TWILIGHT had enveloped the Simien Mountains, high up on the roof of Africa, when a series of high-pitched screams pierced the cold night air. The din increased. Shifting position on the rocks where I was seated, I waited patiently.

There was movement to my left and, as my eyes adjusted to the dark, a troop of some 100 Gelada baboons suddenly appeared from the plains below, heading towards the rocky cliffs for the night. As they nimbly descended the rock face and entered the caves for protection from hyenas, leopards and wolves, they squabbled amongst themselves.

The dominant male bared his enormous canine teeth and, for nearly half an hour, chased away bachelors before each baboon found its own shelter and quiet was restored. This phenomenon, I learned, is a nightly occurrence in the Simien Mountains.

Ethiopia may be overshadowed by wildlife tourism offered by some of its neighbours but it is quickly gaining ground as my adventure would prove.

I had booked a four-day backpacking trip with Boundless Ethiopia PLC, traversing mountain trails and camping along the way. It is one of the best ways to photograph the extraordinary Ethiopian wildlife in their natural habitat.

After a one-hour flight north from Addis to Gondar I was met by a driver who took me to the small town of Debark. Here I met my guide, Yonas, and a local scout named Eshete. The latter had walked from his village three days away to find work. He carried a Russian-made Second World War rifle for protection from predators.

The first day’s hike, at a mere five or six kilometres, was a bit of a warm-up, Yonas Informed me. Even so, we spotted Gelada baboons foraging on grassy hillsides. When I kneeled down in front of them to take pictures, they kept moving forward to surround me. An added bonus was seeing a trio of Klipspringers, a species of antelope found only in the highlands of East and Southern Africa. They are considered nocturnal so to see them at midday, drinking from a stream, was a pleasant surprise.

Equally compelling was the beautiful landscape we encountered throughout the hike. Erosion over millions of years has carved these rocks and cliffs which descend into valleys some 1,500m below. I was reminded of northern Arizona and Utah.

When we arrived at the Sankaber camp, Yonas helped me set up the tent I had brought from Canada. Though tents, sleeping bags and mats are provided I preferred my own gear. The company had arranged the guides, scout, mules to carry food, cook and supplies as well as the necessary permits to enter Simien Mountain National Park, a UNESCO world heritage site. All I had to do was survive the thin air.

Sankaber sits 3245m (10,646 feet) above sea level. Prior to the journey I had spent four days in Addis (2345m) which helped me acclimatise to the altitude and lessen the chances I might suffer the symptoms of altitude sickness: headache, insomnia, loss of appetite and nausea.

After a dinner of spaghetti and meat sauce served up by the travelling camp cook, it was early to bed.

I have always found sleeping at high altitudes difficult, however, I was overcome by fatigue and after I woke up from a dream I realised I had slept. Yonas informed me that we would be hiking roughly 12 kilometres the second day ending in Gich at 3601m (11,814 feet).

The cook provided scrambled eggs mixed with tomatoes, onions and green peppers. Before I had finished my plate he arrived with a second helping. I soon understood he and his colleagues were concerned with my lack of appetite, not to mention my insistence on carrying my own backpack. Stubbornly, I wanted the full-on experience.

Part of the hike this day was on a narrow trail which wound vertically through a forest. I concentrated on following Yonas’s feet in front of me, stepping where he stepped. At one point I bumped into a low-hanging tree branch because I was so focused on moving forward. The rocks and a muddy uphill section made it impossible to find a rhythm.

One of the wildlife species I had listed as my priorities to photograph was the Lammergeier or "bearded vulture". This bird of prey has a wingspan of around nine feet and is unique in that it is able to digest animal bones. Lammergeier wait for other animals to pick carcasses apart then descend to snatch the bones. From a lofty height they drop these bones onto a rocky surface smashing them to mouth-size bits.

After three hours of hiking in the hot sun we approached a river where we were to eat the tuna sandwiches our cook had provided. It was then that Yonas spotted a Lammergeier following the river’s course.

I slipped off my backpack and lifted my camera and 150-600mm lens and raised it to find the bird circling back towards us. At this altitude and fairly tired from the hike I found it hard to hold both my breath and the camera. I fired off a short burst, then after it passed by I looked at what I had captured: a half-dozen blurry shots but one keeper. Then we settled down on some rocks in the shade to eat.

Other hikers were enjoying the lunch break too. I had met a pair of young women from Dubai, flight attendants for Emirates Airways. One was extremely fit and had climbed Mount Kilimanjaro earlier in the year. The other was troubled by the altitude. A mule was assigned to follow her so that she had a ride when she needed one.

Later that evening once we had set up the tents, Yonas encouraged me to go with him to the ridge overlooking the Gich camp to watch the sunset and to see the baboon troop. It took us half an hour but it was well worth the effort. On a trail below us he spotted a young Walia Ibex. This is another endangered species found only in the Simien Mountains. Only a few hundred remain.

It was apparent the young one had become separated from its family as it paced this way and that in a frantic search. Although I was able to tick off another of my favoured wildlife photography subjects, Yonas’s words haunted me: "Without its family it might not survive the night."

The temperature plummeted and when I awoke my tent was covered in frost. Breakfast of pancakes and coffee prepared us for the longest day – a 17km hike during which we could descend a mountainside then climb a staggering 1,200m on another. That was tough. But when we arrived in Chennek that afternoon I knew the hardest part was over.

After dinner as I reclined in my tent reading, Yonas approached saying someone had spotted an Ethiopian wolf. Though there wasn't enough light to take a decent photo I did see the wolf on a hill near the camp. Apparently it had been attracted by the smell of food.

Despite the frost and rain throughout the evening I managed a good night’s rest. After breakfast I told Yonas I would like to sit on the nearby ridge for a few hours and wait for wildlife to come to me. One of the Dubai ladies joined us and for three hours we watched Gelada baboons, Klipspringers, Lammergeiers and yellow-billed eagles in our vicinity.

The Simien Mountains are filled with landscapes and wildlife found nowhere else on earth and as I flew back to Addis I was delighted I had experienced such a fantastic journey. No doubt more adventure travellers are bound to visit in coming years.

Paul Gains travelled to the Simien Mountains with Boundless Ethiopia Tours PLC (www.boundlessethiopia.com) and the Ethiopian Tourist Organization (www.ethiopia.travel)