One of the world's rarest penguins has impressed researchers with the lengths it will go to in order to find food.
The Fiordland crested penguin, also known as the tawaki, is one of the world's rarest penguins - and it's also one of the least studied.
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Researchers were keen to learn more about the small birds and study their migration habits after they finish breeding.
"We knew that they were a migratory species, but considering that they live and breed on the New Zealand mainland, we thought that they wouldn't have to travel far," says Thomas Mattern from the Otago University Zoology Department.
The shy birds live in dense forests in Milford Sound and South Westland, nesting beneath rocks and tree roots. Once their chick has fledged, tawaki need to pack on the weight in preparation for their annual moult.
Scientists fitted GPS satellite trackers to 20 birds, aiming to track their movements in real time.
"All the way to the Auckland Islands, carried onto Macquarie Island, and then were halfway down to Antarctica within a couple of weeks," Mr Mattern says of the birds' journeys. "It was insane."
The champion of the group swam almost 7000 kilometres in two months - easily a record for the penguin species.
Researchers think the sub-Antarctic trek may be instinctual, although they're not entirely sure why the birds are willing to expend so much energy on the marathon journeys.
"If it's some special food that they're seeking down there, it has to be one hell of a special food to travel that distance," says Mr Mattern.
The flightless birds spend 80 percent of their lives at sea. It's hoped knowing where they go - and how they're foraging offshore - will help scientists protect the threatened Tawaki from further decline.