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How Do Penguins Feed Their Chicks?

How Do Penguins Feed Their Chicks?

By Sian Liversage

It’s easy to say that you can learn a lot from watching a penguin colony, from their hunting behaviours to how they raise their chicks. Many of us have watched documentaries of penguins incubating and hatching their chicks, but one thing that has always baffled me and many others, is how do they store food to feed their chicks? It turns out, the answer isn’t as simple as you may think – there are multiple ways in which they care for their young as I explain below.

Penguins first must hunt for their food

All penguins hunt in the same way; they either catch their prey in the water or they can scrape krill off the underside of the ice. They do not have teeth, but instead have a very sharp bill to do this. Their mouths and tongues are lined with spines that point back towards their throat, making it easy for them to swallow prey such as squid, shrimp and fish.

Swallowing their food to store it for later 

If a penguin has chicks, it will catch and swallow its food, then “store” it for later to feed to its chicks. Of course, some will also be kept for themselves to enable the parent to continue to survive and hunt for prey. Chicks cannot digest food like their parents, therefore, the parents need to convert it into a form that the chicks can eat. There are a few ways of doing this; the first way is regurgitation; the second way is the equivalent to “refrigerating” the food; and finally, the third way is a secretion that is made from the digested food.

Regurgitation

This is when a penguin will catch its food and partially digest it, which will take a few hours. When the parent reaches its chick, and the food has been digested enough, it will cough the mixture back up and allowing the chick to eat it directly from the parent’s bill. This feeding method is often seen on documentaries so keep a lookout!

A Gentoo Penguin feeding its chick in Antarctica. Source: Penguins International Photo Library
A Gentoo Penguin chick getting a huge meal. Source: Penguins International Video Library

“Refrigeration”

This is a genius evolutionary method that enables penguins to keep food for several days. The parent will swallow the prey whole and store it inside their stomach. This food is kept at body temperature, and inside the stomach there are enzymes which prevent it from digesting.

Penguin “Milk”

When it comes to feeding their chicks, males and females will take turns. In some penguins, Emperor Penguins in particular, the male will care for the chick for several weeks while the female is out hunting and gorging on prey. During this time, the male produces a secretion to sustain the chick and ensure its survival. Penguins, being birds, don’t have “milk” like mammals do.  Instead, they produce this secretion which is sometimes called crop milk. This is a fatty, high protein food that is developed in their crop (a pouch in their throat) and given to chicks during key developmental stages. Although it is nothing like mammal milk, the benefits of this crop milk are very similar to the benefit young mammals get from milk. 

Inside of a penguin. Web: https://sciencing.com/penguins-feed-their-chicks-4567587.html

Conclusion

Chicks need constant feeding throughout their development in order to stay happy and healthy, and it can easily be said that without their parents’ remarkable evolutionary techniques and physiology, the chicks would no doubt perish. 

Penguins have such a different way of feeding that so many other species. Let us know what you think.  And please help us to continue to provide you with penguin news articles by donating to Penguins International.

Read more about penguins in some of our other blogs:

References

E, Lee. 2019. How do penguins feed their chicks? Webpage: https://sciencing.com/penguins-feed-their-chicks-4567587.html

Penguin Science. Diet and Feeding answers. Webpage: https://www.penguinscience.com/education/ask_answers_1.php

Ocean Syrup. 2019. Do penguins make milk? Webpage: https://oceansyrup.com/do-penguins-make-milk/

What Lies Inside the Penguin’s Mouth

The inside of a penguin's mouth

What Lies Inside the Penguin’s Mouth

By Megan Spofford

I recall as African Penguin zookeeper how during feeding times, certain penguins preferred to be fed certain types of fish over others, and most preferred to be fed the head of the fish first (only 1 out of the 40 preferred to be fed tail first). If those penguins were offered an unpreferred item, or in an unpreferred way, the penguin would open its bill and sling its head quickly to the side to shake the fish I had given it from its mouth. In those instances, I had quick glimpses inside the mouth of the penguin, and honestly, it almost looked like something out of a horror story!

What the inside of a penguin’s mouth looks like.

A quick description of a penguin’s bill

From the outside, a penguin’s mouth, the bill, is one of its defining characteristics. There are variations in color for each species of penguin, which can be beautiful, like the King Penguin. The bills are hard keratin formations (keratin is the tissue that makes up human hair, giraffe hooves, and rhino horns). It has a hook on the end that helps a penguin to grip items. (This, of course, comes in handy since penguins do not have arms or hands like us.) There are also two nares on either side of the bill so the penguin can breathe with its bill closed, and which additionally serve as exit points for secretion of the highly concentrated salts they ingest.

What are those spiky things inside a penguin’s mouth?

By shifting focus to the inside of the mouth, we encounter that horror that I mentioned. Of course penguins do not have teeth, but it sure looks like their tongue and the roof of their mouth does! Those teeth-looking structures on the tongue and palate are actually comprised of soft keratin spikes called papillae. They appear sharp on the top, and curve backwards toward the back of the mouth.

What are the functions of those papillae on a penguin’s tongue?

First off, you may notice that those spiky papillae all point toward the back of the penguin’s mouth. Those work a bit like a fish hook. The penguin can grab onto a slippery fish and that food will now only move in one direction – down the penguin’s throat!

All tongues have papillae, including ours, but the penguin’s is more pronounced. It is believed that the reason for this is the function of the tongue. Animals that have “protruding papillae” are typically food collectors. Penguins certainly have pronounced papillae, and collect their food in the ocean! Tongues that have papillae that do not appear to protrude are said to use their tongue as a means to push the food around the mouth, and down the esophagus. Penguins can do this as well, although it has not been well documented. More than likely, the movement is limited, but it can move from side to side, and up and down. Finally, there are tongues that are meant to lie flatly so that food can travel down the esophagus when placed in the correct position. For penguins, all three of these functions seem to apply, with the latter being most applicable to chicks.

Anatomy of a penguin tongue

Underneath the papillae are fatty tissue, connective tissue, mucus glands, and serous glands. The salivary glands are present toward the back of the mouth, and secrete both mucus and serum. In a study conducted on Magellanic Penguin oral structures, salivary glands were present from day 1, but continued to develop, and secrete more beneficial mucus as the subjects got older. Most other birds maintain the same level of development of gland and mucus secretion from birth onward. It was once believed that seabirds who ingested foods from the marine environment would have smaller glands that secreted lesser amounts of mucins because the food was already lubricated by water. However, evidence from the study on Magellanic Penguins supports the theory that the salivary glands have a specific purpose other than to function based on their diet. The purpose could be for any of the following reasons: to break down food, protection from minor injuries, and keeping harmful organisms from creating disease in the mouth. 

What about penguin taste buds?

Most species of birds lack the gene receptors for sweetness, but penguins have even fewer taste buds. Some studies have found that only the receptor genes for salty and sour flavors showed up in penguin species. It’s hypothesized that umami, bitterness, and sweetness gene receptors evolved out of the penguin sequence, because their ancestors lived in cold environments where those receptors do not function well. 

How cool, (horrendous!), and unique is the penguin mouth?!?!

Do you want a mouth, or taste buds, like penguins? Did you like what you learned by reading this blog? Leave a comment below. And please help us to continue to provide you with penguin news articles by donating to Penguins International.

Read more about penguins in some of our other blogs:

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King Penguins

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References:

Hall, Danielle, and Bill Fraser. “Penguins.” Ocean Find Your Blue, Smithsonian, 18 Dec. 2018, ocean.si.edu/ocean-life/seabirds/penguins.

Kobayashi, K, et al. “Fine Structure of the Tongue and Lingual Papillae of the Penguin.” Archives of Histology and Cytology, U.S. National Library of Medicine, Mar. 1998, www.ncbi.nlm.nih.gov/pubmed/9557966.

Paxton, et al. “The Leeds Histology Guide.” The Histology Guide, Faculty of Biological Sciences, University of Leeds, 1 Jan. 1970, www.histology.leeds.ac.uk/oral/tongue.php.

Samar, Maria Elena, et al. “Histochemical Study of Magellanic Penguin (Spheniscus Magellanicus) Minor Salivary Glands during Postnatal Growth.” Wiley Online Library, John Wiley & Sons, Ltd, 19 Nov. 1999, onlinelibrary.wiley.com/doi/pdf/10.1002/%28SICI%291097-0185%2819990201%29254%3A23.0.CO%3B2-7.

Friend or foe? Knowing penguin predators. Part I

magellanic penguins

Friend or foe? Knowing penguin predators. Part I

by Nataly H. Aranzamendi

Penguins feed on fish, plankton and all kinds of jellyfish standing at the top of the food chain. Most top predators do not worry much about being eaten, since they are generally the hunters. But penguins are not quite at the top of the food web, more in the middle, a position called a mesopredator. Penguins have some natural enemies threatening them both in the ocean and on land. Let’s meet their most famous aquatic foes.

A List of Penguin Predators

Leopard Seals

Leopard seals are vicious hunters with a bad reputation. Their big size (almost 3.5 m on average and up to 320 kg)1, solitary nature and aggressive behavior give most people the chills, especially when seeing them hunt underwater. Although leopard seals prey on large proportions of fish, Emperor penguins comprise their main penguin prey. There are also records of leopard seals attacking King, Adelie, Rockhopper, Chinstrap and Gentoo penguins1,2. Their favorite hunting technique is the ambush. Leopard seals hover under ice edges, almost completely underwater waiting for the birds to jump in the ocean1.

Photo Source: Papa Lima Whiskey, ShareAlike 4.0 International (CC BY-SA 4.0)

One of the leopard seal’s favorite tactics is to wait for juvenile penguins to jump in the water for the first time. Seals know that young penguins are still not experienced in the water, and in particular have difficulty at swimming and hunting simultaneously, thus these young penguins become a relatively easy prey to catch.

Seals also wait for those moments when penguin abundance is at its greatest, for example, during the breeding season2. Leopard seals attack adult penguins during foraging trips. Penguins have no choice, as they need to venture into the ocean regularly, because they need to feed their partners and offspring. The leopard seal’s successful hunting technique makes them one of the most feared predators in the Antarctic ecosystem.

Orca killer whale
Photo source: gailhampshire from Cradley, Malvern, U.K [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)]

Killer Whales

Killer whales have a diverse diet, but it has been observed that different populations specialize in specific types of prey3 . Although penguins are not their main prey items, the orca’s distribution range overlaps with that of several penguins in Antarctica, therefore, it is not surprising that orcas occasionally feed on penguins.

Orcas have been recorded preying on Emperor, Gentoo and Chinstrap penguins3,4. The magnitude of the predation impact by killer whales on penguin populations has not yet been quantified4. Two types of orcas have been identified chasing penguins: type B, seal specialists and type A, whale specialists, although with no records of predation for the latter3.

Unlike leopard seals, orcas are highly organized social animals that live in family groups. Killer whales have shown fascinating hunting techniques and an extremely advanced communication system between members. One thing that is absolutely fascinating about killer whales is that such behaviors are passed from generation to generation and now scientists believe that this is a clear evidence of animal culture3.

One technique used by orcas to catch penguins and seals is to perform “wave hunting.” In this technique, swimming groups create waves that are aimed to flip pieces of floating ice where penguins are resting. Once the ice is flipped, there is (almost) no escape for the prey3 .

Sea Lions

The evidence for sea lions and fur-seals preying on penguins is more extensive. Although most sea lions are largely dependent on fish and smaller marine vertebrates, many of them have been recorded preying on penguins.

For example, Antarctic fur seals have been documented preying on King Penguins ashore5. Similarly, South American sea lions have been observed attacking and killing Rockhopper and Gentoo penguins in Argentina, Chile and the Falkland Islands6,7. Sea lion predation on penguins has been observed both during swimming at sea and while resting on land.

Finally, there are records of New Zealand sea lions feeding on yellow-eyed penguins. In this case, the sea lions are from a recovering population with numbers steadily increasing. This increase may cause a major threat to these endangered penguins if predation rates intensify8 .

So far, we have discovered a variety of penguin enemies living and hunting in the same waters as penguins. Nonetheless, penguins are also at risk on land, where more enemies await for adults and their offspring. Stay tuned to discover our next story.

To be continued….

What do you think about where penguins sit on the food chain? 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:

References:

https://en.wikipedia.org/wiki/Leopard_seal

Penney, R. L., & Lowry, G. (1967). Leopard seal predation of adelie penguins. Ecology, 48(5), 878-882.

https://en.wikipedia.org/wiki/Killer_whale

Pitman, R. L., & Durban, J. W. (2010). Killer whale predation on penguins in Antarctica. Polar Biology, 33(11), 1589-1594.

Hofmeyr, G. J. G., & Bester, M. N. (1971). Predation on king penguins by Antarctic fur seals. Vol 4.

Rey, A. R., Samaniego, R. S., & Petracci, P. F. (2012). New records of South American sea lion Otaria flavescens predation on southern rockhopper penguins Eudyptes chrysocome at Staten Island, Argentina. Polar biology, 35(2), 319-322.

Cursach, J. A., Suazo, C. G., & Rau, J. R. (2014). Depredación del lobo marino común Otaria flavescens sobre el pingüino de penacho amarillo Eudyptes c. chrysocome en isla Gonzalo, Diego Ramírez, sur de Chile. Revista de biología marina y oceanografía, 49(2), 373-377.

Lalas, C., Ratz, H., McEwan, K., & McConkey, S. D. (2007). Predation by New Zealand sea lions (Phocarctos hookeri) as a threat to the viability of yellow-eyed penguins (Megadyptes antipodes) at Otago Peninsula, New Zealand. Biological Conservation, 135(2), 235-246.

Rockhopper Penguins change their minds when it comes to eating

Southern Rockhopper Penguin

Rockhopper Penguins change their minds when it comes to eating

by Nataly H. Aranzamendi

Rockhopper penguins comprise two different species: the Southern and Northern Rockhoppers1. Currently they are distributed and inhabit many offshores sub-Antarctic islands.

Rockhoppers are among the smaller species of penguins and they are better known to us thanks to their ability to displace using both feet performing little jumps (i.e. hopping). Unlike other penguins that slide on their bellies to get from one place to another, Rockhoppers are audacious climbers, because their habitat is very rocky, hence the “rock-hopper” name.

Unlike other penguins that love a fishy diet, Rockhopper diets are largely based on krill and other small invertebrates. This means that optimal levels of prey abundance are heavily influenced by fluctuations in oceanographic conditions, like temperature, the mixing of the water, and concentration of phytoplankton.

Southern Rockhopper Penguins have critical food moments during their breeding cycle

For adult Southern Rockhoppers, a critical “food” moment occurs during the reproductive cycle2 . Every year, male Southern Rockhoppers return to shore in small groups after months of oceanic life. Females show up a few days later, and the breeding season begins. Year after year, Rockhoppers return to their same old nests and start a new clutch.

After laying two eggs, moms and dads hang around their nests for a few days, before the male leaves for 2 to 4 weeks to feed in the ocean. When the male returns, it is the female’s turn to replenish her reserves. This will occur when the eggs are about to hatch. During this period, females are in charge of feeding, while males are in charge of chick guarding. Males will only eat again approximately 3 weeks after that.

Such a long cycle of eating and non-eating means that for males, the first foraging trip during incubation is the most critical for their survival. In a recent study2 , researchers have discovered that this critical foraging period is not as predictable as we thought before.

Sometimes Southern Rockhopper Penguins forage near-shore, other times they go far off-shore

Between 2011 and 2014, 62 male Rockhoppers from different colonies in the Falkland Islands were followed during the incubation period. These penguins were equipped with GPS loggers and time-depth recorders to record all the vital information about their journeys and the environmental conditions they encountered.

The researchers were surprised when they saw the data. Looking at the first years’ data (2011-2013), some of the penguins performed short daily trips in shallow waters and returned to spend the night at their nests, instead of engaging in the usual 3-week long trip. In 2014, however, most of the penguins went back to the previously known foraging patterns, in which they explored far away distances and stayed offshore for several weeks, while the female stayed incubating the eggs.

Photo Source: Liam Quinn from Canada [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)]

Southern Rockhopper Penguins will show some level of behavioral placticity

Such findings show that some species are capable to change their habits to some degree. In biology, this is known as behavioral plasticity, meaning that some species can show certain flexibility in behavior (e.g. choosing long vs. short foraging trips) when conditions fluctuate. As predicted, most of these behavioral changes were in relation to oceanographic conditions prevalent during those years. Years that showed a decrease in SST (sea surface temperature) were those in which penguins foraged mostly short distances, while years with normal to increased SST where those in which males foraged offshore. Fluctuations in temperature conditions and the amount of mixing in the water column most likely had impacts on the distribution of phytoplankton, which eventually serves as a good predictor of the presence of krill and small invertebrates, these penguins’ favorite food items.

What does this mean for the future of Rockhoppers? Such variations in temperature conditions could affect the energy expenditure in penguins. Years with decreased SST will mean better energy efficiency balance by penguins, because their prey will be available within a close range from the colony and penguins will not have to travel as far. In contrast, an increase in sea surface temperatures in the South Atlantic and Southern Oceans will inevitably force penguins to travel longer distances, threatening the survival of males. A warming planet therefore poses a threat for Rockhoppers, as increasing SST and alterations in water column mixing within the ocean have already been recorded and are predicted to continue.

It is our duty to safeguard our planet, for the health and future of Rockhopper Penguins and all other creatures that will be impacted by these changes.

Rockhoppers…are they different that what you thought? Did you learn something new by reading this post? Let us know what you think. 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:

References:

https://en.wikipedia.org/wiki/Rockhopper_penguin

Pütz, K., Harris, S., Ratcliffe, N., Rey, A. R., Poncet, S., & Lüthi, B. (2018). Plasticity in the foraging behavior of male Southern Rockhopper Penguins (Eudyptes chrysocome) during incubation in the Falkland/Malvinas Islands. Polar Biology, 41(9), 1801-1814.

Fish is a Superfood for Adélie Penguin Chicks

Adelie Penguin

Fish is a Superfood for Adélie Penguin Chicks

by Nataly H. Aranzamendi

Adélie Penguins are the most widespread species of penguins. They can be found along the entire coast of the Antarctic continent. Although Adélie Penguins live on sea ice, they need ice-free land to breed1.

During the breeding season, Adélie Penguins form colonies clustered together in larger “mega” colonies which might contain thousands or even millions of individuals. These variations in size and location makes them vulnerable to climatic fluctuations. With the reduction of sea ice taking place due to global warming, most Adélie Penguin populations have decreased over the past 25 years1.

Every year between October and November, at the end of the southern spring and beginning of summer, Adélie Penguins go back to their colonies and build nests made of piled up stones. Both parents take turns incubating the eggs. Once the chicks are born, they remain in the nest for approximately three more weeks before joining communal crèches1.

It is at this moment that parents need to provide chicks with the best possible food available, in order to secure their survival. In a recent study2 that analyzed 20 years of data from 1996 to 2016, scientists have tried to understand which factors can guarantee the successful growth of Adélie chicks and their chances to survive their first year, so they are able to return to the colonies.

Some penguins are increasing while other penguins are decreasing.

Scientists compared two areas in Antarctica: the Ross Island colonies and the Anvers colonies2. Penguin numbers are increasing in the first island while decreasing in the latter. Both sites also vary in the total numbers of penguins. The first island has the largest and most dense colonies.

Another difference between both study sites is that penguin parents in the Ross colonies fed their chicks mostly with Antarctic silverfish and crystal krill, while parents in the Anvers colony fed chicks almost exclusively with Antarctic krill.

Turns out that the difference in diets at the chick stage has immediate consequences in their survival2. Survival rates for the chicks fed with fish were higher than those fed exclusively with krill. The “fish chicks” also had higher return rates to the colonies after they left their nests. The body mass of the “fish chicks” that returned compared to those who did not was a difference of 219 g, which is approximately 6.5% of body mass at that stage. This shows that the amount and quantity of food that a chick receives can eventually affect the demography of penguin colonies.

Does penguin fish prey stay consistent throughout the breeding season?

However, the competition between penguin parents increases as the breeding season progresses. This was inferred by the negative trend that the researchers found in the proportion of fish in a chick’s diet over time. Fish became scarcer as time progressed and some chicks even started losing weight. Such an effect was more noticeable in larger colonies2.

When digging more in the data, the researchers found that in order for parents to keep up with the chicks’ demands, they had to take longer trips and dive at deeper waters looking for fish.

So, it looks like even though most parents prefer to feed their chicks with nutritious fish at all times, it is not always so easy to do it. The fact that such important food sources can have plentiful consequences might also help to explain why some colonies have been recruiting small numbers of new individuals every year.

Do penguins have enough silverfish left to eat?

 

 

Photo Source: The Antarctic Sun

The good news for Adélie Penguins is that the stocks of Antarctic silverfish are not commercially exploited and for now their numbers have remained stable3. However, an urgent next step is to quantify the proportion of these fish in the diet of all Adélie penguin chicks in other colonies.

At the moment, it still remains uncertain how the current changes in climate will affect these penguins, their prey and this delicate balance. Adélie Penguins are one of the best studied birds in the world in relation to changes in the environment developing in the Southern Ocean, but there is still a lot that needs to be discovered.

The continuous reduction in sea ice cover plus increasing sea levels puts Adélie Penguins as perfect candidates for habitat loss. It will be necessary to keep Adélie Penguins under the spotlight, to track further changes in their colonies and to keep monitoring their chick survival, a very important life-stage that impacts the demography of this species.

What a diet these Adélies have! Did you know about this? Let us know your thoughts.

Also check out some of the other blogs we have:

References:

https://en.wikipedia.org/wiki/Ad%C3%A9lie_penguin
Ainley, D. G., Dugger, K. M., La Mesa, M., Ballard, G., Barton, K. J., Jennings, S., … & Wilson, P. (2018). Post-fledging survival of Adélie penguins at multiple colonies: chicks raised on fish do well. Marine Ecology Progress Series, 601, 239-251.
Gon, O. & Vacchi, M. 2010. Pleuragramma antarctica. The IUCN Red List of Threatened Species 2010: e.T154785A4633007. http://dx.doi.org/10.2305/IUCN.UK.2010-4.RLTS.T154785A4633007.en. Downloaded on 30 January 2019.

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