Borneo is the third (or fourth - I can't remember exactly) biggest island in the world, and the home to a staggering array of diverse and unique wildlife. Our destination was the amusingly named Pangkalan Bun, which is the gateway to Tanjung Puting National Park. However, whilst Borneo might be big on strange creatures, it is also big on being big - meaning that it takes days to get anywhere, usually requiring a combination of buses and planes.

Unperturbed, we finally made it to the park, where we boarded our klotok (a typical Borneo houseboat, that would be our home for three days (there are no roads or tracks within the park, so the rivers are the only way around)). Suitably equipped with captain, guide, and four bottles of arak (local spirit that gives you hair on the palms of your hands), we headed into the jungle. Anyone who has seen Apacalypse Now can imagine what the scenery is like, as the river winds its way deeper and deeper in. Squawks of exotic birds (egrets, kingfishers, hornbills...) replied to the gibbering screams of monkeys (Proboscis monkeys, long-tailed macaques...). The foliage hung over the river, blocking out much of the light, making it cool, despite the strong sun. A crocodile slithered off the bank into the water, encouraging us not to swim in it.

Our main objective, however, was the elusive orangutan - a primate that shares 95% of our DNA, and which only lives in a few locations in Indonesia and Malaysia. Illegal logging, and hunting, have reduced their numbers drastically, but government inititiatives to protect these creatures, and their fragile environment, are said to be making a difference over the last few years, thankfully.

The park is home to a population of orangutans that have been reintroduced to the wild, after being seized by the authorities from traders who take them from the wild to be pets. It is also the home of many wild orangutans. On our trip, we were fortunate enough to see a family of three of the latter, eating in the trees by the side of the river, as well as around 10 that had been reintroduced (these ones are always young and orphaned, and given orangutans are reliant on their mother for the first 6-7 years of their lives, need human help for feeding and general maintenance).

When you see these creatures close up, you can see how agonisingly similar to humans they are in their physical characteristics and their behaviours. They play with each other, are curious about observers, and can be extremely cheeky. The park rangers know each of the reintroduced orangutans by name, and can tell visitors about their unique traits (one, called Princess, has mastered a basic communication technique that allows her to convey messages to humans).

The days in the park were spent spotting wildlife, from as soon as the sun came up (sleeping on deck means it's impossible to stay asleep after sunrise), until after it disappeared. The evenings saw us working our way through the arak (no easy task, but we did what we had to do), and trying to avoid the millions of mosquitoes which infested the vicinity, as well as their precious cargo of malaria, dengue fever, encephalitis and so on.

Borneo has without doubt been a major highlight of the entire trip. We hardly scratched the surface, but this isn't surprising given vast swathes of the island remain unmapped, hiding goodness knows what natural treasures.

Next stop....Sulawesi.