*Since, for some reason, this is my most popular post, I have decided to update it as well as write additional information for those of you interested in the animals of Antarctica!*
Contrary to the extreme conditions in Antarctica, there is an abundance of life on the continent, most of it relying heavily on the Southern Ocean’s high productivity (thus there is higher biodiversity along the coast). Nonetheless, there are very few animals which spend their entire lives on the main land. The largest purely terrestrial animal in Antarctica is the flightless midge (Belgica antarctica), which reaches an impressive 0.5 inches in size. The snow petrel (Pagodroma nivea) is one of only three birds that breed exclusively in Antarctica. The Emperor penguin (Aptenodytes forsteri) is the only penguin that breeds during the winter in Antarctica (because it is too large to cram its breeding cycle into the brief polar summer), while the Adelie penguin (Pygoscelis adeliae) breeds (in the early summer months) further south than any other penguin.
The Southern Ocean is vitally important in the entire Antarctic food web, the base of which is phytoplankton. Feeding directly on the phytoplankton is krill – generally a broad collective term applying to 85 or so species of small shrimp-like crustaceans (order Eucarida). Of special interest is the Antarctic krill (Euphausia superba), which can reach 10,000 – 30,000 individual animals per cubic meter.
In terms of biomass, they are thought to be one of the most successful animal species on the planet. Their ecological role is essential to Antarctica in that almost all Antarctic consumers rely either directly or indirectly on them as a food source. It is amazing to think that the largest animal on the planet, the blue whale (Baleanoptera musculatus), feeds exclusively on krill! The populations of krill and all other Antarctic animals – and indeed you could go so far as to include all oceanic life, and in turn all life on Earth – are intricately linked. **I won’t delve into this important issue too far, but unfortunately it has emerged in recent years that the populations of krill have been decreasing all around the world (reportedly by as much as 90%). The reasons for this are many – of course, overharvesting by humans (for krill oil supplements, dried krill, etc.), but also due to climate change…krill populations increase when there is more pack ice at the poles – and of course with the melting of ice…there is less krill. Whatever the causes, the effects are far-reaching, and not hard to imagine – collapse of marine ecosystems around the world.**
The most damaging effect of living in extremely low temperatures is the formation of ice within the cells and tissues of living things. Ice can rupture cell membranes, and/or irreversibly damage their delicate machinery. Every Antarctic animal has evolved adaptations in different ways to cope with the harsh environment, and is an interesting study in itself.
Many animals will lose water as they become colder, thereby increasing concentrations of sugars, salts, and other cellular and tissue constituents. This ability to dehydrate, and recover rapidly when the temperature rises, is seen in plants such as lichens and mosses, the eggs and larval stages of some insects, and most evidently in the invertebrates.
Ice fish (suborder Notothenioidei) produce “anti-freeze” substances in their bodies that prevent the formation of ice. They also have enzyme systems that are highly efficient and allow them to remain active at low temperatures – their activity in water at 32F is close to that of a temperate water fish at 68F. They also lack red blood cells (they are translucent, like ice!) for carrying oxygen around their bodies. The RBCs are not needed since oxygen is so highly soluble in cold seawater. This also means that their blood is much thinner, again allowing the fish’s metabolism to be much lower – great for conserving vital energy.
All endothermic (warm-blooded) vertebrates living on or around Antarctica – penguins and other sea birds, seals, and whales – rely on thick layers of blubber to insulate them from the cold environment. In addition to this excellent insulation, endothermic animals also produce metabolic heat. Endothermic vertebrates, besides the blubber, also have extensive fat deposits throughout their bodies which can be drawn on as a source of energy in times of fasting. Sea birds’ feathers provide additional insulation, with a layer of down close to the skin and an outer layer of closely overlapping feathers. Preen oil, secreted by a gland near the tail and spread over the feathers with the bill, produces a waterproof seal. *I will try to write up a special post on the penguins soon, which is the goal of our research, and the very reason I am travelling to Antarctica!*
A great variety of insects, birds, and land mammals live in the high Arctic all year round. In contrast, only a handful of tiny invertebrates, and not one single land vertebrate, can survive the Antarctic winter. Remember, the continent’s largest permanent inhabitant is a 12 mm midge! Only microscopic life survives throughout the year, of which there is a stunning diversity – midges, copepods,. tardigrades (the infamous and amazing “water bears”), rotifers, collembola (springtails), nematodes, and protozoans – all perfect examples of extremophiles.
Other famous Antarctic animals include the seals and the whales – mammals adapted to life in the cold ocean waters. The Antarctic coast is home to five species of true (or ‘earless’) seals – the ones without an external pinna (flap) to their ears. Four species – the Weddell, Ross, leopard, and crabeater seals – are all closely related to each other. The fifth, the Southern elephant seal, can be found only on the east Antarctic coast and the surrounding Antarctic islands. Seals are not very nimble on land, and can often be approached while snoozing and sunning themselves. But in the water, they transform into swift, lively, agile, and strong creatures. Males will defend specific breathing holes in the ice. Of all southern seals, the best known is probably the Weddell seal, with its big eyes and adorable expression. Most notorious is the leopard seal – a vicious predator which hunts penguins and all other seal species with much gusto. They are usually solitary creatures, seldom seen in groups, unlike Weddells. Orca whales (along with the leopard seals) are the main predator of all the seals. Crabeater seals seem especially vulnerable.
There are six species of baleen whales that frequent the Southern Ocean and can be seen around Antarctica. These are the blue, humpback, southern right, minke, fin, and sei whales. The southern right whale is one of the most endangered animals in the world – and definitely the most endangered whale species – with only about 4000 individuals left. **Fun Fact: 18th century whalers named these slow-moving, inshore-visiting whales ‘Right’ whales because they were easily caught, they floated after being killed, and they yielded much oil and long baleen plates.** The blue whale is, as everyone knows, the largest animal that ever lived…yet very little is known about their life cycles, as they are one of the more mysterious creatures of the oceans despite their gargantuan size. Exactly how big are they? Their heart alone weighs 2 tons (as much as an African elephant), and a human could crawl through their arteries. They consume enormous amounts of krill (a single whale up to 1.5 metric tons/day!) in a method of feeding known as “lungeing”. The whale seeks out the giant concentrations of krill (which is what limits them to certain areas like the Antarctic ocean and submarine canyons). They then open their jaws and allow their mouths to be flooded with the ocean water containing dense concentrations of krill. During this process, the pleated skin of their under-mouth/throat region expands immensely, transforming the cigar-shaped beast into something more reminiscent of a bloated tadpole. They close their jaws, and use their tongues to push the water out, while their baleen traps the krill inside. Blue whale feeding is considered to be the largest biomechanical action in the animal kingdom. While I mentioned earlier that the largest animal in the world is feeding on such a tiny one, another way to look at it is this: the largest animal in the world is taking bites off a giant superorganism that is hundred of times bigger than them. This is a makes them more of a predator, rather than a “passive feeder” as they are so often described.
The toothed sperm whale is also an Antarctic visitor, and so is the orca “whale” – which is really a member of the dolphin family. Both are “true” predators in that they pursue their prey and catch/kill it with their teeth.
Finally, I guess I should mention the bird life of Antarctica. All the Antarctic birds are sea birds – the penguins of course being the most obvious. Don’t worry – I plan on doing a whole separate post on penguins as soon as I can! So let me mention some of the other avian inhabitants. Some of the more common ones are skuas, cormorants, petrels, fulmars, and albatross. Skuas (especially) and petrels are fierce, and often vicious, predators of penguin eggs and chicks. The smallest Antarctic bird is the storm petrel – at 10 cm in length. The largest Antarctic bird is the Southern royal albatross, with a wingspan of 9 feet! Hopefully I will get to see some of these majestic birds. And I would love to get a bird to stuff while I am there – Dr. Emslie said for sure a penguin, which would be a bit of a crafty challenge.
Well, I think this concludes my brief coverage of some of the wonderful animal life of Antarctica. I know it is far from complete, but after spending several hours on this post, I think its time to call it quits. I wish I had more time to go into more detail, because everything is so fascinating…but…I think it is a nice little taste. I hope I have provided you with a little more knowledge about the wonderful continent that is Antarctica!