Cause identified Why the African penguins are dying en masse

The number of African penguins is falling dramatically. The population of the endangered species on two islands off the coast of South Africa is estimated to have fallen by around 95 percent between 2004 and 2011.

Keystone-SDA

07.12.2025, 20:51

SDA

A study by British and South African scientists now provides an explanation for this decline: the scarcity of the main prey, sardines and anchovies, plays an important role, especially during the annual moult. During this phase, the penguins have to fast for around three weeks and need a lot of fish before and after, as the group led by Richard Sherley from the University of Exeter writes in the journal "Ostrich: Journal of African Ornithology".

The spectacled penguin (Spheniscus demersus) is the only penguin species that breeds on the southern coasts of the African continent, often on offshore islands. The International Union for Conservation of Nature (IUCN) has listed it as "Critically Endangered" on its Red List since 2024.

"Current, almost complete count data on the number of breeding pairs show an alarming acceleration of the decline," it writes on its website. "The predicted population decline amounts to more than 80 percent over three generations, both now and in the future." Possible reasons for the decline are "the effects of competition with commercial fishing and climate-related shifts in prey populations".

62,000 penguins starved to death

Sherley and colleagues focused on two important breeding colonies of African penguins on Dassen Island and Robben Island. An estimated 62,000 penguins died there from lack of food between 2004 and 2011. This corresponds to around 95 percent of the 65,000 animals that bred on the islands in 2004.

The researchers found a close correlation with the availability of sardines (Sardinops sagax) and anchovies (Engraulis capensis). They used the food composition of Cape gannets (Morus capensis) as an indicator. The diet of this seabird has been measured over many years. Cape gannets also like to feed on sardines and anchovies, so the composition of the fish they eat indicates their availability.

"Between 2004 and 2011, the sardine population off the west coast of South Africa was consistently below 25 percent of its peak, which apparently led to a severe food shortage for the spectacled penguins," Sherley is quoted as saying in a statement in the journal.

According to the authors of the study, the penguin moult is a very critical time: it lasts around 21 days. During this phase, the animals are on land and do not hunt, so they have to fast. In order to survive this period, they have to eat a fat pad in the weeks leading up to it. "If food is hard to find before or immediately after the moult, their reserves are not sufficient to survive the phase," Sherley emphasizes.

Large food requirements after the moult

The annual moult is necessary because the insulating and water-repellent effect of the feathers diminishes over time. An earlier study showed that penguins travel at a hunting speed of around 14 kilometers per hour before moulting, whereas they reach around 19 kilometers per hour with a fresh coat of feathers.

During moulting, African penguins lose around 47 percent of their body weight, which also affects their muscle mass. In order for them to regain their strength after the moult, a large supply of food is required, otherwise they are at risk of starvation even after the moult is over.

In order to protect the animals, the South African government had set up no-fishing zones around six colonies of African penguins, which are home to 76 percent of the species' global population. According to critics, however, these zones were too small, which is why they were extended this year.