McMurdo Sound and Pram point were chosen by early explorers as places to land, as it was as far south as the sea ice would regularly disperse. The same breaking up of the sea ice that allowed the early ships access also allows visitors more suited to the harsh condition.
As the permanent ice shelf hits solid land, pressure ridges in the ice form, causing fracturing which allow the seals to pop up, and find a nice patch of ice to lay up on.
Of the three main species that we were lucky enough to see, the Weddell Seal (Leptonychotes weddellii) was definitely the most languorous as well as the most numerous. An occasional roll over, or flop in to the water was generally the best we could hope for. In the solitude of staring out into the white expanse off Hut Point, often the only hint of the presence of a seal amongst the broken ice along the shore line was the occasional snuff as it rose for air, before slipping gracefully beneath the floes again. These seals were hunted for the meat and flesh, including to feed huskies and other dogs used in Antarctica. Current worldwide estimates are somewhere up to 1,000,000, distributed mainly in Antarctica and other sub-antarctic islands. They grow up to 400-450kg, with occasionally being measured over 500kg. The can grow up to 3.3m long.
An ever present source of surveillance was provided by the petulant skua. Antarctica’s version of the seagull roamed the skies, ready to snap up any scraps left behind by any careless visitor. For the even more rookie newb who opted to take an open plate of food out of a building, they were known to be the victim of a marauding skua ready to take what they could get. And if someone was really fresh, apparently a couple of biscuits (I guess I should call them cookies if they are baked by Americans) in the hood of the jacket would be enough to have one descending on top of you.
The South Polar Skua (Catharacta maccormicki) is the only wildlife to have been reported to have been seen at the South Pole. It has a transequitorial migration, heading up as far north as Greenland and Alaska during the Antarctic winter. Other than scavenging off the odd human discard, it’s primary source of food is fish. It does predate on penguins, and has been recorded to live off penguins alone if a rookery provides sufficient food. Its ability to find something of value out of rubbish has led to the communal donation shed to take its name, for the storage of one persons discarded sombrero or slippers, or the source of another’s Hawaiian shirt.
An adventure to Antarctica wouldn’t be complete without seeing at least a penguin or two. In between learning the ropes of the McMurdo clinic and seeing some patients, there was ample opportunity to spot for the allusive penguins. Aided by 24 hour light and a perpetual source of fellow penguin spotters, frequent trips yielded a few sightings of the awkward Adelie pengions. Upon getting a job in Antarctica, several of my colleagues in New Zealand insisted in showing me videos of the much-maligned on land co-ordination of these beautiful animals, with the not so subtle intonation that my co-ordination was at a similar par. Whilst their on land awkwardness cannot be denied as they transition from a waddle to a belly slide, their ability to move in the water and project themselves out onto the ice sheet is remarkable. We were lucky enough to see 4 Adelie Penguins (Pygoscelis adeliae) over the 10 days we were there. Unfortunately, the much more majestic Emperor Penguin was not in the vicinity, with its main nearby breeding ground being Cape Crozier, on the far side of Ross Island. It was to this site, that three members of Scott’s crew in 1910 undertook mid winter, in what became detailed in the “Worst Journey in the World”. They returned with specimens that they hoped would prove an evolutionary link between birds and reptiles.
As part of the weekly life at McMurdo, the Sunday science lecture gave us a chance to hear about some of the fantastic science projects that the base supported. We were lucky enough to hear from one of the world leading Adelie experts about the effects global warming and other changes were having on Adelie numbers on the continent. This was my take on his talk.
Essentially, climate change is leading to increasing sea ice around the Ross Sea, but decreasing amounts around Palmer Station on the Antarctic Peninsula side (closest to South America) as well as longer sea ice seasons in the Ross Sea and shorter seasons in the peninsula side. This is due to increasing circumpolar winds having to rise over the Andes of South America, and therefore sucking warm air in from the South Atlantic.
The Adelie need specific sea ice conditions to live. With too much ice, it cannot get from its breeding grounds out to open water to hunt. It is not tolerant of too little either.
Chinstrap and Gentoo penguins (two other species) that are more tolerant of warmer conditions, so therefore increase numbers with loss of sea ice. Hence numbers of Adelie are dropping around the Antarctic Peninsula, but increasing Gentoo and Chinstrap numbers.
With the banning (well almost) of whaling now allowing whale numbers to recover, krill numbers have been depleted as the major food source for Whales. This affects penguin numbers as it is also a major food source for them. After whalers had killed the biggest and more majestic whales in the late 19th century and early 20th century, they moved on to the less impressive Minke Whales. When Minke whales were killed in 1970s and 1980s, Adelie penguins increased during this time. But now as Minke are returning, they also are competing with ‘great’ whales. This is causing greater competition for food.
Another confounder is the process of ‘Polynya’ (a Russian word meaning wind driven sea clear of sea ice). This has increased in specific coastal areas. The melting of the ice sheets in these small pockets are allowing more viable breeding grounds so has allowed numbers to increase.
And lastly, a major new impactis the fishing of Antarctic toothfish. This increadibly valuable yet slow growing fish is found in the Antartic waters. Taking of the large fish mean that there is less competition with penguins for silverfish food.
So for the humble Adelie…Inceasing Sea ice = bad.
Polynya = good
Return of whales = bad
Toothfish fishing = good