African penguins living off the coast of South Africa have suffered a catastrophic population collapse over the past two decades, largely because they have been unable to find enough food to survive their annual molting season.
A new study estimates that on two of the species’ most important breeding islands—Dassen Island and Robben Island—about 95% of the penguins that bred in 2004 died within just eight years.
The research, conducted by scientists from South Africa’s Department of Forestry, Fisheries and the Environment and the University of Exeter, was published in Ostrich: Journal of African Ornithology.
The crisis is tied to disappearing sardines, the penguins’ main food source.
Between 2004 and 2011, sardine numbers off western South Africa fell to less than a quarter of their former levels.
According to co-author Dr. Richard Sherley, this shortage likely resulted in the loss of about 62,000 breeding adult penguins. The decline is so severe that African penguins were officially listed as Critically Endangered in 2024.
Molting is a dangerous time for penguins because they must stay on land for around 21 days while they replace all their feathers.
Their old feathers are no longer waterproof, and until the molt is complete, they cannot enter the ocean to hunt. To survive this fasting period, penguins must build up substantial fat reserves beforehand and recover quickly afterward.
If they cannot find enough fish before or after molting, they simply do not survive the process.
Environmental shifts have also played a major role. Changes in water temperature and salinity made sardine spawning less successful along the west coast, pushing more spawning events toward the south coast.
Despite this shift, most fishing activity remained in the west, driving exploitation rates of sardines up to 80% in some years and worsening the crisis for penguins.
To understand the impact of food shortages, researchers analyzed 20 years of data from Dassen and Robben islands, including counts of breeding penguins and molting adults.
They also used survival estimates based on tagged birds and compared them with a prey availability index developed from the diet of Cape gannets, another seabird that eats anchovies and sardines. The data showed a clear link: when sardine numbers fell, adult penguin survival—especially during the molt—dropped sharply.
The collapse seen on these islands is part of a wider trend. Across southern Africa, African penguins have declined by nearly 80% in the last 30 years. While rebuilding sardine populations depends heavily on unpredictable environmental conditions, researchers say better fisheries management could help.
Reducing sardine catches when their numbers fall below 25% of maximum levels may allow more fish to survive and reproduce. Some conservation groups argue this is essential for penguin recovery, though the approach remains debated.
Several direct conservation efforts are already underway, including providing artificial nests, rescuing starving or injured birds, improving predator control, and closing large fishing areas near major penguin breeding colonies.
South Africa has recently banned purse-seine fishing around its six largest penguin colonies, giving the birds better access to food during their most vulnerable life stages.
Researchers continue to monitor penguin health, breeding, foraging behavior, and survival trends. Dr. Sherley says the hope is that combined conservation efforts—and more cautious sardine fishing—will finally slow the decline and, over time, allow the species to recover.
