Standing amidst the variety of life on display in the Skretting Diversity Gallery, it's easy to forget that all these organisms are part of a food web - even the weird ones. We might not think that penguins fall into that "weird" category, but these little hunters are not squeamish when it comes to food. Let's see what's on their menu.
The right fish
Most species of penguin are piscivores, meaning their diets consist of fish. For some like the African penguin, an abundance of small, nutrient-rich fish like anchovies or pilchards is vital to help them go through a fasting period - when they starve for weeks while growing new feathers, and for feeding healthy meals to their young.
The wrong fish
When easily-hunted, nutrient-rich fish are in poor supply, as is the case caused by overfishing and climate change around South Africa, penguins need to resort to alternative fish species. Examples are Atlantic horse mackerel (Trachurus trachurus) and the pelagic goby (Sufflogobius bibarbatus), which are often accessible but do not contain all the nutrients the penguins need. Eating these fish means the penguins need to spend more time hunting and consume even more than before.
In Antarctic and sub-Antarctic waters, where small migratory fish are less common, penguins have adapted to eating crustaceans like krill, which is the main food source for small penguins like the Adélie and chinstrap penguins. African penguins are generalists and can also eat shrimp if needed, but this is not a sustainable diet for them, and they are not adapted to hunting this type of prey like northern rockhoppers are (the species of rockhopper here at the Aquarium).
Although jellies are very poor in calories, at least four species (Magellanic, Adélie , yellow-eyed and little penguins) are known to actively prey on jellyfish, even when more nutrient-rich prey are available. Scientists speculate that it may be that jellies provide penguins with a nutrient not present in their other prey, such as collagen, or that the penguins selectively prey only on carnivorous jellies - thus consuming all the microscopic animals that the jellies have collected.
Squid is quite low in calories compared to an oily fish like anchovy, but when they migrate in large numbers the energy that is saved by eating nearby squid more than makes up for a hungry penguin. Gentoo, rockhopper and emperor penguins all routinely prey on the seasonal migrating squid, and our local African penguin will prey on squid opportunistically when available.
Why does it matter?
Humans like to eat the same calorie-rich foods that penguins do. When we overfish the species that penguins rely on, they need to swim farther to eat food that contains fewer nutrients. For African penguins and other species with semi-fixed colonies, this means that adults are unable to eat enough to provide enough energy to feed both themselves and their young. The result - an ecological trap that leads to the abandonment of chicks and a decline of endangered penguins.
The solution? Support sustainable seafood programmes - like the WWF SASSI Green List.
Follow the March of the penguin:
If you missed the QR code tour during your Two Oceans Aquarium visit and would like to catch up on the extra penguin information that was shared, you can do so here:
- What do penguins eat?
- African penguin colonies
- Microscopic threats to penguins: Parasites
- The bioaccumulation problem
- How to speak the penguin language
- How do we prepare food for the penguins?
- Penguins of Marion Island: The "other" African penguins
- Why do rockhopper penguins have crests?
- Biodiversity and penguins
- Penguins are predators too: How penguins hunt