A natural terminal Pleistocene decline of African penguin populations enhances their anthropogenic extinction risk

The African penguin Spheniscus demersus, endemic to the coast of southern Africa, has suffered anthropogenic-driven population declines since 1900 and is now listed as Endangered on the IUCN Red List. Conservation efforts currently underway are informed by the species’ adaptive response with respect to colonisation capacity and breeding success, vulnerability because of anthropogenic competition for prey species, and global climate change. Here, we show how the available nesting habitat of African penguins likely declined precipitously post the Last Glacial Maximum, driven by island inundation as sea levels rose naturally, before anthropogenic global warming. The average size and numbers of islands around the southern African coast decreased almost tenfold between ∼15 kya and the mid Holocene (∼7 kya). In addition, the geographic distribution of islands shifted predominantly away from the South African west to the south and east coasts. The natural decline of island habitat likely caused a decline in the penguin population, which is likely relevant in current assessments of the vulnerability of this species to novel anthropogenic drivers of population decline. The status of the African penguin as a post-Pleistocene refugial species has amplified its extinction risk due to anthropogenic impacts, despite natural resilience to paleoclimatic change afforded by an apparent capacity for habitat colonisation and evident persistence through late-Pleistocene bottlenecks.