The bactrian camels' origins are still disputed

The proposed trans-national protection zone would extend an existing Mongolian reserve, the Great Gobi Strictly Protected Area, across the border into the Chinese province of Xinjiang.

Environmental officials in the province say an international conservation effort is required, as the camels often move back and forth across the border into China to look for new sources of water and food.

China has already established one reserve - the size of Poland - in the Lop Nor region of Xinjiang, a former nuclear testing zone.

Salt water

Bactrian camels are some of the rarest and least studied animals on the planet.

As few as 300 wild animals are thought to remain

The camels, which roam the vast arid spaces of the Gobi Desert, are thought to be the ancestors of the world's domesticated two-humped camels and the only mammals in the world capable of surviving on salt water.

Its main enemy is the wolf. But as the Gobi is exploited for its mineral resources, the camels have come under increasing threat from hunters and illegal miners.

Bactrians were originally thought to have been descended from escaped domesticated stock used by Mongolian herdsmen.

However, recent DNA testing suggests that in fact they are the genetically pure descendants of the original wild animals which, three or four million years ago, crossed from what is now North America into Asia over a land bridge in the Bering Straits.

It is thought that the world's entire camel population, including the more common single-humped dromedary camel of Arabia and South Asia, is descended from these original animals.