I TIP-TOED carefully along the rough jungle trail in the direction of the periodic loud grunting sounds, peered cautiously through the leaves, and there he was: a big proboscis monkey sitting on a branch in a shaft of sunlight, munching on tender young leaves.
His fur glinted reddish-brown in the sun and his enormous red nose - the proboscis that gives the monkey his name - testified he was the alpha male of the band of monkeys I could hear crashing through the treetops all around.
At the clicking of my camera shutter he briefly flicked his eyes in my direction, confirmed I was no threat, and resumed filling his face.
Although to his harem of females he was obviously the pinnacle of sex appeal, to my eyes he was a strange sight, with that massive conk and a big, round stomach, apparently swollen with the gases produced by the process of digesting those leaves.
The natives of the eastern portion of the island of Borneo once ruled by Holland, who had no love for their masters, apparently called the proboscis "Dutch monkeys", considering both to be ugly creatures with big noses and pot bellies. A bit unkind to both parties, I thought.
This was the first proboscis monkey I had seen close up and, though he certainly wasn't beautiful, he did have a certain ... hairy charisma.
We were in Borneo on the inaugural visit of the new expedition ship Orion II, a cruise I chose because I was keen to explore the island's tropical jungle, experience the diverse local cultures and see our close relations the primates, especially proboscis monkeys, which have long fascinated me (partly because I used to joke unkindly that my dad looked like one).
In the course of the 10-day trip we saw orangutans at Semenggoh Wildlife Centre, met Dyak headhunters outside Kota Kinabalu, visited a traditional fishing stilt-village in Bandar Seri Begawan, marvelled at the golden palaces and mosques of the oil-rich Sultan of Brunei, and admired the spectacular colours of massive hornbills, delicate butterflies and prolific fungi in the forests of Sarawak and Sabah.
But during our first few forays into the Borneo jungle, though we heard the calls of proboscis, gibbons and macaques, we didn't see any. Now, at the Bako National Park, we were surrounded by them, and felt like true explorers.
Even getting here from the ship had been an adventure, involving a long Zodiac ride past amazing rock formations, a squelch through thick mud to the shore and finally a sweaty walk to where a network of boardwalks extended through a mangrove swamp.
This is where the crab-eating macaques and proboscis monkeys come to feed at low tide and as we arrived, a proboscis troop was right at the end of the boardwalk.
Unfortunately, the racket made by a lot of eager tourists clattering over a rickety wooden path was rather off-putting so the troop promptly headed off.
I did get a good look at one big old fellow, apparently a recently deposed alpha male, who sat upright for a while using a mangrove as a chair, but then dolefully climbed on to all fours and followed his former harem down the coast.
Fortunately, we learned there was a network of jungle tracks nearby, one of which followed the coast in the same direction as the troop had gone, so a small group of us decided to try to catch up.
It was tricky to walk over a surface covered with tree roots and boulders, and the high humidity under the forest canopy meant I was soon dripping with sweat, but the sound of monkeys moving invisibly through the treetops above suggested we were on the right track.
The rest of our group carried on down the track - where they eventually came across a troop of silvery langurs - but my wife Chris and I stayed put and we were soon rewarded as the proboscis monkeys started to appear.
Given that these are endangered animals found only on Borneo - and their position is worsening because of the massive clearance of forest for palm oil plantations - it was a special experience.
In the flesh, proboscis monkeys are surprisingly large, the head and torso of a big male reaching up to 72cm long; their lanky arms and legs make them even taller, plus they have thick white tails up to 75cm in length.
But it's the noses that are their really distinctive feature, sometimes reaching 17cm, which is a massive hooter by any standards. Our expert guides on the ship had explained that the massive noses not only attract mates but also serve as a resonating chamber to amplify calls - a bit like my dad's amazing snoring I guess - and when the monkeys get excited their noses swell with blood and become even bigger.
The alpha male I came face-to-face with in the jungle didn't have a nose that big but it certainly hung a long way down his face. As he ripped leaves off the branches and stuffed them into his mouth I half expected that he might hit his own nose but it didn't seem to be a problem.
I spent some time watching as he climbed from one feeding spot to another, trying with mixed success to photograph him through the surrounding leaves, gazing in awe as he occasionally dived from a thick branch into the leafy boughs of a neighbouring tree, trusting his ability to grab a handhold.
Eventually he moved away from the track and I could see him no longer but, luckily, following some crashing noises not far off I located a feeding female, easily identifiable by her pert pointed noise - much smaller than the male's but still large by any normal standards - then a younger male, his nose presumably not yet big enough to represent a threat, and several more females.
Altogether Chris and I must have spent a couple of hours watching entranced as the proboscis family climbed, fed, dived from tree to tree and communicated around us. It was fascinating.
When we finally left, worried about missing the last Zodiac back to our ship we realised the excitement, heat and humidity had left us exhausted.
But we quickly revived when, back at park headquarters, we found a supply of cold bottled water, discovered to our relief that the Zodiacs were running late so there was time for a rest ... and had the chance to be entertained by a troop of macaques.
In one tree there was a large grumpy male, resplendent with whitish beard, being groomed by an attendant female, and several mothers with babies, one of them particularly young, cuddling them protectively. The tiniest baby, eyes bright with curiosity, kept trying to make the acquaintance of the big male, whose warning hiss and bared teeth showed he did not want to be bothered.
In a scene reminiscent of parks and supermarkets around the world, the mother kept having to dash to get her baby out of trouble, only for the youngster to get into a fresh scrape the moment she started to relax.
At the headquarters itself, several more macaques were getting up to monkey business stealing food and drink from unwary backpackers. I saw one greedy fellow digging into a whole packet of biscuits and another sipping from a can of coke. It was like watching a bunch of naughty teenagers creating mayhem at a shopping mall.
But, cute though the macaques were, when I think of that visit my mind always goes back to the sight of that big-nosed old fellow sitting in the sun and enjoying his food ... just like my old dad.
Getting there: Singapore Airlines flies up to three times daily from New Zealand to Singapore and then beyond to Bandar Seri Begawan five times a week. The airline's regional SilkAir flies to several destinations in Borneo including Kuching, Kota Kinabalu and Balikpapan.
Getting around: Orion II has a range of Borneo departures next year in January-February and again in July-October. Ten-night fares start from $10,100 per person. See Orion Expedition Cruises or see your travel agent.
Jim Eagles visited Borneo with help from Singapore Airlines and Orion Expedition Cruises.