Buffet buddies: footage reveals that fierce leopard seals work together when king penguin is on the menu



A wild leopard seal on South Georgia.
James Robbins, Author provided

David Hocking, Monash University; Alistair Evans, Monash University, and James Robbins, Plymouth University

Some people don’t like sharing their food – we all have a friend who gets cranky when you steal a chip from their plate. For wild animals, this makes sense, because any food shared is energy lost that could otherwise have been used to pursue more food.

So it was a big surprise to discover wild leopard seals feeding alongside one another while eating king penguins at South Georgia, a remote island in the southern Atlantic Ocean. On top of this, they may have even been cooperating with each other to eat these enormous seabirds.

Location of the study.
James Robbins

We report this fascinating observation in a new study published today in the journal Polar Biology.

Can’t we just all get along?

Leopard seals have a ferocious reputation as one of the top predators in the Antarctic ecosystem. They are infamously the “principal enemy of the penguin”, as immortalised in the film Happy Feet.




Read more:
When mammals took to water they needed a few tricks to eat their underwater prey


But when they eat penguins, leopard seals are normally highly territorial, scaring off rivals by lunging at them with a fearsome set of teeth. Animal-mounted cameras have even revealed that leopard seals ambush each other to steal captured prey.

But that’s not what was seen when the film crew working on the Netflix documentary series Our Planet visited South Georgia. Instead, they were astonished to find wild leopard seals floating alongside one another dining together on a king penguin carcass, taking it in turns to tear off pieces of food.

Too costly to fight

Given how aggressive leopard seals normally are around food, why were these seals behaving so out of character?

Consider this: if you were at an all-you-can-eat buffet and a stranger sat at your table and began eating your food, would you chase them away or let them share with you, knowing you could easily get more afterwards?

When food is very abundant, it may well be cheaper to share than to fight. Penguin colonies offer a near-constant supply of potential prey, attracting scores of predators. In this case, up to 36 leopard seals were seen near the colony at the same time.

So if a seal paused feeding to scare or fight off a rival, there is a good chance a third seal would sneak in and steal the food. In this situation it makes more sense to focus on eating as much as possible, as fast as possible – tolerating some food theft if necessary so as to avoid wasting energy on fighting that would risk losing the prey altogether.

The seals didn’t get along perfectly all the time. We saw some aggression, but perhaps this is to be expected if they are just tolerating each other out of necessity.

Even in our observations, the seals didn’t always get along – note the prey item floating in the water where it could easily be stolen by a third seal.
Dion Poncet

Do leopard seals cooperate to eat large prey?

Another explanation for these unexpected observations is that leopard seals might be cooperating to make it easier to consume such large prey.

Unlike northern seals, leopard seals don’t have clawed paws to help them hold prey. Instead, they have paddle-like flippers with tiny claws, forcing them to vigorously thrash the prey from side to side in their teeth to tear it into pieces small enough to swallow. This energy-intensive eating style is even harder when the prey is large – like adult king penguins.

Unlike northern seals, leopard seals have a paddle-like flipper that lacks the large claws needed to hold and tear food.
James Robbins
Tools of the trade: Leopard seals use their strong front teeth to kill penguins, while the trident-shaped cheek teeth act as a sieve for trapping tiny krill.
David Hocking

Alternatively, if two animals hold the prey between them, one can act as an anchor while the other tears off a chunk of meat. This saves a lot of energy that would otherwise be wasted shaking the prey around.

Group feeding behaviours filmed using a drone, showing two leopard seals dining together on an adult king penguin.
Illustration by Kai Hagberg. Photos by Silverback Films.

This type of cooperative food processing is actually quite common among aquatic top predators, such as killer whales and crocodiles, that can’t easily hold onto food.

The unusual case of the sharing seal

This last possibility made us rethink the interpretation of a famous encounter between a wild leopard seal and National Geographic photographer Paul Nicklen. On entering the water, Nicklen was repeatedly approached by a seal that appeared to be trying to feed him a penguin in an act of unexpected altruism. But perhaps this was not a free gift, but an offer to cooperate.




Read more:
The birdlife of South Georgia is handed another chance


The latest discovery is a great example of how new technology can help researchers make close-hand observations of wild animals. By using a camera drone, the film-makers could fly above the animals without disturbing them, allowing them to observe behaviours that have so far gone unnoticed.

The remoteness of Antarctic ecosystems can make it hard to connect with the wildlife there, but these advances in technology are helping to provide new windows into this icy world. The Conversation

Wild leopard seal lunging at scavenging seabirds off Bird Island, South Georgia.
James Robbins

David Hocking, Postdoctoral fellow, Monash University; Alistair Evans, Associate Professor, Monash University, and James Robbins, Visiting researcher, Plymouth University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Curious Kids: how can penguins stay warm in the freezing cold waters of Antarctica?



Emperor penguins have uniquely adapted to their Antarctic home.
Christopher Michel/flickr, CC BY-SA

Jane Younger, University of Bath

Curious Kids is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.


How can penguins and polar bears stay warm in the freezing cold waters of Antarctica? – Riley, age 8, Clarksville, Tennessee USA.


Thanks for your question, Riley. The first thing I should probably say is that while a lot of people think polar bears and penguins live together, in fact they live at opposite ends of the Earth. Polar bears live in the northern hemisphere and penguins live in the southern hemisphere.

I’m a penguin researcher so I’m going to explain here how penguins can stay warm in Antarctica.

There are four species of penguins that live in Antarctica: emperors, gentoos, chinstraps, and Adélies.

All these penguins have special adaptations to keep them warm, but emperor penguins might be the most extreme birds in the world. These amazing animals dive up to 500 metres
below the surface of the ocean to catch their prey, withstanding crushing pressures and water temperatures as low as -1.8℃.

But their most incredible feat takes place not in the ocean, but on the sea ice above it.

Surviving on the ice

Emperor penguin chicks must hatch in spring so they can be ready to go to sea during the warmest time of year. For this timing to work, emperors gather in large groups on sea ice to begin their breeding in April, lay their eggs in May, and then the males protect the eggs for four months throughout the harsh Antarctic winter.

It’s dark, windy, and cold. Air temperatures regularly fall below -30℃, and occasionally drop to -60℃ during blizzards. These temperatures could easily kill a human in minutes. But emperor penguins endure it, to give their chicks the best start in life.

Emperor penguins have special physical and behavioural adaptations to survive temperatures that could easily kill a human in minutes.
Flickr/Ian Duffy, CC BY

A body ‘too big’ for its head

Emperor penguins have four layers of overlapping feathers that provide excellent protection from wind, and thick layers of fat that trap heat inside the body.

Emperor penguins have a small beak, small flippers, and small legs and feet. This way, less heat can be lost from places furthest from their main body.
Anne Fröhlich/flickr, CC BY-ND

Have you ever noticed that an emperor penguin’s body looks too big for its head and feet? This is another adaptation to keep them warm.

The first place that you feel cold is your hands and feet, because these parts are furthest from your main body and so lose heat easily.

This is the same for penguins, so they have evolved a small beak, small flippers, and small legs and feet, so that less heat can be lost from these areas.

They also have specially arranged veins and arteries in these body parts, which helps recycle their body warmth. For example, in their nasal passages (inside their noses), blood vessels are arranged so they can regain most of the heat that would be lost by breathing.




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Curious Kids: Why do sea otters clap?


Huddle time

Male emperor penguins gather close together in big groups called “huddles” to minimise how much of their body surface is exposed to cold air while they are incubating eggs.

This can cut heat loss in half and keep penguins’ core temperature at about 37℃ even while the air outside the huddle is below -30℃.

The biggest huddles ever observed had about 5,000 penguins! Penguins take turns to be on the outer edge of the huddle, protecting those on the inside from the wind.

Incredibly, during this four-month period of egg incubation the male penguins don’t eat anything and must rely on their existing fat stores. This long fast would be impossible unless they worked together.

The biggest huddles ever observed had about 5,000 penguins!
Flickr/Ars Electronica, CC BY

Changing habitats

Emperor penguins are uniquely adapted to their Antarctic home. As temperatures rise and sea ice disappears, emperors will face new challenges. If it becomes too warm they will get heat-stressed, and if the sea ice vanishes they will have nowhere to breed. Sadly, these incredible animals may face extinction in the future. The best thing we can do for emperor penguins is to take action on climate change now.




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Curious Kids: is water blue or is it just reflecting off the sky?


Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.The Conversation

Jane Younger, Research Fellow, University of Bath

This article is republished from The Conversation under a Creative Commons license. Read the original article.

World’s Largest King Penguin Colony Has Collapsed


The link below is to an article reporting on the collapse of the world’s largest King Penguin population.

For more visit:
https://www.theguardian.com/world/2018/jul/30/worlds-largest-king-penguin-colony-has-declined-by-90

Penguins under threat from drowning in fishing nets



File 20171130 12029 4drhxl.jpg?ixlib=rb 1.1
Bycatch: penguins can easily drown in nets designed to ensnare fish.
NZ Ministry of Fisheries

Ursula Ellenberg, La Trobe University

Fishing nets pose a serious risk to the survival of penguin species, according to a new global review of the toll taken by “bycatch” from commercial fishing. Fourteen of the world’s 18 penguin species have been recorded as fishing bycatch.

Among the species under threat are Tasmania’s little penguins and New Zealand’s yellow-eyed penguins, as detailed in a review, published in the journal Endangered Species Research.

The review shows the level of bycatch is of greatest concern for three species: Humboldt and Magellanic penguins, both found in South America, and the endangered New Zealand yellow-eyed penguins.

On New Zealand’s South Island, yellow-eyed penguins are down to fewer than 250 nests. Previous population strongholds have declined by more than 75%. Conservative population models predict local extinction of yellow-eyed penguins by 2060, if not earlier.


Read more: Shrinking Antarctic glaciers could make Adélie penguins unlikely winners from climate change


Penguins are among the world’s most iconic and loved birds, despite the fact that many people never get to see one in the wild. Indeed, the opportunities to do so are diminishing, with ten of the 18 penguin species threatened with extinction. After albatrosses, penguins are the most threatened group of seabirds. And, like albatrosses, bycatch is thought to be a serious issue for some species.

On land, many penguins are now well protected, thanks to the efforts of conservation researchers, government agencies, community groups and tourism operators. Where many penguins were once vulnerable to attack from introduced predators, or to habitat loss from farming or development, today the biggest worry for many penguin chicks is how to get more food out of their parents.

Time to eat yet?

But below the waves it’s a different story. Over thousands of years, these keen-eyed seabirds have evolved to catch food in the depths, while avoiding natural predators such as seals and sharks. But they cannot see the superfine nylon fishing nets invented in the 1950s which fishers now set in penguin foraging areas.

Little penguins, whose scientific name Eudyptula minor literally means “good little diver”, typically forage in the upper 20 metres of the ocean, with each dive lasting about 90 seconds. The larger yellow-eyed penguin – Megadyptes antipodes, the “big diver of the south” – prefers to hunt on the seafloor some 80-90m down, holding their breath for 2-3 minutes before coming up for air. If they do not encounter a fishing net, that is.

Gillnets (also called set nets) in particular are very dangerous for penguins. These nets are set in a stationary position rather than being dragged through the water. They are designed to catch fish around their gills, but can just as easily snare a penguin around its neck.

If it gets tangled in a net, a penguin will panic and drown in minutes. In Tasmania, nets with more than 50 drowned little penguins have been found washed ashore. Other penguins are found on beaches with characteristic bruising from net entanglement around their necks.

Nets are deadly to little penguins.
Eric Woehler, Author provided

When a penguin is killed at sea, this has knock-on effects back at the nest. The chicks will die of hunger or fledge underweight, with little chance of surviving their first year at sea.

The breeding partner left behind will probably skip a breeding season; some penguins never find another partner after losing their mate. I have seen them calling plaintively from their nest, or even going down to the shore in the evening to look out to sea, before returning to their nest all alone.

Declining numbers

In New Zealand, the endangered yellow-eyed penguin is declining. Current population models predict their extinction on the New Zealand mainland by 2060, or potentially even earlier. Yellow-eyed penguins are facing many threats mostly because they are simply living too close to humans.

Whereas threats on land are reasonably well managed, threats at sea need urgent attention. Marine habitat degradation by industries that damage the seafloor will take decades to recover. Similarly, pressures from climate change will not have a quick enough fix to save yellow-eyed penguins from local extinction.

There is one thing, however, we can change immediately: the needless death of penguins in fishing nets. This will give already struggling penguin populations a bit of a breather and maybe even the resilience required to deal with the many threats they face in their daily fight for survival.


Read more: New behaviour leaves Antarctic penguins on the shelf


Judging by the number of penguins washed ashore with net injuries, many fishers simply discard penguins’ carcasses at sea rather than reporting bycatch or working towards solutions to mitigate it.

Do we really want penguins to drown for our treat of fish and chips? Less destructive fishing methods are available that do not cause penguin bycatch and the death of other protected species.

But these more selective fishing methods would require fishers to change gear, which costs money. Currently, there is very little legal or commercial incentive for fishers to do anything about penguin bycatch.

The ConversationBut there are a couple of things you can do. Please do not just buy any fish with your chips – ask which species it is and how it has been caught. You can use a sustainable seafood guide, such as New Zealand’s Best Fish Guide or Australia’s Sustainable Seafood Guide. That way you can help the penguins snag a safe fish supper of their own.

Ursula Ellenberg, Honorary Lecturer, La Trobe University

This article was originally published on The Conversation. Read the original article.

Shrinking Antarctic glaciers could make Adélie penguins unlikely winners of climate change


Jane Younger, University of Tasmania

Penguin numbers exploded in East Antarctica at the end of the last ice age, according to research published today in BMC Evolutionary Biology. Despite their image as cold-loving creatures, the increase in Adélie penguin numbers seems to be closely linked to shrinking glaciers, raising the possibility the these penguins could be winners from current climate change.

Adélie penguins are one of only two penguin species that live on the Antarctic continent. Their cousins, emperor penguins, may be the movie stars, but it is the Adélies that are the bigger players in the Southern Ocean. They outnumber emperors by more than ten to one, with a population of over 7.5 million breeding adults and counting.

Given the abundance of Adélie penguins and their crucial role in Southern Ocean ecosystems, there has been a great deal of interest in understanding how the species is likely to respond to future climate change.

There are more then 7 million of these guys in Antarctica.
Jane Younger, Author provided

Sensitivity to sea ice

Breeding colonies have been monitored for decades to determine the effects of a changing environment on the penguins. A common finding of many of these studies is that Adélies are highly sensitive to sea ice conditions.

Unlike emperor penguins, Adélies do not nest on the sea ice, but they must cross it to reach their nests on land. As everyone knows, penguins are not the most efficient walkers, and in years with a lot of sea ice their journeys to and from the ocean to feed their chicks can become lengthy. With a longer wait between meals chicks are less likely to survive.

In an extreme case, extensive sea ice at one breeding colony had a devastating impact in 2014, and not a single chick survived.

Based on these observations over years and decades, there has been concern that changing sea ice conditions, including increases in certain parts of Antarctica, could have a serious impact on Adélie penguin numbers in the future.

Short-term vs long-term climate change

However, the climate change that is taking place now is not a decadal trend. Rather, the shrinking glaciers and ice sheets, changing sea ice conditions, and shifting currents and weather patterns represent a global change to a new climate.

We therefore set out to understand how Adélie penguins in East Antarctica were affected by the last big shift to a different climate: the ending of the last ice age.

Following similar methods to our previous study on emperor penguins, we used genetic data to uncover the trend of the Adélie population in East Antarctica over the past 22,000 years.

Researchers have been investigating penguins to see how they might respond to climate change.
Laura Morrissey, Author provided

The end of the ice age

We found that, as for the emperor penguins, Adélies were far less common during the ice age. This is not at all surprising since most of their nesting sites would have been covered with glaciers and their feeding grounds encased in sea ice that never melted.

Following the end of the ice age 20,000 years ago, temperatures increased slowly, and after a few thousand years of warming the glaciers and ice sheets began to shrink. Fast forward to 10,000 years ago and the annual sea ice melting cycle that we see today was established.

Given the sensitivity of Adélie penguins to sea ice changes today, we predicted that Adélie numbers would remain very small until 10,000 years ago when sea ice conditions became similar to what they are now.

However, the penguins surprised us again. We found that the number of Adélies exploded by around 135-fold, but the expansion pre-dated the sea ice change by at least 3000 years.

Penguin numbers exploded at the end of the last ice age.
Jane Younger, Author provided

Shrinking glaciers

The proliferation of Adélie penguins in East Antarctica began during a period of ice sheet and glacier retreat, which would have increased the amount of ice-free ground available for nesting.

A study of Adélie penguins at the Scotia Arc, on the opposite side of the continent, found that numbers in this region rose 17,000 years ago. That expansion was several thousand years before the growth of the East Antarctic population, but coincided with the shrinking of glaciers in the Scotia Arc. This lends further support to our conclusion that it was glacier retreat, rather than changing sea ice conditions, that caused the hike in Adélie penguin numbers after the last ice age.

This is an important finding, as it suggests that the effects of climate change on a species over thousands of years can be quite different to the effects over years or decades. Given the long-term nature of contemporary climate change, we suggest that it is critical to consider millennial-scale trends alongside decadal ecological studies when predicting the effects of climate change on a species.

Could penguins benefit from future climate change?

Glaciers and ice sheets in Antarctica will continue to shrink. As this happens, ground that was previously covered in ice will become suitable for Adélie penguin nesting. In regions with adequate food supplies and where sea ice conditions remain favourable, Adélie penguin numbers may continue to grow.

A recent study using satellite images showed that one breeding colony in the Ross Sea grew by 84% between 1983 and 2010, as a direct result of a glacier shrinking by 543 m and uncovering new nesting sites.

While it seems that East Antarctic Adélie penguins might come out on top as climate change winners, it is important to keep in mind that for penguins to flourish their food supplies must be plentiful enough to meet the demands of a growing population. Whether this will be the case in the future remains to be seen, as Adélie penguin prey species, such as Antarctic krill, are threatened by both climate change and commercial fisheries.

The Conversation

Jane Younger, Postdoctoral research fellow, University of Tasmania

This article was originally published on The Conversation. Read the original article.