The forest trails are the heart of Tiwai. Walk quietly with a guide and the canopy starts to move: colobus monkeys, Diana monkeys, sooty mangabeys, and sometimes the distant calls of chimpanzees. The island's size makes sightings possible without long expeditions, though nothing here behaves on a visitor schedule.
The walking is not technically hard, but it is hot, humid, and muddy after rain. Wear proper shoes, carry water, and give yourself time. A rushed one-hour loop misses the best part, which is letting the forest settle around you.