A dramatic decline in one of the main food sources for South Africa’s penguins has created famine conditions that could push the species toward extinction. Large numbers of birds living along the country’s coastline appear to have died during their annual molt, a vulnerable period when they cannot enter the ocean to feed because their feathers are not yet waterproof.
A study published in Ostrich: Journal of African Ornithology by scientists from South Africa’s Department of Forestry, Fisheries and the Environment and the University of Exeter suggests that dwindling food supplies left many young penguins without the fat reserves required to endure this critical phase.
Severe decline in survival rates
In two key breeding sites for the African penguin (Spheniscus demersus) — Dassen Island and Robben Island — researchers estimate that about 95 percent of the birds that bred in 2004 died within the following eight years due to a severe shortage of food.
According to the study, sardine stocks off South Africa’s west coast remained below 25 percent of their historical maximum between 2004 and 2011. “This appears to have created a major food shortage for African penguins, leading to the loss of roughly 62,000 breeding adults,” says Dr. Richard Sherley, co-author and conservation biologist at the Centre for Ecology and Conservation.
These findings underscore the urgent need for improved management practices that protect and support long-term survival of African penguins, who were classified as critically endangered in 2024, thus necessitating restoration of key feeding areas by replenishing sardine biomass with healthy populations as the next step for their future, according to researchers.
Molting: a period of extreme vulnerability
African penguins undergo an annual molt during which they shed old feathers and grow new ones — a process crucial for insulation and waterproofing. Throughout this three-week period, the birds must remain on land, unable to hunt and entirely dependent on fat reserves accumulated beforehand.
“They have evolved to store large amounts of fat, then fast while their bodies metabolize these reserves and even muscle proteins to survive the molt,” Dr. Sherley explains. “If food is scarce before or immediately after molting, they simply do not have the reserves needed to survive. This is precisely the danger they have faced in recent decades.”
Climate pressures and overfishing
Since 2004, sardine biomass has fallen below 25 percent of its maximum in nearly every year, driven by changes in water temperature and salinity that have made spawning more successful along the southern coast than the west. Despite this shift, most fishing activity remained west of Cape Agulhas, resulting in high levels of overfishing in the early 2000s.
The research team analyzed breeding-pair counts and molting penguin numbers on Dassen and Robben islands from 1995 to 2015. They also incorporated adult survival estimates from a capture–mark–recapture analysis covering 2004–2011. These survival rates were then compared with an index of prey availability.
“Adult survival, particularly during the molting period, was strongly linked to prey availability,” Sherley says. High exploitation rates — which peaked at 80 percent in 2006 — likely worsened mortality at a time when sardine stocks were already declining due to environmental factors.
This pattern is not confined to the two islands studied. “Similar declines are occurring elsewhere,” Sherley adds, noting that African penguin populations worldwide have fallen by nearly 80 percent over the past 30 years.
Food availability and conservation efforts
The prey-availability index is based on the proportion of anchovy and sardine in the diet of Cape gannets, a seabird with the widest foraging range in South Africa and therefore a reliable indicator of fish abundance.
Penguin recovery will be challenging, as it depends on improved sardine reproduction — something heavily influenced by environmental conditions. Still, targeted measures may help. “Management strategies that reduce sardine fishing when biomass drops below 25 percent and allow more adults to survive to breeding age could make a real difference,” Sherley says.
Additional conservation actions are already in place, including artificial nests, predator control, and rescue and rehabilitation programs for adults and chicks. Purse-seine fishing has also been banned near the six largest breeding colonies to ensure penguins have better access to prey during key periods.
Researchers continue to monitor breeding success, chick health, foraging behavior, population trends and survival rates.
“We hope that recent conservation interventions, along with reduced pressure on sardine stocks when abundance falls below 25 percent, will begin to slow the species’ decline and eventually support its recovery,” Sherley concludes.
