The shapes above me belong underwater, I think to myself, gazing up through the trees at the beautiful, blue-and-rose dusk.I'm exploring the spiny forest, an eco-region of startling menace that's unique to southern Madagascar. Tangled thickets of mimosa, alluaudia and octopus trees claw the air, their branches bristling with thorns. Silhouetted against the darkening sky, they're as jagged as a reef.

"Are there really lemurs here?" I ask.

"Plenty," says the forest warden who's leading the way.

"And they've never been hunted?"

"For the Antandroy, my tribe, that's fady — it's taboo," says the warden. "We believe lemurs are living spirits, and if we harm them, the spirits might harm us in return."

The writer Dervla Murphy once called this drought-resistant forest a botanical lunatic asylum, and I can understand why. Madly twisted, it's like nowhere else I've ever been. And things are about to get even stranger. Suddenly, I'm eye to eye with a wild sifaka: a ghost-white lemur with a sooty mask and an inquisitive stare. It pauses, then calmly leaps from one thorny tree to another, landing feet-first with nail-biting precision. It's hard to believe that primates can survive here at all, let alone travel without spiking their feet.

"It's a Verreaux's," whispers Andreas Miha, my guide. "There's another one just over there."

I hold my breath as the sifaka drops to the ground, then watch, entranced, as it bounces to its companion on two legs, its furry arms raised in a teddy bear matador pose.

After a few days in the wilds of Madagascar, I'm beginning to accept strangeness as the norm. Isolated since the age of the dinosaurs, this thousand-mile-long island is so stuffed with oddities that every day reveals a new bizarre sight.

Within its distinctive, walkable landscapes, nature and culture intertwine. But, inevitably, times are changing, and the ancient taboos protecting certain species are beginning to fade. With good agricultural land in ever-decreasing supply, deforestation is rife, and isolated rural communities need strong incentives to keep their native forests intact. And, for a growing number of villagers, sensitively-managed eco-tourism projects are providing exactly that.

My base in the spiny forest is Mandrare River Camp, a remote, eco-friendly set-up in a stately grove of trees, wreathed in folklore and aflutter with birds. Its comfortable tents gaze across the broad Mandrare River to Ifotaka Community Forest, a precious belt of tamarinds, acacias and alluaudias, sacred to the Antandroy. They bury their dead there, investing huge sums in elaborate ceremonies and tombs. Once the feasting is over, it's said the spirits of their ancestors, the tromba, hover peacefully among the trees. Created by British adventure travel enthusiast Edd Tucker Brown, Mandrare River Camp is one of the first places in the country to capture the mood of a classic African safari — think gracious service, lantern-lit evenings and crackling campfires. But, as you'd expect on this idiosyncratic island, there's a twist.

Instead of waking to the distant roaring of lions, my mornings begin with the gentle sound of singing and splashing, as Antandroy women tend their plots on the riverbanks and children giggle in the shallows. And rather than watching wildlife from a rumbling 4WD, I explore the intriguing landscape on foot, padding through forests in the cool of the day and, after sunset, scanning for shining eyes with a torch. For now, few eco-tourists make the long journey to Ifotaka, a quiet, traditional corner of the Androy region, around 650 miles south of the capital, Antananarivo. But the Antandroy's spiritual relationship with nature makes it a fascinating place to be. Strolling appreciatively through their forests, I have time to absorb tiny details, from chameleons wobbling on branches to delicate medicinal plants. And to my delight, besides sifakas, I see other extraordinary primates — sportive, mouse and ring-tailed lemurs. Plenty of them.