Blue Whales of Antarctica: Three Populations of Giants

The Antarctic blue whale, which is endangered, falls into three genetically distinct populations. This was the conclusion of a recent study conducted by researchers at Australia’s Flinders University and published in Nature’s Scientific Reports. These marine mammals, which are the largest animals on the planet, are found in the waters of the white continent during the austral summer to consume massive quantities of krill, their only source of food. It is suspected that the three populations split up during the southern winter to reproduce in different parts of the globe. It’s possible that they disperse toward the three large oceans of the southern hemisphere: the South Pacific, the South Atlantic and the Indian Ocean.

What makes this discovery important?

Twentieth century whaling in Antarctica brought the blue whale to the brink of extinction. Between 1928 and 1973, its population plummeted from approximately 239,000 to 360 individuals. Although the population seems to have increased slightly since whaling was banned in 1972, this sub-species remains fragile and threatened.

Some populations of Antarctic blue whales might be more vulnerable than others, depending on the threats that they encounter along their migratory routes and in their respective reproduction grounds. It is therefore important to take into account the existence, composition and distribution of the different populations when implementing conservation measures.

Methodology

By comparing the DNA of multiple individuals, researchers at Flinders University have determined that Antarctic blue whales fall into three groups. But to reach this conclusion, an enormous sampling of DNA was needed. To collect DNA from a whale, researchers must perform a biopsy: using a crossbow, they fire a bolt-tipped arrow, which is used to harvest a tiny piece of skin and fat, all without immobilizing the whale and disturbing it for but a few seconds. For this study, researchers used samples from a total of 142 individuals taken during expeditions conducted under the auspices of the International Whaling Commission beginning in 1990.

Now what?

The migratory routes and reproduction grounds of Antarctic blue whales remain an enigma. Unravelling this mystery, notably by means of satellite telemetry, would help to ascertain the composition and distribution of the different populations and thereby better protect them. However, at the end of the day, tracking these giants of the sea for thousands of kilometres is a tremendous technological challenge!

Sources:

Towards population-level conservation in the critically endangered Antarctic blue whale: the number and distribution of their populations.

Antarctica’s blue whales are split into three distinct populations