112 | Chapter 6
in the maelstrom of rain, salt spray and driving wind, and finds itself
who knows where. Tales of such seabird ‘wrecks’ will end the present
chapter.
For the very obvious reason that they cannot fly, penguins live their
lives on a smaller spatial scale than, say, albatrosses. Nonetheless, as we
have seen in earlier chapters, the scale can be hundreds or even thou-
sands of kilometres. A long way to swim, and swimming requires more
energy per kilometre covered than does flying. One feature of penguin
swimming, very obvious to anyone who has seen them onscreen or in
the flesh, is the habit of frequently leaping clear of the water in the man-
ner of a porpoise. For porpoises and dolphins, the behaviour, character-
istic of higher speeds, has been suggested to save energy. This is because,
at higher speeds, the drag associated with swimming is higher when the
bird is within three body diameters of the surface than when it is swim-
ming at greater depth. In addition, the extra time above the surface due
to leaping clear could facilitate a necessary gulp of air – and note that
fish, which do not breathe air, do not porpoise.
As so often in science, a story which seemed secure wobbled when
new study techniques could be brought to bear. This has happened to the
energy- saving explanation of penguin- porpoising. Japanese researcher
Ken Yoda, now of Nagoya University, is bold enough (or rash enough?)
to assert on his personal website that there are no animals on earth that
cannot be tracked.^2 Using accelerometers, his team has been able to doc-
ument the swimming behaviour of Adélie Penguins at sea. Even in the
absence of ice, Adélie Penguins collecting food for chicks spend only
about 1 percent of their time at sea porpoising, and only some 4 percent
of the total distance swum is covered using this technique. These obser-
vations seem to undermine the energy- serving idea, prompting Yoda to
wonder whether porpoising, mostly employed near to shore, is actually
primarily a tactic for avoiding predators that are most likely to be en-
countered near to shore.
Penguins could also save energy by travelling in the same direction as
ocean currents. The Iles Crozet in the Southern Ocean are a penguin
stronghold, and the largest King Penguin colony in the archipelago is
home to around half a million pairs. What a tumult of throaty calls and
flapping flippers. When breeding, the birds mostly forage to the south