The bamboo and hagenia forest on the volcano slopes is gorilla habitat. Treks range from around an hour to most of a day depending on which family you are given and where they have moved; the guides ask about fitness for exactly this reason. Once you reach them you have one hour, at a required distance, wearing a mask.

The bamboo zone also holds golden monkeys, an endangered Albertine Rift endemic that moves in large, fast troops. Trekking them is a separate, much cheaper permit and a genuinely worthwhile half day — leaping monkeys in bamboo are hard to photograph and delightful to watch.

The higher slopes and craters on Bisoke and Karisimbi are day hikes with crater lakes, giant lobelias and Afroalpine vegetation.

Dian Fossey's research camp and grave, reached on a separate hike, is where the conservation story that saved these animals began.

Trekking runs year-round; the drier months of June to September and December to February make the trails less punishing. Rain is possible in any month at this altitude.

Permits and practicalities

Rwanda's gorilla permit costs 1,500 US dollars for foreign visitors, with substantially reduced rates for Rwandan and East African citizens and for African residents, and a discount available when combined with visits to Rwanda's other parks. Golden monkey permits are 100 dollars with a small daily quota.

Book three to six months ahead through the Rwanda Development Board or a licensed operator. Kigali is only two to three hours away by good road, which makes this the easiest gorilla destination to reach — and the most expensive. Hiring a porter costs little and is the right thing to do.