Mass Starvation Decimates South Africa’s Penguins As Food Supplies Collapse

Because a key food source dropped to less than a quarter of its peak levels in 17 of the past 20 years, the findings could be crucial for securing the penguins’ long-term survival.

Penguins living along the coast of South Africa appear to have died in large numbers during their molting season, a period when they cannot enter the water to feed. The study’s authors report that shrinking food supplies likely left many birds unable to build the energy reserves they need to survive this vulnerable stage.

On two key breeding sites for the African penguin (Spheniscus demersus) — Dassen Island and Robben Island — researchers estimate that roughly 95% of the penguins that bred in 2004 died within the following eight years because food was too scarce to sustain them.

These findings come from a new investigation by scientists from the South African Department of Forestry, Fisheries and the Environment and the University of Exeter in the UK. Their work was published on December 4 in the peer-reviewed journal Ostrich: Journal of African Ornithology.

“Between 2004 and 2011, the sardine stock off west South Africa was consistently below 25% of its peak abundance and this appears to have caused severe food shortage for African penguins, leading to an estimated loss of about 62,000 breeding individuals,” says co-author and conservation biologist Dr. Richard Sherley, from the Centre for Ecology and Conservation – a world-leading research and education hub, based at the University of Exeter.

According to the researchers, these results highlight the need for improved management practices that could help protect the species and support its long-term survival.

“In 2024, African penguins were classified as Critically Endangered, and restoring sardine biomass in key foraging areas would seem to be essential for their long-term survival.”

A Period of Extreme Vulnerability

African penguins go through a yearly molting cycle in which they lose their old feathers and grow new ones. This renewal is essential for maintaining proper insulation and staying water-proof while swimming.

During this time, the birds cannot enter the ocean because their missing feathers leave them exposed to cold water. As a result, they must stay on land and are unable to hunt for roughly 21 days, the typical length of the molting period.

To make it through this stretch without eating, the penguins must build up substantial fat reserves beforehand.

“They are evolved to build up fat and then to fast whilst their body metabolizes those reserves, and the protein in their muscles, to get them through molt,” explains Dr. Sherley, whose research focuses on using long-term data on animal populations to examine human impacts on, and interactions with, the oceans.

“They then need to be able to regain body condition rapidly afterward. So, essentially, if food is too hard to find before they molt or immediately afterward, they will have insufficient reserves to survive the fast.”

This is exactly the peril the penguins have faced in the last couple of decades.

Environmental Shifts and Fishing Pressure

Since 2004, all but three years have seen the biomass of the sardine Sardinops sagax, a key food for African penguins, fall to less than 25% of its maximum abundance off western South Africa.

“Changes in the temperature and salinity of the spawning areas off the west and south coasts of South Africa made spawning in the historically important west coast spawning areas less successful and spawning off the south coast more successful,” says Dr. Sherley.

“However, due to the historical structures of the industry, most fishing remained to the west of Cape Agulhas, which led to high exploitation rates in that region in the early to mid 2000s.”

In their study, Dr. Sherley and colleagues analyzed counts of the number of breeding pairs and molting adult-plumaged penguins on Dassen and Robben islands from 1995 to 2015.

“These two sites are two of the most important breeding colonies historically—holding ~25 thousand (Dassen) and ~9 thousand (Robben) breeding pairs in the early 2000s. As such, they are also the locations of long-term monitoring programs,” adds study co-author Dr. Azwianewi Makhado from the Department of Forestry, Fisheries and the Environment.

The authors factored in estimates of adult penguin survival rates based on capture-mark-recapture analysis for 2004–2011.

Survival rates and the proportion of breeders that failed to return to their colonies to molt were compared with an index of prey availability developed for the region.

“Adult survival, principally through the crucial annual molt, was strongly related to prey availability,” Dr. Sherley says. “High sardine exploitation rates—that briefly reached 80% in 2006—in a period when sardine was declining because of environmental changes likely worsened penguin mortality.”

Losses are not just confined to Dassen and Robben, the team notes. “These declines are mirrored elsewhere,” Sherley said, adding that the species has undergone a global population decline of nearly 80% in the last 30 years.”

Tracking Prey Availability Through Cape Gannets

The prey index—developed by the team in a previous study published in the ICES Journal of Marine Science—is based on the proportions of anchovies and sardines, both of which are eaten by African penguins, in the diet of another bird, Cape gannets (Morus capensis).

“Cape gannet diet is thought to be a good ‘sampler’ of the availability of sardine and anchovy because they are the most wide-ranging of the seabirds in Southern Africa that feed on these species,” explains Dr. Makhado.

Picking up the penguin population going forward, the team note, is a “difficult” proposition—as the required improvement in sardine spawning is fundamentally dependent on environmental conditions.
However, there are measures we could take, Dr. Sherley says.

“Fisheries management approaches that reduce the exploitation of sardine when its biomass is less than 25% of its maximum and allow more adults to survive to spawn, as well as those that reduce the mortality of recruits [juvenile sardines], could also help, although this is debated by some parties,” he explains.

Meanwhile, several conservation actions have been put into place to protect the penguins directly; these include the provision of artificial nests, predator management, as well as the rescue, rehabilitation, and hand-rearing of adults and chicks.

In addition, commercial purse-seine fishing has recently been prohibited within the vicinity of the six largest breeding colonies in South Africa. This, Dr. Makhado says, “is hoped [to] increase access to prey for penguins at critical parts of their life cycle, such as during chick rearing and pre- and post-molt.”

With this study complete, the researchers are continuing to monitor the breeding success, chick condition, foraging behavior, population trajectory, and survival of African penguins.

Dr. Sherley concludes: “We hope that the recent conservation interventions put in place, together with reduced exploitation rates of sardine when its abundance is less than 25% of the maximum threshold, will begin to arrest the decline and that the species will show some signs of recovery.”

Reference: “High adult mortality of African Penguins Spheniscus demersus in South Africa after 2004 was likely caused by starvation” by Robert JM Crawford, Richard B Sherley, Lynne J Shannon, Alistair M McInnes, Tegan Carpenter-Kling and Azwianewi B Makhado, 4 December 2025, Ostrich.
DOI: 10.2989/00306525.2025.2568382

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