'Walk quickly' our guide tells us. 'Fire ants.' And we wonder, again, why is this fun? But it is. It is one of the most stirring experiences in Borneo: walking through the Danum Valley Conservation Area, a forest that is older than our species. And while this is no open African savannah, and spotting animals can be difficult in the brush, the wildlife is all the more amazing for that: iridescent flying lizards, curious frogs, emerald pit vipers and, peering from behind its headlight eyes, an adorable slow loris.