What Do Penguins Eat? Their Diet & Food Sources

Penguins eat almost exclusively marine animals, with the three main food groups being krill, fish, and squid. The exact mix depends heavily on the species and where it lives: an Adélie penguin in Antarctica might eat little besides krill for months on end, while a little penguin off the Australian coast fills up on sardines and cod. That variation makes “penguin diet” a surprisingly rich topic, because the 18 living species have carved out feeding strategies suited to everything from tropical equatorial waters to the edge of the Antarctic ice sheet.

How Diet Varies by Species and Region

The broadest dietary split among penguins runs along a temperature gradient. Species that breed in and around Antarctica tend to eat enormous quantities of Antarctic krill. Adélie, chinstrap, and gentoo penguins all fall into this camp. Krill can make up the vast majority of their diet during the breeding season, supplemented by smaller amounts of fish and squid depending on local availability. Stable isotope studies in the Ross Sea show that even within this group, diets shift spatially and seasonally: Adélie and emperor penguins at different colonies show measurable differences in what they eat and where they forage, depending on sea-ice conditions and the time of year.¹

Emperor and king penguins, the two largest species, lean more heavily on fish and squid. King penguins, for instance, target small lanternfish (myctophids) that live in deeper water. Tracking data from king penguins show they make deep daytime dives exceeding 100 meters to reach these prey, with a recorded maximum depth of 304 meters, while at night they make much shallower dives, likely following the daily vertical migration of their prey toward the surface.² Those deep dives give them access to food that smaller, shallower-diving species cannot reach.

At the other end of the size spectrum, little penguins (the smallest species, found around southern Australia and New Zealand) eat mostly small coastal fish. A multi-year study of a little penguin colony tracked clear diet shifts between breeding seasons: in one year the birds ate primarily sardines, and the following year they switched to red cod, consuming roughly 150 grams of a dominant fish species per day. As each breeding season progressed, the colony’s diet broadened to include a wider variety of fish rather than depending on a single species. Over two breeding seasons, the colony extracted an estimated 1,300 tonnes of biomass from their coastal ecosystem.³

Tropical and temperate penguin species, like the Galápagos penguin and the Humboldt penguin along the South American coast, depend heavily on schooling fish such as anchovies and sardines. These species are particularly sensitive to changes in ocean temperature because warm-water events scatter the dense fish schools they rely on.

How Penguins Catch and Eat Their Food

Penguins are pursuit divers. They chase prey underwater using their flippers for propulsion, and different species have evolved dive profiles that match their preferred prey. Shallow-diving species like Adélie penguins mostly stay within the upper water column, scooping up krill swarms relatively close to the surface. King penguins, as noted above, regularly exceed 100 meters and can reach over 300 meters, with individual dives lasting up to about eight minutes.² Emperor penguins dive even deeper still, holding the record among all penguin species.

Catching slippery fish underwater requires some anatomical help. Penguin tongues are covered in large, backward-pointing, spine-like papillae that grip prey as it enters the mouth and prevent it from escaping.⁴ If you have ever seen a close-up photograph of a penguin’s open mouth and been startled by the rows of fleshy spines, those are these papillae. They are not teeth, but they serve a similar gripping function. Penguins swallow their prey whole, so the papillae are essential for hanging on to a wriggling fish during the trip from capture to stomach.

Their eyes are another crucial adaptation. Penguins need to see well both above and below water, which is an optical challenge because the way light bends changes drastically between air and water. Studies of penguin eyes show they achieve this with a relatively flat cornea whose optical power varies widely across species, and there is good evidence that many penguins achieve sharp focus in both environments.⁵ This amphibious vision lets them spot and track fast-moving prey in murky or dimly lit water at depth, then navigate on land or ice without difficulty.

Dealing with All That Salt

A question most people never think to ask about penguin diets is how the birds handle the massive salt load that comes with eating marine animals and inevitably swallowing seawater. The answer involves a specialized organ called the supraorbital salt gland, located above the eyes. This gland filters excess sodium and chloride from the blood and excretes a highly concentrated salt solution that drips out through the nostrils. You can sometimes see penguins shaking their heads to flick away the salty drips.

Research on African penguins (also known as jackass penguins) showed that after being given a seawater dose equal to about 10 percent of body weight, the birds excreted roughly 85 percent of the fluid volume within nine hours but only about 62 percent of the salt load in that time. The salt gland handled about 31 percent of total fluid excretion but accounted for about 42 percent of the total salt removal, meaning it punches well above its weight in clearing the most concentrated solutes. The cloaca and digestive tract handled the larger share of total fluid but at a lower salt concentration.⁶ This research also highlighted that the digestive tract plays a bigger role in water and salt balance than biologists had previously appreciated.

Adélie penguin chicks have fully functional salt glands from the moment they hatch, which makes sense given that their very first meals are regurgitated marine prey delivered by their parents. Their kidneys also produce urine that is more concentrated than that of most other bird species, giving them a second line of defense against salt overload.⁷

Feeding Chicks and the Cost of Regurgitation

Penguin chicks cannot hunt for themselves. They depend entirely on their parents, who go to sea, fill their stomachs with prey, and then return to the colony to regurgitate the partially digested food directly into the chick’s mouth. In Adélie penguins, this process continues for about 50 to 60 days until the chick fledges and heads to sea on its own.⁸

Regurgitating meals repeatedly takes a measurable physiological toll on the parents. Every time an adult penguin vomits up food for its chick, it loses gastric acid along with the meal. Over weeks of frequent feedings, this acid loss shifts the parent’s blood chemistry toward a condition called metabolic alkalosis, where the blood becomes less acidic than normal. Researchers tracking Adélie penguin blood chemistry throughout the breeding season found that blood pH shifted from around 7.54 in the early guard stage to 7.47 later on, and this tracked with rising chloride loss and bicarbonate accumulation. The effect reversed later in the season when parents spent more time at sea and had fewer opportunities to feed chicks.⁸ In other words, feeding your chick literally changes your blood chemistry.

The energetic demands of breeding also involve extended fasting. Male emperor penguins hold the record: they can fast for up to four months while incubating the egg through the Antarctic winter, surviving on fat reserves accumulated before the fast begins. Penguins also fast during their annual molt, when they cannot enter the water because their feathers are not waterproof. To prepare for molt fasts, they build up both fat and protein stores beforehand.⁹ The ability to toggle between marathon feeding trips and prolonged starvation is one of the defining features of penguin biology.

How Much Penguins Eat in Aggregate

Individual penguins eat modest amounts per day, but penguin colonies can be enormous, and their collective appetite is staggering. Macaroni penguins at South Georgia, one of the largest breeding colonies in the sub-Antarctic, consume an estimated 8 million tonnes of krill annually.¹⁰ That is a serious draw on the local krill population and illustrates why penguins are considered key players in Southern Ocean food webs. Even a relatively small colony of little penguins can extract over a thousand tonnes of fish from its coastal ecosystem in two breeding seasons.³ These numbers matter for fisheries management and for understanding how changes in prey abundance ripple through marine ecosystems.

Threats to Penguin Food Supplies

Because penguins depend on a relatively narrow range of prey, anything that disrupts the abundance or distribution of krill, small fish, or squid can hit penguin populations hard. Three major threats stand out.

The first is climate change, particularly in the Antarctic Peninsula region, where warming has reduced sea-ice extent and, with it, krill density. Antarctic krill depend on sea ice for key parts of their life cycle, so less ice means fewer krill. Research on chinstrap and gentoo penguin populations found that warm winters with low sea ice, when combined with high fishing catch, elevated the probability of population declines the following year.¹¹ The interaction between climate and fishing is the critical point: either stressor alone might be manageable, but together they amplify each other.

The second threat is the krill fishery itself. The Southern Ocean krill fishery harvests krill primarily for aquaculture feed and omega-3 supplements. Models predict that increased fishing pressure offshore reduces penguin food intake, leading to lower survival and reproduction. The behavioral dynamics of krill make this worse than simple biomass removal would suggest, because krill swarm behavior means localized depletion can have outsized effects on nearby predators.¹² That said, the picture is not uniformly grim. A study of macaroni penguins in the Scotia Sea found that spatial overlap between the birds and the fishery was negligible because the penguins ranged widely across the open ocean while the fishery operated in a few small areas on shelf edges. Under current management, competition between macaroni penguins and the krill fishery appeared to be low.¹³ The degree of competition depends on which species, which fishery zone, and which season you are looking at.

The third major threat, especially for tropical species, is El Niño. When El Niño warms the surface waters of the eastern Pacific, the cold, nutrient-rich upwelling that supports anchovy and sardine populations weakens or disappears. Humboldt penguins in Peru suffered massive mortality during the severe 1982-1983 El Niño, especially among juveniles, along with widespread nest abandonment and reproductive failure.¹⁴ Galápagos penguins experienced a similar population crash during the same event and have been recovering very slowly since, in part because El Niño events have become more frequent in recent decades. Under the most severe warm-water conditions, penguins simply starve.¹⁵ For a species with a small, geographically restricted population like the Galápagos penguin, long-term warming trends are an existential concern.

Microplastics in the Penguin Food Chain

Even in Antarctica, penguins are ingesting microplastics. A study of dead gentoo penguin chicks on King George Island examined the stomachs and upper intestines of 14 individuals and found a total of 378 microplastic particles, averaging about 27 pieces per bird.¹⁶ Since chicks eat only what their parents regurgitate, these plastics must have been present in the prey the adults caught at sea or in the seawater they swallowed while foraging.

A broader survey of penguin scat across Antarctica detected microplastics in about 15 percent of Adélie penguin samples, 28 percent of chinstrap samples, and 29 percent of gentoo samples. Polyethylene, the most common plastic used in packaging, accounted for about 80 percent of the identified microplastic particles. More than half of the scat samples also contained cellulose fibers attributed to human activity.¹⁷ The long-term health effects of microplastic ingestion in penguins are not yet well understood, but the finding that these particles have reached the digestive tracts of chicks in remote Antarctic colonies underscores how far plastic pollution has spread through marine food webs.

How Scientists Figure Out What Penguins Eat

Studying penguin diets is harder than it sounds. You cannot follow a penguin underwater and watch it eat. Historically, researchers relied on stomach lavage (flushing the stomach and identifying what comes up) or dissecting dead birds. These methods work but are invasive and give only a snapshot of the most recent meal.

Modern approaches are more creative. DNA metabarcoding of penguin feces can identify prey species from genetic traces left in the droppings, even when the prey items are too digested to recognize visually. This technique was used across seven sites in the Ross Sea region to build a broader picture of Adélie penguin diets without disturbing the birds.¹⁸

Stable isotope analysis is another powerful tool. Different food sources leave distinct chemical signatures in an animal’s tissues. Carbon isotope ratios can indicate whether a penguin was feeding in offshore or nearshore waters, while nitrogen isotope ratios reveal the animal’s position in the food chain. By analyzing different tissues that grow at different times of year, such as feathers, eggshell membranes, and fresh guano, researchers can reconstruct diet across multiple seasons from a single sampling visit.¹⁹ This approach has even revealed how penguin diets have changed over thousands of years: isotope measurements from ancient bones and eggshells show that during the last ice age, Adélie penguins relied more on fish, then shifted toward krill as sea-ice conditions changed during the warmer Holocene period.

Satellite tracking rounds out the picture. By attaching small GPS or time-depth recorders to penguins, researchers can map foraging trips, identify how deep and how far the birds go, and connect that information to the prey available in different ocean zones. Combining satellite data with isotope analysis and DNA from droppings gives a multi-layered view of penguin feeding ecology that no single method could provide alone.

Diet Flexibility and Why It Matters

One of the more underappreciated aspects of penguin diets is how flexible some species can be. The little penguin study mentioned earlier showed an entire colony pivoting from sardines one year to red cod the next, a shift driven by changes in local prey availability rather than any preference on the birds’ part.³ Within a single breeding season, these penguins also shifted from relying on one dominant prey type to a more diverse mix as that prey became scarcer. This kind of foraging plasticity is a buffer against environmental variability: a penguin that can switch prey species when its usual food becomes hard to find is more resilient than one locked into a single food source.

Not all penguins have this luxury, though. Species that breed in extreme environments with limited prey diversity, like the krill-dependent Adélies in the high Antarctic or the anchovy-dependent Humboldt and Galápagos penguins in upwelling zones, have far fewer alternatives when their primary food disappears. For those populations, a bad krill year or a strong El Niño event does not just mean harder work. It means starvation, breeding failure, and population decline. The long-term trajectory of penguin populations worldwide will depend in large part on whether their food sources can keep pace with a changing ocean.