According to an article from Nine news: "The male foal was born to Tinka and Bataai, and we're hoping he will soon have a play mate with a few other horses looking pregnant."
It's always surprised me there hasn't been more interest in holding this species from the New Zealand zoos. Both Hamilton and Orana have the space and being an equine, they're easy to import from a range of countries.
Fillies are often retained within their natal herds and new stallions brought in, but there will always be a surplus of colts that need accomodating.