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Emma Williams

Penguin Digestive Systems – Penguin preppers and their secret militia

King Penguin

Penguin Digestive Systems – Penguin preppers and their secret militia

by Emma Williams

Spending most of your life at sea creates a big problem for a penguin digestive system; what to do when you are on land, separated from your food source. Penguins have evolved an apparently simple solution. Penguins are hoarders. Extremely accomplished preppers, they carry their own personal larders with them. A penguin’s digestive system can become a perfectly adapted storage cupboard of undigested food. The food reserves are used sparingly when they come on land to moult and to breed.

The penguin digestive system allows them to build up large reserves of adipose tissue, protein and lipids

On closer inspection, the solution is not quite so simple. To get through often long periods of fasting, penguins build up large reserves of adipose tissue, protein and lipids. However, this ability is not sufficient on its own; they enlist the help of a secret militia without whom they could not survive: Gastrointestinal microbiota. Penguins are not alone in housing this army of helpers. Most animals, including ourselves, have co-evolved GI tracts teeming with useful microorganisms that play a vital role in digestion. In the “feast and famine” world of penguins, they seem to really have their work cut out.

The penguin digestive system is teeming with useful microorganisms that play a vital role in digestion

These mini ecosystems have been studied widely in mammals but have been largely neglected in penguins. This imbalance has now started to be addressed and a comparative study of GI microbiota in penguins1 has yielded some very interesting results. The researchers looked at the inhabitants of the GI tracts of four different species of penguin: King Penguin (Aptenodytes patagonicus), Gentoo Penguin (Pygoscelis papua), Macaroni Penguin (Eudyptes chrysolophus) and Little Penguin (Eudyptula minor). They studied the gut contents of wild birds by examining their faecal samples.

A healthy Chinstrap Penguin in Antarctica

Thirteen different phyla were found in the penguins. The two most dominant were Firmicutes, literally strong skin, a phylum that are active in carbohydrate metabolism, and Bacteroides, a group of anaerobic bacteria particularly helpful in converting sugars. Both microbiota are also commonly found in mammals. Actinobacteria and Proteobacteria, vital for gut homeostasis, were also found to be strongly represented in the penguins. Each of the four species of penguin studied were discovered to possess different microbial makeups in their digestive systems. The prize for most diverse microbial composition goes to the Macaroni Penguin followed by King Penguin, and Little Penguin with Gentoo Penguin being a valiant runner-up.

It is likely that diet, environment, and phylogenetic differences account for the variation in gut microorganisms. Another study that looked at the GI microbiota of Chinstrap Penguins (Pygoscelis antarctica)2 found that age played a part. There were significant differences between the internal communities of adults and those of chicks. Interestingly, these differences were also apparent between parents and their own offspring suggesting that environmental factors are more important than genetic factors in the chick microbiota.

As well as their vital role in nutrition and energy release, the GI army is also ready to fight inside the penguin digestive system. These micro-soldiers create a formidable force, a close-protection squad, shielding their host from marauding invaders: Pathogens. Bacteroides in particular benefit their host animal by preventing infection by potential pathogens that may colonize and infect the gut.

The complex community of microbiota defend against illness and disease. Little is known about this process in penguins. Indeed, researchers1 discovered many “unclassified” bacteria within penguin digestive systems. As yet we do not know the significance of these atypical army of residents, but they are likely to have some role in digestion as well as health and disease.

Worryingly, human pathogens have also been documented in the GI tracts of wild penguins1, including Campylobacter, Heliobacter and Streptococcus. The impact of these pathogens on the health of wild penguins is not yet known, although a human pathogen has been implicated in the death of a Little Blue Penguin in captivity3

Due to their tendency to live in dense colonies and to huddle closely together, penguins are particularly susceptible to pathogen transfer. The potential for catastrophic spread of disease is likely to be high.

Of course, if penguins are hosting significant numbers of human pathogens without ill-effects perhaps they might hold the key to human immunity.

What is clear is that penguins need their carefully evolved and sophisticated micro-militia within their digestive systems. They play a major role in the release of energy reserves, nutrition, metabolism and immunity. Disruption of these micro-ecosystems is likely to be disastrous to their hosts health and well-being. Knowledge and understanding of these complex inner communities and the relationship with their penguin hosts is still in its infancy. It is an exciting branch of study that just might provide new insights that lead to benefits for both humans and penguins. Long-live the penguin digestive system militia!

What amazing digestive systems penguins have. Please let us know what you learned by reading this blog. We enjoy bringing you this information. And we appreciate any type of support you can provide us, so please consider donating to Penguins International.

Also read some of our other blogs:

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  1. Dewar, M.L., Arnould, J.P.Y., Dann, P., Trathan, P., Groscolas, R., & Smith, S. (2013). Interspecific variations in the gastrointestinal microbiota in penguins. Microbiology Open, 2 (1), 195-204.
  2. Barbosa, A., Balague, V., Valera, F., Martinez, A., Benzal, J., Motas, M., Mira, A., & Pedro-Alio, C. (2016). Age-related differences in the gastrointestinal microbiota of chinstrap penguins (Pygoscelis antarctica). PloSone,
  3. Boerner, L., Nevis, K.R., Hinckley, L.S., Weber, E.S., & Frasca, S. (2004). Erysipelothrix septicaemia in a little blue penguin (Eudyptula minor). Journal of Veterinary Diagnosis, 16, 145-149.

Penguins and Their Chicks: Super-Parents

King Penguin and its chick

Penguins and Their Chicks: Super-Parents

by Emma Williams

A common misconception about penguin parenting, instigated by polar explorers in the 1960s, was that penguins regularly deserted their chicks. It was believed that they deliberately starved their chicks in order to force them to leave the breeding colony. This was founded on observations that the chicks of King Penguins (Aptenodytes patagonica) weighed more than adult birds and lost this weight prior to fledging. The desertion theory was subsequently generalised to other penguin and seabird species such as Albatrosses1. 

Reproductive effort is a balance between the benefit of increasing offspring survival and costs, including mortality, of the parent. Any increase in parental care must therefore be finely weighed against the price paid. Fundamentally, this boils down to the harsh question: Are they worth feeding?

There are many parenting strategies for successful breeding

Rabbits often produce one litter a month, turtles yield hundreds of hatchlings and provide no parental care, Robins lay 3-4 clutches per year, about half of the chicks do not survive. Penguins tend to go for the opposing parenting strategy of “putting all your eggs in one basket”. And often there is only one egg. 

Far from deserting their young, penguins are super-parents. Compared with most sea-birds, penguins have a very long pre-fledge duration; from 56 days in the Adelie Penguin (Pygoscelis adeliae) to a staggering fifteen months in the King Penguin. Penguin parental care can be divided into two periods. During the guard phase, penguin parents brood the chicks intensively, the female often returns to the sea to forage during this period, which can last up to 37 days. In the next phase the chicks form tight groups, or creches as they’re called1. 

For King Penguin parents, each fledgling represents a huge investment. They first breed when they are around three years old. The parents spend one summer and two winters raising their young. The chicks’ weight loss, as observed by the explorers, can be explained by fluctuations in food availability. King Penguin chicks pile on the calories, lay down fat deposits and balloon to their maximum weight at four months old. A second peak occurs at around ten months. This enables them to survive long periods without food when their parents are foraging. King Penguins are serially monogamous with both parents sharing all hatching and rearing duties. They cannot raise a chick every year which explains why eggs as well as quite large chicks can be seen at the same time in King Penguin colonies2

Penguin parents are even featured in movies

The astonishing parental care provided by the Emperor Penguin (Aptenodytes forsteri) has been popularised by films such as March of the Penguins and Warner Brothers’ Happy Feet. The female lays a single egg that is incubated by the male during the long Antarctic winter. A great deal of the 65-day incubation period is spent in darkness. Standing for weeks, balancing an egg on their feet, with no food, in temperatures down to minus 40 Celsius must be the epitome of good parenting. The female devotes this time to replenishing her food reserves in the open sea. On her return, these penguin parents take turns foraging at sea and caring for the chick in the colony. They are truly long-distance commuters taking foraging trips of one to three weeks averaging over 650 km per trip. They go to great lengths, literally and metaphorically, to care for their young.

The chicks need to gain significant reserves, particularly in the month prior to fledging. A study looking at the diving behaviour of adult Emperor Penguins provisioning chicks during this period, documented some record-breaking feats. They are the deepest diving of all the penguins with dives of over 500m logged. Many dives were well over ten minutes in duration, with the average number reaching more than 200 per day3.

As if this wasn’t enough, Emperor Penguin parents face an additional challenge in successfully rearing a chick: They breed on seasonal sea-ice. The chicks therefore need to fledge before the ice melts in mid-to-late summer. It truly is a race against time.

Penguin chicks hatch into some of the harshest conditions on earth. To survive independently they need to be able to hunt and capture food, often on their first-ever trip to the sea. To do this they need to be strong, fast and capable. The Gentoo Penguin (Pygoscelis papua) manages this challenge in a unique way. A study found two behaviours not shown in other Pygoscelis species: Delayed dispersal of young, and extended parental provisioning4.

Gentoo Penguin feeding its chick

Whilst Adelie Penguins and Chinstrap Penguins (Pygoscelis antarcticus) fledge in a mass exodus on their first trip to the sea, Gentoo chicks take their time and several practice trips. Most Gentoos first go to sea at 70 days old and make approximately five trips in a fortnight before fledging. What is so special about Gentoo Penguins is that they continue to feed their chicks during this period. It is likely that this extended provisioning helps the chicks to hone their hunting skills before fully fledging4.

With extensive pre-fledge periods, long-distance commutes, deep dives, and comprehensive parental provisioning in harsh conditions — often to raise a single chick — penguins justly deserve the accolade “super-parents”.

Do you love the super-parenting of penguins? 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:

  1. Burger, J. The ‘Desertion Period’ in Seabirds. Proceedings of the Colonial Waterbird Group, vol. 3, 1980, pp. 16–26. JSTOR,
  3. Kooyman, G.L. &. Kooyman, T.G. Diving Behavior of Emperor Penguins Nurturing Chicks at Coulman Island, Antarctica, The Condor: Ornithological Applications, Volume 97, Issue 2, 1 May 1995, Pages 536–549,
  4. Polito, M.J. & Trivelpiece, W.Z. Mar Biol (2008) 154: 231.
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