Scientists believe they have discovered the biggest migration of wild animals on Earth, with an aerial survey revealing vast herds of gazelle and antelope on the move in southern Sudan in a region which had been assumed to have been denuded of its wildlife by years of civil war.

The Wildlife Conservation Society, together with the autonomous government of South Sudan, announced at a press conference in New York on Tuesday that a study of the area’s fauna had revealed an abundance of antelope, particularly of white-eared kob, in breathtaking numbers.

Flying over an area of about 5,90,000 sq kilometres, scientists witnessed a column of animals in their seasonal migration through grasslands and swamps that was 50 miles (80 km) long and 30 miles across.

They estimated the population of the white-eared kob — a chestnut coloured and medium-sized antelope — at about 8,00,000.

Add to that other species including the topi and the Mongalla gazelle, and the total number of migratory animals is put at 1.3 million, approaching the scale of one of the world’s greatest natural events, the Serengeti migration of wildebeest and zebra across east Africa.

“I have never seen wildlife in such numbers, not even when flying over the mass migrations of the Serengeti,” said Michael Fay, a field scientist with the WCS, who conducted the survey.

The discovery of wildlife in such gigantic numbers astonished Dr Fay and his fellow conservationists, because the Serengeti migration, which occurs between July and October each year as a way of avoiding the impact of the dry season, was considered to be unrivalled. The findings also came as a surprise as the region’s long-running civil war had been assumed to have led to environmental devastation.