Marked population reduction in Antarctic fur seals challenges their Least Concern category

Abundant species listed as Least Concern on the IUCN Red List may receive limited conservation attention if this classification reflects insufficient data rather than genuine population stability. The Antarctic fur seal, currently the world's most abundant otariid, remains listed as Least Concern despite documented regional declines within its core range in the Southern Ocean's South Atlantic region. To reassess this classification, we analysed population trends for South Georgia, the South Orkney and the South Sandwich Islands, which together comprise ca. 97% of the global population, using long-term survey data. Monitoring over 47 years revealed rapid, synchronous declines at South Georgia and South Orkney Islands, with a sustained downturn since 2000 which outlasted sub-decadal fluctuations. At South Georgia, annual change averaged −3.93% [95% CI: −2.73; −5.13] since 2007, reducing the estimated population by ca 1.5 million to ca 1.98 million seals in 2022. Over three generations (26 years), the population reduction was −0.57 [−0.65; −0.48], with a 0.92 probability of exceeding 50%. This meets the IUCN A2 criterion for listing the subpopulation as Endangered, as the underlying causes remain unresolved and are unlikely to be reversible in the near-term. By contrast, the South Sandwich Islands population increased annually by 3.12% [2.59–3.66]. Given that South Georgia alone (ca. 96% of global abundance) disproportionately influences species-level trends, and considering that the next largest subpopulations, Bouvetøya and the South Shetland Islands, are also declining, our findings indicate that the current Least Concern category is inaccurate and warrants a global reassessment of the species' conservation status.