"While he appeared to be improving a little, he was clearly masking the full extent of its condition - a survival tactic animals often employ."
The rare olive ridley sea turtle spent a night at the National Aquarium of NZ in Napier last week before it was rushed to Auckland for further treatment.
The species usually lives in the Pacific Ocean's warm water, so there were immediate concerns for the animal's welfare when it washed up at Blackhead Beach in the middle of a Kiwi winter.
"It was really good that he came in to us, as we could make him more comfortable and do our best to give him the best possible chance," Leech said.
Zoo vets were waiting for the full results from the post mortem.