Auckland Zoo has bred and hand-reared bat pups. The tiny short-tailed bats twins (pekapeka) were born in November.
The male and a female weighed four grams and are now a healthy adult weight of around 14 grams.
The parents are descendants of a population from the Tararua Ranges in the lower North Island.
They came from a group that were relocated by the Department of Conservation to Kapiti Island in 2005-06.
Clinical services coordinator Mikaylie Wilson said their mother had given birth to twins earlier but they did not survive.
''From this experience, we knew she wasn't able to cope with raising two, so the decision was made to pull the first twin at two days, and then at two weeks, the second pup was failing to thrive so we pulled it as well."
A portable incubator was set up that mimicked a nursery in the wild, keeping them warm and secure.
''The temperature of the incubator was at 28 to 29 degrees and we were feeding them every four hours," she said.