The buffalo are on the move.
The swimmer in the Zambezi has picked up a stalker on his border crossing from Zimbabwe to Zambia; an enormous crocodile. We watch breathlessly from the Zambian side, willing the old bull to safety as the croc closes in on his buttocks, until he bursts up the river bank in a convulsion of hoofs and horns and blunders off into the trees.
The air is filled with tiny butterflies on a longer international journey. Wherever you find the blue flowers of wild basil in the bountiful autumn of southern Africa - our spring - you find brown-veined white butterflies on a north-east flight path, dancing along their migration route from South Africa to…"Kenya!" I shout impulsively, like the class swot, forgetting I am merely an observer and not in competition with the bona fide students.
Wrong. But our tutor is gentle with the misinformed. "I've heard people say that, but there's no evidence for it. Why would they fly as far as Kenya when they have everything they need to feed and breed here in the Zambezi Valley?" Derek Solomon isn't just a wildlife expert of mighty reputation; he is the guide who guides the guides. Zimbabwean by birth, he now lives in South Africa, where he runs his own safari operation near Kruger National Park. But he's also in demand as a lecturer-in-the-field. He is spending a few days at Chiawa Camp to refresh the skills of its team of guides.
In my next life I plan to work in the African bush - filmmaker, researcher, tracker, tea-bearer, anything will do - and I never miss an opportunity to learn more from its masters of bushcraft. This opportunity is a chance I'm privileged to seize. The seasonal camp has just re-opened after the rains, and there is time for instruction before Chiawa's immaculate standards and prime riverbank site in Lower Zambezi National Park bring safari tourists to fill its spectacular tented rooms. In the seraphic light of early morning I trundle into the bush with Solomon and three of the guiding team, listening, looking and learning as he invites them to identity bird calls, digest the latest science on species behaviour, and update the names of tree families.
This is my third visit to Chiawa and the Lower Zambezi valley, which is one of my favourite places on earth. Downriver from Victoria Falls, between the vast reservoirs of Lake Kariba and Mozambique's Cabora Bassa dam, the Zambezi idles its way across a rift in the earth's crust and spreads into channels and ox-bow pools among islands clumped with elephant, buffalo and hippo. Permanent water makes for permanent game in the protected wilderness of its reserves, and when the little plane from Lusaka skims the Zambezi escarpment and banks over the shining river my heart lurches with excitement - and recognition.
I know what to expect of Chiawa. Breakfast with elephant, who wander at will through the giant mahogany trees, snacking from the combretum bushes beside the kitchen. Lunch on the water with rafts of hippo and fly-pasts of fabulous water birds, our dining room a flat-bottomed boat. Drinks in the bush to a soundtrack of sunset noises: the bark of a baboon commander ordering his troop to their roost, the eerie call of a fish eagle summoning her mate, the territorial roar of the pride male as the local lions prepare to hunt. And then the African night, opening like a great black flower to a fanfare of crickets and frogs, scattering its stars like brilliant pollen across the sky.
I also know to expect the unexpected, including one of those we-are-all-six-people-away-from-everyone-in-the-world moments; or in this case two people. Ten years ago, on my first visit, I was met at the bush airstrip by the camp's owner, Zambian-born Grant Cumings, every inch the strapping, sun-tanned safari guide from central casting. As we boated downriver to Chiawa, Grant mentioned he'd just got married "to a Glasgow girl" on the banks of Loch Lomond, and that her father had been in the newspaper industry. And yes, of course, not only did I know his new father-in-law but my husband had been a close colleague.
Which is how I know that this year Grant and Lynsey Cumings, who brought a degree in hospitality management from Strathclyde University to her new life in the Zambezi valley, celebrate their 10th wedding anniversary. Not quite the half century clocked up by Zambia - the former British colony celebrates 50 years of independence in October - but an occasion to reflect on the success of an award-winning family business which has held its own at the competitive end of upscale safari tourism. "We are always looking to improve what we do," Lynsey tells me, "whether it's bringing in people like Derek for guide training, holding photography workshops, or just making sure the snacks we serve with sundowners are a bit more imaginative than cheese straws."
One Chiawa innovation, when Grant introduced red filters on the powerful spotlights used on night game drives, has increased sightings of the elusive nocturnal aardvark. More importantly, all the game is visibly more relaxed in their rosy glow. I've always felt a little uneasy about night drives in Zambia's national parks (not every wildlife authority allows them) as it's all too easy for over-enthusiastic guides to spook the game. Elephant get cranky in the spotlight's beam, and because lion and leopard, like domestic cats, have eyes which reflect the light to improve their night vision they can take "unfair" advantage of dazzled antelope. Give the game a break, is my instinct - and the red filters do just that.
For the Cumings family, which includes Grant's parents, the business is a way of life. They spend their time between their home and office in Lusaka and the bush house which Grant built when their first child was born. Scott was nearly three on my last visit, and Lauren nine months, and for these bush babies the house had to be "predator proof", with solid timber walls, re-inforced window screens and tightly-fitting, snake-resistant doors. "A large python would find a baby an acceptable snack," Grant said. Not just snakes; baboons and monkeys can be dangerously curious, and an infant's cry is attractive to lion, leopard and hyena. Like the bleating of a buffalo calf it signals: "Young animal in trouble. Easy target."
But Scott and Lauren, darlings of the camp staff, had 40 pairs of eyes to watch over them as well as their parents and nannies and are now at school in Lusaka. Visits to Chiawa are confined to holidays, and when the camp closes for the rainy season and the Zambezi waters rise their parents take them on trips to family in London and Glasgow. "They love the bush," say Lynsey, "but they may not want to make their lives in the safari business and we need to show them the wider world - which last year included Disney World!"
This time it's adults only, and something of a Scottish field trip: Lynsey, her two sisters, a guest from Perthshire who visits annually, and me. The English honeymooners - there are always honeymooners at Chiawa, with a secluded suite to match their expectations - respond comfortably to the Caledonian ascendancy and receive their reward. While I'm attending one of Derek Solomon's tutorials they are on a game drive, the only guests present at a spectacle so rarely witnessed, we are all consumed with envy. Guides have spent 30 years in the bush and never seen elephants mate - an event which so excites other elephants that the mighty coupling attracts spectators from every pachyderm family in the neighbourhood.
As ever, the raw drama of the Lower Zambezi valley, the skill and commitment of Chiawa's guides, have delivered the unexpected. Over sundowners Matthew and Sarah share their photos and pride. It's their first safari. What are the chances? They have seen a young cow, possibly a virgin, receive the metre-long penis of an experienced bull, possibly to begin her 22-month journey towards motherhood. They have seen and heard the other cows salute the mating couple with ceremonial trumpeting and enthusiastic rumbles, as if anticipating the birth. Think of the dinner table conversations back in London. Is there a honeymoon anecdote to follow this?