Staff at Auckland Zoo got a surprise today when they discovered a second Sumatran tiger cub.
A cub was born at the zoo on Thursday, after 10 years of planning and preparation.
But when the mother, Molek, turned around today zoo staff discovered a second cub.
Abi Smith, from the zoo's marketing department, said staff were "all very excited".
"We think there's only two, but then we thought there was only one. It seems one was just more adventurous and was out and about climbing (and so got noticed)."
She said the zoo keepers would not interfere with the bonding process and would "stay well back and hopefully get some photos".
The zoo announced a name competition to decide the name of the first cub, but Ms Smith said they will probably name the second one internally.
The cubs would probably not stay at the zoo because the species was so endangered, but it would be nice for the cubs to grow up together while they remained at the zoo, Ms Smith said.
She said the flood of messages and public support since the cubs' birth was "heartwarming".
Auckland Zoo carnivore team leader Andrew Coers said Molek, who is eight, had come to motherhood quite late in life.
Molek has started eating again - something she stopped a few days before birth and immediately after.
"The birth is a highlight of the conservation efforts of the zoo to help this critically endangered tiger.
"It's great to finally have a Sumatran tiger cub at Auckland Zoo. The cub is particularly genetically valuable as two-year-old dad Oz's bloodline is not represented in Australasian or European zoos."
