The pup was born in the shallows at St Kilda Beach last September.
It was the first leopard seal pup known to have been born on the New Zealand mainland since the 1970s.
The pup failed to thrive, and by the next morning was weak and unresponsive.
It was euthanised after being assessed by a veterinarian and a Department of Conservation staff member as being unable to feed, even if the mother returned.
The pup, named Kana by the Otakou Runanga and prepared by Marlborough taxidermist Peter Wells was unveiled at the Otago Museum's HD Skinner annex yesterday, bound eventually for display.
University of Otago zoology student and leopardseals.org research assistant Giverny Forbes said the death had a huge silver lining.
''She's probably taught us the most of any leopard seal in New Zealand so far.''
It underwent a full serious of MRI and CT scans, giving new knowledge about the early life stages of the leopard seal.
Doc coastal Otago ranger Jim Fyfe said the number of sea leopard sightings in New Zealand had increased markedly in the past 10 years. It was unclear what was behind the increase in sightings.
''It could be that their numbers are increasing, or it could be that they are struggling for food and venturing further north.''
