There's a scuffle going on in the undergrowth; a troop of baboons has crept up to steal the chimps' fruit. The alpha male screams his outrage and charges to and fro, sending the baboons packing – but not for long. They soon sneak back, dodging around their larger relatives and grabbing whatever they can.
I watch in fascination from a little boat close by. Thanks to the Chimpanzee Rehabilitation Trust in the River Gambia National Park, I'm enjoying the rare privilege of viewing the Gambia's population of rehabilitated chimps at close quarters, on pristine forest islands that are also home to callithrix and red colobus monkeys, not to mention several hundred species of birds. It's a stunning setting. The tropical gallery forest dangles its fronds and lianas right down to the water, the dense vegetation an impenetrable mass on either side of the river.
There's a real sense of wilderness about this place. Perhaps it's the way I arrived, by motorboat skimming up the river; warm evening air rushes past, laden with insects that bat my eyelids and cheeks, while egrets and herons wing to roost. Badi Mayo camp itself seems like a distant outpost, a twinkling light in the gathering darkness that turns out to be a snug lamplit cabin with welcoming armchairs and a table laid ready for dinner. There's a climb up a winding pathway to my cosy safari tent, and I go to sleep to the sound of hippos grunting below. Dawn brings a revelation – from the tent's stilted balcony, I have a magnificent view of the river Gambia and the islands that are the chimps' home.
The project is a conservation success story that began in 1969, when forester Eddie Brewer and his daughter Stella took an orphaned chimp off the hands of a passing trader. Hunters in forests to the south had heard that good money could be made from baby chimps; the mothers were simply shot. Soon, the Gambian government granted the Brewers permission to confiscate any captive chimps arriving in the country, and to care for them within the newly established Abuko Nature Reserve. But care in captivity wasn't enough; rehabilitation was Stella's dream. This slowly became a reality in the gallery forests of the National Park, further upstream. Now, 19 original chimps have bred successfully to reach a population of over 70; they're into their third generation, the young ones totally wild.
I'm shown something of the bigger picture in the village, where the school and clinic are supported by the chimp project. Boat trips upriver and along tranquil creeks reveal pods of hippos, and thousands of aquatic birds wheeling and calling at sunset. So much beauty and interest, and what's incredible is that I have it all to myself. It's a puzzle, because only four hours away on the coast lie a string of hotels and resorts. The Gambia is Africa at our fingertips, just within range of short-haul charters from London or Manchester. A jewel of a country, about half the size of Wales, it's an easy access point for anyone wanting to see some of Africa's life and landscape. So where is everyone?
It's not even as though upriver means roughing it. As well as Badi Mayo, there are luxury lodges such as Mandina River Lodge, nearer the coast. This is also set in rich gallery forest, bordered by savannah and mangrove swamps. Here, I'm given my own personal guide, Amadou, and together we explore the mangroves by dugout canoe, or go on long bird-watching rambles through the woods. I'm struck by the orchestra of birdsong: with Amadou's help, I learn to pick out the string section of doves, intertwined with the melancholic mews of hornbills; tropical whistles of gonoleks and wattle-eyes are just some of the solo turns.
I'm treated to a close encounter, too. One morning we take the dugout along the river and explore the site of a disused lodge. I look up to see a host of angular faces hanging from the rafters: a colony of roosting fruit bats. Excited, I whip out my camera, turn on the flash and crane my neck to start clicking. This isn't popular with the bats. The flash wakes them up, and they signal their distress in time-honoured fashion; something wet and salty plops into my mouth. Hastily, I splutter and spit it out, hoping Amadou doesn't notice my less-than-elegant attempts to clean my mouth out.
We walk on towards the village, passing a magnificent kapok (silk-cotton) tree. Amadou explains that villages often have one at their centre, under which the elders can sit. We spot the brilliant yellow feathers of a golden oriole flitting around its branches.
Wandering back, we pass a villager who has just met a puff adder up a palm tree. These snakes are highly venomous, so he's killed it, and is dragging it behind him by a length of palm frond. It's an impressive specimen, a good metre long, and I bend down to touch it. The cool skin spasms at once, and I leap back.
"Are you sure it's dead?" I demand.
The man assures me it is: the movement is a reflex, which also enables snakes to bite after death. I give it another stroke , and watch in fascination as the muscles writhe.
"What will he do with it?" I ask Amadou, as we head for the dugout.
"Make juju to sell in the market," he replies, a reminder that animism is still practised by a minority of Gambians; the arrival of Islam (later interspersed with pockets of Christianity) has failed to erase older beliefs.
It's been an interesting morning, but despite kapok, oriole and puff adder, I'm feeling somewhat preoccupied. I'm sure I can still taste salt. "Amadou," I say, nervously, as he paddles against the tide. "Do those fruit bats carry rabies?"
Amadou grins. "They drop on us all the time," he says. "Not harmful."
Badi Mayo and Mandina River Lodge, then, offer upriver experiences of pristine, protected environments, and both support local communities. But what's possible if you are travelling on a tighter budget? I decide to find out, starting with a day trip to Abuko Nature Reserve from my guesthouse on the coast. To reach it from the main town, Serrekunda, I hop into a bush taxi crammed with locals, pay the vast sum of 6 dalasi (about 14p), and trundle along for half an hour to the entry of the reserve. For well under a fiver, I pay both the entry fee and a generous tip to my guide, who's knowledgeable and good fun. We wander around the tropical forest for hours, spotting ospreys and western bluebills, giant kingfishers and wattled plovers, while callithrix and red colobus monkeys crash energetically around in the trees.
Dust-clad bush taxis carry me far upriver, up to Janjanbureh and Bansang, where by chance I meet the head of forestry for the region. He takes me to see nascent community projects in the forests. They're not quite ready for tourism, but will soon offer wandering trails through the woods, glimpses of rare and magnificent birds, and insights into village life. It's an encouraging government initiative, providing villages with the incentive to protect big sections of forest.
Trundling westwards again, I drop in at Tendaba camp, which houses visitors in cheap and cheerful rondavels – pretty whitewashed huts. Situated on the edge of vast tidal flats, it has an expansive feel. I sit and watch waders stalk around at low tide, while fiddler crabs scuttle out of their way. From here, a boat trip into the Bao Bolon Wetlands reveals woolly-necked and yellow-billed storks, hamerkops and western reef herons; we spot a Nile crocodile and a massive monitor lizard, both slithering off between the muddy mangrove roots.
So far, so good. But the greatest discovery of all is my final stop: a village named Tumani Tenda, only an hour or so from the airport, which comprises a community of seven extended families. Nine years ago they got together to open a small tourist camp adjacent to the village itself. Situated on a mangrove creek, it's a haven of tranquillity. Simple huts are furnished with little more than a bed and a mosquito net; water is from the village well. But there's a sense of order and harmony that's almost indefinable: quiet self-respect, and respect for visitors, permeates everything that happens here.
I realise there's one part of the Gambia's wildlife that I've yet to fully appreciate: its fish. So I opt to go out in a dugout canoe with a fisherman to see what we can pull in. For a good third of the country's length, the Gambia's waters are brackish – hence the mangrove swamps – with salt-water species living happily in the creeks. We drift along gently, and I watch as the fisherman casts his weighted net. He pulls it in, and we inspect it eagerly. Nothing. He goes through the process again. Still nothing. I don't mind; it's a gorgeous setting – brown-headed parrots fly overhead, while egrets skulk in the shallows.
The fisherman continues his rhythmic process, and at last, luck is ours. We bag a barracuda and two red snappers. They're small, but big enough to eat. And at the end of the day, with mountains of fresh vegetables from the village garden, we do exactly that.
The writer flew to the Gambia with Fly Thomas Cook (0901 576 0576; www.flythomascook.com), which offers flights to Banjul from Gatwick, Manchester, East Midlands and Bristol. From Gatwick, prices start from £179 return. Banjul is also served by Astraeus (01293 568666; www.flyastraeus.com) from Gatwick.
The Gambia Experience (0845 330 2087; www.gambia.co.uk) offers a seven-night twin centre holiday combining Badi Mayo and the Mandina Lodges at Makasutu from £1,237 per person.