Antarc­tica

There’s lit­tle south­ern com­fort for an­i­mals cling­ing on to sur­vive in Antarc­tica’s un­for­giv­ing land­scape of ice.

BBC Wildlife Magazine - - SEVEN WORLDS | ONE PALNET -

The south­ern­most con­ti­nent in the world is the fifth largest. About 98 per cent of it is cov­ered per­ma­nently by ice with an av­er­age thick­ness of 1.9km. Yet, de­spite all that ice and with lit­tle more than 100mm of pre­cip­i­ta­tion per year, Antarc­tica is tech­ni­cally a desert, the largest on Earth. It is, how­ever, cold… very cold!

The cold­est air tem­per­a­ture ever recorded by con­ven­tional means was –89.4°C at Rus­sia’s Vos­tok Sta­tion in July 1983, but sen­sors mounted on satel­lites have lo­cated even colder tem­per­a­tures. On the East Antarc­tic Plateau ground tem­per­a­tures reg­u­larly reach –98°C dur­ing a po­lar win­ter night, the cold­est place on the planet.

Liv­ing on the edge

As ice dom­i­nates life on the Antarc­tic main­land and in the sur­round­ing South­ern Ocean, it is a chal­leng­ing place for liv­ing or­gan­isms to sur­vive, but sur­vive they do, with the snow pe­trel and Antarc­tic skua breed­ing the fur­thest south of any an­i­mal. They nest on rocky out­crops that stick out of the ice, some sites up to 440km from the sea. Aside from em­peror, chin­strap and Adélie pen­guins, which nest on Antarc­tica, there is pre­cious lit­tle else. Res­i­dents are no big­ger than mites, ne­ma­todes, spring­tails and wa­ter bears, along with al­gae, fungi, lichens, mosses, liv­er­worts and a cou­ple of small plants, mostly on the Antarc­tic Penin­sula.

Sea-ice sur­rounds the con­ti­nent, dou­bling its size as the sea freezes in win­ter. Un­der that ice is a com­pletely dif­fer­ent world, where in­ver­te­brates reign supreme. The Seven Worlds team dived be­low the ice in McMurdo Sound, the south­ern­most nav­i­ga­ble body of wa­ter, and found the sea

floor cov­ered by colour­ful starfish, brit­tlestars, feather stars, sea urchins, sea cu­cum­bers, cup corals and sea anemones, a far cry from the blackand-white world at the sur­face.

Some an­i­mals have grown into gi­ants, like the sea spi­ders with a leg span of 14cm, and, while the crew were there, they wit­nessed some­thing un­usual. A jel­ly­fish’s sting­ing ten­ta­cle had made con­tact with a sea anemone, and be­gan to reel it in. What it hadn’t re­alised is that the anemone was at­tached to the bot­tom, and it was ac­tu­ally reel­ing it­self to­wards a sticky end!

Cold, hard choices

In amongst the sea-ice lives the Wed­dell seal, which oc­curs the far­thest south of any mam­mal. It can only sur­vive amongst the ice by cre­at­ing sev­eral breath­ing holes that it keeps open by scrap­ing the ice with its teeth. When its teeth wear down, it ei­ther starves, be­cause it can­not catch fish, or it drowns be­cause the breath­ing holes freeze over. The Wed­dell seal, not sur­pris­ingly, is the seal with the short­est life­span. Life in the Antarc­tic ei­ther em­braces ice – like the snow pe­trels and Wed­dell seals – or avoids it, by liv­ing more to the north, on and around sub­antarc­tic is­lands, as ele­phant seals, king pen­guins and al­ba­trosses do. The price they pay, how­ever, is that they are not alone. They must com­pete for food and liv­ing space with mil­lions of oth­ers.

The Seven Worlds Antarc­tic team headed for South Ge­or­gia, home to ele­phant seals and king pen­guins. For wildlife cam­era­man Mark MacEwen, the first sight of the is­land was be­yond any­thing he’d dreamed.

“St An­drew’s Bay is an amaz­ing am­phithe­atre with a huge cres­cent of beach backed by jut­ting moun­tains. As you drop an­chor just off­shore, the sound of what amounts to a wildlife cho­rus hits you. There are the deep bass gut­tural calls of the bull ele­phant seals, which re­ver­ber­ate across the

“You could feel the ten­sion on the beach. The sound at the mo­ment the male ele­phant seals clashed could be felt through the ground.”

bay, mixed with the cries of hun­dreds of thou­sands of king pen­guins.”

The crew were there to film the epic bat­tles be­tween bulls, and the com­ings and go­ings of penguin par­ents. Mark took on the seals.

Bat­tle of the gi­ants

“Male ele­phant seals are huge,” Mark re­calls, “like noth­ing you’ve ever seen be­fore. A mass of blub­ber up to 5.8m long and weigh­ing 4,000kg. But they are sur­pris­ingly fast for an an­i­mal of that size.

“We were there to cap­ture the mo­ment when large sin­gle males try to take over the harems, and you can feel the ten­sion on the beach. I wanted to get in amongst the fight­ing, and the an­i­mals would tower above me. The sound at the mo­ment they clashed could be felt through the ground. It re­minded me of that mo­ment in Juras­sic Park when a tramp­ing T. rex made rip­ples in the glass of wa­ter!”

The seals were not the only gi­ants to be fea­tured in the Antarc­tic episode. One of the more en­cour­ag­ing sto­ries, from a con­ser­va­tion point of view, was the re­turn of the great whales. Hump­back whales are now bub­blenet feed­ing in large num­bers and south­ern right whales have re­turned to their for­mer breed­ing and feed­ing sites. But the big­gest sur­prise was the sight of hun­dreds of fin whales – the world’s sec­ond largest an­i­mal – feed­ing on krill swarms in Drake Pas­sage, pos­si­bly the largest ag­gre­ga­tion of great whales ever filmed.

1 Stand­off: leop­ard seals hunt pen­guins as the birds leave the safety of the ice to reach open sea. A grey-headed al­ba­tross atop its chick. Vast num­bers of birds and mam­mals gather on South Ge­or­gia is­land to breed. The south­ern right whale pop­u­la­tion has grown to over 2,000 in­di­vid­u­als since their pro­tec­tion.

Mark films a clash be­tween two 4,000kg bull ele­phant seals at St An­drew’s Bay. Many sub­antarc­tic is­lands are free of pack ice and host ex­tra­or­di­nary bio­di­ver­sity. 5 Be­neath 3m-thick ice in McMurdo Sound, where tem­per­a­tures re­main above freez­ing all year round, the seabed teems with kalei­do­scopic life.

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