Friend or foe? Knowing penguin predators. Part I

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 penguins^1,2. 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.

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 penguins^3,4. 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 Islands^6,7. 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.

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

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 (https://creativecommons.org/licenses/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

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Penguins and the Evolution of Technology

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: https://upload.wikimedia.org/wikipedia/commons/4/42/GPS-24_satellite.png, 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

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:

1. https://en.wikipedia.org/wiki/Global_Positioning_System
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.
4. https://theconversation.com/epic-duck-challenge-shows-drones-can-outdo-people-at-surveying-wildlife-90018
5. https://en.wikipedia.org/wiki/Artificial_intelligence
6. https://www.zooniverse.org/projects/penguintom79/penguin-watch/about/research
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.

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Rockhopper Penguins change their minds when it comes to eating

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.

April 2019