The world population of saiga antelope has halved in less than two weeks after 140,000 animals perished on the Kazakhstan steppes without any obvious cause.

Shocked conservationists found entire herds dead or dying with saiga littered over the vast open grasslands, mostly mothers or newborn calves.

Any young animals that escaped the mass mortality are now unlikely to survive.

Saiga, with their strange elephant like probosces used to filter dust, have already been all but wiped off the map by poachers keen to cash in on their valuable horns which sell at £2 a gram on the Far East medicine markets.

The horns are powdered down and used to make a cooling drink said to bring down fevers.