Scientists have confirmed the existence of an ancient dog species in one of the world's most remote places — the mountains of Papua New Guinea and Indonesia's Papua provinces.
The international team led by scientists from Indonesia's University of Papua captured evidence of the New Guinea highland wild dog during a 2016 expedition to an austere, high-altitude region near the Grasberg mine, one of the world's largest copper mines.
The discovery is the first confirmed sighting of the species in more than 40 years.
The dogs are believed likely to be the same species as the New Guinea singing dog, a wild dog that has been bred in captivity since several pairs were taken from the remote New Guinea highlands on both sides of the border in the 1950s and 1970s.
There are about 200 New Guinea singing dogs in zoos around the world, but little is known about the ancient breed famous for their unique vocalisations.
However, scientists are certain it shares ancestry with the Australian dingo.
American zoologist James McIntyre, who had been searching for the elusive dog for years, joined the team as an adviser on a leg of the research that took them to the slopes of Papua Province's highest mountain, Puncak Jaya.
Mr McIntyre led his own expedition in the 1990s to the highlands of north-western Papua New Guinea — however while his team heard chorus howling at dawn and dusk, they made no sightings.
He remained certain the elusive canid species still roamed the highlands' cloud forest terrain, several thousand metres above sea level.
"I had the opportunity to speak to many remote villagers there, and it seems like every different village has some kind of story pertaining to the highland wild dog," he said.
"The dog has been woven into the fabric of their culture and their tradition."
While there have been several sighting reports since his initial expedition, it wasn't until last year that Mr McIntyre found what he considered to be credible scientific evidence pointing not only to the existence of healthy populations, but also of the dog's curious nature.
"We were travelling up this beautiful valley and it consists of three terraced lakes that eventually wind up at two active glaciers.
"I was broadcasting audio howls of North American coyotes — a male and female coyote, a female coyote in distress, and coyote puppies in distress," he said.
Mr McIntyre said while the sounds were not species specific, any kind of different noise or howl in another animal's territory was likely to evoke curiosity.
He even took off his boots at one stage of the journey and left behind bare footprints.
On his return, Mr McIntyre found fresh dog pawprints next to his own footprint.
"So in fact, I didn't find those dogs, they found me," he said.
The researchers set photo traps, lacing the ground with scents they hoped would lure the dogs, and waited.
"It wasn't until the very last day, after the weather had cleared for a while, that I got any photos whatsoever," Mr McIntyre said.
"I don't mind saying out loud that I squealed when I finally saw documentary proof of these animals."
A window into the history of Australia's dingoes
The highland wild dog is seen as a "pristine" canid — an example of how dogs were at the time they began being domesticated.
Mr McIntyre said the discovery of the ancient dog in such a remote location was enormously important to the understanding of dog and human co-evolution.
"So this can tell us a lot about the history and the pre-history of Papua New Guinea and just the migrations of the people and the dogs and how they got to where they are today," he said.
Mr McIntyre said a full investigation of the dogs' DNA would prove the highland wild dog, the New Guinea singing dog and the dingo are "the only animals on the planet that are even remotely related to each other".
"Years ago, Australia and New Guinea were attached by a land bridge when the oceans were much shallower than they are now, and it was probably one species of dog that lived in both countries.
"When the water rose and the land bridge was eliminated, the dogs that were isolated on the island of Australia adapted and evolved [into] dingoes," he said.
"And the dogs that were isolated on the island of New Guinea seemed to retreat to the highlands and evolved and adapted to what they are today."
Tensions in Papua province a barrier to research
Scientists associated with the newly-formed non-profit New Guinea Highlands Wild Dogs Foundation, of which Mr McIntyre is president, plan to return to the same area in July this year to trap the dogs and give them a thorough examination.
Although villagers across the New Guinea Highlands reported signs of the dog, the proximity of the Grasberg mine to the 2016 discovery was considered a boon for researchers.
Mr McIntyre said scientists faced extensive barriers getting to the Indonesian side of New Guinea island, which is subject to a simmering insurgency by Indigenous West Papuans seeking independence.
"I had been trying to get into Papua province for three-and-a-half years and there are many political hoops that we have to go through in order to get in there, and it seems as though at times they are reluctant to bring foreign researchers in there," he said.
The mountainous island of New Guinea is one of the most richly biodiverse places on earth.
He said the mine operators had helped facilitate the recent expedition, and had indicated they would do so again.
Mr McIntyre said it was crucial for the highland wild dog team also to include local scientists to be involved in the preservation of their national heritage.
"We certainly couldn't do it —and we wouldn't do it either — without the association of a Papuan University," he said.
"I made sure, and I will make sure in the future, that any of the students and any of the professors that we have be Papuan."