
This pink caterpillar, which belongs to the Alcon blue butterfly,
has been collected because, to them, it smells just like the young
of their own nest.
They become controlled by the imposter's intoxicating scent,
and feed the butterfly larva even more regularly than they do their own.
There's another way this imposter pulls off its deceptive trick,
when it's inside the nest, the butterfly larva makes a strange chattering noise.
To our ears, it's very faint, but it's clear enough to other insects.
This is it.
(LARVA CHATTERING)
And this is the sound that's made by a queen ant.
(QUEEN ANT CHATTERING)
To worker ants, these calls are very similar.
And they react by treating the butterfly larva
as if it's one of their own.
Caterpillars of the blue butterfly are impressive imposters.
Not only do they mimic the scent of the ants, but their queen's calls too.
This seems to trump the death's-head hawkmoth's ability as a nest invader.
But the hawkmoth may also be using sound to trick its victims.
Remember the eerie squeak that was thought to be so frightening?
(SQUEAKING)
There.
The hawkmoth makes this sound inside the beehive
when it enters to steal honey.
It's been suggested that this might calm the bees
because the squeak is thought to sound like the piping call
that the queen honeybee makes to pacify her workers.
We can't be sure if the call and the strange skull marking
evolved to deceive bees, but we can be certain that the death's-head hawkmoth's
life as an imposter is more curious
than the superstitions that have surrounded it for hundreds of years.
The cuckoo and the hawkmoth are both audacious imposters,
but the cuckoo's ability to make its victim raise its young
is perhaps the most accomplished deception of all.