Cocoa passion on oil-rich island
They provide quality control for new plants and, in the eyes of a plantation owner like Claudio Corallo, they are more than welcome.
"Monkeys are good at choosing only the best cocoa pods, which they open and then strip off the beans inside," he explained as we stomped through the tropical undergrowth.
"They stuff their mouths until their cheeks swell but all they want is the sweet mush on the outside of the bean.
"Once they have sucked them dry they spit them out all at once and they germinate on the ground. If I see a cluster of seedlings out in the jungle I know they must be top-quality plants straight from a monkey's mouth."
Overhead the foliage shuddered and branches cracked but all I saw of a group of mona monkeys was some fast-moving shadows.
We ploughed on through the bush, Claudio looking as cool and relaxed as you would expect of a well-to-do Tuscan born in Florence, and me simply looking sweaty and clumsy.
Principe lies almost plum on the equator off Africa's west coast and is covered in dense primary rainforest, kept lush by temperatures and humidity levels more akin to a pressure cooker.
It was formed by undersea volcanic activity and was never actually part of Africa so, like the Galapagos Islands off the Americas, it has its own unique ecosystem rich in birds, orchids and other flora.
Some of the birds have wonderful sounding names like Dohrn's Thrush-babbler and I was half hoping to catch a sight of one. But when my glasses steamed up for the umpteenth time I gave up and concentrated on what Claudio was saying.
"Now here you see a cocoa plant and just look at the size of the stem," he said enthusiastically.
It looked pretty big to me, about the width of a telegraph pole, and was heavy with the red, orange and yellow pods that grow - rather bizarrely to my eye - straight out from the trunk.
"This is why this place is so special," Claudio was whispering. "These cocoa plants pre-date all modern hybrids of today's mass market.
"This is an ancient plant producing cocoa with a taste more authentic than any other in the world."
I am no chocolate connoisseur but in the cool of Claudio's hi-tech factory - an old shipping container with air-conditioning - my first experience of his chocolate was unforgettable.
The Corallo family does not yet have shiny wrappers or packaging and instead I was offered a few chippings from a solidified pat at the bottom of a plastic tub.
Presentation might have been poor but the taste was sensational - a deep, rich chocolate flavour garnished, in this case, with tiny nuggets of ginger.
And what is more, my amateur enthusiasm is shared by some of the world's best chocolatiers.
The buyer for Fortnum and Mason in London's Piccadilly raves about Claudio's work to revive a plantation set up almost 200 years ago by Portuguese colonists.
Back in the 19th Century, the Portuguese built "rocas", or plantations, all over Principe and Sao Tome on a scale that beggars belief.
Some of them were the size of Versailles with manor houses, schools, churches, clinics, offices, even cobbled streets.
But it was all done on the back of slave labour, so brutal these little islands almost sparked a war between Britain and Portugal in the 1800s.
When the islands won independence in 1975, the cocoa price collapsed, production fell, and the jungle swiftly moved to reclaim the terraces.
For Claudio it has taken years to restart production at the Terreiro Velho plantation.
Principe is so economically backward that until the mid-1990s the only means of transport was a fleet of tractors, and so remote that to travel there from the African mainland took several days' sailing.
It has been a labour of love to just make the two-storey plantation house habitable.
"The undergrowth reached almost to the first floor and we had been working three months before we found a 30-foot staircase in the garden reaching down to a terrace," he said, as he prepared coffee on a rickety Chinese oil burner.
Claudio's wife, Bettina, has recently recovered from cerebral malaria.
The driers - crucial to cocoa production - had to be imported piece by piece from Italy; even now, nine years later, Claudio is camping on a homemade bed in a room with no windows and only part of a roof.
But with a workforce of 30 local labourers who are - thanks to the plantation - earning a wage for the first time in decades, Claudio has clear plans to turn what is now a modest cottage industry into something bigger.
Only then will he worry about putting the roof back on the house.
There is an old wives' tale on the islands about a lucky goblin found deep in the forest known as a gou-gou.
If you are fortunate enough to meet a gou-gou you must catch him - so the story goes - feed him well, and he will make endless wealth for you; a bit like the golden goose story of my childhood.
The gou-gou myth seems to me a pretty accurate description of the oil fever which is gripping the islands right now.
If any oil revenue comes it will be a long time in the future.
Better, in my opinion, to rely on cocoa and Claudio's tree-top troop of monkey helpers.