"In the census we did in 2010, these mountain gorillas were 880; in 2015 we did another census that showed we have 1,063" in the Virunga massif and the Bwindi park, ranger Felicien Ntezimana told AFP, before leading a hike into the mist-covered forest where the animals live.

Thanks to this revival, the mountain gorilla, known for its thick, shiny fur, is now listed as "endangered" by the International Union for Conservation of Nature, while other great apes remain "critically endangered".

The animal has come a long way since the 1980s when decades of poaching caused its population to plunge to just 250 across the Virunga range, and famed American primatologist Dian Fossey was murdered in the Rwandan park allegedly because of her anti-poaching efforts.

Stronger security measures and efforts to win over local villagers have helped turn the mountain gorilla's fortunes around.

Today, 10 per cent of the cost of each $1,500 park ticket goes towards community projects while five per cent is allocated to a compensation fund for villagers.

Far from being hated and feared as they were in the past, the gorillas are now seen as key to the community's financial future, says Jean-Baptiste Ndeze, an elderly inhabitant of Musanze, a town bordering the park.

"Tourists throw money at them, which... comes back to us in the form of food, shelter and good livelihood," he told AFP.

Infanticide and disease

While the tourism sector contributed $25 million to Rwanda's economy pre-pandemic, the park's success in conservation has led to unforeseen consequences.

Twenty-five years ago, the Rwandan authorities were monitoring about 100 apes in the forest. Today, about 380 gorillas call it home, according to an official count.

As a result of tourism and interaction with researchers, the primates are accustomed to humans, and they are increasingly unafraid to venture into populated areas as their own habitat grows cramped.

"We have seen gorillas more frequently coming out of the park and looking for food outside... also they tend to move further away from the edge of the park," said Felix Ndagijimana, who heads the Dian Fossey Gorilla Fund in Rwanda.

The results can be dire.

The powerfully built animal -- an adult male can weigh up to 200 kilogrammes (440 pounds) -- is vulnerable to human diseases such as influenza, pneumonia and Ebola.

Rising gorilla numbers have also raised the likelihood of fights between the primates which can often prove fatal for the species' youngest members.

After seeing population growth slow a decade ago, Ndagijimana and his colleagues carried out a study which showed a staggering five-fold increase in infanticides.

"Infanticides are a big problem because it can have a huge negative impact in the gorillas' population increase," he told AFP.

Displacement

The problem is much more pronounced in Rwanda than in neighbouring countries.

Only one gorilla family lives on the Ugandan side of the Virunga range, while the Congolese park is "huge" compared with the Rwandan forest, says Benjamin Mugabukomeye from the International Gorilla Conservation Programme, a regional organisation.

In a bid to address the issue, Rwanda plans to extend its park, adding 23 per cent more surface area over the next decade.

The ambitious project is due to start next year and will displace around 4,000 farmer households.

"It's a process we are undertaking very, very carefully," park director Prosper Uwingeli told AFP, adding that officials were conducting feasibility studies and designing detailed relocation sites.

The authorities intend to compensate the displaced families and house them in newly constructed "model villages" -- with a prototype already visible in Musanze.