Conservation sleuths have partly solved the mystery of how a dead stoat came to be on Rakiura-Stewart Island in a case that has now become an intriguing whodunnit.

The Department of Conservation (DOC) is baffled as to why a dead stoat was taken to the island and planted on Stewart Island's Great Walk.

The stoat was found on the Rakiura Track last month.

Its injuries were consistent with being caught in a trap and an analysis of its stomach found mouse hair, indicating it had recently eaten a rodent, although Rakiura is free of mice and stoats.

DOC southern South Island director Aaron Fleming said the findings indicated the stoat was most likely killed by a trap elsewhere, transported to the island and placed on the walking track.

"It's a relief to have this part of the mystery solved and know that Rakiura remains stoat-free," he said.

"An unchecked stoat population would've been a disaster for kiwi and other vulnerable native species here.

"Rakiura is one of the best places in the country to encounter kiwi in the wild. We know from other places with stoat populations that kiwi chick survival can be as low as zero without sustained predator control."

The stoat would be genetically tested, although results would not be able to pinpoint where it had come from, Fleming said.

"It's baffling why anyone would take a dead stoat to Rakiura and put it on a busy walking track. If anyone has any information about the stoat and how it came to be on Rakiura, please contact us on 0800 DOCHOT," he said.

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