Whole genome sequencing has revealed a global fall in the numbers of killer whales during the last Ice Age, at a time when ocean productivity may have been widely reduced, according to researchers at Durham University.
The scientists studied the DNA sequences of killer whale communities across the world.
They found a severe decline in whale numbers leading to a bottleneck and consequent loss of genetic diversity approximately 40,000 years ago when large parts of the Earth were covered in ice.
The only exception to this was found in a killer whale population off the coast of South Africa that retained high variations in genetic diversity.
As greater genetic diversity indicates larger population size, the researchers believe the South African community of killer whales escaped the bottleneck faced by other communities.
They said an important factor could have been the Bengeula upwelling system – which delivers nutrient rich cold water to the oceans off South Africa – remaining stable despite the last glacial period.
This nutrient rich water would have been able to sustain the supplies of fish and dolphins that killer whales in this part of the world feed on.
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