I don't understand why they could not have been taken back to their country of origin if the zoo felt it could not cope

Les Ward, Advocates for Animals

Edinburgh Zoo said it had hidden nothing from the public and that officials had been left with no option other than to destroy the animals.

The zoo continues to care for three adult oryx and one baby.

A spokesman for the Born Free Foundation said the zoo acted immorally by allowing the animals to be born knowing that it could not look after them properly.

And Les Ward of Advocates for Animals added: "It was wrong to kill these animals. I don't understand why they could not have been taken back to their country of origin if the zoo felt it could not cope."

The Arabian oryx prefers dry, near-desert conditions and can survive without water for long periods. It is now almost extinct, and another - the scimitar-horned oryx of the Sahara - is on the endangered list.

Oryx live in herds of up to 60 and new-born calves are able to run with their parents and other adults immediately after birth.

Both males and females possess permanent, narrow, straight horns. The females are slightly longer and slimmer than the males.

These horns can be used to lethal effect and the oryx has been known to use them to kill lions. They are also the reason this animal is sometimes called the sabre antelope.