The 'miracle' birth of rare twin giraffes turned to tragedy after one of the calves died aged just a week old.

Auckland zoo, New Zealand, celebrated New Year's Eve with the births of male and female giraffe twins – only the 30th pair to have been documented in history. But the occasion was overshadowed by the knowledge that they had been born prematurely and were small.

The female twin made a good start to her life, standing and feeding in a normal manner, but the male was weak and unable to suckle his mother independently. Eventually, vets made the heartbreaking decision to euthanise him.

Zoo keeper Nat Sullivan said: "It's been an emotionally and physically exhausting experience but that's part of the job. I've been zookeeping now for 15 years and this has got to be one of the most unusual and privileged things I've ever been a part of. Unfortunately we haven't had the best result, the most ideal, but we're pretty stoked with the little girl."

Vets will continue to monitor the female calf and her 7-year-old mother for whom it was her third pregnancy. Giraffes typically gestate for 15 months and give birth standing up - meaning calves fall 2m to the ground upon entering the world. The twins father was 19-years-old.

The world's giraffe population has fallen by 40% in the last 30 years, resulting in them being placed on the International Union for Conservation of Nature's 'vulnerable' to extinction Red List.