More than 60,000 African penguins vanished from two of South Africa’s most important breeding islands in less than a decade, and scientists say they now understand why. A study published in the journal Ostrich: Journal of African Ornithology has revealed that the collapse of sardine stocks triggered an unprecedented wave of starvation, wiping out more than 95 percent of the colonies on Dassen Island and Robben Island between 2004 and 2012.The discovery highlights a crisis unfolding across the entire species. African penguins have declined by nearly 80 percent globally in the past thirty years, and the dramatic losses on these islands show how dangerously close they are to disappearing altogether.
Penguins died due to the collapse in food supply
The research, conducted by the University of Exeter and South Africa’s Department of Forestry, Fisheries and the Environment, found that the birds died primarily because their main prey fish virtually disappeared. Sardine biomass fell to less than 25 percent of its historical maximum for years, creating conditions that made it impossible for many penguins to survive.Around 62,000 birds are thought to have died between 2004 and 2011, a period when sardine stocks remained critically low. The study argues that these shortages were driven by environmental shifts in the region, including warmer and saltier waters that disrupted sardine reproduction, combined with sustained fishing pressure that continued even as sardine numbers collapsed.
Starvation during the moult proved fatal
One of the most striking findings concerns the penguins’ annual moult. During this process, African penguins shed and regrow their feathers, which means they cannot enter the water to hunt for about twenty one days. They rely entirely on stored fat and muscle to survive this fasting period.Lead researcher Dr Richard Sherley explained that if penguins are unable to find enough food before the moult, or immediately afterwards, they simply do not have the reserves needed to stay alive. With sardines in short supply, thousands of birds entered the moult already weakened, and many never recovered.
Colonies that once thrived now nearly empty
Dassen Island and Robben Island were once strongholds for African penguins, hosting tens of thousands of breeding birds. By 2012, more than 95 percent of these populations had disappeared. The islands now serve as stark reminders of how quickly a species can collapse when its food chain fails.The losses formed a major part of the evidence that led to African penguins being classified as critically endangered in 2024, with fewer than 10,000 breeding pairs remaining worldwide.
Fisheries mismanagement under scrutiny
Marine conservation experts say the crisis also reflects long term failures in managing sardine fisheries. The study found that commercial fishing continued even when sardine numbers fell below safe biological thresholds. Removing prey fish at such low levels meant penguins had little chance of recovering their strength after the moult or feeding chicks successfully.Some scientists argue that the penguin die off was not an isolated event but part of a wider pattern affecting several sardine dependent species in South African waters.In recent years, South Africa has introduced fishing bans around the six largest penguin breeding colonies to reduce competition for sardines. Other interventions include providing artificial nests, controlling predators and rehabilitating undernourished chicks.There are early signs of stabilisation in a few colonies, although researchers warn that recovery remains uncertain. Sardine stocks must rebuild to sustainable levels before penguins can begin to recover their population strength.
A species on the edge
The study concludes that future success depends on strict limits to sardine fishing whenever stocks fall below 25 percent of their maximum abundance. Allowing sardine numbers to rebuild would give penguins a chance to survive the moult and raise chicks more successfully.For now, the mass die off on Dassen and Robben Islands remains one of the most severe wildlife losses in modern South African history. It also stands as a warning that without urgent action, one of Africa’s most iconic seabirds could disappear within a generation.
