A little-known penguin in New Zealand makes an epic journey for food, a new study has found.
The Fiordland penguin (Eudyptes pachyrhynchus), or tawaki as it’s locally known, lives in the forests of New Zealand’s rugged southwestern coastline. Every year, after the penguins have raised their chicks, an exhaustive period during which the tawaki can lose up to half their pre-breeding body weight, the birds set out into the sea in search of food. They have about three months from December to February to put on weight in time for their annual moult: a three-week energy-intensive process when the penguins grow a new set of feathers. During this period, the birds have to remain on land and cannot go out to hunt.
Until recently, researchers did not know where the penguins went to feed during the pre-moult period to restore their weight, or how far they traveled from their breeding colonies. Now, they have an answer.
A team of researchers tagged 17 tawaki with satellite transmitters and tracked their movements from November 2016 to March 2017. In less than three months, the birds made a round trip of up to 6,800 kilometers (4,225 miles). This makes it one of the longest-known pre-moult penguin migrations to date, researchers report in the study published in PLoS One. Macaroni and Rockhopper penguins from Marion Island in the southwest Indian Ocean, by contrast, have been reported to travel between 700 and 900 kilometers (435 and 560 miles) away from their breeding colonies.
On a day-to-day basis, the penguins’ journeys increased over time. During the first third of their journey, they swam about 20 kilometers (12 miles) per day, increasing it considerably to an average of 80 kilometers (50 miles) or more per day toward the end of the trip.
“Tawaki go on a big trip once their chicks have fledged,” Thomas Mattern, a penguin researcher at Otago University in New Zealand, said in a statement. “On this trip the penguins need to recover from the exhausting chick rearing duties and pack on weight in preparation for their annual moult. One would think that the birds try to conserve as much energy on this trip as possible. But what we found is, simply put, crazy.”
The penguins went nearly halfway to Antarctica to hunt, traveling to the subtropical front south of Tasmania or to the sub-Antarctic front, both highly productive feeding areas.
The question, however, is why the tawaki need to go so far out to the sea for food during the summer months when the waters around mainland New Zealand are also teeming with fish at this time. Two other species of New Zealand penguins, the little penguin (Eudyptula minor) and the yellow-eyed penguin (Megadyptes antipodes), tend to stay around their breeding colonies all year round, suggesting that there’s enough food close to the land.
The researchers don’t have an answer yet. But they speculate that it could be a matter of instinct, something the tawaki are genetically predisposed to do.
The species belongs to a genus of penguins called the crested penguins that likely evolved in the sub-Antarctic region, researchers say. While most other crested penguins, such as the erect-crested penguin (Eudyptes sclateri) and the snares penguin (E. robustus), occur only on sub-Antarctic islands, tawaki live far away on the New Zealand mainland. The researchers think that traveling such long distances to reach the sub-Antarctic region could be a behavior that the species has carried over from an ancestral crested penguin.
However, the results reported in the study come from a few individual tawaki and cover just a single year. A more accurate picture of the penguins’ migrations could emerge after more penguins are tracked over the years.
With an estimated 5,500 to 7,000 mature birds remaining in the wild, the tawaki is considered one of the rarest penguin species in the world, and is listed as vulnerable on the IUCN Red List.
Mattern, T., Pütz, K., Garcia-Borboroglu, P., Ellenberg, U., Houston, D. M., Long, R., … & Seddon, P. J. (2018). Marathon penguins–reasons and consequences of long-range dispersal in Fiordland penguins/Tawaki during the pre-moult period. PLoS ONE 13(8): e0198688. https://doi.org/10.1371/journal.pone.0198688