The government has little control over great swathes of the country, much of it dense rainforest.

The journey involves hiking through dense rainforest, tiptoeing across torrents and sleeping in remote jungle villages.

At night, however, they come alive, actively hunting in the dense rainforest—that's when researchers conduct their surveys.

The lack of roads and dense rainforest are making access to remote villages difficult for health workers, who are also confronted by hostility and suspicion.

I teetered on a narrow metal bridge gently swaying 170ft above dense rainforest - from this height, it resembled gigantic florets of broccoli.