An elusive New Zealand penguin species has wowed scientists who tracked it travelling as far as 7000km - an equivalent distance between Auckland and Indonesia - in just eight weeks.
The endangered Fiordland penguin or tawaki inhabits the rugged and inaccessible coastline and fiord systems of southwestern New Zealand.
But scientists had much more to learn - and a team from Otago University, Antarctic Research Trust and the Global Penguin Society have been studying its small population and breeding biology.
"Tawaki go on a big trip once their chicks have fledged," explained Dr Thomas Mattern, of Otago's Department of Zoology.
"On this trip the penguins need to recover from the exhausting chick rearing duties and pack on weight in preparation for their annual moult."
Throughout this so-called pre-moult journey, time was of the essence as the birds only had eight to 10 weeks before they have to make landfall again to replace their entire plumage at once.
During the moult, the penguins cannot go out to feed and have to stay on land for three weeks, so it is important for the birds to gain a lot of weight during this journey.
"One would think that the birds try to conserve as much energy on this trip as possible," Mattern said.
"But what we found is, simply put, crazy."
The study revealed, in a relatively short period of time, the penguins travelled enormous distances towards Antarctica to reach the subantarctic front almost 3000km south of New Zealand and Tasmania.
After only eight weeks they returned to the breeding sites to moult, having travelled as far as 7000km during their foraging - something which co-author Dr Klemens Putz described as an "incredible achievement" for a flightless seabird.
"The question is why the penguins leave on such an epic journey, at a time when the ocean productivity along their coastal breeding sites reaches its peak," said Putz, of the Antarctic Research Trust.
"There should be more than enough food for them just on their doorstep."
The authors believed the penguins might be following an instinct rather than an actual need to forage in subantarctic waters.
"Tawaki are one of several crested penguin species, a group that likely evolved in the sub-Antarctic region," Global Penguin Society president Pablo Garcia-Borboroglu said.
"Most crested penguins breed on islands that are located close to the subantarctic front, a productive oceanic region that surrounds the Antarctic continent.
"Tawaki, on the other hand, breed very far north from this region."
The researchers believed the penguins travelling such huge distances just to reach this region might reflect a remnant behaviour from an ancestral crested penguin species.
Moreover, it cast new light on the current distribution of the species.
"So far, we thought that tawaki used to breed all over New Zealand, and that hunting pressure in the past 500 years caused the species to retreat to the remote areas they breed in today," Mattern said.
"However, considering that breeding further north would add another few thousand kilometres to the penguins' journey, it appears that tawaki breed exactly where their migratory behaviour allows them to."
The findings come months after scientists were awed by another penguin's New Zealand odyssey.
Young juvenile penguin Takaraha was tracked swimming nearly 1000km up the coast of the South Island, but later had to euthanised after suffering a critical flipper injury.