Every year, Fiordland penguins (also known as Tawaki penguins) go on a mammoth 2-month trek. They swim up to 2,500 kilometers (1,550 miles) from their breeding site on the west coast of New Zealand's South Island to their feeding sites down south. Then, they swim back again. Thanks to research recently published in the journal PLOS One, the first to track the migration pattern of these birds, we now know where they go, we just don't know why.
Scientists at the University of Otago, New Zealand, tagged and monitored 17 adult penguins (10 male and seven female) using satellite transmitters. They then compared the migration patterns to oceanographic data (surface temperature and currents).
Due to faults with the tags, only nine birds could be tracked to the breeding ground and five were tracked all the way back again. From that information, though, they were able to locate two feeding sites: one south of Tasmania at the subtropical front and a second further south towards the subantarctic front.
During the migration, the birds travel between 3,500 and 6,800 kilometers (2,200 and 4,200 miles) over a period of 69 days or so, reaching speeds of 20 to 80 kilometers (12 to 50 miles) per day. This is all particularly impressive when you consider the fact that this may be close to the maximum swimming speed for penguins.
In fact, the Tawakis kept going for so far and for so long that at first, the researchers thought the data was lying to them. Thomas Mattern from the University of Otago told AFP he was "flabbergasted" by the results.
But here's the thing. This gargantuan task may be entirely pointless. According to the researchers, Tawakis leave the New Zealand coast exactly when the seas are at their most lucrative from a fishing perspective.
The Tawakis set off around mid-November (right after breeding season) before returning to New Zealand's South Island in mid-January to begin their annual molt, an intense 3-week process of growing new feathers.
"The penguins leave the New Zealand coast at a time when the ocean's productivity is nearing its peak, so from that perspective, traveling thousands of kilometers seem to make little sense," Couronne said in a statement.
Which begs the question, why do they bother?
"We believe that this extraordinary behavior could be a remnant from an ancestral penguin species that evolved further south in the sub-Antarctic region before populating the New Zealand mainland. This would also explain why the species breeding range is concentrated to the southern coastlines of New Zealand; if breeding further north, this migratory behavior would simply not be feasible," he added.
It is also worth pointing out that there are limitations to the data. Since only five individual penguins could be tracked to completion, these results could be an anomaly rather than an accurate interpretation of the annual Tawaki migration. To find out, the team have tagged another 48 penguins to track their movements next year.