By Susanne Bard

Scientists analyzing ancient and modern polar bear DNA have concluded that in just three generations, populations have been moving northward, toward more persistent sea-ice. The bears hunt many animals, but seals make up the majority of their diet. Hunting seals requires sea ice. And it’s melting fast.

USGS Biologist Lily Peacock led the study, which appears in the journal PLoS ONE. “We see this unidirectional increase in gene flow from southern Canada towards the Canadian Archipelago, and this suggests that the genes are essentially moving northward,” she says.

The researchers found that the world’s polar bears cluster into four groups genetically. The recent gene flow has been from the southern Canada population and the eastern Polar Basin population into the more northerly Canadian Archipelago population. They’re not sure what a fourth group, the western Polar Basin population, has been up to.

In contrast, when they looked at historic populations – from 100,000 years ago – the researchers found completely random gene flow – equal movement from south to north and vice versa. This suggests that back then, the hunting wasn’t any better in either direction.

Climate modelers predict that sea ice will be the most persistent into the next century in the Canadian Archipelago. So managers may want to look into focusing conservation efforts there. However, it’s unknown whether the sea-ice conditions there are ideal for hunting seals.