Part III: Antarctica and Academe - Scott Polar Research Institute

crop of clumsy, uncoordinated swimming weaners. In other research it has been
found that only 3% of leopard seal stomachs examined in September and October
had seal remains, whereas 25% of those collected in November to March had seal
remains.
I had earlier done some indirect research on this problem which involved
measuring the spacing of pairs of scars on crabeaters, which was on average 6.8 cm
and leopard seal canine teeth are only 5.7 cm. apart; the killer whales teeth were
spaced more closely at 3.6 cm. The ratio between leopard seal tooth spacing and scar
spacing was 1:1.18. Now the average length of crabeater seals over a year old was
228 cm and we can assume that the spacing between the scars had increased since
they were inflicted, as the seals grew in length (because the scars are placed more or
less across the body, not along it). Applying the relation between tooth spacing and
scar spacing to adult body length predicted a crabeater body length of 193 cm for the
mean body length at origin. This was identical with the average body length (l92.7
inches, given above) of animals with fresh scars! It is equivalent to an age of 4-5
months, or February - March which is in close agreement with the observation, also
mentioned above, that weaned pups do not begin to show fresh wounds until late
February! This independent work indicated that most scars are inflicted in the
middle of the first year of life, as the probability that the young crabeater will escape
increases. There can be little doubt that leopard seals take a very high toll of
crabeater pups, and this is probably the major cause of mortality.
However, killer whales do attack crabeater seals.
On the floes the crabeaters most often hump along like a Weddell seal - almost
like caterpillars, often sliding a few yards in between activity; they only make the
'swimming' motion if pressed, as when chased by a leopard. The leopards often
move like an elephant seal, but with their fore-flippers only partly spread, or like the
Weddell, with the fore-flippers pressed into the side of their body. Occasionally they
make the lateral 'swimming' motion, and we observed this is the ‘fast mode’ in
chasing prey over the ice.
We moved along the south side of Livingston Island in leads in the pack, still
looking for seals. We weighed a weaner and collected a female in a mated pair, and
went on to collect a few more, but on the whole there were few seals that day.
Livingston Island and Mount Friesland were in cloud most of the day, but there were
some lovely lighting effects. The pack remained fairly dense, the floes covered in
new snow. We saw a few penguins - Adelie, chinstrap and gentoo and the usual
other birds, with more snow petrels and Wilson's petrels than usual. Owing to the
heavy pack ice we made slow progress and stopped for the night at 9 o’clock, stuck
in the pack again. There was a beautiful sunset sky - a range of blues, apple green,
apricot, pink and purple - reflected in the still leads. We could see Three Brothers
Hill at Potter Cove, King George Island, on the horizon.
Next morning, continuing into Admiralty Bay, we reached our encampment at
Ezcurra Inlet by 10 o’clock. The fast ice had broken back to Dufayel Island and there
were not many seals left. We left Torger, Ian and Don to break camp and ‘Hero’ went
across to Martel Inlet so that the rest of us could count seals and look for tagged ones.
However by the time Doug, John and myself set off on the count it was blowing and
overcast. There were about 60 Weddells and a similar number of crabeaters on the
fast-ice. Two of the Weddells were still suckling pups and there were several
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