Curator of terrestrial vertebrates Dr Colin Miskelly tells the ninth instalment of the unfolding story of the emperor penguin that went where none had gone before.
It is four days since the world’s most famous penguin escaped down the stern ramp of the Tangaroa. After two months of intense scrutiny, you might think that he was slipping into the obscurity of being a speck in the great southern ocean, and the anonymity of being one of over 300,000 emperor penguins on the planet. No such luck! Thanks to the Sirtrack KiwiSat 202 satellite transmitter glued to his back, his every move is watched by millions of adoring spheniscophiles around the world. But that is hyperbole; the duty cycle of the transmitter has it turned on for only 7 hours per day. This means that for 17 hours a day he can swim wherever he likes without anyone telling him that he is swimming in the wrong direction (as long as he ends up further south when the transmitter turns on again).
What does his track tell us after 96 hours? Overall, he has travelled about 100 km in a south-easterly direction, travelling at a rate of about 1.2 km per hour (29.3 km per day). But where would he have ended up if he had floated passively on the surface, allowing currents to carry him like inanimate flotsam? We have the answer to that due to the known movements of 30 Global Drifter Program buoys that have passed near Campbell Island (data from NIWA).
Campbell Island sits in the path of the mightiest oceanic current on the planet, far more massive than the Amazon River. Driven by strong westerly winds, the Antarctic Circumpolar Current south of New Zealand flows eastward at a rate of nearly 150 million cubic metres per second. This is about 150 times the water flow of all the world’s rivers combined.
On average, the drifter buoys near Campbell Island moved in an east-northeast direction at an average rate of 10.5 km per day. This means that if the penguin had not been actively swimming, he would now be about 42 km east-northeast of his release point. If passive movement due to the Antarctic Circumpolar Current is allowed for, the distance that the emperor penguin has travelled by active swimming is approximately 91 km in a south-southeast direction at a rate of 1.1 km per hour (26.9 km per day).
If he keeps on this track and speed, he will reach the pack ice off Marie Byrd Land (between the Ross Sea and the Amundsen Sea) about the end of November. Will he find other emperor penguins there? Yes – as the attached map shows, there are two known and two probable emperor penguin colonies along this remote stretch of the Antarctic coast. The probable colonies have never been visited by humans; they were discovered by satellite imagery detecting faecal staining on the fast-ice, known to be characteristic of emperor penguin colonies.
This strong easterly drift also raises the question of where the peripatetic Peka Peka penguin came from. If he travelled as far east as he did north on his way to New Zealand, then it is likely that he came from one of the colonies in the Australian Antarctic sector, rather than from one of the cluster of colonies on the western side of the Ross Sea.
Previous blogs on this topic:
For later blogs on this bird: