Once Kingo has eaten all the food he can lazily reach, he descends, grabbing a hawser-size vine and sliding down through midair like a fireman. In minutes, the rest of his clan, one by one, have all twirled down the mighty vine.

Their path through the forest is frustratingly erratic. Left, right, looping left again, Mongo recording each change in direction on a GPS device. But Kingo knows where he's going and shortly reaches his destination, a gigantic Gambeya tree. It's the end of the dry season, and there's little bambu fruit on the ground. Kingo tears open a small red globe, chews out the flesh, discards the rind. Kusu, right on his heels, takes up the rind and gnaws away. Ekendy gets Kingo's next leftover. Still, there's not enough fruit to keep Kingo's interest, and he moves on.

They are nonchalantly grazing their way through the forest when George happens to discover a mobei fruit on the ground. She hungrily begins ripping it open with her teeth while simultaneously trying to keep quiet about it and sneak away from her relatives. No luck.

Kingo, keenly aware of food of any kind, either smells the fruit or hears George eating. Instantly he is pounding through the jungle, bellowing. George cowers, and he knocks her down and snatches the fruit from her grasp. George whimpers and scuttles away while Kingo sprawls out on his fat stomach, props his elbows up on the ground, and gorges. "Food is everything for Kingo," Mongo whispers.

Eat, sleep, move. Eat, sleep, move. That's the life of a gorilla.

The total range of the Kingo family is about six square miles (15 square kilometers), sections of which overlap with the ranges of other gorilla families. At least nine other groups inhabit parts of Kingo's home range. Western lowland gorillas are not territorial, and their relatively frequent encounters with other groups of gorillas are often surprisingly peaceful. By contrast, groups of mountain gorillas are almost always aggressive with one another, with chest-beating, screaming, and charging. Doran-Sheehy has shown that dominant males in western gorilla families may be related (such as brothers, half brothers, or fathers and sons), which may help explain their remarkable tolerance of one another.

Late that afternoon, Kingo is traveling fast—no stopping, no dawdling—his huge arms pulling him through the tangled verdure. His family races along behind him. To keep up, Kusu hitches a ride on Mama's back, Ekendy piggybacks onto Mekome, Gentil and Bomo cling like ticks to their mothers' breasts.

They're moving so fast we lose them in the jungle. But the trackers are not worried. They know where Kingo is going: to the swamp.

The next morning it takes two hours to reach the gorillas. The trail descends into stagnant pools of green water and crotch-deep mud beneath a ceiling of thorn-encrusted lianas. And yet, when we finally break out into a clearing, it's a scene as idyllic as the jungle gets.

Butterflies the size of birds flit about in the sunshine; spiders as big as a child's hand are sunning themselves on roots; frogs are belching, dragonflies darting, bugs humming, and all manner of birds piping or cawing, hooting or cooing. And right in the middle is Kingo. He's up to his chest in a pond, pulling up the stringy roots of kangwasika swamp herbs, washing them in the water, then sucking them down like spaghetti. Seated smack in his own salad bowl, he couldn't be happier.

Actually, the whole family appears pleased. None of them can get near Kingo, of course, but they've each found their own place in the sun. Ugly is a little distance away, gently holding Bomo as if she's about to give the baby a bath. Kusu and Ekendy are heard but not seen, crashing gleefully through the reeds. George is unseen and unheard. Beatrice is nursing quietly in her own serene patch of swamp. Mekome is seductively edging into Kingo's pond. And Mama is up a tree nimbly popping termites into her mouth.

Just one big happy family.