Whales of Antarctica: Giants of the Southern Ocean

Whales are part of an incredibly varied group of highly specialised aquatic mammals known as cetaceans.

These animals range greatly in size, from porpoises measuring just over a metre in length to the largest animal on Earth, the extraordinary blue whale. Blue whales can reach around 24 metres long and may weigh as much as 84 tonnes.

Whales have experienced remarkable evolutionary transformations as they adapted to living in the ocean, making it difficult to imagine what their distant ancestors looked like. Fossil evidence has shown that whales originated from much smaller mammals that lived on land before entering aquatic environments more than 50 million years ago.

The word “whale” is generally used to describe the “great whales.” This group includes the largest toothed whale, the sperm whale made famous by Moby Dick, as well as the large baleen whales that were heavily exploited and brought close to extinction.

Cetaceans are broadly separated into two main categories. One group consists of toothed whales, which possess teeth for catching prey. The other includes baleen whales, which capture small organisms by filtering seawater through specialised structures called baleen.

Toothed whales

Four species of toothed whales occur in Antarctic waters: the sperm whale, southern bottlenose whale, orca or killer whale, and southern fourtooth whale. With the exception of the sperm whale, these species are considerably smaller than baleen whales and were not subjected to extensive commercial hunting.

All toothed whales possess teeth, allowing them to capture relatively large prey such as fish and squid. Killer whales have a broader diet and also prey on animals including penguins and seals, often working together in coordinated groups.

Baleen whales

Six species of baleen whales are found around Antarctica: the enormous blue whale, fin whale, southern right whale, sei whale, minke whale, and humpback whale.

The term “baleen” comes from the large, brush-like plates inside the whale's mouth. These plates function much like a filter, allowing baleen whales to strain tiny organisms from seawater. Their diet can include krill, plankton, and various small crustaceans.

Whale migration

Many whales living in the Southern Ocean undertake seasonal migrations, travelling toward warmer tropical waters during the Antarctic winter. These warmer regions provide safer conditions for newborn calves, which would have difficulty surviving in the extremely cold waters farther south.

When the austral spring arrives, the whales travel back toward Antarctica, following the retreating edge of the sea ice. This region is highly productive biologically and offers an abundant source of food for whales returning to feed.

Young calves generally remain alongside their mothers for several years as they participate in these yearly migrations. Female whales typically do not reproduce again until their existing calf has become independent.

Whale exploitation to protection

The commercial exploitation of whales, driven by the valuable oils and other products obtained from their bodies, contributed significantly to the expansion of ocean exploration by seafaring nations.

More than 1.3 million whales were killed in Antarctic waters during the twentieth century. Before large-scale exploitation began, the Antarctic blue whale population is estimated to have exceeded 225,000 individuals. Today, fewer than 2,000 are believed to remain.

As the severe decline of whale populations became increasingly recognised, the whale emerged as an important symbol of the modern conservation movement. Today, these animals are understood to play an important role in maintaining healthy marine ecosystems.

At the same time, millions of people now have the opportunity to experience whales at close range through whale watching, a modern industry that has developed as an alternative to the destructive whaling practices of the past.