Aloud howl lifted from the darkness in the otherwise silent expanse of mountains. I was huddled around a fire with Alabacho, my guide. There it was again. Closer. "It's an Ethiopian wolf," he said, excitedly. We were camping in the Simien mountains, the setting for some of Africa's best trekking, and one of the last refuges of this extremely rare but beautiful animal. The mountains form one of the continent's largest ranges, towering over the far north of Ethiopia, and topped by Ras Dashen, its highest peak at 4,620m, and the fourth-highest in Africa (Kilimanjaro tops out at 5,895m).
The first stop on my journey through this mighty range had been Debark, where visitors have to pay before entering the national park. A two-day drive from Addis Ababa, the country's capital, or three hours from Gonder's airport, Debark is typical of small Ethiopian towns; it's ramshackle and dusty. The mountains are remote, with no hotels or guesthouses, so travellers must carry all their food and gear for their trek.
Debark's park office is where I first met Alabacho. He arranged the mules and muleteers to carry everything we needed, as well as the compulsory armed scout.
That night, I slept on the edge of the park at the Simien Lodge Hotel, which claims to be Africa's highest at 3,260m. The Simiens are often compared to Arizona's Grand Canyon, and it's easy to see why. Escarpments peer over the brow of one another; in places, terrifying precipices drop vertically for over a mile. The deep, sunless gorges reveal lapfuls of green trees against a backdrop of myriad pinnacles and spires, created millions of years ago when volcanic eruptions violently eroded the basalt.
Rosita Forbes, a writer who reached the mountains in the 1920s, saw Simien's rock formations, and wrote: "When the old gods reigned in Ethiopia, they must have played chess with these stupendous crags."
The following morning, as the sun peeped over the mountaintops, our scout arrived. Adano turned up with an AK47 slung over his shoulder and three mulateers: Andalacacho, Engidu, and Mamoo, who led the only horse in our team. It was for riding when the journey became tough and was also brightly festooned with pompoms. We loaded our bags onto the mules and set off.
Our first descent took us through steep pockets of forest where erica arborea trees leant gnarled, twisting trunks over the cliff edges, lichens hung like candyfloss from their boughs and Abyssinian roses bloomed cheerfully.
Lammergeyers – bearded vultures – flaunted their huge wings, black and vivid, over the enormity of space within the many ravines. "They are increasingly rare, like so much of Simien's wildlife," said Alabacho. It's because of these rare species and the threats to these magnificent mountains from overgrazing, over-population and erosion from farming that the range was placed on Unesco's List of World Heritage in Danger 15 years ago.
We stumbled upon a huge group of gelada monkeys, which are found only in the Ethiopian highlands. According to Alabacho, they are "the planet's most sociable monkeys", living in enormous bands of up to 800. The males have shaggy, lion-like manes that flare out exuberantly as they run. On their chests, they have a large red patch of skin shaped like a dolphin tail.
That night we camped at Sankaber on a spur at 3,240m, before climbing higher the next day. We passed along rocky paths through an epic landscape awash with heath forests, scented wild thyme and St John's wort. We crossed a natural narrow rock bridge with a frightening drop on either side.
Cheeky children from the park's scattered hamlets, wearing patched trousers and traditional woollen hats with a pumpkin-like stem poking up, shepherded their animals close by. All the while, spectacular views sprang from the escarpment, with chasms revealing precipitous cliff faces, crags, infinite jagged mountains and plateaus.
Then we climbed up through the hills to the stunningly located village of Gich, with its remote tukul mud huts and precipitous fields of cereal crops. Swallows dipped through the air like fighter planes. Above lay the beautiful high steppe, all shivering grass prickled with giant lobelia plants, stretching out seemingly endlessly.
The next morning, frost had painted everything snow-white. The muleteers sat draped in blankets and lammergeyers stalked the campsite, squawking. Then, after another day of walking through prairies and past glorious silver-flowered hillsides covered in helichrysum, we reached the final campsite at Chennek.
It was here that I heard the wolf howl. Unfortunately, I didn't get the chance to see one, despite asking locals throughout the journey about recent sightings. Sadly, the Ethiopian wolves, endemic to the country's Afro-alpine regions, are now fantastically rare. "Only 450 are left in the wild," Alabacho told me, "with just 40 living in this park."
I did, however, get to see the rare and endemic walia ibex, a type of goat, browsing through the dappled light of a forest pocket. The herd was quite large, with enormous curved horns, old-man beards and what looked like black-and-white schoolboy socks pulled up below their knees.
After trailing them through the forest, they moved down onto the steep cliffs and grassy ledges of the escarpment, suitable for only the most fearless climbers. Unable to follow, I laid on a rocky ledge above and watched them, then made my own return, back from the wilds of the Simien mountains.
Travel essentials: Ethiopia
* BMI (0844 8484 888; flybmi.com) and Ethiopian Airlines (020-8987 7000; ethiopianairlines.com) fly from Heathrow to Addis Ababa. All BMI flights stop off in Amman, making the journey over 10 hours; some Ethiopian flights are non-stop (eight hours) while others touch down in Rome.
* Ethiopia Simien Tours, based in Gonder (EthiopiaSimientours.com) offers itineraries in the Simien Mountains from £205 per person for a four-day trip, including national park entrance fee, official guide, game scout, cooking gear, food, water, mules and muleteers.
* The writer booked a car with Maranata Tours (maranataethiotravel.com) for the journey from Addis Ababa to the Simien Lodge, which cost £200 for two days, with fuel and driver.
* British passport-holders can get a £14 single-entry tourist visa on arrival at Addis Ababa airport. You can also apply in advance at the Ethiopian Embassy (020-7838 3897; ethioembassy.org.uk).