Marojejy national park was for decades open only to botanists but visitors can now trek into the mountains in order to see the fabled silky sifakas

It was dawn, deep in the jungle of Mount Marojejy, when my guide and I first caught sight of the family of silky sifakas – six snow-white, metre-high lemurs perched in the treetops. The rising sun had bathed the cliffs beyond them in liquid amber and, as we peered up, their pale coats were wreathed in smoky golden light. The locals call them angels of the forest – and we now understood why.

The silky sifaka is not only one of the world's most beautiful creatures, it is also among the rarest: fewer than 2,000 survive, all around Marojejy national park. And they are just one of several reasons to visit this great massif, perhaps the most spectacular peak and the richest repository of strange flora and fauna in the whole of Madagascar. It has a fearsome reputation, but recently built paths and campsites of sturdy huts now make a trip to its summit (almost) as doable as a weekend in Snowdonia.

In 1952, French botanist Henri Humbert declared it Madagascar's greatest treasure and closed it to the public. Marojejy reopened as a national park in 1998 and, for years was accessible only by a muddy, overgrown path – a sure route to sprained ankles and a gift to leeches.

My guide was Erik Patel, a young American primatologist who recently featured in a David Attenborough-narrated documentary on the silky sifaka, and is director of the Duke University Lemur Centre's Sava conservation project in Antananarivo, the island's capital. Madagascar is grindingly poor and "Tana" – as the locals call the capital – is a ramshackle place of barefoot children and rough carts pulled by zebu, or humped cattle. But it is hauntingly beautiful, too, with a cobbled old town on a hill.

Leaning Rock in Marojejy national park. Photograph: Kevin Schafer/Four Corners PR

An hour's flight north revealed the shocking extent of the island's ongoing deforestation – red gashes where entire denuded hillsides had collapsed. Then, at last, the rainforests of Masoala national park spread out below, and we alighted in the coastal town of Sambava. An hour's drive inland, cooks and porters awaited us at Marojejy's visitor centre. And from there, it was an hour's walk to the foot of the mountain, through green paddy fields and villages where women winnowed rice beneath spreading mango trees.

Marojejy's battlements thrust skywards quite suddenly from these idyllic surroundings and, where they rise, the primary-growth rainforest begins. Gradually, we started spotting its peculiar and magnificent inhabitants – a crimson millipede eight inches long; a troupe of grey-brown bamboo lemurs, leaping and whirling from creeper to trunk; a sleeping boa draped luxuriously around a branch.

Our camp consisted of five huts, including a dining area, half-way up the mountain, with a sublime view over a waterfall and a jungled gorge. I never made it to the summit. Erik's scouts predicted the sifakas would pass the camp the next day and I decided the chance to see them beat the extra legwork.

While we waited, we rambled up into the cloud forest nearby – a misty region of ferns and palms, orchids and giant saw-toothed pandanus leaves. The next day, the animals set off on their daily journey through the forest, leaping from tree to tree as we lumbered after them. Soon, their leaps came so thick and fast that the overwhelming impression was of flight, making a couple of hours following them on foot exhausting.

Zoma Market, Antananarivo. Photograph: Tom Cockrem/Getty Images

But the steep terrain in this region has been the animals' saviour. In recent years, gangs have run rampant in the rainforests, feeding demand for tropical hardwoods in China. And, while many of the locals I met around Marojejy had put themselves heroically in harm's way at one time or another to protect the park, logging is now resurgent in some parts. The presence of tourists and the income they bring is one of the best defences against it – another reason to pay an early visit to this last redoubt of the silky sifaka.

• The trip was provided by Rainbow Tours, which can tailor-make an eight-night holiday with four nights in Marojejy national park, two nights in Sambava and two nights in Antananarivo for £3,545pp (two sharing), including all flights, meals, transport, guides and porters