Ouch, you little bastard,” Diane McTurk shouts, as Flood the otter bolts out of the barn door and runs across the ranch yard, which basks in dusky sunlight. “He bit my foot,” she shrieks, sprinting after him, agile despite her 75 years. She speaks the clipped colonial English of another era. “Come, my heart, my love, my life,” she coos, “you’re not supposed to chew me.”

Flood is the 37th giant river otter that Diane has adopted here at her ranch, Karanambu, on the edge of the Rupununi River. He was abandoned by his mother at six weeks old; Diane found him growling beneath a cupboard in a nearby Amerindian village and brought him home in a red handbag. Eventually, he will be rehabilitated back into the wild. Diane has no children. “These otters are my children,” she had told me earlier.

The McTurk family has long welcomed visiting naturalists to these 125 square miles of grassland, low forest, lagoons, creeks and rivers that lie in the centre of Guyana. Gerald Durrell and David Attenborough came in the 1950s, and Diane herself is now renowned for her success in rehabilitating giant river otters into the wild.

I follow her out across the yard. I can hear Edward, Diane’s nephew, in the main barn, shouting into a radio that crackles over the airways, trying to organise a plane drop-off of urgent supplies.

“There’s a proper, excuse my language, balls-up going on,” Diane yells across the yard as she chases after Flood. Eventually, she manages to corner him between the barn and a timber pile, engulfing him in a dirty towel. “He’s trying for a second swim, the naughty scamp. But it’s past his bedtime,” she says, carrying him back across the yard.

“Tell them over and out, over and out,” she shouts to Edward before disappearing into the vast structure of the barn, which is roofed with palm leaves, its walls open to the wind and rain. Built by Tiny, Diane’s father, it was meant to be inhabited only until a permanent house replaced it.

That was never built, and now Diane sleeps in the centre of the old barn, on a small bed beneath the roof that lets in monsoon showers. Flood sleeps in Diane’s bathroom, on a pile of wet towels placed inside a cat basket. Visitors fare better, sleeping in one of five comfortable cabana-style huts.

Despite her decrepit surroundings, Diane manages to look immaculate at all times. She returns now without Flood, a silk scarf tied around her head à la Grace Kelly, her beige slacks only slightly muddied with paw prints.

“Do we have homemade fudge?” she shouts to Edward. “The boat’s waiting and we’re late. I need to mollify them.” Edward points and continues his negotiations over the radio. Diane grabs the fudge and shouts “Come on”, running off, down to the river.

Dansford and Kenneth, Diane’s tracker and guide, are waiting patiently in a small motorboat, shaking their heads.

“I know, I know,” says Diane, wading into the water and clambering into the boat. “Sorry, I’m a disaster.” They are both Guyanese, Dansford slightly sullen with shyness, Kenneth all smiles. The latter wears a knife in his belt.

“Did you bring the rum punch, man?” Diane is asking Kenneth. He nods as Diane rustles in a cool box, then unsteadily pours us a drink.

The sun has almost set as we motor out into the wide expanse of the clear Rupununi River. The light is sepia, the shadows are long. We speed along the centre, the wind in our hair, the call of howler monkeys in the trees along the banks. Diane’s silk scarf ruffles behind her. Somehow, she maintains her elegant composure, straight-backed, swan-necked.

“My great-great-grandfather was the first to settle here,” she says, her attention shifting to me. “I think I take after him – hopeless in all business matters.” She laughs, and you can tell she was once a great beauty. The boat slows and we turn off into a narrow creek where the light is ghostly, all shadows and silhouettes.

Dansford shines a light onto a world of skeleton trees. Giant spiders’ webs light up in the glow. Bulldog bats skim across the water. A huge orange caterpillar falls from a branch onto my shirt.

Diane flicks it off with one hand and sips her rum punch. “They burn,” she says casually, then continues her story. “I took over the ranch from my brother in 1977. I was hopeless, but hopeful. I tried planting sugar, fruit trees. Both failed. I planted cashew nuts, but villagers stole them and sold them back to me. Desperate for money, I asked friends who visited to leave money instead of champagne. That’s how we got into hospitality. Now tourists dine with me like friends and I show them the heart of the Rupununi.”

Dansford cuts the engine. Kenneth is hacking off hanging branches with a large machete. The insects, attracted to the light, are flying into my face. I spit them from my mouth as a sharp blade of razor grass slashes my cheek.

Just when it seems we are going to be stuck there for the night, the grasses part and we drift out onto tranquil waters that are covered in giant lily pads. Silently, we float through them, the only light cast by the torch and the new moon above.

“There,” Diane whispers, pointing to a beautiful white flower, its petals half open. “The Victoria amazonica lily,” she says. “It only opens at night, for three nights, closing before the sun comes up.”

We watch in silence, sipping rum punch. It takes 45 minutes for the lily to unfold its petals. “On the final night, it stays open,” Diane whispers when the fully-fledged flower lies before us, pink-centred and Karanambu pineapple-scented. “And, as the bleeds into the white petals andBRAZIL the flower dies. It’s the most beautiful death. I should like toRu u uniRiver die like that.”

As we return to Karanambu, Diane is suggesting that, after dinner, we go out to find black caymans. Her zest for life is insatiable. Suddenly she is standing up in the boat.

“Flood,” she shrieks. “I don’t believe it. You’ve got out. Oh, you’re hopeless.” From the water, two eyes glint in the torchlight – then, quick as a flash, Flood dives beneath the surface.

“Oh, Flood,” she laughs. “Come back, my heart, my love, my life. Come back.” With that, she clambers into the shallows and wades after him.

Travel details

Last Frontiers (01296 653000, www.lastfrontiers.com) can tailor-make holidays throughout the region. An 11-day trip to Guyana, including a stay at the Karanambu Ranch, and taking in Georgetown (the capital), the 740ft-high Kaieteur Falls and the Makushi Amerindian tribe’s thatched village of Surama, starts at £2,990pp.

Accommodation at Karanambu is in cabana-style rooms, with erratic and rudimentary plumbing and electricity, but the beds are comfortable and well netted. Most of the rooms have an ensuite bathroom.

The price includes flights with Virgin Atlantic from Gatwick to Barbados, and the onward connection with Liat to Georgetown, transfers, tours and full-board accommodation (except in Georgetown).

Or try Exsus (020 7292 5060, www.exsus.com), or Trips Worldwide (0117 311 4403, www.tripsworldwide.co.uk).

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