When scientists first arrived at Ngogo...
...they discovered an advanced chimpanzee society.
Over the decades, that society
grew to become the biggest chimp group
ever known.
They expanded their territory,
dominated the forest,
and built an empire.
But rivalries developed,
and the empire divided.
A small but powerful band of males broke away to form their own group.
They became...
the westerners.
Chimps that lived together for years...
...became enemies.
And now...
their rivalry
has turned deadly.
It's still just a few days
since the central chimps
found Pork Pie dead.
It's not known what chimps understand about death...
or whether they grieve.
But the loss of Pork Pie has clearly had an impact.
For the central chimps,
the world has become more dangerous.
Christine's baby is now nine months old.
When she first arrived,
her sister, Nadine, was neglected.
Now she's a little older,
and her personality is beginning to develop...
she's begun to add to Nadine's life.
They're not only sisters.
They're best friends.
Ngogo is never richer in food
than when Chrysophyllum is in fruit.
And it brings the chimps together.
Jackson is still under pressure.
Abrams is back in his place,
but he won't give up.
Jackson needs to remind everyone who is in charge.
While Jackson is focused on dominating at home,
other chimps are standing guard at the western border...
alert to the new threat they face.
Abrams is here.
And so are several other adult males.
But they have no way of knowing
when the westerners will strike again.
The life of an alpha male isn't easy.
But it comes with benefits.
Generally, the higher a chimp's rank,
the more opportunities they have to mate.
Mature females like Bartoli
normally give birth every five or six years.
Bartoli's son, Herzog, is six years old now,
and she's ready to get pregnant again.
She could do a lot worse than Jackson's genes.
But she needs to be cautious.
Jackson is big,
powerful, and unpredictable.
She needs to keep herself and Herzog safe...
and ensure that Jackson is calm.
Herzog finds the whole thing confusing.
But as a young chimp,
he has to stay close to his mother.
Whatever she's doing.
Jackson is making his move.
By waving a branch,
he's asking Bartoli to follow him...
and mate.
And Bartoli seems keen.
Herzog makes an attempt to break it up.
But it's too late.
Jackson got what he wanted.
And so did Bartoli.
But it's been a tiring day.
Female chimps mate with multiple males.
So there's no guarantee
Jackson will be the father of Bartoli's baby.
He stands a good chance though.
Because it's happened before.
Although Jackson doesn't know it,
Herzog is his son.
Chimps don't always hunt because they are hungry.
In fact, usually the opposite is true.
They hunt much more
when they are well-fed and bursting with energy.
When Chrysophyllum is in full fruit,
hunting goes into overdrive.
Chimpanzees don't conserve resources...
or think about the nature of what they are eating.
With this many kills,
meat sharing is highly political.
For Jackson, this big duiker
is an opportunity to strengthen his position
by sharing with his allies.
Today, he's favoring another high-ranking male.
Peterson.
But just as important
is who he's excluding.
Wilson is an up-and-coming young male.
He's strong,
and he's ambitious.
Jackson is not including him.
And he's taking it badly.
The males can be aggressive around meat,
and the females need to tread carefully.
Christine wants a share.
And she's willing to take the risk.
Wilson is watching carefully.
Christine got what she came for.
But she may not get to keep it.
Wilson is taking out his frustrations.
Fortunately, the baby wasn't hurt.
But Christine needs to take her family away to safety.
This is a quiet part of the forest,
away from most of the group.
But Christine is not alone.
Gus can't offer protection from a chimp like Wilson.
But at least he can offer some comfort...
to Christine and her family.
Abrams' challenge to Jackson has stalled.
Jackson is propped up by some powerful allies.
And Abrams is lacking support.
But now there's another ambitious young chimp
with a grudge against Jackson.
This could be the beginning of a powerful alliance.
For now, Abrams and Wilson
are joining a group of males to patrol westwards.
Jackson is not with them.
As powerful as he is in his own territory,
Jackson fears the west.
He grew up in the west
and was allies with the westerners for many years.
But when the group split,
he deserted them
to reign as alpha of the bigger central group.
As conflict erupted,
the western males targeted Jackson.
He escaped with his life.
But he still bears the scars.
The westerners are a threat to all the central males.
But they hold a bitter grudge against Jackson.
And he fears them to this day.
The borderlands are filled with Chrysophyllum.
The westerners are spending more and more time here feeding.
After killing Pork Pie,
they've grown in confidence.
And there are chimps in the group that won't stop there.
Rollins and Damien will always want more territory.
The western males are getting stronger.
They are constantly displaying.
The westerners are getting ready to make their move.
And Richmond is at the center of it.
He's not alpha anymore,
but he's still a chimp to be feared.
Bergl is back to full health.
And that's not his only progress.
He's regularly grooming with Garrison,
who seems to be a good influence.
And he's even started to bond with the west's patrol leaders.
Wrestling is a good test of strength.
And it gives Rollins and Damien a chance to see what Bergl is made of.
The westerners need every chimp they've got.
If they're going to claim this area for themselves,
they'll have to confront the central chimps in their own territory...
...and push them back.
For this, they need numbers.
So they'll travel in force,
males and females together.
Bartoli and Herzog are near the borderlands,
getting some peace away from Jackson and the other central males.
It's much needed.
But she has no idea what's coming.
If they're caught,
Herzog could be killed.
A western male is chasing Bartoli into the canopy.
She and Herzog have been separated.
But Herzog won't leave his mother.
He's going to try to protect her.
He's got the attacker's attention.
But now they're both trapped in the canopy...
at the mercy
of the western males.
But the westerners aren't attacking.
They're moving on.
A lone family is not what the westerners are looking for.
Bartoli and Herzog
slip away together.
The westerners are pushing deeper into the central territory.
And some chimps
are beginning to hesitate.
For Carson, the risk is too great.
And she's going to put E.O.'s safety first.
Many females and younger chimps
will drop out with the threat of real battle.
And Joya
is choosing to follow Carson home.
A chimp like Bergl should fall back too.
He's too young and too small.
But Bergl is staying.
He's grown in confidence.
And for him, conflict is in the blood.
Although neither of them know it...
he is Rollins's son.
The western males are deep inside the central territory.
And they can sense their enemies are close.
The central chimps have been caught off guard before.
But not this time.
This time, they're ready.
When two big groups come face-to-face,
the outcome is always unpredictable.
The westerners attack.
And the centrallers meet them head-on.
Bergl is right in the middle of it.
The westerners are pushing the centrallers back.
But some chimps still haven't joined the battle.
If the centrallers are going to fight back,
it will be now, behind their alpha.
Jackson is face-to-face with his old rivals.
The same chimps that tried to kill him years ago.
Jackson shows no fear.
And his group get behind him.
The westerners have been pushed back.
And they're retreating.
The central chimps have held off their rivals.
But Jackson has been injured in the battle.
He defended his territory.
But at what cost?