Orangutans

  Mating...   For every species on Earth, it is vital   for the survival of the fittest.

He is absolutely massive!

But the way some creatures make babies   is quite extraordinary.

Look at your little head!

We've come to the rainforest in Borneo   to uncover the reproductive secrets   of one of our closest relatives --   orangutans --   where the most dominant males are true kings.

I would never have expected that in a million years.

Sex is a precarious balancing act.

WOMAN: This is fantastic.

We're finally seeing them mating.

Birth is remarkably human...   and babies learn to survive high in the jungle canopy.

This is what life is all about.

"Sex in the Wild" is made possible in part by   Borneo.

I'm here with veterinary scientist Mark Evans   to explore the mating strategy   of the largest tree dweller on the planet --   the orangutan.

But first we have to find one, and that's not easy.

You'd think something that was bright orange would be easy to see against a green background, but they blend right into the shadows.

EVANS: But they are out there.

They are definitely out there.

As an anatomist, I've worked with many animals,   but I've never seen an orangutan in the wild.

There's a nest up there, Joy.

REIDENBERG: Can you see anything moving up there?

No, I can't.

Orangutans make huge nests, but this one seems to be empty.

I see it, I see it.

I've got it, I've got it!

Right at the top of the tree, grazing away.

Look at that animal!

Absolutely magnificent.

REIDENBERG: I think it's a male.

It's got like almost like a beard on its chin.

We think we've spotted a large male,   a rare sighting,   but we need to get a closer look.

He is absolutely huge, Joy.

Oh, yeah!

Let me see.

Look at his cheeks.

They're really big.

He's got a big bald head and really large cheeks on either side.

He's a dominant male.

How lucky are we to be able to find him -- he's 50 feet from us.

He's probably the only one on this river.

Unusually for primates,   orangutans live solitary lives.

A dominant male will patrol a massive territory   with an area of nearly 20 square miles.

There will be lesser males and females,   freely roaming his kingdom...   but in such a huge range, finding each other isn't easy.

To explore how these solitary animals find mates   in this vast jungle, we need to get closer to them.

So we're on our way to Sepilok Orangutan Sanctuary.

Here, orphaned orangutans are taken in and hand reared.

This way.

In Borneo, rainforest is often cleared   to make way for plantations   and orangutans are killed in the process,   leaving babies without mothers.

There you go, my friend.

REIDENBERG: Good boy.

But these orphans have a second chance.

This sanctuary has been set up to rehabilitate them   and get them back into the wild.

EVANS: They're quick movers when they get on these ropes.

Very keen.

You're very acrobatic, look at you.

EVANS: You are a show-off!

[Reidenberg chuckles] EVANS: Oh, sweetheart, thank you!

That's really sweet of you, but I've eaten.

REIDENBERG: That was very nice.

EVANS: You can have that there.

Thank you very much.

But I'm fine.

You have it.

It's interesting the way they've got these ropeways that take them out into the forest itself.

REIDENBERG: So they have freedom, and if they really want to take off into the forest, they can.

When these young orangutans are ready,   they will swing out into the protected forest   around the sanctuary to raise their own families.

The adult orangutans in this area are used to humans.

So it's an ideal place to investigate   the reproductive secrets of these great apes.

Mark's heading off with some local tree climbers   to help him get high into the canopy   for a closer look at a male orangutan.

While the sanctuary's veterinarian, Dr. Sen Nathan,   is introducing me to a 13-year- old orangutan called Anne.

She grew up here and was released into the wild   several years ago,   but she recently returned, heavily pregnant.

Wow, look at that nice big belly.

Orangutan pregnancies last around 8 to 9 months --   almost the same as us!

How close is due date for her?

NATHAN: Probably another 2 to 3 weeks.

REIDENBERG: Really?

Oh, she's very close.

Is this her first baby?

Yes, I asked my rangers who the father is -- they don't know because she has had so many boyfriends.

[Reidenberg laughs]   Dr. Nathan wants to make sure mother and baby are doing well.

NATHAN: So that's a really nice strong rhythm.

REIDENBERG: I definitely hear it, yes.

So what are you checking for now -- discharge?

NATHAN: Yes.

You can see that.

REIDENBERG: Yes, I see the discharge.

NATHAN: It's basically some pre-colostrum.

REIDENBERG: It's clear, not like milk.

It's got some of the antibodies in it?

NATHAN: It would.

So many aspects of an orangutan's pregnancy   are similar to our own.

Even down to the level of hormones,   which prepares the body for birth.

REIDENBERG: Yeah, there's movement in there.

It's okay.

So when the baby comes through the birth canal, the pelvis needs to widen, so some of these hormones are causing all of the joints in that area to open up.

I know that's true in humans and it makes it really hard for pregnant women to stand for a long time -- that's why you give a seat to them on the bus.

And it's very painful.

So for an orangutan do the hormones also cause the joints to loosen up like they do in people?

NATHAN: Yes, they do.

REIDENBERG: Does that make it uncomfortable, does she get cranky?

NATHAN: Yes!

Very, very, very cranky!

In the wild she would probably be resting a lot in a nest and only coming out for feeding.

REIDENBERG: So when they're resting in the nest, there's not a lot of pressure then on the pelvis and it gives her a chance perhaps to save a little energy.

But as she's foraging she's still got to carry not only her own weight but the weight of that baby around.

So her energy needs must be very different from when she is not pregnant.

NATHAN: Totally different.

REIDENBERG: She gets supplements in her diet like folic acid?

NATHAN: Folic acid, calcium is given.

REIDENBERG: Funny, that's the same thing I had to take when I was pregnant -- folic acid and calcium.

NATHAN: Hopefully in the next two weeks, we'll have a baby orangutan here.

Dr. Nathan and his team will look after Anne   at the sanctuary until her baby arrives.

But in the wild, she would be swinging --   heavily pregnant -- through the trees to seek out food.

Orangutans do everything high up in the canopy.

Anne found a mate up there   and eventually she'll raise her baby up there, too.

To see how the bodies of these animals have adapted for life   in the trees, I want to get close to a young male   called Mico who is hanging out near the sanctuary.

Like Anne, he was raised here as an orphan   but he's now back in the wild.

I'm hoping he'll let me get close enough   to see his anatomy in action.

But whilst it's easy for him, getting up in the trees   takes a bit more effort for me.

How the hell do orangutans do this so quickly?

[Panting] Some of them will be my age, so I haven't even got that excuse!

It is hard work!

Look at him -- he's making it look like a total breeze!

Very few experiences beat this.

To be off the ground, sharing the rainforest with an orangutan is unbelievably special!

Mico is a 14-year-old adult male;   he weighs around 100 pounds, over half my weight.

We share an awful lot in common -- we're both great apes, but these guys will spend more than 90% of their time off the ground.

When it comes to reproduction, they have to find a mate, have sex, give birth and raise their young, all without their feet hardly ever touching the ground, and that presents a whole stack of anatomical and behavioral challenges.

They have shoulder joints and hip joints that are much more mobile than ours and have a much bigger range of movement.

They would be utterly phenomenal at yoga!

Their arms are much longer and stronger than their legs   and the tendons in their hands and feet hold the bones   in a naturally hooked resting position.

This means they can grip with minimal muscular effort.

All very useful adaptations for having sex in the trees!

Just look at him go now.

Right, he's on the rope -- he's eating it.

MAN: Abort!

Abort!

Abort!

EVANS: We're going down.

Free?

Where's he gone?

Where is he, the little devil?

I've just had to do an emergency descent because this young adult male decided to take over all the climbing equipment.

He was chewing through my rope which was phenomenally dangerous, but a perfect illustration of just how agile and athletic and acrobatic these animals are.

Mico is in prime condition   and is certainly capable of mating up there.

But first he has to find a female.

I'm heading off to a feeding platform to investigate   how orangutans attract mates in the forest.

I've been told there is a female in the area called Ceeti   who is sexually active.

Wow!

Hi.

Oh, I get a foot too?

[Laughs] There's a male orangutan coming right now, just at the top of the trees there.

He's heading over to this wooden feeding platform here, so they're gonna be putting fresh fruits out, which is not a natural situation when you think about, because humans are putting food out, but in fact it mimics something that does happen in the jungle.

Orangutans are usually solitary animals.

Periodically the trees have these mass fruiting events.

When this happens, the trees all fruit at once   and the orangutans come from miles to gather in one spot.

It is an opportunity for them to socialize over food   and to find mates.

The same happens here at the feeding platform.

Mico, the male Mark met in the canopy,   has just shown up.

He's not the biggest, boldest, bravest male out there, but this is a chance for him to mate with a female.

And it's not long before Ceeti arrives.

They're definitely putting their heads together and they're definitely interested in each other.

They're very close together -- looks like she's grooming him -- or maybe they're sharing a little piece of food.

Ceeti is 12 years old.

Female orangutans have periods just like us   and she started menstruating four years ago.

She has been seen having sex with several different males   but has yet to get pregnant.

When they show some intimacy with each other, sometimes that can be a prelude to seeing some mating behavior.

Mico, the 14-year-old male, is also sexually mature.

When he moves away, Ceeti chases after him.

That's pretty incredible because usually it's the other way around in the animal world -- Usually it's the males chasing the females, but she is definitely interested in following him and perhaps getting him to mate with her.

This orangutan courtship looks like it's heading   for an inevitable climax high in the trees.

Over the next few days, I watch out for our young couple.

I finally catch up with them at the edge of the sanctuary.

These are the same two orangutans we saw earlier.

Ceeti the female has been following Mico the male.

The two of them are staying very close together and I think she's trying to get him interested in her for mating.

After several hours of bonding, Mico makes a move.

You can definitely see he's excited, his penis is up.

It looks like he's masturbating himself with his feet right now, while he's sniffing her genital area.

It looks like they are ready to mate.

And there, now he's mating her.

This is fantastic.

We're finally seeing them mating.

We've been chasing them as they've been chasing each other all around the forest, but finally they've come together.

The whole process seems extremely gentle, very almost slow motion.

And this may last for 30 or 40 minutes, which is a long time for mating, I mean compared to humans -- average is maybe two to four minutes.

But these guys will go at it for the better part of an hour.

But this sex may not lead to a baby.

Like humans, a female orangutan has a monthly menstrual cycle.

She can only get pregnant   for six days in the middle of that cycle.

It's impossible to tell if Ceeti is fertile right now   just by looking at her.

In most primates,   the female displays the fertile stage of her cycle   with swollen genitalia.

It's a visual cue that says, "I'm ready to have a baby,   so go ahead and mate with me!"

But the female orangutan is different --   just like female humans, she does not display her fertility.

I can't tell whether she is ovulating, and actually the male can't tell either.

That actually results in a very clever strategy on her part.

Mating with multiple males when she isn't fertile   could be a way of protecting her future offspring.

This strategy ensures that all the males that she mates with think they're the father, and the advantage there is that they won't try to harm the baby after it's born.

But maybe there's another explanation.

Could she be having sex for pleasure?

We don't know if orangutans experience orgasm,   although females do have a clitoris.

What we do know is that when Ceeti is fertile,   she will try to seek out a much more impressive male   than Mico.

She'll want a dominant male.

Dominant male orangutans are the kings of the Borneo jungle.

They are nearly twice the size of all the other adult males   and rule over their own area of forest.

Lesser males stay out of their way,   but females seek them out.

Any male orangutan can become dominant   at any time in his adult life.

It's not clear what triggers the change.

What we do know is that it's   one of the most dramatic transformations   in the natural world --   the orangutan equivalent of becoming   the Incredible Hulk.

With a surge of testosterone,   his skeleton starts to grow again.

He almost doubles in size.

He grows a fine long coat   and develops huge pads of facial tissue on each cheek.

Because of these phenomenal facial flanges,   this orangutan king is known as a flanged male.

As an anatomist, I'm fascinated   by these impressive cheeks and what purpose they may serve.

They could be for attracting females.

Primates certainly use facial features to attract mates.

Here in Borneo there's a species of monkey   with a very suggestive facial appendage.

Jonathan Chai is researching proboscis monkeys   and knows how to draw them in.

[Imitating monkey call] "Ow" and "uh-oh"?

[Laughter] This is the male calling the girls in?

-Can I try it?

-Sure.

[Imitating call] I sound more like a bird!

These bizarre looking monkeys   are unique to the island of Borneo.

Their native name is belinda-utan,   which means Dutchman,   because local legend suggests the Dutch colonizers   had similar large bellies and big noses.

The males of this species are pretty obvious to spot   because they have a permanently erect penis   and the most dominant male grows an incredibly big nose.

These monkeys can tell us a lot about how we primates   attract mates using our faces.

Here he comes, here he comes.

So is this the Alpha male?

CHAI: Yes.

-Does this one have a name?

-Halihandro.

REIDENBERG: Halihandro!

That's the female.

The mating will start when the female gives a sign to the male.

REIDENBERG: So the female starts...

Pushing the lip like this.

So they're showing the pink of the lip like that, so that's like kissing -- I'm sexy!

[Laughter] There she goes, she's doing it now!

So after she does this lip thing, he'll wiggle his nose?

CHAI: Yeah.

So the girls think that's very sexy, a big nose?

It's basically a walking penis face, right?

So the girls look at that nose and go, "Impressive nose!

We know what else is impressive about this guy, right?"

A big waggly nose may seem   like an odd way to attract a mate.

But primates are visual creatures   and these proboscis monkeys are not alone   in their use of visual adornment.

With mandrills, it isn't size that matters -- it's color.

Their bright blue and red faces   match their genitals and rear ends.

The most dominant male has the brightest colors.

Dominant uakari monkeys go for red bulges on their heads.

Snub nosed monkeys use warty lips to show off status.

And humans have their own forms of visual adornment   to draw attention to their faces.

For dominant orangutans, those big cheeks could well be   a visual display to make it clear who is king.

But as impressive as these cheeks are,   in a dense jungle,   orangutan males can go for days without contact.

They need another way to draw females in from a distance.

[Orangutan calling]   The call of the flanged male   is the most penetrating sound in the jungle.

Flanged males are the only orangutans that have   the anatomy to produce this sound.

[Calling]   EVANS: We're going to see what effect   this incredible call has on other orangutans.

Scientists investigating this call   have recommended an experiment.

That missed.

First, I need to throw a line over a high branch   to get a speaker up into the trees.

No.

Here you go then, clever-clogs.

The sanctuary's veterinarian, Dr. Sen Nathan,   is giving me a hand.

That is really irritating!

Really irritating.

We have our own version of a tree dwelling flanged-male.

I'm going to play a recording   of an orangutan king's long-call.

Stop there!

Research has shown that the flanged male   sends out his long-call every night,   in the direction he plans to travel the next day.

Fertile females respond by lining up in his path,   ready for sex.

Mico and Ceeti are still in the nearby trees.

We want to see how they respond   to the flanged male's long-call.

If Ceeti is fertile, she may show interest,   but we expect Mico may run away   when he hears the call of a king.

Right, Sen, here goes.

Two seconds and it should fire up.

Here it comes!

[Call plays] Look at that.

Clocked it straight away.

Do you see the way he moved around her and almost like pushed her backwards to say, "I'll deal with this."

[King call continues] It's interesting his eye line is absolutely directly at that speaker and she is looking, but she's much less interested.

Okay, so moving away now and trying to get higher.

Hang on, let's get a closer look.

[King call continues] NATHAN: Is he trying to do what I think he's trying to do?

EVANS: They are mating now.

Yeah!?

NATHAN: Oh, yeah.

That is extraordinary.

Oh, my God, he's masturbating now!

What is going on, Sen?

What is going on?

Look, he's got a massive erection!

I would never have expected that in a million years.

NATHAN: Same here.

We expected Mico to move away   from the sound of the dominant male,   but instead he's holding his ground   and has just mated with Ceeti!

That's a pretty bold thing to do, isn't it?

Because if that was a real flanged male and actually went, "Hang on a minute, are you trying to take over my territory here?

I have the girls in this area," that could end up in a full-on fight, and they're pretty ferocious!

NATHAN: Oh, it could have.

Dr. Nathan has a theory to explain Mico's bold behavior.

NATHAN: Take a look at Mico, look at his cheekbone.

He is actually developing the tell-tale signs of flange coming out.

I bet you a year from today, two years from today, the flange will be getting bigger.

EVANS: If he is in the early stages of becoming a flanged male, that could help explain why he's reacting like this, because I was expecting him to just leg it and disappear, but he couldn't have done anything more different.

Mico may have sensed an opportunity   to become a flanged male   because the existing dominant male may be losing his power.

Orangutan kings   can only sustain their strength and status   for so long before their dominant features   begin to fade and they stop breeding.

Then they'll disappear into the jungle   to live out their old age in peace.

Another male then takes his place   and transforms into a king.

This new king will have to defend the boundaries   of his territory   and fight ferocious battles with neighboring kings.

But he won't need to fight   the lesser males within his kingdom.

Amazingly, just the presence of a flanged male is enough   to prevent the lesser males from transforming   into the dominant state.

How he does this is a great biological mystery.

But there is one scientist who has a theory.

Before travelling to Borneo, I visited the Los Angeles Zoo   to meet biologist Dr. Graham Banes.

He thinks the answer to how flanged males   hold back the development of all the other males   lies within those impressive cheek flanges.

We're going to a restricted area of the zoo   to study the cheek pads of Bruno,   a 35-year-old flanged male,   who has been an orangutan king for over 10 years.

Wow!

BANES: Hi, Bruno.

REIDENBERG: Unbelievable, he's enormous!

BANES: So if you want to take just one.

Graham has spent many years   tracking orangutans in the wild, but this year   he has been visiting zoos all over the U.S.A.   to take samples from orangutan flanges.

If you want to swat against his face and rub his cheek pad and see if you can get anything off, any secretions or sweat coming off.

REIDENBERG: Good boy!

BANES: Ready, Bruno?

REIDENBERG: So you're looking for some kind of secretion coming off of the skin?

BANES: Yeah, so it could be some kind of sweat or some other fluid that's coming off, and we want to just get it onto the swab and into here.

REIDENBERG: He was very good, wasn't he?

BANES: He was probably the best one so far.

REIDENBERG: So you've done a lot of these?

Yeah, Bruno is probably number 26 so far.

REIDENBERG: And what are you finding from the solutions you're collecting?

BANES: There's definitely some chemical signal, some smell or pheromone coming off the cheek pads.

Smell is really underappreciated, I think.

You can see about up to eight million different colors, you can hear about half a million different tones, but you can smell up to a trillion different smells.

REIDENBERG: Wow!

Smell is often used to signal dominance.

[Lemur calls]   Ringtail lemurs are famous for their stink fights.

Using scent glands on their wrists,   the males anoint their tails and waft the chemicals   at rivals to win the fight.

And it's thought the dominant female cotton-top tamarind   uses pheromones to stop the other females   from becoming fertile.

BANES: It does look as though there is some difference between the chemicals coming off the flanged males and the un-flanged males.

So there's only ever one flanged male in an area and maybe this smell signifies to other males that they shouldn't develop, it suppresses them and keeps them in this sub-adult, un-flanged form.

Graham's theory is that,   as the dominant male patrols his kingdom,   all the other males receive his unique pheromone signal.

This sets up a chain reaction of brain signaling   and hormone messages   that ultimately crushes their testosterone   and leaves them suspended in the untransformed adult state.

Being the only flanged male in an area is a huge advantage.

The king will attract most of the fertile females.

Studies have shown he will father   half the offspring in his kingdom.

His genes will dominate the next generation.

Back at the sanctuary,   Anne the pregnant female is getting heavier every day.

And the team is keeping a close eye on her   in anticipation of the baby arriving.

But out in the wild, the males leave pregnant females   completely on their own.

Mothers must fend for themselves   and ultimately give birth in a nest high in the trees.

It's hard to believe that a nest built of twigs and leaves   can be strong enough to support such a large animal and a baby.

Mark's going back into the tree tops to investigate further.

EVANS: I've spotted an abandoned nest near the sanctuary   and I want to explore its structure.

I'm about twice the weight of a pregnant orangutan   so it will be interesting to see   if this nest can support me.

I have always wanted to be able to see what it must feel like to rest in an orangutan's nest, and this is my opportunity.

Right, I'm going to pull myself slightly along towards you, so if I can have some slack behind me?

Okay, here we go.

More.

More.

This is [bleep] mad!

I am hyperventilating a little, but I think I have every justification to be.

That's better.

Hang on.

A bit more.

I'm now lowering into the nest.

The nest is taking a little bit of my weight now, just stop there two secs!

More.

More.

The tension has gone off this high wire.

I am now resting in an orangutan's nest a hundred feet off the ground!

The guys on the ground are absolutely tiny!

What a remarkable structure!

It's blowing a little bit in the breeze.

It actually feels really comfortable.

Why am I surprised?

They build great nests!

It is... really lovely.

What looks like a random collection of leaves   is actually an ingenious construction.

Science over the last couple of years has shown that orangutans have a knowledge of the mechanics of wood and they use that knowledge in a very clever way.

And a great illustration of how they do it is here behind me.

This is called a green stick fracture, and when they snap a branch like this so that it's still connected to the tree and then brought that branch underneath to make the base.

But then by interweaving several of these greenstick fracture branches together you create a safe platform.

But even cleverer with this nest are these uprights you see here.

The orangutans snap them off but use these as almost upright pillars to be able to weave the other branches around to make it incredibly solid.

You'd be hard pushed to knock this nest out of this tree.

Orangutans might not know it, but they are clearly   accomplished structural engineers.

All orangutans will make nests to rest in.

We spotted Mico building this one.

It took Mico just a matter of minutes   to make his comfortable nest.

It's one thing building a nest for a nap,   but imagine giving birth up here.

What a contrast to how we human beings give birth.

You know, I think of my own boys born in a hospital in a maternity ward surrounded by midwives and loads of high-tech kit and family around for support.

And even then it's tough enough.

To do it up here in a nest you've built yourself, over a hundred feet off the ground, completely on your own.

It is mind blowing to have a baby up here.

Being so high in the canopy,   orangutan births are very private,   hidden away from predators and us.

A birth has never been filmed in the wild.

But last year at Durrell Wildlife Park in Jersey,   a world leading center for orangutan breeding,   the keepers recorded this rare footage of Dana,   a 25-year-old orangutan,   preparing for the birth of her first baby.

Late in the evening   she becomes unusually active and starts to prepare her nest.

Within a few hours, she begins to give birth.

She immediately starts cleaning her baby,   who clearly has a good set of lungs.

[Baby screeching]   Like most animals, she eats her nutritious placenta.

She is keen to show off her new baby girl,   which the keepers named Kia.

Dana was able to deliver baby Kia all by herself.

Thanks to their anatomy,   orangutans have relatively straightforward births.

A large oval shaped gap in their pelvis allows the baby   to pass through the birth canal in one smooth movement.

Humans, on the other hand, have a different shaped pelvis   to allow us to walk on two legs.

Our babies must twist through 90 degrees   to get their large heads through an awkward passageway.

Because of this complicated birth,   we are one of the few animals that will often have help   with the delivery of our babies.

Dana's birth went well and back in her enclosure at Durrell   she's an excellent mother to baby Kia.

But not all orangutan births go so smoothly.

I've left Borneo and have come to Durrell Wildlife Park   to meet Neil MacLachlan,   an obstetrics and gynecology surgeon   more at home in a hospital than a wildlife park.

10 years ago he was rushed here to perform   the world's first orangutan Caesarean section.

A 39-year-old orangutan   called Gina was in trouble.

Her baby's placenta was blocking the birth canal.

She would have bled to death without human intervention.

No veterinarian at Durrell knew how to perform   an orangutan Caesarean,   but Neil had done many on humans.

The hope was that Gina's anatomy   was close enough to humans for his medical team   to save her and her baby.

At this stage they had no idea if the baby was alive.

The baby wasn't breathing.

[Cheering]   But the team successfully resuscitated the newborn.

The new baby boy was named Jaya.

[Newborn calling]   Gina had been anesthetized for the operation   so the team didn't know if she would accept Jaya as her own.

Gina?

You ready to go?

[Baby crying]   The bond was instant.

Good girl, Gina!

Ah, it's your baby!

What a good girl!

I was there when she was released back, and the mother just came and picked her up as if she had never known she'd been away.

MAN: How did that feel?

MacLACHLAN: Everyone was really very touched by seeing her just pick the baby up and carry on as if nothing had happened.

It was brilliant.

Today, 10 years after the Caesarean,   Neil is back to perform a full physical check-up   on the mother, Gina, to find out   if she can have another baby.

She is anesthetized for the examination.

Even though she's 49 years old,   she may still be able to get pregnant.

We think that orangs carry on breeding until they die.

-So no menopause?

-Probably not.

Neil wants to make sure she is fully recovered   from her Caesarean and whether she should be allowed   to mate and get pregnant again.

He does an ultrasound scan and discovers something surprising.

Gina's uterus is about half the normal size.

MacLACHLAN: If I'd been led in here today and asked to examine this patient blindfolded and I looked at the scan and I looked at what we found, I would say this is a 60-year-old human, a post-menopausal woman.

But we've always thought these guys don't go into menopause, they keep cycling for their entire lives.

Yes, well, that may not be right.

Blood tests confirm Neil's suspicions   that Gina has been through menopause,   something that has never been documented in orangutans   until now.

What's happening, I think, is that these animals are living for longer in captivity and that's what happened in humans.

Most women, pre-Victorian times, didn't live to the menopause because other illnesses took them away, but now that they live to 83, a woman now spends, you know, a good third of her life in a post-menopausal state.

EVANS: What an extraordinary finding though, to prove that potentially orangutans go into menopause.

That's ground-breaking science.

Gina has a remarkable gynecological history.

She was the first orangutan to have a Caesarean   and now she's the first to be   scientifically proven to have been through menopause.

Gina quickly recovers from her examination.

She continues to show us that orangutans   are more like us than we ever dared think.

Back in Borneo, I'm on my way to catch up   with another female orangutan   who's learning to be a mother for the first time.

We've just heard that Anne,   the pregnant orangutan at the sanctuary,   gave birth overnight.

So this is her.

Where is your baby?

There you are!

Look at your little head!

Look at your little head!

-Is it male or female?

-Male.

EVANS: Male, okay.

Mum looks so, so chilled out with baby on her chest.

She's, what, 13 years old and she spent the first seven years of her life, mum, here, but then she did go back to the wild and was completely wild until she was pregnant.

And then she came back here, which is amazing, isn't it?

Maybe she knows that this area is safe and there is people that can take care of her.

She is being really amazing with that baby, isn't she?

LAURA: Yes, she is.

She's very protective of him.

EVANS: Do you know there's something extraordinarily human about what we are looking at now, isn't there?

So what's the plan from here now?

LAURA: We give a chance for Anne to take care of her baby in the cage for the time being so we can monitor whether she is a good mother for the baby or not.

Hopefully she is a good one, and I believe in her, and maybe after that we will think about releasing them back into the wild so that the baby will learn more new things in the wild, not hand raised by us humans.

EVANS: Her baby now has an opportunity to grow up wild and that's what he needs -- seven or eight years, one to one attention from his mum, from Anne, to teach him how to be an orangutan, how to survive out there in the wild, to be able to ultimately find his own mates and to reproduce again because fundamentally, biologically, this is what life is all about -- making babies.

In the wild, orangutan babies are in constant contact   with their mothers for their first year.

When they are two years old,   they'll try swinging on their own.

By this stage they're learning to eat solid food   and are able to make basic rain covers.

They can build nests by the age of three.

But even when they are 6 years old, they still struggle   to move through the jungle on their own.

It's not until around 8 years old that they're finally   ready to survive alone.

For their mothers, spending so much time rearing a single baby   is a huge investment.

Eight years is the longest natural interval between births   in the animal kingdom.

What are you doing?

Oh, no, you have to walk.

You have to walk.

NATHAN: You have a lazy orangutan with you.

REIDENBERG: I certainly do.

The orphaned babies at the sanctuary   have lost their natural mothers,   but Dr. Sen Nathan and his team are hand-rearing them   for the first eight years of their lives.

The most important skill for them to learn is how to climb.

That's a boy!

Oh, right.

There you go!

I noticed when we brought the babies out they were clingy.

They grabbed the clothing, they grabbed so easily on the ropes.

Do they have that from the beginning?

From the beginning and in fact they have it right up to they are five, six, seven, even adults, but I suppose they need it when you're up in the forest trees 40 feet from the ground.

REIDENBERG: Yeah, it's survival necessity to grab like that.

Especially to hold onto mum as she's moving through the trees.

Humans have a reflex just like that, called the Moro reflex.

So, young babies, a couple weeks old, if they feel like they're falling, they start reaching up like this.

And I remember so clearly when my older daughter was only a little bit less than a month old, we were travelling on an airplane and every time the plane changed altitudes, the arms would come up like this!

I felt so bad for her because she was asleep but the arms still came up like this every time.

And it's just an innate reflex.

When we are first born, just like orangutan babies,   we reach with our arms in the Moro reflex.

And if our hands and feet are touched,   we immediately grip.

This is called the palmar or plantar grasp.

These innate responses are probably a vestige   from when our ancestors lived in the trees   just like orangutans.

We lose these reflexes within the first six months.

But orangutan mums are constantly   roaming the treetop canopies looking for food --   so their young need to grip on tight and enjoy the ride.

There was a study done on orangutans that showed what comforted them versus what comforts human babies and it was really interesting to see where the differences were.

So human babies were comforted by human faces and they love just looking at a human face, it would make them calm.

Orangutans didn't care about the face at all.

What they liked was to have their bellies pressed.

Being comforted by physical pressure makes sense   if you are clinging to your mother   while swinging in the trees.

But our dependence on faces and advanced social communication   are thought to be important differences that separate us   from all the other great apes.

There is a legend among the locals.

They believe that one time before -- I mean it's a legend -- orangs could talk.

But humans started making them slaves so they stopped talking.

Maybe that was smarter!

[Laughter]   Orangutans may not speak,   but we shouldn't dismiss their own unique intelligence.

We know orangutans are capable of copying behavior   and showing signs of advanced learning.

This ability to learn from others is key   to the success of orangutans and all the great apes,   including us.

EVANS: The older orphans at the sanctuary   are five to eight years old;   some of them are ready to survive on their own.

There is only so much humans can teach them.

They need to learn   from each other and from wild orangutans   they can see in the forest.

REIDENBERG: They're really, really good at learning.

They're incredibly good at mimicking so if they can see some of the wild ones out there and mimic what they're doing, hopefully they can catch up those eight years and learn how to make a nest properly, how to stay in the trees overnight and not feel like they have to come back to the shelter.

And we share so much in common with them.

We like to think of human beings as somehow being separate.

Often people don't even refer to human beings as great apes.

But we are so incredibly closely related.

It's brilliant when you see them using these ropes that go out into the forest, and particularly when you see them, a couple of them are hanging onto the rope and swing in to a tree and grab the tree and they're like between two worlds.

And it's, which do I let go of?

REIDENBERG: It's wonderful to go in a little further each day until they finally feel they can let go of this human environment and stay totally in the wild.

Hopefully these young orangutans   will return to the rainforest.

The females will choose their mates.

Some males may even become orangutan kings.

And ultimately these great apes, like us in so many ways,   will produce their own young high in the treetop canopies.

Next time on "Sex in the Wild,"   we're in Australia to discover mammals   with one of the strangest reproductive strategies of all,   the marsupials.

We'll uncover the life-giving secrets of their pouches... -I see it!

-There it is!

...their bizarre sexual anatomy...

This tube is a third vagina.

Look, it's got a huge chest.

...and their impressive fights for mates in the outback.

"Sex in the Wild" is made possible in part by   To learn more about this program, visit...   "Sex in the Wild" is available on DVD.

To order, visit shopPBS.org,   or call 1-800-PLAY-PBS.