"Oh, Janet, don't look," comes the cry from within our pack of transfixed voyeurs. Alas, some warnings just seem to have the opposite effect and instead of averting our gaze our eyes fall immediately upon this visual offence.
The big male we called Alistair, in an obvious state of preparedness, quickly responds to the lascivious signals from the female and the rest requires no further description. We titter and feign prudery as the act continues while the rest of the troupe, including the jealous and similarly eager bachelors, looks on. That famous cult rock hit from ‘Nine Inch Nails' somehow comes to mind.
Proboscis Monkeys (Nasalis larvatus) are a highly social, intelligent, arboreal (tree-dwelling) mammal endemic to Borneo. The name comes about, not from their 'ever ready' alertness, but from the distinctive nasal appendage. Locals once called them the Dutchman Monkey for their similarity to the bulbous red European nose.
The troupe, as we are quickly learning, is governed by a single dominant male whose job description is pretty straightforward – and the girls keep him up to the task as there is always another vigilant bloke ready to cut his grass.
Here at the Labuk Bay Sanctuary, it is hard to imagine a better place to observe these otherwise secretive and reclusive primates. The sanctuary came about almost by accident when local palm oil baron, Michael Lee, was engaged in the clear-felling of mangroves along the Kinabatangan River in eastern Sabah in 1994. Short of food from their quickly vanishing forest, the naughty proboscises started raiding workers' huts with the predictable result. Hearing of this disruption on his plantation, Lee came over to see for himself. Instead of calling for the animals' eradication, he set aside about 160 hectares of riparian (riverside) forest for the protection of this endangered species.
Such has been the success of the Labuk Bay Sanctuary that it is now a fixture on any serious nature lover's itinerary and provides a much more dynamic spectacle (if you'll excuse the understatement) than the nearby Sepilok Orang Utan Rehabilitation Centre where you watch a couple of dozy apes gorge themselves on bananas. Don't get me wrong, Orang Utans are drop-dead gorgeous and the little ones impossibly cute, but the interaction is strictly managed and the international volunteer park wardens eagerly enforce the separation. Labuk Bay, by contrast, is a riotous frenzy as Alistair and his excited entourage swarm noisily across the viewing platform oblivious to the human obstruction.
But before you think there is lots of tummy tickles and back-scratching, human contact with any primate, especially wild ones, is not a good idea.
"Orang Utans share 97 per cent of human DNA and while proboscis monkeys share somewhat less, the transmission of mutually infectious disease is a distinct possibility," says expedition leader Mick Fogg putting on his stern face, "so as much as you are tempted, PLEASE don't touch the monkeys."
Mick has spent most of the last year of his life putting together Orion Expedition Cruises' (OEC) inaugural Borneo itineraries and by the look of things, he's done a pretty fair job for the many repeat passengers and his demanding governors. While there's a heavy bias to natural attractions, there's plenty of culture and history too.
Meanwhile, spare a thought for poor Alistair. As we turn to say our farewells to the boisterous gathering, he's engaged in a standoff with another would-be suitor keen to enjoy some of his lifestyle. Maybe we're not that far removed from our simian cousins after all?
Roderick Eime, from Travography, is a professional travel journalist based in Sydney. While he prefers the path less travelled, he has been spotted in 5-star hotels and resorts.