Blog articles on fun facts and interesting information written by our penguin experts.

Penguin Pride – Same Sex Behaviour in Penguins

Martin Franklin with Humboldt Penguin

Penguin Pride – Same Sex Behaviour in Penguins

by Martin Franklin

With June being LGBT+ Pride Month in many places around the world, it seems an appropriate time to write about some of the many documented examples of penguin couples that frequently display same-sex sexual behaviour (including courting displays, sexual activity and nest-building activity).

Before diving in, however, it’s worth mentioning (given the potentially misleading title above) that the generally accepted collective noun for a group of penguins is not a (leonine) “pride”, but rather a “raft” (if they are in the water), or a “waddle” (if they are on land).

Same Sex Behaviour in Penguins

Same-sex sexual behaviour has been observed in numerous penguin species, including King penguins at Berlin Zoo, African penguins at Toronto Zoo, Gentoo penguins at Sea Life Sydney Aquarium, and Chinstrap penguins at Central Park Zoo in New York. In the latter case, the relevant pair (Roy and Silo, both male) even successfully incubated another pair’s egg, resulting in a chick named Tango. This in turn even resulted in a popular children’s book called “And Tango Makes Three“.

Same Sex Behaviour in Wild Animals

Such behaviour is not limited to penguins, of course: same-sex sexual interaction has been observed in hundreds of animal species1, in both zoos and in the wild. In some cases, this may be “sociosexual” behaviour designed at least in part to achieve a social goal (e.g. facilitating food sharing, forming alliances, reducing social tensions or facilitating reconciliations), as seen, for example, in bonobos2. In other cases, however, such behaviour appears to have no sociosexual element. For example, around 8% of rams in particular domestic sheep breeds seem exclusively to choose to mount other males rather than females when given the option3.

But back to penguins, and, in particular, Humboldt penguins (a species I observe on a near-daily basis, in the course of my work as a bird keeper at ZSL London Zoo). Zoo am Meer Bremerhaven in Germany has reported same-sex sexual behaviour in Humboldt penguins, and the same is true of our observations at ZSL London Zoo.

In this context, it’s particularly serendipitous that the Humboldt penguin is named after the Humboldt ocean current (off the west coast of South America), which itself is named after the Prussian naturalist Alexander von Humboldt, who himself the evidence indicates to have been homosexual (or possibly bisexual).

Excluding recently hatched chicks, there are currently 93 penguins on Penguin Beach at ZSL London Zoo (77 adults and 16 juveniles). This number, along with the male/female split being broadly equal, means these birds have significant partner-choice. There are currently 34 nesting pairs, of which 3 are established same-sex pairs.

The first of these are Ronnie and Reggie (pictured, both 17 years old), a highly vocal and well-built all-male pair who certainly make their presence known on the far right-hand side of the beach, and who think little of barging other penguins out of the way at feeding time. (People with knowledge of the Kray Twins, who terrorised the East End of London in the 1950s and 60s, will appreciate the appropriateness of these birds’ names). They do, however, also have a nurturing side: recently when another pair’s egg needed incubation, Ronnie and Reggie took on the job, diligently taking it in turns to incubate the egg themselves.

Ronnie and Reggie (© Martin Franklin/ZSL)

Next up are Zimmer (21 years old) and Nadja (16), our only all-female pair (pictured). Zimmer also happens to be our oldest penguin: the species can live up to around 20 years in the wild, but can fare significantly better than that in zoos (due to better nutrition, better medical care, lack of predation, and the absence of negative human impact on their environment).

Zimmer and Nadja (© Martin Franklin/ZSL)

Martin (17) and Dev (13) are our other all-male couple (pictured), and tend to hang out on the left-hand side of the beach. We placed a new nest box in this area of the beach recently, and within a couple of hours this pair had abandoned their old nest box and established themselves inside the new one.

Martin and Dev (© Martin Franklin/ZSL)

Finally, mention must be made of Rainbow (1) (pictured), who was named on the Pride Parade weekend around this time last year, and whose name was chosen specifically in honour of the LGBT+ community. She even sports identity beads on her wing reflecting this – the only penguin on the beach not to have a bead sequence that references its year of hatch. As Rainbow is still a juvenile, it remains to be seen with whom she may choose to form a pair-bond in the future.

Rainbow (© Martin Franklin/ZSL)

Did you learn something new about penguins by reading this blog? A nice way to wrap up LGBT Pride Month. Let us know your thoughts. Also, please help us continue to learn more about penguins by donating to Penguins International.

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1 Bagemihl, B. (1999). Biological exuberance: Animal homosexual and natural diversity. New York, NY: St. Martin’s Press.

2 de Waal, F. B. M. (1987). Tension regulation and nonreproductive functions of sex in captive bonobos (Pan paniscus). National Geographic Researcher, 3, 318–338.

3 Roselli, C. E., Larkin, K., Resko, J. A., Stellflug, J. N., Stormshak, F. (2004). The volume of a sexually dimorphic nucleus in the ovine medial preoptic area/anterior hypothalamus varies with sexual partner preference. Endocrinology, 145, 478–483.


© Martin Franklin 2019

Martin Franklin is a bird keeper at ZSL London Zoo, and works extensively with Humboldt penguins. Any views or opinions expressed in this article are the author’s own, and do not necessarily represent those of ZSL.

A conservation story: Humboldt Penguins

Humboldt Penguin

A conservation story: Humboldt Penguins

by Nataly H. Aranzamendi

The Humboldt Penguin is a species found along coastal Peru and Chile. Extremely dependent on food brought by cold waters, this species faces many human-induced threats. Lately, scientists have been trying to protect their remaining colonies to ensure the survival of these penguins. Let’s discover what’s on the horizon for these fellows!

The first time I visited a colony of Humboldt Penguins was in 1992. At the time, I was only a kid and I was not sure why we had to take such a long trip just to go to the beach. My family promised me that the trip was worth it, because we were going to see many interesting wild animals.

Our first stop was locally known as Playa Pinguino or “Penguin Beach.” I remember I was initially disappointed, because the beach did not look like a nice place for swimming and instead there were slimy seaweeds everywhere. However, that initial feeling quickly vanished, when everyone started pointing towards the rocks. That is when I saw little clumsy figures jumping out of the ocean — the first time I saw Humboldt Penguins.

Map showing the breeding range of Humboldt Penguins

Penguin Beach is probably not a good place for swimming — but the birds love it!

I discovered later that due to the great faunal diversity that includes sea lions, seabirds and plenty of endemic fishes, this site, known as Punta San Juan, was formally upgraded to a protected area in 2009. Nevertheless, this area has been managed for extractive purposes since 1909 and the monitoring of Humboldt Penguins was already in place when I visited that colony. Currently, Punta San Juan holds one of Peru’s largest colonies of Humboldt Penguins and has an active seabird-monitoring program.

Humboldt Penguin populations have suffered several human impacts throughout their range in the past. This species has experienced dramatic declines in numbers and a disappearance of breeding colonies1 , now being classified as Vulnerable.

In the past, the biggest threat to Humboldt Penguins was guano harvesting

Historically, the Humboldt Penguin was affected by extensive guano harvesting in both Peru and Chile, which disturbed their nesting habitat. Moreover, during the El Niño event of 1982-1983, the global population experienced a 3-fold drop from approximately 16,000 – 20,000 birds down to 5,000 – 6,000 individuals1. Despite high uncertainty about the future of their populations, the management of key colonies could bring good news for this species.

The biggest threats for Humboldt Penguins are entanglement on fishing nets, competition for food with commercial fisheries, human disturbance in colonies, invasive predators (e.g. rats and mice) and poaching of adults. “Research that targets the most important threats for Humboldt Penguins could bring promising results for colony management,” explains seabird expert Dr. Carlos Zavalaga to me, a full-time researcher of the Marine Ecosystems Research Unit of Universidad Científica del Sur, Lima Peru.

What steps are being done to protect Humboldt Penguins now?

According to Dr. Zavalaga, there are still many challenges ahead to achieve total protection of penguins, but several research organizations have projects underway targeting the most pressing issues. For example, in Peru they are working to determine at-sea movements of penguins to examine how they use the area around their colonies and how this overlaps with commercial and artisanal fisheries. In addition, they are trying to understand the effects of anthropogenic disturbance (e.g., fishing proximity, tourist boats) on breeding penguins.

“We have conservative estimates that along the Peruvian coast, penguin populations and breeding sites might be increasing since the early 90’s. Even in Northern Peru, there were islands with no recent records of breeding penguins and now they are showing signs of recovery,” added Dr. Zavalaga. Such protection efforts are only possible thanks to coordinated work between universities, NGOs, the government and private (national and foreign) conservation organizations.

If the research shows significant overlaps between foraging ranges of Humboldt Penguins and the areas used for fishing, it will be of utmost importance that the government establishes Marine Protected Areas around those colonies. Such areas will support a decline in the frequency of negative interactions between penguins and humans, but will also strengthen the protection of a fragile ecosystem.

Visiting the penguin colony when I was a child had a long-lasting positive impact in my life and I feel optimistic knowing there are so many organizations, researchers and volunteers engaged in protecting such an iconic species. I could not imagine a future without Humboldt Penguins.

Did you know about Humboldt Penguins or what do you think about them? 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:


BirdLife International 2018. Spheniscus humboldti. The IUCN Red List of Threatened Species 2018: e.T22697817A132605004.
Downloaded on 14 May 2019

Friend or foe? Knowing penguin predators. Part II

Friend or foe? Knowing penguin predators. Part II

by Nataly H. Aranzamendi

Penguins are both predators and prey — they are in the middle, so they are called mesopredators

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.

Some penguin predators live right in the colony with penguins

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.

Penguins don’t have many natural predators on land

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.
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.

The journey of young Emperor Penguins

Emperor Penguins

The journey of young Emperor Penguins

by Nataly H. Aranzamendi

The lives of young Emperor Penguins have long been a challenge to study, owing mostly to their harsh Antarctic habitat. But now, scientists are beginning to get some insight into their early years. Let’s find out more about their secret journeys.

Emperor Penguins are the only penguins breeding through the tough Antarctic winter. Adult Emperor Penguins perform difficult journeys during the breeding season in order to feed themselves, and repeat these journeys later to feed their offspring.

Two key periods in the life of an Emperor Penguin

There are two key feeding periods during breeding for Emperor Penguins. One is after egg-laying, which occurs approximately between autumn and mid-winter in the Southern Hemisphere. At this time, females need to rebuild their body reserves, so they march towards the sea for feeding, while the males stay on the ice incubating the egg.

The second critical period takes place during the chick rearing period, from mid-winter to December when the female comes back and it’s the male’s turn to eat something and collect food for the chick. After these long journeys and summer begins to bring life to the surrounding ecosystems, the food becomes close enough and plentiful enough that both parents can alternate this role more frequently.

Feeding places of breeding Emperor Penguins are often found around their colonies in open water areas surrounded by sea ice or in pack-ice regions further off-shore. Both areas provide a variety of food items for breeding penguins, e.g. Antarctic krill, Antarctic silverfish or glacial squid, which are very important for their survival.

What do juvenile Emperor Penguins do after leave the colony?

However, to date, we have been unaware of what happens with juvenile Emperor Penguins after they fledge. Where do they go when they leave the colony for the first time? Young Emperor Penguins depart in December and travel far north mostly to ice-free waters, but their journey from there on has remained unknown, only until recently.

Since juveniles leaving the colony for the first time are probably still learning their best foraging techniques and the best places to eat, scientists have always assumed that young penguins went far away avoiding the sea ice during winter.

In a recent study following young Emperor Penguins, scientists have untangled this journey, giving us further clues about their behavior during their first years of life1.

Scientists gathered information on penguins’ journeys by putting transmitters on 15 juvenile penguins. To be more specific, they looked at their trajectories, traveling distances, depth and temperatures for almost a year since they left their natal grounds.

The maximum distance that a penguin traveled was 7800 km and the farthest distance from the colony was 3500 km. The penguins first traveled north to approximately 53 degrees South latitude and then later around March they started heading back south, remaining around sea-ice. This was a surprise for researchers, as they expected penguins staying in ice-free open waters year round. Instead they remained around sea ice areas at most times (49% of the total recorded trip).

Penguins were mostly active during the day (63% of their time diving) when dives were the deepest, and then during twilight (32%). Nocturnal dives only occurred in 5% of the cases.

Young Emperor Penguins go on an exploration of their environment.

Young Emperor Penguins explored their environment in different ways depending on the season. During summer, just after they departed the colony, they started their journeys diving in the sea ice around the colony and slowly going northwards into open water. At this time, the dives were the shallowest and it was only later during winter when the deepest dives were recorded. The reason why penguins explore deeper waters and the variation found throughout seasons is most likely related to prey availability.

Areas around ice support abundant food resources, particularly under ice. It provides a substrate for ice algae and zooplankton, which could explain the shallow dives of penguins at daylight and twilight. In autumn, krill larvae and other crustaceans are more abundant outside the sea ice, therefore the movement patterns are outside the region of the sea ice. In winter, krill migrate to deeper waters and the penguins are forced to follow them.

Photo source: Ian Duffy from UK [CC BY 2.0 (]

A question that remains unanswered is how do young penguins know where and when to forage? It is likely that foraging strategies are learned with exploratory behaviors during the first months of life in the water. But perhaps there are additional genetic predispositions leading the way as well. Finding out more about the capacity of young penguins to rapidly learn about prey distribution in an efficient way is crucial for their future, as young birds are often more sensitive to environmental fluctuations than are adults. The future of this charismatic species will therefore be better predicted and understood if we keep studying these mysterious and unknown behaviors.

Did you know all this about Emperor Penguins? They have quite the life! Let us know what you learned and/or 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:


Labrousse, S., Orgeret, F., Solow, A. R., Barbraud, C., Bost, C. A., Sallée, J. B., … & Jenouvrier, S. (2019). First odyssey beneath the sea ice of juvenile emperor penguins in East Antarctica. Marine Ecology Progress Series, 609, 1-16.

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 (]

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:


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

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.

The choice of non-breeding penguins: To fast or not to fast?

Gentoo penguins

The choice of non-breeding penguins: To fast or not to fast?

by Nataly H. Aranzamendi

Non-breeding penguins are an important portion of any penguin population and we know very little about them. Let’s explore new hints about their biology.

There are two critical points in the annual cycle of birds: the time of molt and the time of reproduction. Both processes are highly energetically demanding, and it’s often assumed that birds need to be in good condition before engaging in any of them.

Penguins don’t typically start breeding for a few years

For marine birds like penguins, sometimes it takes a couple of years before they are ready to start breeding. During this period of development, juvenile penguins might remain close to their natal colonies or they might choose to stay at sea for an extended period of time. In biology, we classify those penguins as non-breeding individuals. Non-breeding birds aren’t necessarily juveniles, however, and may be skipping a particular breeding season. This happens if a bird cannot successfully find a mate, its mate doesn’t return to the nest, or, for some penguins species such as King penguins, they often only breed every other year. But for other non-breeders, there doesn’t appear to be an obvious reason for skipping a breeding season.

Until now, the activities and changes in non-breeding birds have remained a mystery due to the difficulty to catch them in one site (i.e. they are not attached to any nest anymore) and the difficulty to follow them in their journey at sea.

Scientists have always believed that non-breeding birds are in poorer condition than breeders, because they might have less body reserves to engage in breeding and so they choose to skip it.

Alternatively, non-breeders maintain higher body reserves at all times in comparison to breeders, because they are not exhausted by the costs of raising offspring. Since breeding entails variable cycles of fasting and foraging, this assumption is likely. However, to date, no one had quantified such variation in conditions.

Where do non-breeding penguins go?

Luckily, not all non-breeding birds stay at sea and some remain around their colonies at the time other individuals decide to start breeding. This is good news because it could offer the opportunity to monitor those birds and understand how they conserve their body reserves.

In a recent study1, researchers have been able to quantify changes in condition in non-breeding penguins over several years. This study used data from a wild colony of Adélie penguins in Antarctica and from a captive colony of Gentoo penguins in an aquarium in Australia.

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In this study, the comparison between wild and captive individuals would allow scientists to control for the main factor that is thought to influence condition: food limitation. While the wild individuals would be restricted by the availability of food, captive ones will have unrestrained access to food.

The findings were surprising. Unlike previous expectations, both breeding and non-breeding birds went through similar mass fluctuations throughout the breeding season.

Some years showed differences, for example, where breeding female Adélie penguins were heavier than non-breeding individuals before egg laying or when the chicks were in crèches. However, the overall pattern showed similar changes for both groups in all years.

Surprisingly, this pattern of mass fluctuations was also observed in the captive population of Gentoo penguins.

Why do penguins eat so much if they’re not going to breed?

Photo Source: Boaworm [CC BY 3.0 (]

Scientists were puzzled by such findings. Why do non-breeders go through such changes if they have no need to gain reserves to breed? If this is in relation to food limitation, then why is such pattern also observed in captive individuals?

The answer seems to be found in the intrinsic physiological cycles that are regulated by hormones. Although this was not explicitly tested in this study, it seems to be the only logical explanation for such a ubiquitous pattern. Similar responses observed in other seabirds could offer more evidence. In puffins for example, body mass gain during good months increases the chances of survival during periods of less food. Alternatively, such mass gain could buffer mass loss of individuals during colder months.

Scientists believe that such mass fluctuations could be triggered by changes in light (i.e. photoperiod), which could explain why the weight changes are noticeable in breeding and non-breeding individuals.

This is quite interesting and could change the way we have always thought about penguins and breeding in relation to food limitation.

It is still unknown what happens with the birds that remain at sea throughout the year. Would they also experience a change in body mass? In order to answer that question, we will have to keep following these penguins and find out!

Breeding, non breeding. Food, no food. Light, no light. So much info! What did you learn be reading this? Please share your thoughts. Also, please help us continue to learn more about penguins, their habits and more by donating to Penguins International. We more than appreciate your support!

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

Emmerson, L., Walsh, S., & Southwell, C. (2019). Nonbreeder birds at colonies display qualitatively similar seasonal mass change patterns as breeders. Ecology and Evolution 10.1002/ece3.5067

Penguins and the Evolution of Technology

Southern Rockhopper Penguins

Penguins and the Evolution of Technology

by Nataly H. Aranzamendi

The advance of technology has brought a new dimension to our lives. Now it is increasing our knowledge of penguins’ lives as well.

Techie Penguins

Penguins live mysterious lives. Once they leave land and jump back into the water, they start fast journeys to unknown locations. Their lifestyle adapted to water makes it impossible for humans or most machines to follow them in their underwater journeys.

The development of technology and satellite tracking has opened up new horizons in the understanding of this secret life that penguins lead. To uncover their trajectories, the most popular tracking devices used are GPS (Global Positioning System) data loggers.

Tracking penguins by satellite

A GPS is a satellite-based navigation system that operates with several satellites. GPS satellites circle the Earth in a precise orbit and each satellite transmits a unique signal that allows devices to know the precise location of the satellite1. By combining all signals, such devices can inform us of the exact location of any organism that is carrying a GPS. In fact, we can find many penguin projects on the internet that transmit the journey of penguins in real time!

Satellites can also aid scientists by providing information from hard-to-reach colonies in remote areas. For example, a recent study has found that “penguin poo” can be accurately spotted using satellite images2. The identity of adult or juvenile Adélie Penguins and Chinstrap Penguins could be discerned based on the guano coloration observed.

Another common device deployed in penguins is accelerometers. These devices measure the change in speed divided by time. Accelerometers are often accompanied by sensors measuring temperature and pressure. This allows scientists to measure how fast and how deep a penguin swims, while simultaneously recording temperature conditions. A penguin’s encounters with prey can also be inferred from the accelerometer’s data output, due to the particular speed at which penguins swim when following prey in the water3.

Drones have been demonstrated to be allies of scientists, too. In a recent study4, scientists tested if drones were better than humans at counting birds in colonies. They found that in effect, drones performed better than humans and had better counting estimates.



Photo source:, The original uploader was Narmo at Polish Wikipedia. [Public domain]

Artificial intelligence and penguins

The development of artificial intelligence (AI) is another recent tool to study penguins. AI is sometimes referred as “intelligence demonstrated by machines” which can correctly interpret external data, learn from it and complete tasks in a flexible automated manner5.

In the case of penguin research, scientists are using cameras to replace human observers and to monitor penguin colonies6. Using automated all-time recorded images from those cameras, online users are able to observe birds and score their behaviors. The machines standardize this process and then make it measurable for the scientists to interpret.

The flexibility of AI allows the program to work out which information is meaningful and to correct for possible misinterpretations. This is only possible because more than one person works on images simultaneously, and computers source the correct information based on whether people agree or disagree in each annotation. If proved useful, this method will aid bird monitoring in places where human presence might disturb wildlife and disrupt their behavior.

Studying penguins through DNA analysis



Little Penguin
A Little Penguin

Using DNA analyses for diet

The development of molecular genetic tools is improving our knowledge of penguin behavior as well. The use of molecular tools has helped undercover the identity of fish found in the diet of penguins. In the past, this was done by looking at fish otoliths (ear bones) found in diet samples and by trying to identify the species by analyzing individual otoliths one by one!

Nowadays, molecular analyses can do this automatically and reveal additional unknown components of a penguin’s diet. For example, it was recently discovered that Little Penguins eat more salps than previously thought7. These gelatinous plankton might quickly decompose inside the penguin’s guts, and that is possibly the reason why its identity was overlooked until now. It is only with the aid of molecular tools that scientists are beginning to untangle the mysteries of penguin dietary habits.

The advancement in technology is opening new doors that could be crucial in the conservation of wild animals, especially penguins. Several initiatives of citizen science are also opening opportunities for us, the general public, to be able to participate and collaborate analyzing animal data. Now everyone has the chance to do science and monitor penguins from the comfort of their homes.

AI is moving us ahead every day. Now it can help us watch penguins from the comfort of our own home. How great?!  What are your thoughts? Please help us continue to learn more about penguins, their habits and more by donating to Penguins International. We more than appreciate your support!

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

2. Waluda, C. M., Dunn, M. J., Curtis, M. L., & Fretwell, P. T. (2014). Assessing penguin colony size and distribution using digital mapping and satellite remote sensing. Polar biology, 37(12), 1849-1855.
3. Sánchez, S., Reina, R. D., Kato, A., Ropert-Coudert, Y., Cavallo, C., Hays, G. C., & Chiaradia, A. (2018). Within-colony spatial segregation leads to foraging behaviour variation in a seabird. Marine Ecology Progress Series, 606, 215-230.
7. Cavallo, C. R., Chiaradia, A., Deagle, B. E., McInnes, J., Sanchez Gomez, S., Hays, G. C., & Reina, R. D. (2018). Molecular analysis of predator scats reveals role of salps in temperate inshore food webs. Frontiers in Marine Science, 5, 381.

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 (]

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:


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.

A story of prehistoric Crested Penguins

Fiordland Penguin

A story of prehistoric Crested Penguins

by Nataly H. Aranzamendi

Humans have caused the decrease of many island birds, but did humans cause the disappearance of some prehistoric penguins from New Zealand as well? Let’s find out.

Several members of the genus Eudyptes, known as crested penguins, live in the New Zealand archipelago. These species are: the Erect-crested Penguin, the Snares crested Penguin and the Tawaki (a.k.a. Fiordland Penguin). The isolated Pacific island is quite well-known for its stories of bird extinctions. Many taxa including birds and mammals have disappeared from New Zealand due to human pressure, excessive hunting and/or the presence of introduced predators.

The reason why island animals are so vulnerable to new pressures lies in the fact that they have evolved isolated, in a situation where many of them have lost their anti-predator defenses, becoming an easy target for introduced predators and hunters.

Photo Source: travelwayoflife [CC BY-SA 2.0 (]

Are crested penguins more sensitive to decline than other penguins?

Due to several studies showing that crested penguins have been declining since the 20th century, many scientists have assumed that crested penguins have been susceptible to human disturbance possibly since historical times, when the first humans arrived to the archipelago.

In a recent study1 using historic and modern DNA analyses from fossil records, scientists have tried to understand if the current distribution of crested penguins are due to extinction during prehistoric times caused by humans or due to range shift in the distribution of current species.

To test their hypotheses, the study used material from 84 prehistoric bone samples, initially identified as belonging to crested penguins. Those fossils were dug out in mainland New Zealand and right now are deposited in museum collections found in New Zealand and Australia.

How are prehistoric penguins being studied?

The analyses of crested penguins focused on the genetic diversity from genetic markers. The first analysis indicated that New Zealand had six prehistoric penguins inhabiting the island. Possibly, one of the new taxa identified corresponds to a previously undescribed lineage of crested penguin. Such findings indicate that New Zealand had a higher penguin diversity in the past.

The analyses found also that although the range of some penguins might have decreased in extent (e.g. Tawaki), their genetic diversity had remained relatively constant, meaning that it was probably not affected directly by humans. Similar findings were detected across the other species in relation to their genetic diversity. Such findings contrast with what has been found for other New Zealand animals, like fur seals or the Fouveaux shag, which were probably targeted by the first human settlers and that currently show reduced genetic diversity.

It is likely that the southern part of this island has remained relatively isolated and experienced less human pressure in comparison to the northern parts of the island, behaving as a refuge for penguins. In fact, no fossil record of New Zealand South Island endemic penguins exists in the archeological deposits from the North Island, ruling out that the Maori traded with penguins at that time.

The researchers argued that it is also likely that when European settlers arrived, many parts of the South Island were too isolated and remained inaccessible to them. This isolation could explain why the populations of Tawaki remained relatively stable.

Prehistoric penguins still remain a mystery.

The main cause of the disappearance of other prehistoric penguins remains a mystery. Most likely changes in environmental conditions or food sources might have played a big role in the likelihood of extinction of those species, just as it has been found for prehistoric penguins elsewhere.

This study highlights that some island species can be more resilient than others to human disturbances. It is really important for the future of any insular animal population to maintain adequate levels of genetic diversity.

More importantly, including genetic diversity assessments in future conservation proposals will secure the accurate management of species, as well as conservation decisions for penguins. The use of genetic tools in conservation biology has potentially a very bright future ahead.

As for crested penguins, we need to keep investigating which are the most immediate threats that are causing their decline. We want to see them “hopping” for many more centuries ahead.

What do you think after reading about New Zealand and crested penguins? Did you learn anything new? Read some other fun things about these animals we love:

Also, tell us what else you’d like to learn about penguins! We’re here for you.

Cole, T.L., Rawlence, N.J., Dussex, N., Ellenberg, U., Houston, D.M., Mattern, T., Miskelly, C.M., Morrison, K.W., Paul Scofield, R., Tennyson, A.J.D., Thompson, D.R., Wood, J.R., Waters, J.M., Ancient DNA of crested penguins: Testing for temporal genetic shifts in the world’s most diverse penguin clade, Molecular Phylogenetics and Evolution (2018), doi:

How will climate change affect King Penguins?

king penguins

How will climate change affect King Penguins?

by Nataly H. Aranzamendi

Recent changes in climate are impacting a variety of species worldwide, and penguins are certainly not immune. King Penguins in particular are extremely sensitive to these changes in their environment.

The King Penguin is considered an indicator species for climate change. With many of their major colonies declining in numbers in recent years, scientists have turned their attention to the causes and consequences of climate change on this species, and the potential actions that could save it from extinction.

Basic information about King Penguins

The King Penguin is an apex predator living in the sub-Antarctic region. King Penguins exclusively breed in year-round ice-free islands scattered throughout the Southern Ocean. To eat, they follow fish stocks around the Antarctic Polar Front, a boundary between colder, saltier water closer to Antarctica and the warmer less salty water of the South Atlantic Ocean.

King Penguins are central place foragers which means that they travel from their nesting sites to a distant foraging location, rather than just passing through an area exploring or traveling at random. Thus, King Penguins have foraging and breeding grounds distributed in a fragmented landscape.

A recent study1 that monitored the current and ancient conditions of penguin distribution and prey availability has found that the foraging range of King Penguins is displacing southwardly, possibly in response to warming waters. As a result, penguins will have to travel farther to find their prey. This implies that for many populations located in islands in which the foraging range is shifting, there will be decreasing numbers in the future. For example, the Crozet Island population, one of the largest colonies of King Penguins, is already showing declines since the past decade.

When environmental factors change suddenly, species can adjust to these changes using behavioral plasticity (i.e. changing behaviors) or by rapidly evolving. For example, penguins could change behavior and colonize new islands (i.e. disperse) and/or could start traveling farther distances.

What does that changing climate mean for King Penguins?

However, scientists have found that penguins traveling further are putting their energetic balance at risk, eventually having lower reproductive success. If that balance is altered in several hundreds of individuals at a colony, it will be disastrous.

In order to predict what will happen with King Penguins in the upcoming decades, scientists had to first reconstruct a palaeohabitat of the species’ demography, based on old climatic records and genome information. This allowed them to understand the primary causes of population changes.

They found out that massive changes in the ocean’s primary productivity caused large population changes in the past for penguins. Therefore, prey availability would be the most important limiting factor for the King Penguin’s distribution in the future.

If the worst scenario of climate change occurs, many big colonies will witness dramatic declines in numbers, because the distance to their foraging grounds will increase considerably. Most of the colonies negatively impacted are located in the northern range of the species’ distribution. The colonies at the South of the Antarctic Front will probably be the best refugia for King penguins, places such as South Georgia Island. Potentially, there will also be new colonies that could be recolonized.

The low genetic diversity of this species as well as the long time to mature and produce offspring will most likely not allow rapid adaptive evolution in this species. Changes in foraging conditions would be required for penguins to survive. Eventually, the outcome for many individuals could be local extinction or dispersal to new islands (if available).

How does the future look for King Penguins?

The predictions that scientists made for total numbers are dramatic. In the worst scenario, up to 70% of the present breeding pairs of King Penguins could disappear. Moreover, almost 50% of the current world population could lose their habitat, especially those located in the largest and northernmost colonies. Such predictions do not even take into account possible simultaneous changes that could impact penguin prey.

In summary, recent data is providing more and more evidence of our negative impact in the natural world due to climate change. Many species will lose their habitat due to range shifts everywhere, not only King Penguins. It is our responsibility as human beings to work together in this climate crisis and not let our planet drift toward the worst scenario in the upcoming decades. King Penguins will be really thankful.

A King Penguin feeding its chick

Did you know this about King Penguins? What do you think and/or what did you learn by reading this?

Learn more about penguins by reading some of our other blogs:


Cristofari, R., Liu, X., Bonadonna, F., Cherel, Y., Pistorius, P., Le Maho, Y., … & Trucchi, E. (2018). Climate-driven range shifts of the king penguin in a fragmented ecosystem. Nature Climate Change, 8(3), 245.

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