NARRATOR: It is a place as intriguing as it is beautiful.
Roughly 20 miles off the coast of West Africa,
Bioko sits alone in the Atlantic Ocean,
a volcanic relic now blanketed in equatorial rainforest.
The island has been cut off from the mainland for 12,000 years.
Today, it hosts some of the rarest species in the world,
including the drill.
The secret life of these shy, endangered primates
is now revealed for the first time.
Motuku, a large male, dominates this part of the forest.
He is a king, as his name implies in the indigenous Bube
language.
He sits at the head of this large troop,
a family group of around 10 females,
daughters, and adolescent males.
These notoriously reclusive animals
aren't habituated to humans.
This first intimate glimpse reveals
it is a male-dominated society.
As alpha, Motuku jealously guards his females
from all challengers.
His daughters will likely stay with the troop all their lives,
but he will kick his sons out when they reach breeding
age, around six years old.
It's November, the beginning of the dry season on Bioko.
40 miles to the north lies Malabo, the capital
city of Equatorial Guinea.
But the further south you go on the island, the denser
the rainforest becomes, and the fewer
humans have set foot there.
Sunlight is at a premium in Bioko's ancient jungle.
Trees battle each other to soar high
into the canopy, which is alive with rare species
like the great blue turaco.
Down on the forest floor, it's raining fruit.
The troop's having breakfast.
Motuku helps himself to a little mana from heaven.
The troop has just welcomed its newest member, a young male,
barely visible as he clings to his mother, perched on a rock.
His name is Zipote, the little one.
His mother, Tiki, is one of the highest-ranked females
in the group, so Zipote will be a pampered little forest
prince.
He's more precious than his mother knows.
There are as few as 3,000 drills left
in the wild, most of them living in a tiny patch of forest
on the mainland.