By Tim Ecott
The forest groans, squeaks and rattles.
Even a light breeze causes the giant fronds of the coco-de-mer trees to rub against one another with a sound like the creaking rigging of an old wooden schooner.
Underfoot there is the loud crunching of huge dead leaves.
With the outer husk removed, the coconut closely resembles a female human bottom
I have visited the Vallee de Mai many times in the past 20 years, but each time I go I learn something new.
This time I am accompanied by Dr Christopher Kaiser-Bunbury, an ecologist who studies the networks of life supported by the palms.
"There's nowhere on earth like the Vallee de Mai," he enthused, as we stepped through the thick dry leaf litter.
"All this dead matter prevents any other plants taking root and competing with the cocos-de-mer.
"Look how the giant leaves blot out the sky above. They starve all the other plants of light too. It's almost like they have a strategy."
The Vallee de Mai is probably the most visited tourist spot in the Seychelles.
People flock here to see the coco-de-mer, partly because it is the biggest seed in the world - a true botanical curiosity - and partly because it is, well, best described as a rude shape.
On the tree, the coconut is a giant green orb, but inside, with the outer husk removed, it closely resembles a female human bottom.
The male trees grow enormous catkins with hundreds of yellow flowers
The erotic connotations of the coco-de-mer are obvious whether or not you are a royal honeymooner.
In China, the meat of the nut is taken as an aphrodisiac.
And as if the nut's rotund charms were not enough, the trees themselves are clearly male and female.
While the female trees bear the nuts - which grow for about seven years before they fall - the male trees grow enormous catkins, giant phallus shaped tubes studded with hundreds of delicate yellow flowers that give off a musky odour.
In Seychelles creole, the fruit is called "coco fesse" which crudely translates as "bum nut".
For Chris Kaiser-Bunbury, the charms of the coco-de-mer go well beyond schoolboy humour.
"What the tourists often don't appreciate," he says as we stand surrounded by the towering palms, "is how many other unique species live here, supported by these amazing trees".
A Seychelles legend says that during a full moon the coco-de-mer trees walk around the forest in order to mate
And then, so well camouflaged that I struggle to identify it as an animal at all, we spot a giant bronze gecko found only on the male trees.
Several of these creatures, including a breed of fruit fly that lives on the rotting husks of the coco-de-mer, are found nowhere else in the world but here in the Vallee de Mai.
Air of mystery
The coco-de-mer remains mysterious.
Female coco-de-mer trees bear the largest seed in the plant kingdom
Their lifespan is unknown, some say 500 years, or more.
And why are they found nowhere else on earth?
The granitic islands of Seychelles are known for their lush green slopes.
But the Vallee de Mai is a dry forest, and the leaf litter formed by the dead coco-de-mer leaves is a tinder box.
The Seychelles Islands Foundation which looks after the Vallee has cut a series of fire-breaks along the hillsides.
Part of the reason it is so dry is that the palms have evolved their giant leaves to capture as much as 98% of any rain that falls.
The leaves funnel the water straight down towards the base of the palm, ensuring that no other plants benefit.
"Most plants try to disperse their seeds away from the 'parent'," Chris Kaiser-Bunbury told me.
"But it seems that coco-de-mer nuts tend to germinate naturally very close to the mother tree.
"That's because she's found an ideal spot for growing, and the offspring will have a higher survival rate if they don't stray too far."
And indeed, with the nuts weighing 50lb (23kg) or more, there is no way for the wind or animals to disperse them anyway.
A Seychelles legend says that during a full moon the coco-de-mer trees walk around the forest in order to mate.
That is how they produce their erotically shaped "love nuts".
Standing under the dense, green canopy, with the lilting cry of the black parrot echoing through the trees, it does seem like a place where stranger things have happened.