Along the banks of the mighty Zambezi River in the high plains of northern Zimbabwe, a troop of chacma baboons tend to their daily routines in accordance with the rules of social order that make for a stable and cohesive community.

Alliances can mean the difference between life and death, as each day brings a myriad of challenges. Months of searing heat and drought grip the land, and ambushes by rival troops and predators such as leopards, crocodiles, and pythons pose imminent threats.

A rare set of twins born to the dominant male and female face an especially difficult trial. In an environment where only a quarter of infants survive their first year, the odds are stacked against them. But their “royal parentage” could carry some advantages for their survival.

In the Zambezi, privilege can be lost as quickly as it is gained. A large male from a neighboring troop enters their ranks, determined to unseat the dominant male. In a swift and decisive battle, the king is deposed and the entire stability of the troop is thrown into turmoil. Under the rule of the new alpha male, the twins are no longer safe — the intruder has cast his eye on their mother. But the infants are not yet weaned and until they are, their mother will remain sexually unavailable. For the tyrant, the equation is simple and brutal, but just how far will he go?

The rains are late and the dry season stretches into its eighth month. Competition for food brings the troop’s inherent rivalries to the surface, and bouts of infighting break out. The alliances that were once the binding thread of the group begin to come undone.

Meanwhile, only one of the twins has survived, and he must grapple with his brother’s murder, his father’s overthrow, and a mother whose affections have been commandeered by the one responsible for the heinous deeds.

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Online content for Murder in the Troop was originally posted April 2006.

The Zambezi is known as the “River of Life” across southern Africa, but surviving by the river near Victoria Falls is not always easy. During the rainy season the Zambezi has a fierceness and a power that is deadly to both animals and humans. At the peak of the rainy season, almost 300,000 gallons of water cascade over the falls every second.

Despite the danger, many birds, reptiles, fish, and mammals call this area home. And a fisherman, known as Mr. White, has lived in a nearby town for 74 years, spending almost every day by the falls. NATURE joins Mr. White as he tells us Zambezi’s story — a story of the changing seasons and many moods of the river.

During the dry season, life gravitates to the river by Victoria Falls. As the sun beats down and the water level lowers, grass-covered islands above the falls are exposed. Families of elephants from the surrounding savannah flock to the Zambezi to make the river crossing. Predator and prey rely on the river for water, and pairs of bee-eaters and pied kingfishers dig nests in the exposed muddy banks. Fish eagles raise their young and teach them to hunt, and hippos crowd the waters.

Life flourishes, for a while. And then, months later, clouds gather in the sky and rising waters force many animals to leave. It is the rainy season, and Victoria Falls becomes magnificent again – her voice rising from a whisper to thunder.

Victoria Falls premieres Sunday, May 17, 2009 at 8pm (check local listings).