Uncovering the migration secrets of whales

Genetic analysis of skin samples from southern right whales at feeding grounds at South Georgia Island in the southwest Atlantic Ocean shows the whales that gather there are more closely related to those in South America than to those in South Africa, scientists say

Southern right whale mother and calf on their Brazilian wintering ground Credit Karina Groch

The remote South Georgia Island was historically a key feeding ground for multiple whale species, including southern right, blue and fin whales and humpbacks, due to the abundance of krill in summer.

But numbers plummeted once whaling began with 180,000 whales killed in the South Georgia area in the 20th century. That stopped in the mid-1960s and whale populations have been slowly recovering since.

Because southern right whales have been regularly sighted at South Georgia, in 2018 a British Antarctic Survey (BAS) expedition set out to establish where these whales were born and whether they came from winter calving grounds in Argentina and Brazil, or from South Africa.

Overall the BAS project involves 30 researchers from 11 countries who are studying the population recovery and health of southern right whales in South Georgia waters using acoustics, tracking technology, skin sampling and drone technology.

Analysis of genetic links among whales is critical to understanding how climate change will influence whale feeding grounds and New Zealand’s southern right whales are considered a sentinel species for assessing the potential impacts of global warming.

Dr Emma Carroll from the University of Auckland is involved in the BAS research and says collected DNA, along with new genetic assignment approaches, shows that southern right whales found at South Georgia are more likely to have been born around South America than South Africa.

“Genetic methods are an important tool in linking whale breeding grounds where recovery from whaling is being closely monitored, to feeding grounds that are being impacted by climate change,” she says. “It’s only by understanding these links that we can understand how whale populations will fare in a changing world.”

BAS researcher Dr Jennifer Jackson, who led the expedition to South Georgia, says the strong international collaboration involved in the research is a powerful means of understanding how recovering whale populations are connected over entire ocean basins.

“Working together both to share samples and biological information and to develop common conservation measures is the best way to protect and conserve migratory species such as right whales”.

The research is published in the Journal of Heredity.

Editor’s notes
More on southern right whales:
• Southern right whales were so named because they were the ‘right’ whale to kill, and in the South Atlantic they were heavily exploited by whalers for over 350 years. While catches peaked in the mid- 1800s, it is only in the past three decades that southern right whales have again become regular winter visitors to Argentina, Brazil and South Africa where they use sheltered bays to calve.

• Another population to the west, in Chile and Peru, has not fared so well, and the lack of recovery from whaling has led this population to be declared Critically Endangered by the International Union for Conservation of Nature (IUCN).

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