30 May, 2003 Rothera
A duty that is shared by all those on base is to record the local wildlife. This survey has been continuous for five years and is a useful database for those studying “Higher Predators” and Ecological Dynamics. The sea provides the vast majority of the “food” which supports the wildlife in Antarctica. At the base of the food chain is algal plankton, which “blooms” in the austral summer. Next up the chain, zooplankton proliferates and because of these tiny animals, we get a rich and wondrous ecosystem here on the Antarctic Peninsula.
Some of the wildlife we see around Rothera migrate North in the winter. This month, we have already seen depleting numbers of seabirds and seals. However we have welcomed the beautiful and delicate Snow Petrel (Pagodroma nivea), which is pure white apart from its black beak and eyes. This bird is often seen gracefully flitting above the sea ice and brash. The Southern Giant Petrel (Macronectes giganteus) is also seen utilising its two-metre wingspan to coast effortlessly over the sea. This bird is a scavenger and predator. It uses its sense of smell to locate carrion, but also predates other seabirds by surface seizing them by the head.
The Penguin that is regularly seen around Rothera Point is the Adélie Penguin (Pygoscelis adeliae). Numbers exceeding a hundred are regularly recorded, although there are less in evidence this month due to the encroaching Antarctic winter. The délie is a curious beast; they will enthusiastically come up to you thinking they are about to greet a fellow flightless feathered friend. They will approach within five feet of you before they realise you most definitely are not a penguin. We occasionally get visitations from other penguins. Indeed, a small Emperor Penguin (Aptenodytes forsteri) made a brief appearance standing nonchalantly on some pancake ice. He didn’t stay long, unlike the previous Emperor to Rothera, who hung around base for a few weeks last year. Another bird we share Rothera Point with, is the Blue Eyed Shag (Phalacrocorax bransfieldensis). These birds are very sociable and they often congregate in flocks of up to 200. As the name suggests they do have very prominent blue eyes.
There are five species of seal observed at Rothera. Four true (phocid) seals and the one eared (otariid) seal. The true seals consist of the Weddell Seal (Leptonychotes weddellii), Crabeater Seal (Lobodon carcinophaga), Southern Elephant Seal (Mirounga leonina) and the Leopard Seal (Hydrurga leptonyx).
The fifth seal at Rothera is the ‘eared’ Antarctic Fur Seal (Arctocephalus gazella). There are still a number of Fur Seals to be found round the point. Their numbers reached a high of 50 last month. They can be quite aggressive on land, and it is often necessary to take evasive action whilst finding a route through groups of noisy and smelly territorial fur seals.
The Crabeater will also treat you with disdain and will snarl showing its serrated teeth, which are highly specialised for sieving krill. This seal may typically have battle scars due to close encounters with Leopard Seals and Orcas whilst feeding amongst krill swarms at night.
More common than the Crabbie is the Weddell Seal. Above water, these burley seals are relatively docile compared with the other seals. They are often seen slumbering on the shore oblivious to passers by. A juvenile Elephant Seal was seen this month. This is a rare occurrence, however there is a breeding beach used by Elephant Seals on Anchorage Island 4 miles away. These seals are remarkable divers; they have been recorded diving 1.5km deep and can hold their breath for almost 2 hours. Even though this Elephant Seal was a youngster, it was still twice the size of a Weddell. These gargantuan beasts have fascinating faces with huge dark penetrating eyes, shame about their toilet habits. Last but not least is the impressive Leopard Seal. It has a large evil looking reptilian face and lithe powerful body. It is safe to assume that Adélies are a favourite snack for the ‘Lep’. This is verified by noting the number of badly wounded Adélies that look like they have literally escaped the jaws of death.
Two species of cetacean have been sighted this month. A large pod of around forty Killer Whales (Orcinus orca) were seen halfway between Rothera and Anchorage. Orcas are the largest members of the dolphin family and are unmistakable in that they have a striking black and white pattern. This is true for the Orcas that patrol the waters around Rothera point, except the white patches are stained a rusty yellow colour. This decolourisation is due to Antarctic plankton adhering to the whales skin. The male Orca is much larger than the female and has a very tall dorsal fin (up to 1.8 metres). It is reassuring that there has been no documented attacks by Killers on divers or CTD operators.
The other cetacean, which is regularly seen off the point and from the boats, is the minke whale (Balaenoptera bonaerensis). This is a baleen whale, which feeds primarily on krill by taking huge mouthfuls of seawater and sieving out the plankton with its ‘baleen plates’. This month there has been a few close encounters with minke whales whilst out on the boat taking oceanographic measurements. It makes you feel very small when you are in a 5m rubber inflatable boat, whilst ten tonnes of Minke Whale decides to surface a boats width away.
Many thanks to everyone for the photos!
So far, the sea-ice has not formed on the waters around Rothera. It is expected that when it does form, we will see a marked reduction in wildlife. However the Weddell seal does not retreat because it has specially adapted teeth, which scrape at the ice, enabling it to keep ice holes open throughout the winter.
Andrew J. Miller
Assistant Marine Biologist