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Friend or foe? Knowing penguin predators. Part II

by Nataly H. Aranzamendi

Penguins have a dual life. For most months, they swim in the ocean for food. Afterward, they go back to land for breeding or when they have to change their feathers (i.e. molt). However, danger always lurks at both places.

Giant petrels, Skuas and Gulls

Although adult penguins are generally not worried about flying predators, they turn their alert levels on as soon as they start breeding, because danger hovers in the sky for their chicks1 .

Giant petrels are the most feared predators of penguins. Although most of the time they forage as scavengers, they can be very aggressive hunters when they find suitable prey. Their massive size — up to 8 kg — makes them capable of taking penguin  chicks and even injured adults easily2.

Other feared predators of penguins are skuas. Skuas have mostly been recorded attacking Adélie and Gentoo penguins. Smaller in comparison to giant petrels, they also have powerful hunting abilities. Their best strike is to get chicks at early stages. They prefer to perform in groups, and a group of skuas might terrorize an entire colony at once. Their predation success is higher at the edges of the colonies in comparison to the center, where penguins are generally better protected3.

The skua’s diet is not entirely based on penguins, which also add fish, carrion and sometimes stealing food from other birds to their menu. However, when skua breeding season begins, their dependence on penguins increases greatly. Skuas are often found nesting alongside penguin colonies, as penguins offer a high quality and readily available meal.

Several species of gulls that cohabit penguin colonies also take advantage of a good meal when they see it. Although they are not big enough to prey on adult penguins or chicks, gulls like to harass penguin parents off the nest and then consume their eggs. Oftentimes, many individual gulls attack at once, guaranteeing their success of finding a meal.

White-bellied Sea Eagles

Sea eagles are strong aerial hunters that live in Oceania and parts of Asia. They can reach up to 90 cm and weigh up to 4.5 kg. Sea eagles generally inhabit coastal areas where they look for prey. Their diet is mainly opportunistic, consisting largely on carrion and fish4. But penguins can find themselves on the sea eagle menu as well.

While sea eagles do not hunt penguins in large proportions, in some regions their distribution overlaps with the distribution of Little Penguin colonies, for example in Australia. Little Penguins are the smallest of penguins, reaching only 33 cm, therefore it is not surprising that a sea eagle considers a Little Penguin a decent meal.

Modern predators

The penguin’s inability to fly and the fact that they nest on land are two characteristics that determine their choice of nesting habitat. Over millions of years, penguins have chosen nest sites that lack terrestrial predators. This might explain why a majority of penguin colonies are located in isolated islands or places that are hard to reach by foot for most terrestrial animals.

However, humans in their quest to conquer the most remote parts of planet Earth, have taken invasive predators with them or helped with their expansion indirectly. We are talking about dogs, rats, cats, weasels and foxes, which are the most recent additions of threats to the penguins5.

Each penguin colony is exposed to a varying degree of danger depending on the set of modern predators. Potentially, a single fox could wipe out an entire penguin colony in one visit. Adults are mostly helpless when it comes to defense against these predators, as their inability to fly puts them at risk when defending their nests.

All around the world, scientists and volunteers are fighting an endless battle of invasive species eradication to protect penguins. Luckily, such programs have shown high efficacy in becoming one of the most widespread effective measures for the viability of seabird colonies6.

Nevertheless, this battle is constant, as removing one predator (e.g. cats) might increase the chances of invasion success of other animals (e.g. rats). Therefore, seabird colony management requires constant monitoring and extensive efforts to control for all threats and to guarantee the survival of penguin populations.

We have taken a quick look at penguins’ most feared enemies. Each species has to worry about their own set of predators, as the composition of predators depends on where penguins spend their lives. So far, we do not know much about the invisible enemies of penguins, e.g. diseases, parasites, mosquitoes, etc. but we should remember that these also constitute important potential enemies as well.

What do you think about penguins and…friend or foe? Let us know! Also, please help us continue to learn more about penguins by donating to Penguins International. We more than appreciate your support!

You can also read more about penguins in the following blogs:

Emslie, S. D., Karnovsky, N., & Trivelpiece, W. (1995). Avian predation at penguin colonies on King George Island, Antarctica. The Wilson Bulletin, 317-327.
https://en.wikipedia.org/wiki/Giant_petrel
https://en.wikipedia.org/wiki/Skua
https://en.wikipedia.org/wiki/White-bellied_sea_eagle
Hilton, G. M., & Cuthbert, R. J. (2010). The catastrophic impact of invasive mammalian predators on birds of the UK Overseas Territories: a review and synthesis. Ibis, 152(3), 443-458.
Jones, H. P., Holmes, N. D., Butchart, S. H., Tershy, B. R., Kappes, P. J., Corkery, I., … &; Campbell, K. (2016). Invasive mammal eradication on islands results in substantial conservation gains. Proceedings of the National Academy of Sciences, 113(15), 4033-4038.

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