First ever pictures of endangered Spotted Dear - Telegraph.co.uk

The "interior" of the forest where the animals are known to live measures only about 2000 feet in length, on a plateau, and was virtually impossible to access.

Such was area's isolation that the researchers described it as being akin to "Arthur Conan Doyle's Lost World".

Dr Neil D'Cruze, who led the research, said on Thursday that the traps allowed images to be taken without disturbing the local environment.

"The traps allowed us to see animals we knew were there, but never laid eyes on during our time in the forest," he said.

"After spending 12 very hard days camped in some of the worst field conditions I have experienced (with) lashing rain and just impenetrable forest … we did not actually see the animals with our own eyes.

"The only way we could find access was through a tree that had fallen, which we walked across. Once that tree goes, who knows how access will be gained."

He added: "Gaining images of such globally important species is great news for conservation and shows that Philippine forests continue to harbour many rare and unique species despite the myriad of threats and challenges they face."

Despite "decades of combined experience operating in the forest" no local experts or officials from the Ministry Forest had caught sight of the animal.

"When we came back and showed them the photos, the look of excitement on their face was incredible – it was a real experience," he told BBC Radio Four's Today programme.

Negros is one of just three islands in the Philippines where the two rare animals live in the wild.

Despite the North Negros National Park being subject to official protection, hunters continued to target the animals for recreation.

Little is known about the pigs, which are known to live in small herds of up to six individuals,

"The total population ... is believed to be one of the few viable breeding groups left in world with possibly no more than a couple of hundred individuals surviving," he said.

Meanwhile, there are only about 2500 "mature" deer left in the area.

Dr D'Cruze, a wildlife officer for London-based World Society for the Protection of Animals (WSPA), said hunting was now a "major threat to these mammals".

He said this meant the species were in "critical danger" of being driven to extinction and hoped their expedition would publicise the "biodiversity hot spot".

"It's very sad to think about what could be lost if people stop caring," he added.

"Before you go off looking for endangered animals … you really have to weigh up the impact that your actions will have."

The team are now looking to publish their research.

The forests of the Philippines are also home to other species unique to the area, including the endangered Hazel's forest frog.