Travel – Antarctic on Le Lyrial (Days 8-11)

“Iceberg Alley” is a term used to describe regions where icebergs are frequently encountered due to ocean currents and glacial activity. In the context of the South Shetland Islands, this term refers to the waters surrounding the archipelago, particularly the Antarctic Sound, which separates the tip of the Antarctic Peninsula from Dundee Island. This area is colloquially known as “Iceberg Alley” because of the numerous and often massive icebergs that drift through these waters.

Brown Bluff is a unique location where both Adélie penguins (Pygoscelis adeliae) and Gentoo penguins (Pygoscelis papua) coexist. However, despite sharing the same habitat, they have distinct behaviours, appearances, and interactions.

How to tell them apart?

Adélie penguins are smaller, about 46-71 cm  tall and weighing 3.6-6 kg. The most prominent feature is the white eye ring, and they have a classic black-and-white tuxedo appearance. They have longer tail feathers than gentoos, and are more upright and stiff-legged.

Gentoo Penguins are larger, about 51-90 cm tall, weighing 4.5-8.5 kg. They don’t have a distinctive white eye ring , but have a black head with a wide white stripe extending like a cap from one eye to the other. The have a shorter tail, and are less stiff and waddling more.

When reading around the subject of penguins, you encounter a significant oversimplification in some sources that claim penguins are solitary animals. This often stems from a misunderstanding of their behaviour.

While penguins do spend time alone, especially during foraging trips or molting seasons, the overwhelming majority of species are highly social, colonial birds.

Where does the “Solitary Penguin” myth come from?

• Foraging Behavior: Penguins spend long hours or days at sea alone while hunting, leading to the impression that they prefer solitude.
• Molting Period: When penguins molt, they isolate themselves for 2–4 weeks since they cannot swim and must conserve energy.
• Territorial Disputes: Some species, especially Adélie and Chinstrap penguins, are extremely territorial, leading to frequent aggressive interactions, which might seem like a preference for solitude.
• Misinterpretation of Antarctic Footage: Many documentaries focus on a single penguin navigating ice or facing hardship, reinforcing the lone-survivor narrative.
• Some Species Are Less Social: Unlike Emperor penguins (which form tight huddles), species like the Galápagos or Yellow-eyed penguins are less colonial and often breed in small, scattered groups.

The reality is that penguins are among the most social birds.

Penguins depend on their colonies for:

• Thermoregulation (especially emperor penguins).
• Nesting security (protection in numbers).
• Chick-rearing (parents recognise chicks through vocal calls in massive groups).
• Courtship and lifelong partnerships (many species return to the same mate yearly).

Even when penguins forage alone, they still rely on social structures when they return to land.

Contradictory claims & context

• It’s true that most species of penguins are highly social and form dense colonies.
• Penguins hunt alone and do not interact at sea, but they often leave the colony together and return in waves.
• It’s true that some species of penguins are aggressive and territorial, and don’t cooperative, but they still form massive nesting colonies.
• It is true that some penguins spend months at sea alone, but are entirely dependent on colony life during winter.

Being social, does not mean always being friendly

• Penguins are not solitary, but they are not always cooperative either.
• They form dense colonies, but within those colonies, rivalries and conflicts are common.
• They often forage alone, but some species (e.g., Emperors and Rockhopper penguins) coordinate their hunting efforts.

So do penguins have friends?

Yes! Penguins form strong social bonds:

• Mating Pairs: Many species are monogamous for a season, and some, like Gentoo penguins, reunite with the same mate every year.
• Friendships: Some penguins form long-term bonds with certain individuals, cooperating for protection or preening each other.
• Colony Recognition: Even in massive colonies of thousands, penguins recognize their mate and chick by voice alone.

Some key differences 

Despite sharing the same location, these species have evolved to minimise direct competition by differentiating their habits.

Nesting habits & territory

• Adélie Penguins:
  
  • Prefer flat or gently sloping areas with lots of pebbles for nesting.
  • Highly territorial, and will aggressively defend their nest from intruders.
  • Form tight, dense colonies with high social interaction.
  • ‘Pebble Theft’ they are known for stealing pebbles from each other’s nests, a critical part of their breeding success. 

• Gentoo Penguins:
  
  • Nest slightly higher on rocky outcrops or in areas with less snow accumulation.
  • More spaced out nests compared to Adélies.
  • Less aggressive about nesting materials but still competitive.

Breeding & raising chicks:

• Adélie Penguins:
  
  • Lay two eggs, both parents take turns incubating for ~35 days.
  • Highly synchronized breeding cycles (colonies lay eggs within a short period).
  • Chicks form crèches (nursery groups) for safety.
  • Depart early in the season, as they migrate northward to follow shifting sea ice. 

• Gentoo Penguins:
  
  • Lay two eggs, incubate for 34-37 days.
  • Less synchronised breeding—some pairs breed earlier or later than others.
  • Chicks also form crèches but stay longer in the colony.
  • Non-migratory—stay in the region year-round.

They cohabitation without “getting along”

Adélies and Gentoos live in close proximity but tend to avoid one another. Their interactions are mostly neutral, but tension can arise.

• Why they don’t get along:

  • Competition for Nesting Sites: While Adélies prefer lower areas and gentoos nest higher up, there is some overlap.
  • Different Levels of Aggression: Adélies are more aggressive and will chase Gentoos away if they get too close.
  • Food Rivalry: Both eat krill, squid, and small fish, so competition is inevitable, but Gentoos dive deeper (~200m vs. ~50m for Adélies), which reduces direct food competition.

• Do they ever reproduce together?

  • No, they do not interbreed, they are different species with distinct genetics and breeding behaviours.
  • Even though they sometimes nest in overlapping areas, they recognise their own species through vocal calls, displays, and mating behaviours.
  • No known cases of hybridisation have been observed.

Daily routines & feeding habits

Despite their differences, both species follow structured daily routines.

Adélie Penguins:

• Morning: Depart colony in large groups to feed in coastal waters, targeting krill.
• Midday: Some return to feed chicks, others rest or engage in social behaviors.
• Evening: Return en masse, causing noisy gatherings at the colony.
• Defense: Often chase away intruders, whether they are Adélie neighbours or encroaching gentoo penguins.

Gentoo Penguins:

• Morning: Some leave early, while others linger—less synchronized than Adélies.
• Midday: Take multiple shorter foraging trips; deeper divers than Adélies.
• Evening: Return more gradually rather than in large flocks.
• Defense: More relaxed but still defend their nests from other Gentoos and the occasional Adélie penguin.

Social hierarchy & communication

Penguin communication involves a combination of vocalizations, body movements, and displays, which vary between species and serve different purposes such as mate attraction, territory defense, and chick recognition.

Vocalisations (calls)

Penguins have distinct vocal repertoires, and their calls can generally be grouped into three main types:

• Contact Calls – Used to maintain group cohesion, especially in dense colonies. Example: Adélie penguins emit short, braying calls to stay in touch with their mate or chick.
• Display Calls – Used in courtship, mate recognition, and territory defence. Example: Gentoo penguins perform a trumpeting call, stretching their necks upward while calling loudly to advertise territory or attract a mate.
• Begging Calls – Used by chicks to solicit food from parents. Example: Penguin chicks have distinct, high-pitched calls that allow parents to recognise them in crowded colonies.

Body movements & displays

Penguins rely on physical displays to communicate dominance, courtship readiness, or warnings. Some key movements include:

• Ecstatic Display (Trumpeting) – A courtship or territorial call where the penguin stretches its neck upward, flaps its flippers, and emits a loud call. Seen in Gentoos, Adélies, and Emperor penguins.

• Bowing – A sign of bond strengthening between mates or a submissive gesture. Common in Gentoo and Adélie penguins, where partners bow before each other to reinforce their bond.

• Sideways Gaping & Bill Jabbing -Aggressive display used in territorial disputes. Penguins open their beaks wide, sometimes jabbing at an opponent or intruder.

• Preening & Beak Tapping – Used in pair bonding, where mates preen each other’s feathers or gently tap beaks.

• Stone Presenting (Courtship Ritual) – Gentoo penguins often present a pebble to a potential mate as part of their bonding ritual.

Chick recognition & parental communication

• Penguins nest in noisy colonies, so parents recognize their chicks by unique vocal signatures rather than sight.
• When returning from feeding, parents and chicks engage in a back-and-forth call exchange until they locate each other.

So why do both Adélie and Gentoo penguins nest in close proximity at Brown Bluff?

There are several factors that might explain this:

Limited suitable nesting sites

• Brown Bluff provides ice-free, rocky terrain, which is crucial for both species’ nesting. Since suitable nesting sites in Antarctica are scarce and competition is high, both species may tolerate each other to take advantage of the available space.

Microclimate and protection

• The north-facing cliffs of Brown Bluff offer some shelter from the harsh Antarctic winds, making it a more favorable microhabitat.
• Proximity to cliffs might also offer protection from skuas, which prey on penguin eggs and chicks.

Differences in nesting preferences and timing

• While both species prefer rocky terrain, Gentoo penguins tend to nest slightly higher on slopes, whereas Adélie penguins often nest closer to the shoreline.
• Their breeding seasons overlap but are slightly staggered, which can reduce direct competition.
• Gentoos tend to start breeding a little earlier, giving them a slight advantage in securing preferred spots.

Food availability and colony stability

• Brown Bluff provides good access to the Weddell Sea, where both species can find ample food (krill, fish, and squid).
• Colonies with multiple species can sometimes be more stable in the face of environmental changes—if one species struggles in a given year, the other may still do well, maintaining overall colony viability.

Social tolerance and colony dynamics

• Some penguin species do not always compete aggressively if food is abundant.
• While Adélie’s can be aggressive, Gentoos are known for being more flexible and adaptable, which might allow them to nest near a more territorial species without major conflict.