The lively morning calls of a rare species of gibbon has led to the discovery of the only known “viable” community of the talkative primates in remote Vietnamese forests, conservationists said.

A “substantial” population of 455 critically endangered northern white-cheeked crested gibbons were found living at high altitudes and far from human settlements on the border with Laos, Conservation International said.

Researchers, who had previously found sparse groups in other areas, used the animals’ “loud, elaborate and prolonged” calls to locate the creatures in Pu Mat National Park in Nghe An province, northern Vietnam.

The community represents two thirds of the total number in Vietnam and the “only confirmed viable population” of the variety worldwide.

“This is an extraordinarily significant find, and underscores the immense importance of protected areas in providing the last refuges for the region’s decimated wildlife,” said CI president Russell Mittermeier.

Dr Gibbons, which are threatened across the world, are considered the “most romantic” of primates as they mate for life and serenade their partners with song.

Habitat loss and hunting for the pet trade and the “assumed medicinal value of primate body parts” are among the major threats to the creatures in Vietnam, the CI statement said.

White-cheeked gibbon numbers are thought to have declined by as much as 80 per cent in the last 45 years, according to the International Union for Conservation of Nature and Natural Resources Red List of Threatened Species.

Dr Mittermeier, who also works with the IUCN, described the species as “on the brink of extinction”.

They are believed to be “functionally extinct” in China and while there could be significant numbers in Laos, CI said a lack of research means the situation in the country is unclear.