Diary: New Guinea's secret species

The team is filming in the little-explored forests of New Guinea

An international team of explorers and scientists is on an expedition to the forbidding jungles of Papua New Guinea.

They plan to survey a lost world of volcanoes, caves, mountains and rivers in search of the strangest animals on the planet.

They will have to endure one of the toughest jungles on Earth to step where no scientist has set foot before.

A successful expedition could result in this unique forest being safeguarded forever.

In this weekly diary, the BBC Natural History Unit crew accompanying the researchers will share their adventures.

MONDAY 23 FEBRUARY - LOST WORLD

Twelve months of planning came to a head this week as we finally ventured into the heart of Mount Bosavi.

Helicopter flies the explorers into the centre of the volcano

An extinct volcano blanketed by thick jungle, Bosavi has steep fortress like cliffs protecting a four-kilometre wide crater at it's centre.

We managed to find a weather window and land a helicopter inside.

No outsiders have spent time in this lost world, no scientists have ever been here, and even the scattered local population rarely enter the crater. We all felt this was a truly original exploration.

The crater is paradise found. We are camped next to a crystal clear, fast flowing river, whose water we bathe in, swim in and drink - all at the same time.

Surrounded by pristine rainforests, there are no signs of human life apart from our own and every rock is draped with green moss.

Up close and personal with a tree kangaroo

In this Eden animals are completely naïve. They have never seen people before.

On our first day a bemused tree kangaroo walked through camp.

On our second day, we filmed the monkey-like possum grooming just a few metres away, and last night were were able to pluck a gorgeous woolly coated possum from the lower branches of a tree to give her a cuddle.

But with the many warm blooded animals come numerous leeches.

Paradise has parasites, so at the end of each day we shower under the waterfall and scan our bodies for ticks, mites and leeches. It is a small price to pay for heaven.

Jonny Keeling, producer, Expedition New Guinea

MONDAY 16 FEBRUARY - THREE MEN AND A BOAT

Sweat and blood are the ingredients of a good expedition, and this week saw plenty of both.

The allure of the assassin bug caused George McGavin to risk life and limb

The expedition headed deeper into the jungle in the quest for new species.

The scientists found an enormous cave, with an entrance large enough to house the dome of London's St Paul's Cathedral, and a broad river running deep into the darkness.

Our fish biologist snorkelled the black waters and set a net across the entrance.

Bug expert George McGavin, hovering around the entrance, managed to snag his ear on a spiked vine, fell over with the pain and badly tore his flesh.

As he entered the cave, he split his skull on a jagged stalactite. Undaunted, George fell to his knees, scrabbled around in bat dung and emerged holding an assassin bug.

This almost translucent insect moves its long, flexible legs with the slow-motion grace of a T'ai Chi master. He is mesmerising to watch, but lightning quick when required.

George McGavin swims into the dark and into the unknown...

Tiny flies, drawn to the bat droppings, are grabbed by the assassin, held down and their bodies injected with digestive enzymes.

When their insides turn to soup, the bug sucks them dry. All that remains is a husk.

The film crew followed George's adventures in the darkness

The final act of the assassin is to break up the desiccated shell of its victim and stick those fragments onto the miniscule hooked hairs on its legs; the debris serves as camouflage necessary to snare the next victim.

George took photos to determine if this is a species new to science.

Meanwhile, the fish nets captured a fat toxic catfish, like a grotesque science fiction character with a dozen 5cm long pink tendrils emerging from huge, thick rubbery lips and spines on its fins, and a sting akin to that of a stingray.

George was eager to explore and, ignoring the prospect of being stung by catfish, set off swimming downstream into the blackness. We followed him.

The cameraman and sound recordist perched precariously on a small rubber dinghy with me swimming at the back pushing them. George swam on.

We pursued, water lapping into the boat threatening to destroy our filming gear before we all ended up floating through a low ceilinged passage.

As we rounded the corner, thousands upon thousands of bats dropped from the roof and flapped around our heads.

Bat urine filled the air and bat faeces filled the water. George, still bleeding from his earlier wounds, swam on through the incredible spectacle and we all emerged into the light and back into the sweaty jungle.

Next week is the crux of the expedition. We are moving camp to a huge, unexplored mountain, Mount Bosavi.

It's an extinct volcano covered in forest. We are heading into the 4km-wide crater, which is reputed to be full of leeches.

Expect more blood and sweat.

Jonny Keeling, producer, Expedition New Guinea

MONDAY 09 FEBRUARY - MURDER MOST FOWL

We found the scene of the crime deep in the jungle: a gigantic compost heap with a hole dug in the top.

Nest raiding prime suspect? One of New Guinea's lizards

The mound was built by an incredible chicken-like creature, the scrub fowl. It was this bird that was the victim.

These busy birds scrape the forest floor, raking up dirt and dead leaves to fashion a huge nest the size of a large car.

Inside this nest of rotting vegetation they lay their eggs. This also marks the end of their parental care.

Warmth from the decaying matter incubates the eggs until the young birds eventually hatch and instinctively dig themselves out of the mound to fend for themselves in the rainforest.

They never see their parents.

The mound, we discovered, had been dug out from the top and the eggs raided.

We set a camera trap in case the thief returned. Within a week, we had caught our robber on CCTV. It was a dragon-like monitor lizard.

Monitor lizards are the largest predators in the jungles of New Guinea.

Salvadores monitors are the longest lizards on Earth, growing to more than three metres (10ft) in length.

In base camp, we too have come under attack; not from the lizards, or the crocodiles we've seen in the river, or even the highly venomous snakes we've encountered on the trails, but from a host of other tropical nasties.

These include: multiple vicious wasp stings, poisonous catfish, birds with toxic feathers and fungal foot rot.

The jungle is moving in on us and it's full of parasites, predators and poisonous animals.

Jonny Keeling, producer, Expedition New Guinea

MONDAY 02 FEBRUARY - WORLD OF THE WEIRD

New Guinea is the land of the bizarre: kangaroos that climb trees, carnivorous mice and giant rats bigger than domestic cats.

King bird of paradise gets the royal treatment

Our first find was a strange one; the smallest parrot in the world.

Buff-faced pygmy parrots, no bigger than your thumb, do not eat fruit and nuts but lichen and fungi, and they nest in termite mounds.

As I write, our cameraman is in a mosquito-infested hide staking out their nest hole to see if he can glimpse this peculiar petite parrot and record its calls; "pieces of two" rather than "pieces of eight".

The expedition's bird expert has been setting his nets.

On day one, he caught the most exquisite king bird of paradise, with crimson feathers, violet-coloured feet and a pair of tail streamers each ending with a perfect emerald disc.

Everyone in base camp stopped their work and, for the next hour, the king bird was given paparazzi treatment.

By tracking bats, the team hopes to learn more about the flying mammals

Evening time in base camp and the air is full of bats. They flutter through the dining area feeding on insects drawn to our lights.

We've managed to catch one and stick a miniscule transmitter on its back to see if we can track it to its roost in order to learn more about that species.

Each animal we find makes us realise just how little is known about the extraordinary creatures of New Guinea.

In the coming weeks, we hope to uncover some of those secrets.

Jonny Keeling, producer, Expedition New Guinea