Meet the original migrants of Central Asia

The Asiatic wild ass - or Khulan - roams Mongolia and northern China in massive herds. They migrate nomadically from site to site in search of food and water, covering thousands of kilometers in just a few weeks, with a range of up to 70,000 square kilometers (27,000 square miles) each year. They are threatened by hunting for their meat - as well as by infrastructure that blocks migration.

The Argali - or Marco Polo sheep, named in a book by the 13th century explorer - inhabits the rugged mountains of Central Asia, regularly crossing borders between Afghanistan, China, Kazakhstan, Kyrgyzstan, Tajikistan, Pakistan and Uzbekistan. Prized for their impressive horns, the biggest threat to the sheep is hunting.

Przewalski's horse had been declared extinct in the wild, with the last individual spotted in Mongolia in 1969. But since 1992, reintroduction programs have allowed it to establish a population of about 300 in its historical Mongolia territory. Another 120 of the horses are being released in China seasonally.

The white-tailed or Mongolian gazelle inhabits rolling steppes and plains, undertaking long-distance nomadic journeys throughout the year outside of rutting and birthing seasons. In just 12 months, an individual Mongolian gazelle can range over 32,000 square kilometers.

The goitered or black-tailed gazelle ranges across some 20 countries in the Middle East and Asia. During the winter, it can cover up to 30 kilometers (20 miles) a day in search of food - but takes things easier in the summer months. Heavy poaching has all but wiped out large herds in Mongolia, cutting population numbers in half.

The Bactrian camel makes use of fat stored in two humps on its back for journeys of up to 75 kilometers a day across rocky massifs, arid deserts and sparsely vegetated plains. Hearty wild Bactrian camels have lost their native habitat, and are today only found in three locations in northern China, and in one location in southern Mongolia.

The Asiatic cheetah once raced across Central Asia and the Middle East, but now clings on to survival only on the plains and deserts of Iran. Even these pockets of habitat are under pressure from overgrazing, and droughts made worse by climate change.

The Bukhara deer is found in woodlands and plains of Kazakhstan, Tajikistan, Turkmenistan, Uzbekistan and Afghanistan. When habitat is in good shape, it is unusual for the deer to migrate - but these days an estimated 30 to 50 percent of Bukhara deer move seasonally in search of better living conditions.

Saiga antelopes live on the grassy plains of Central Asia, with spring seeing large herds of females migrating to breeding areas. After dispersing in summer, they gather again in autumn to move to winter feeding grounds. The population dipped precipitously in the 1990s due largely to poaching for Chinese medicine. Researchers are still trying to understand the causes of a massive die-off in 2015.