Fur seals signal their own decline

摘要

A little more than a century ago, humans had pushed Antarctic fur seals (Arctocephalus gazella) to the brink of extinction. Once hunting stopped, their numbers rose, and by the early twenty-first century their population had grown to a few million. On page 462 of this issue, Forcada and Hoffman show that breeding fur seals on the beaches of South Georgia Island in the southern Atlantic are, on average, becoming more heterozygous-an indicator of individual genetic variability that is linked to improved survival and reproductive success. At face value, this seems to be good news, but a more detailed look reveals that it is a worrying symptom of a population that is again declining.