Nairobi (EFE).- Thousands of penguins living off the coast of South Africa likely starved to death en masse during their moulting season due to the collapse of their food supplies, according to a study released Friday.
The research, conducted by scientists from the South African Department of Forestry, Fisheries and the Environment and the University of Exeter in the United Kingdom, revealed that on Dassen and Robben islands – two of the main African penguin breeding colonies – around 95 percent of those that bred in 2004 died within the following eight years due to food shortages.
According to study co-author Dr. Azwianewi Makhado of the department, breeding colonies on Dassen Island hosted up to 25,000 breeding pairs, and on Robben Island, around 9,000 in the early 2000s.
“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,” said study co-author Richard Sherley, from the Centre for Ecology and Conservation at the University of Exeter.
The African penguin (Spheniscus demersus), listed as “critically endangered” in 2024, moults its plumage once a year to maintain waterproofing and thermal insulation. For three weeks, they must remain on land, unable to hunt, and rely on accumulated fat reserves.
“If food is too hard to find before they moult or immediately afterwards, they will have insufficient reserves to survive the fast,” Sherley said.
In every year except three since 2004, the biomass of the sardine has fallen to less than 25 percent of its maximum abundance off western South Africa.
Changes in the temperature and salinity of spawning grounds shifted the reproduction of the sardine (Sardinops sagax) from the west to the south coast, while the fishing industry concentrated west of Cape Agulhas, where exploitation reached peaks of 80 percent in 2006—factors that further exacerbated the scarcity.
According to Sherley, adult survival was “strongly related” to prey availability, and overexploitation in years of low biomass “likely worsened penguin mortality.”
This decline is not isolated, as the global population of African penguins has fallen by almost 80 percent in three decades across its entire range.
Uncertain recovery
Recovery will depend largely on favorable environmental conditions for sardine spawning, something that is difficult to control. However, researchers suggest adjusting fisheries management by reducing catches when biomass falls below the 25 percent threshold.
In parallel, direct conservation measures have been implemented, such as the installation of artificial nests, predator management, rescue and hand-rearing of chicks, and a fishing ban around the six breeding colonies, with the hope of improving access to food during critical phases such as breeding and pre- and post-moulting.
The study was based on records from 1995 to 2015 on breeding penguin pairs. Scientists cross-referenced these figures with survival estimates obtained through capture-recapture analyses, comparing the results with a prey availability index constructed from the diet of the Cape gannet (Morus capensis), another indicator species.”
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,” Makhado stated.
With the study completed, researchers continue to monitor reproductive success, chick status, feeding behavior, population trajectory, and survival of African penguins.
“We hope that the recent conservation interventions put in place, together with reduced exploitation rates of sardine when its abundance is less than the 25 percent of maximum threshold, will begin to arrest the decline and that the species will show some signs of recovery,” Sherley concluded. EFE
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