African penguins feed almost entirely on small schooling fish, with sardines and anchovies forming the backbone of their diet across most of their range in southern Africa. These two species are energy-dense, abundant in the cold Benguela upwelling system, and perfectly sized for a bird that hunts by pursuit-diving. But the full picture of what these penguins eat is more varied and more precarious than those two names suggest, shaped by geography, season, the age of the bird, and the growing pressure of industrial fishing.
Sardines, Anchovies, and the Rest of the Menu
Sardines and anchovies are so central to the African penguin’s diet that fisheries management around penguin colonies specifically targets these two species. Studies of breeding colonies in South Africa have documented that commercial fishing for sardines and anchovies has been experimentally prohibited within a 20-kilometer radius of key colonies to reduce competition with the birds.1Journal of Applied Ecology. Local forage fish abundance influences foraging effort and offspring condition in an endangered marine predator That fact alone tells you how dominant these two fish are in the penguin’s world.
African penguins do not, however, rely on sardines and anchovies exclusively. Long-term dietary studies at Mercury Island off the Namibian coast found that when sardine and anchovy availability was low, penguins turned to a range of alternatives. Hake, horse mackerel, round herring, and squid all appeared in the diet with meaningful frequency. Squid showed up in nearly 40 percent of individual diet samples over more than a decade of monitoring, though it accounted for only about 3 percent of total prey mass.2African Journal of Marine Science. Surviving off junk: low-energy prey dominates the diet of African penguins Spheniscus demersus at Mercury Island, Namibia, between 1996 and 2009 Pelagic fish like anchovy, sardine, and round herring made up large portions of the diet in certain months but were not consistently present year-round, suggesting the penguins take what is locally available.
The title of that Mercury Island study is revealing: “Surviving off junk.” The researchers framed the shift away from energy-rich sardines and anchovies toward lower-quality prey as a survival strategy, not a preference. When the high-calorie staples disappear, penguins eat what they can find, but the nutritional tradeoff has real consequences for body condition and breeding success.
How Diet Varies by Colony
African penguins breed at roughly two dozen colonies scattered along the coastlines of South Africa and Namibia, from the subtropical waters near Algoa Bay on the east coast to the cold, nutrient-rich upwelling zone on the west. The fish available to a penguin at one colony can differ substantially from what is available a few hundred kilometers away, and researchers have used stable isotope analysis of penguin blood and feathers to track these geographic differences in diet.
Isotope studies comparing colonies on different islands have found that the chemical signatures in penguin blood vary significantly between sites. Penguins at St Croix Island, for instance, showed different carbon isotope values than penguins at other colonies, reflecting differences in the base of the food web and the mix of prey species available.3PLoS ONE. Reappraisal of the Trophic Ecology of One of the World’s Most Threatened Spheniscids, the African Penguin These differences are not just academic curiosities. They mean that conservation strategies cannot assume all colonies face the same food situation. A colony surrounded by good anchovy stocks may be stable while one that has lost access to its preferred prey spirals downward.
Tracking data from penguins at Bird Island and Dassen Island showed that birds from different colonies used quite different ocean areas after their annual moult, a period when they need to rebuild fat reserves quickly. Post-moult penguins from both colonies gravitated toward areas of coastal upwelling with cool surface temperatures and high plankton productivity, the conditions that support dense schools of small fish. But the specific patches they targeted were different. Penguins from Bird Island headed to the eastern edge of the Agulhas shelf, while those from Dassen Island traveled to an area north of St Helena Bay that was historically an important sardine spawning ground.4PubMed Central. Important marine areas for endangered African penguins before and after the crucial stage of moulting
How African Penguins Hunt
African penguins are pursuit divers. They swim underwater at speed, chasing down fish schools and catching individual prey items with their beaks. But the way they do this is more sophisticated than a simple underwater chase. Research using animal-borne cameras and dive loggers has revealed that the most profitable foraging strategy involves herding fish schools upward through the water column. Penguins position themselves below and around a school of fish, driving it toward the surface where the fish become disoriented and easier to pick off.5PubMed Central. Group foraging increases foraging efficiency in a piscivorous diver, the African penguin
This herding behavior is significantly more effective when penguins forage in groups. Solitary penguins can catch individual fish, but group foraging allows birds to rotate positions below and around a school, maintaining the upward pressure that keeps the fish bunched and moving toward shallow water. Catch rates improve measurably when penguins work together rather than hunting alone. Most catches during group foraging consisted of fish that had been “depolarized,” meaning the school’s coordinated structure had broken down and individual fish were darting in different directions, making them easier targets.
This cooperative hunting does not just benefit the penguins. When penguins herd fish schools from depth into shallow water, other seabird species take advantage of the situation. Researchers documented that in most observed cases of shared prey encounters, penguins had pushed schooling fish up from depths greater than 33 meters, and diving seabirds like gannets and cormorants only joined in once the prey was near the surface.6PubMed Central. Up for grabs: prey herding by penguins facilitates shallow foraging by volant seabirds African penguins, in effect, act as ecosystem engineers for the surface-feeding bird community. They do the hard work of corralling deep prey, and other species freeload off the result.
What Juveniles Eat Compared to Adults
Young African penguins do not eat the same diet as experienced adults, and the difference shows up clearly in their feather chemistry. Long-term isotope analysis has found that newly grown feathers from juvenile penguins are consistently depleted in both nitrogen-15 and carbon-13 compared to adult feathers.7Endangered Species Research. Long-term stable isotope analysis shows restricted foraging behaviour of the Critically Endangered African penguin In plain terms, juveniles are feeding at a slightly lower position in the food web and in somewhat different ocean areas than adults.
The likely explanation is straightforward: young penguins are less skilled hunters. They disperse more widely after fledging and forage over broader areas rather than targeting the productive hotspots that experienced adults know. This means they may catch smaller or lower-quality prey, feed in less productive waters, or simply be less efficient at catching the energy-rich fish that adults target. Over time, as juveniles gain experience, their diet converges with the adult pattern, but the transition period represents a vulnerability. If prey is already scarce, inexperienced birds are the first to struggle.
Competition with Commercial Fisheries
The single biggest dietary threat facing African penguins is not a lack of fish in the ocean overall but the competition for small pelagic fish with industrial purse-seine fisheries. South Africa’s sardine and anchovy fisheries harvest the same species, in the same waters, that penguins depend on. The overlap is direct and well documented, and it has been a central focus of conservation research for over a decade.8ICES Journal of Marine Science. Commercial fishery no-take zones for African penguins minimize fisheries losses at the expense of conservation gains
Three seabird species in the Benguela upwelling system share sardines and anchovies as key prey: the African penguin, the Cape gannet, and the Cape cormorant. Climate shifts and overfishing have changed the distribution and abundance of these fish over the past two decades, and the three bird species have responded differently. African penguin and Cape gannet populations tracked prey availability closely, declining when fish stocks fell, while Cape cormorants showed a weaker connection to the same prey fluctuations.9Marine Ecology Progress Series. Differential responses of three sympatric seabirds to spatio-temporal variability in shared resources For penguins, which cannot fly to distant foraging grounds the way gannets can, local prey depletion near breeding colonies is especially damaging.
The link between prey availability and colony health is not subtle. Declines in African penguin populations have coincided with altered abundance and availability of their main prey, and the pattern varies across colonies, with some sites hit much harder than others depending on local fish stocks.10PubMed Central. The conservation status and population decline of the African penguin deconstructed in space and time
What No-Take Zones Have Shown
South Africa has experimented with small-scale fishing closures around penguin colonies to test whether reducing competition with trawlers improves penguin breeding outcomes. The results have been encouraging, though not as clean-cut as conservationists might hope.
The most dramatic early finding came from establishing a 20-kilometer no-take zone around a major colony. Within three months of the fishing ban, breeding penguins at that colony reduced their foraging effort by about 30 percent, meaning they were spending less time and energy finding food. Most birds shifted their feeding into the newly protected zone. Meanwhile, penguins at a colony 50 kilometers away, where fishing continued as usual, increased their foraging effort during the same period.11PubMed Central. Marine no-take zone rapidly benefits endangered penguin The contrast was stark: removing fishing pressure near a colony translated almost immediately into easier foraging for the birds.
Longer-term experimental closures at Robben and Dassen islands produced meaningful improvements in chick survival, though the effects on adult foraging behavior were harder to pin down. Measurements of foraging trip duration and maximum distance traveled were highly variable between individual penguins, making it difficult to draw clean statistical conclusions about whether adults were foraging more efficiently during closures.12ICES Journal of Marine Science. South Africa’s experimental fisheries closures and recovery of the endangered African penguin Day-to-day changes in prey availability added noise to the data. The strongest signal came from chick condition and survival rather than from adult behavior, suggesting that the benefit of reduced fishing competition shows up most clearly in reproductive success rather than in how far adults swim on a given day.
The political tension around no-take zones is real. Fishing closures that benefit penguins come at a cost to the fishing industry, and recent analyses have grappled with how to design zones that minimize fisheries losses while still delivering conservation gains. The science suggests that relatively small exclusion zones around breeding colonies can make a meaningful difference, but scaling these up across the penguin’s entire range involves economic tradeoffs that remain contentious.
How Shifting Prey Drives Penguin Decline
Beyond direct fishing pressure, the geographic distribution of sardines and anchovies has shifted in recent decades, likely driven by changes in ocean temperature and current patterns. The area north of St Helena Bay, once a major sardine spawning ground, no longer reliably holds the fish it used to.4PubMed Central. Important marine areas for endangered African penguins before and after the crucial stage of moulting For penguins that historically depended on those stocks, this means longer foraging trips, more energy spent searching, and less food brought back to chicks.
Upwelling intensity matters enormously. African penguins time their breeding and moulting around periods of peak upwelling, when cold, nutrient-rich water drives plankton blooms that in turn support dense fish schools. Wind-driven upwelling increases during summer along parts of the South African coast, boosting productivity in the areas where post-moult penguins forage. If upwelling patterns shift or weaken, the entire food chain that sustains the penguins is disrupted from the bottom up.
The species’ overall population trajectory reflects this food insecurity. African penguin numbers have dropped steeply in the twenty-first century, and the declines have not been uniform. Some colonies have crashed while others have held relatively steady, and the pattern tracks local prey conditions more closely than any other single variable. Colonies near good fish stocks survive; colonies that lose their food base collapse. The dynamic, spatially variable nature of the decline makes it a harder problem to solve than if the entire population were declining for one simple reason.
What Penguins Eat in Rehabilitation
African penguins regularly end up in rehabilitation facilities after oil spills, injuries, or abandonment as chicks. Feeding these birds in captivity requires mimicking their natural diet as closely as possible while accounting for the fact that a sick or underweight penguin cannot process whole fish immediately.
Hand-rearing protocols for African penguin chicks start with oral fluids and progress through a carefully staged diet. Very young chicks receive a blended fish formula that includes vitamin and mineral supplements along with probiotics, fed several times daily at roughly 10 percent of body mass per meal. As chicks grow, they graduate to fish fillets, then fish tails, and eventually whole fish.13PLoS ONE. From incubation to release: Hand-rearing as a tool for the conservation of the endangered African penguin The progression mirrors what would happen in a wild nest, where parents regurgitate increasingly large and intact prey as chicks develop the ability to handle it.
Captive feeding also serves research purposes. Controlled diet-switch experiments, where captive penguins are moved from one prey type to another, have been used to calibrate the isotope tools that researchers use in the field. In one such study, penguins previously fed sardines were switched to a diet of small hake for 49 days to measure how quickly the chemical signature in their blood and claws changed to reflect the new food.14Journal of Experimental Marine Biology and Ecology. Stable isotope turnover in blood and claws: A case study in captive African Penguins These calibration experiments allow scientists to interpret isotope data from wild penguins more accurately, connecting feather chemistry to actual prey species with greater confidence.
Monitoring Prey Capture Underwater
Understanding what penguins eat has traditionally relied on analyzing stomach contents or droppings, methods that are invasive or biased toward prey with hard parts like otoliths and squid beaks. Newer approaches are changing the picture. Animal-borne video cameras have given researchers direct footage of penguins hunting underwater, and machine learning systems can now automatically detect both penguins and fish in these recordings. One deep learning system achieved high accuracy in spotting fish in penguin-mounted video footage and could even identify predation events, moments when a penguin actually caught and consumed prey.15arXiv. Diving with Penguins: Detecting Penguins and their Prey in Animal-borne Underwater Videos via Deep Learning
These tools matter because they can reveal prey species and capture rates in real time rather than after the fact. Traditional stomach sampling tells you what a penguin ate but not how hard it worked to get it or how many attempts failed. Video-based monitoring captures the full foraging sequence: searching, encountering prey, herding, striking, and either succeeding or missing. As these systems improve, they could provide a much richer understanding of how prey availability translates into actual feeding success, filling in the gap between knowing what fish are in the water and knowing how effectively penguins are able to catch them.