"True Seals" and Blue-eyed Shags

A Weddell Seal, on of the True Seals, lounging on the ice

In this post, I am going to talk about two completely different types of animals: True Seals and the Blue-eyed Shag. Let's start with Seals.

There are three different types of Pinnipeds in the world: True Seals, Earless Seals and Walruses.

Chart: X.com

The are six different types of Pinniped in Antarctica. Five are True Seals, which I mentioned when talking about Weddell Seals in a previous post. In addition to the Weddell, these include the Leopard, Ross, Southern Elephant and Crabeater. When we visited, we saw only two of the five – Weddell and Crabeater. 

Antarctica's Seals; Chart: Redbubble

I heard that some people saw a Southern Elephant Seal on one of our excursions, but our Zodiac never found it.

I have seen its cousin, the Northern Elephant Seal, in California

The sixth Antarctic Pinniped is the Antarctic Fur Seal, which  is NOT a True Seal, but rather an Eared Seal more closely related to Sea Lions. I didn't see any Fur Seals, although I have seen them in Africa and in the Pacific Ocean.

Cape Fur Seal, South Africa, and Northern Fur Seal, off the coast of California 

Antarctica has no Walruses. I saw lots of them in Svalbard in 2019.

Atlantic Walrus, Brepollen, Svalbard, Norway

But, before I start waxing poetic about all the other Seals and Sea Lions I have seen, let's get back on track and talk about True Seals in Antarctica.

Also called Earless Seals, Crawling Seals or Phocids, True Seals are, as I said, one of the three main groups of mammals within the Pinnipedia family. They are members of the family Phocidae.

Weddell Seal; Photo: Ship Photographer Sheeren Mroueh

True Seals live in the oceans of both hemispheres and, with the exception of the more tropical Monk Seals, are mostly confined to polar, sub-polar and temperate climates. The Baikal Seal is the only exclusively freshwater species.

They all possess the following traits: ear holes rather than external ears; light tan, silver or gray fur patterned with spots or rings; short front flippers with claws; and fused pelvises with hind flippers bound to the pelvis in such a way that they cannot bring them under their bodies to walk.

Based on my experience, they lie around a lot

True Seals swim by sideways movements of their bodies, using their hind flippers for power and their fore flippers for steering. They are more streamlined than Fur Seals and Sea Lions, with retractable nipples and sex organs.

Since most live in cold waters, they are able to divert blood flow to a layer of blubber underneath the skin to control their temperatures.

Crabeater Seal

True Seals do not communicate by barking. Instead, they slap the water and grunt. 

Let's talk about the ones I saw.

Weddell Seals

Weddell Seals measure about eight to 11.5 feet long and weigh 880 to 1,320 lbs. With a bulky body and short fore flippers relative to their body length, they are among the world’s largest Seals.

That's a big critter

Male and female Weddell seals are generally about the same length, but males weigh less, usually about 1,100 lbs.

The Weddell Seal grows a thin fur coat around its whole body except for small areas around the flippers. 

The descriptions I read said that adults are counter-shaded with bluish-black to dark grey back fur and light grey/silver belly fur. But, many that I saw were shades of brown from a medium rufous to dark sable. In all cases, the color and pattern vary, often fading as the seal ages. 

"Kitty Cat" face

The coat molts around in early summer.

The male tends to have a thicker neck and a broader head and muzzle than the female. 

The Weddell Seal's face has been compared to that of a cat because of its short mouth line, heart-shaped nose and prominent whiskers.

Weddell Seal pups are around half the length of their mother at birth and weigh 55 to 66 lbs. They gain around 4.4 lbs. a day and by six weeks old can weigh around 220 lbs.

I wish we had seen pups; Photo: Earth.com

Adult males often bear scars, most of them around the genital region, and females are often bitten during mating. 

Weddell Seals are commonly found on fast ice (ice fastened to land) and gather in small groups around cracks and holes within the ice.

In the winter, they stay in the water to avoid blizzards, with only their heads poking through breathing holes in the ice. 

"A Weddell Seal In A Breathing Hole." Photo: Alasdair Turner

In summer, they are usually observed lying on their sides when on land.

That's all we saw

Weddell Seals dive to forage for food, maintain breathing holes in fast ice and explore to find more ice holes. They have been observed diving as deep as 2,000 feet for up to an hour.

Top predators in the Antarctic, Weddell Seals eat an array of fish, bottom-feeding prawns, cephalopods and crustaceans. Although seabirds are not usually part of their diet, there have been several sightings of them chasing and killing Penguins in the wild.

That Chinstrap Penguin is brave; Photo: Sheeren Mroueh

A sedentary adult eats around 22 lbs. a day, while an active adult eats over 110 lbs. We certainly saw only the sedentary type.

Scientists believe Weddell Seals rely mainly on eyesight to hunt for food when there is light. However, during the Antarctic winter darkness, when there is no light under the ice where they forage, they rely on other senses, primarily the sense of touch from their whiskers, which are not just hairs, but very complicated sense organs with more than 500 nerve endings that attach to the animal's snout. The hairs allow the Seals to detect the wake of swimming fish and use that to capture prey.

The whiskers are critical to the Weddell's survival

Weddells have no natural predators when on fast ice. At sea or on pack ice, they are prey for Orcas and Leopard Seals, which prey primarily on juveniles and pups.

Depending on the latitude it inhabits, this marine mammal gives birth from early September through November, with those living at lower latitudes giving birth earlier. Weddell Seals usually give birth to one pup per year, but they are one of the few species of Seals that can give birth to twins.

Twins are extremely rare; Photo: USGS

Pups take their first swim around one to two weeks of age. During the first two weeks, mother Weddell Seals distinguish their pups through smell and specialized vocalizations and stay in the same spatial area.

After six to seven weeks, pups are weaned and begin to hunt independently. Weddell Seal pups are not born with brown fat, which is used in other seal species for thermoregulation. Instead, they rely heavily on lanugo, a fine layer of hair on the surface of their skin, to keep warm. Studies also revealed high levels of enzyme activity in the muscles of newborn Weddell Seals, suggesting that a primary thermoregulatory strategy of these seals includes shivering.

At the water's edge; Photo: Sheeren Mroueh

Male and female Weddell Seals communicate through a variety of sounds, "talking" with each other through different "media." When on ice, they can hear the calls of other Seals in the water. Sound waves can be transmitted either through the ice itself or from water to breathing holes. 

Some have vocalizations are described as songs, with repetitive sequences of the same vocal elements. They also commonly produce ultrasonic sounds, the function of which is unknown.

Stretching

It is believed that about 202,000 female Weddell Seals live in Antarctica. This is based on high-resolution satellite images from November 2011 that cover the full habitat range of the species. This number includes only females because males are mostly underwater guarding their territories in November. 

There are likely fewer males than females, as the ratio skews towards females with increasing age. Previous estimates, with lower geographic coverage and thus relying more heavily on extrapolations, tended to be much higher, reporting numbers in the range of 800,000 or so.

Most of the ones we saw were alone

During the early periods of Antarctic exploration, Weddell Seals suffered dramatic declines as they were hunted for food and oil. Populations have since recovered after the elimination of commercial sealing in the 1980s. However, the effects of global climate change are still to be fully determined. 

You can see how short the fore flippers are

Their habitat is extremely temperature sensitive thus making them potentially vulnerable. Changes in the duration and extent of the sea ice and nutrient availability could potentially reduce pups' survival and have important implications for population growth rates. The fact that some populations breed on land in South Georgia could demonstrate ability to colonize different environments, but the extent of this flexibility is not known. 

Crabeater Seals

So far, in my previous blogs, I have only talked about seeing Weddell Seals, but we did, indeed, see some Crabeater Seals later. So, I'll cover them here.

Our good Crabeater sighting

The Crabeater Seal, also known as the Krill-eater Seal, is a True seal with a circumpolar distribution around the entire coast of Antarctica.

They are found primarily on the free-floating pack ice that extends seasonally out from the Antarctic coast, which they use as a platform for resting, mating, social aggregation and hunting.

Crabeaters on pack ice; Photo: Roundglass Sustain

Even though we saw less than Weddell Seals, Crabeaters are by far the most abundant Seal in the world, with somewhere between 7 and 75 million (apparently it is very difficult to estimate populations in Antarctica).

Despite its name, the Crabeater Seal does not eat Crabs, but rather the Krill that is so plentiful in Antarctic waters. It has finely lobed teeth adapted to filtering their prey. 

Freaky-looking teeth; Photo: Go-Geeking

Consequently, they don't compete with other Antarctic Seals for food. And, among Krill-feeding Whales, only Blue and Minkes extend their ranges as far south as the pack ice where Crabeater seals are most frequent.

Adult Seals grow to an average length of 7.5 feet. Females are longer and heavier than males, although their weights fluctuate substantially according to season; females can lose up to 50 percent of their body weight while nursing and males lose a significant proportion of weight as they attend to their mating partners and fight off rivals. 

Was this one fighting? Or attacked? Photo: Sheeren Mroueh

During summer, males typically weigh 440 lbs. and females 474 lbs., but they can reach 660 lbs. Pups are about 3.9 feet long and 44 to 66 lbs. at birth. While nursing, pups grow at a rate of about 9.3 lbs. a day and grow to be around 220 lbs. when they are weaned at two or three weeks (no wonder moms lose weight!).

Crabeater seals are covered mostly by brown or silver fur, with darker coloration around flippers. The color fades throughout the year becoming very blonde in the summer. Recently molted seals appear darker. Pups are born with a light brown, downy fur and then molt at weaning. Younger animals are marked by net-like, chocolate-brown markings and flecks on the shoulders, sides and flanks.

The speckling would indicate a young Seal

Their bodies are comparatively more slender than other seals and the snout is pointed. Crabeater seals can raise their heads and arch their backs while on ice and they are able to move quickly in the water (up to 16 mph) if not overheated. While swimming, Crabeaters sometime porpoise (leaping entirely out of the water) and spyhop (raising the body vertically out of the water for visual inspection).

Underwater; Photo: Roundglass Sustain

Crabeater Seals are usually scarred either from Leopard Seal attacks (around the flippers); for males, from fighting with other males during the breeding season (around the throat and jaw); and, for females; from males during mating (also around the throat).

Our guy was bloodied

The most gregarious of the Antarctic Seals, Crabeaters have been observed on the ice in aggregations of up to 1,000 hauled out animals and in swimming groups of several hundred, breathing and diving almost synchronously. 

They sometimes hide from predators below icebergs; Photo: Roundglass Sustain

These aggregations consist primarily of younger animals; adults are more typically encountered alone or in groups of up to three. Crabeater seals give birth from September to December. Rather than aggregate in reproductive rookeries, females haul out on ice to give birth singly.

Young Crabeater Seals experience significant predation by Leopard Seals, with first-year mortality possibly reaching 80 percent. Orcas hunt pups and adults, but generally prefer other, slower Seals.

Waving good-bye

Leopard Seals

The second-largest species of Seal in the Antarctic (after the Southern Elephant Seal), the Leopard Seal is one scary character. The first time I saw one in a movie, I thought it was a bad CGI of a Seal designed to make it look scarier. I mean, it looks like a dinosaur! 

CGI on left is close to real on right: Left photo: 8 Below; Right photo: Animalogic

It has only one natural predator – the Orca. But the Leopard Seal seems to be a threat to practically everything else that lives in Antarctica, particularly Penguins. 

The are Penguins' biggest predator; Photo: The Economist

The Leopard Seal has a distinctively long and muscular body shape when compared to other seals. The overall length is 7.9-11.5 feet and weight is from 440 to 1,320 lbs. Females are slightly larger than males.

Teeth similar to Crabeater teeth; Photo: BBC

They have thick necks; massive jaws; long, sharp front teeth; and lobed molars that lock together to sieve Krill. 

The Leopard Seal's coat is counter-shaded with a silver-to-dark-gray blend, a distinctive spotted "leopard" pattern on the back and a paler, white-to-light-gray color on the belly.

Most Leopard Seals remain within the pack ice throughout the year and are solitary during most of their lives with the exception of a mother and her newborn pup. The estimated population ranges from 220,000 to 440,000.

Just hangin'; Photo: Lindblad Expeditions

During the summer, males produce loud songs or calls for many hours each day. While singing, the Seal hangs upside down and rocks from side to side under the water. It arches its back and inflates its neck and chest. As it sings, the chest pulses. 

Adult male Leopard Seals have only a few stylized calls, some are bird- or cricket-like trills and others are moans. 

Calls are believed to be a part of a long-range acoustic display to protect territory or attract a potential mate.

Males mate with multiple females during the breeding season, which is December and January, shortly after the pups are weaned. In preparation for the pups, the females dig circular holes in the ice as nests of sorts for the babies. A newborn pup weighs around 66 pounds and is usually with its mother for a month. Males don’t participate in pupcare, going back to the solitary life after the breeding season.

Female and pup; Photo: TripAdvisor

Research shows that, on average, the dive limit for juvenile Leopard Seals is around seven minutes, meaning that during the winter, they can’t eat Krill, which live at lower depths in the winter. This might occasionally lead to co-operative hunting larger prey.

When hunting Penguins, the Leopard Seal patrols the waters near the edges of the ice, almost completely submerged, waiting for the birds to enter the ocean. 

In this case, dinner may have come to the Seal; Photo: National Geographic

It kills by grabbing the Penguin’s feet, then shaking the bird vigorously and beating its body against the surface of the water. Yikes!

When we were at Hydrurga Rock (I'll post on it later), we thought we saw a juvenile Leopard Seal. But, it's probably just a young Weddell.

Maybe, but I think not

Blue-eyed Shags

I promised before that I would talk about Blue-eyed Shags. 

Blue-eyed Shag

As I did research for the blog, I solved a mystery that had been puzzling me: several species of Cormorant/Shag are collectively known as Blue-eyed Shags. We saw two: in Argentina, Imperial Cormorants; in the South Shetland Islands and Antarctic Peninsula, Antarctic Shags. 

Top: Imperial Cormorants; Bottom: Antarctic Shag

According to what I read, experts have a hard time determining how many types there are; there may be from eight to 14 species. So maybe I shouldn’t be so embarrassed that I was confused.

Shags and Cormorants are essentially the same kind of bird and the two names resulted from two different species in the UK, one of which was called a Shag and the other a Cormorant. As new species were discovered, the namers just picked one or the other.

Look at that face!

Large aquatic birds, Blue-eyed Shags stand about 30 inches tall and have up to a 49-inch wingspan. 

The namesake "blue eye" is actually blue skin around the eye. The eye is black.

But, even though named for their eyes, their most defining characteristic is a bumpy yellow caruncle on the forehead that looks like it would obscure their vision. 

The head, wings, and outside of the thighs are black and the underparts and central back are white. 

Small nesting colony in Paradise Bay

The bill is hooked and the naked pink webbed feet have large black claws that help with climbing the rocky cliffs they nest on. Males are larger than females and have larger bills.

Juveniles are duller and browner than adults and don't have the caruncle or white patch on their back. 

The wings of this species are extremely strong and are powerful in flight with continuous wingbeats disrupted by some gliding. Flight speed can reach 30 mph.

Flying low over the water

Blue-eyed Shags are found on the Antarctic Peninsula, South Shetland Islands and Elephant Island, but not on the main Antarctic continent.

Resting on a glacier

Although they don’t migrate, colonies may move short distances to find waters that aren't frozen in order to feed. The current population of the Antarctic variety is stable, with an estimated 20,000 individuals worldwide. That low number surprises me. Maybe we saw them all.

A blue-eyed Shag displaying

They mate with only one partner each nesting season, but may change partners between seasons. 

Males attract breeding partners with displays.

Typically, colonies breed on low rocky cliffs near the water. Colonies usually have of 20-40 pairs, but larger colonies of up to 800 pairs have been observed.

Sometimes, they share breeding colonies with other birds, like the Gentoo Penguins here

Both genders build a nest from feathers, seaweed and ocean debris. Materials are then connected with feces and urine. 

Shag mating pairs often steal nesting material from other couples. The final nest shape looks like a cone with the tip cut off, similar to a volcano. Nests are sometimes reused for years.

They keep the nest clean by directing poop over the edge

Blue-eyed Shags lay two to three eggs on average, but up to five have been observed. Both parents incubate the eggs for 28-31 days. Because chicks hatch without a protective down coat, parents must keep them warm for the first few weeks. After about three weeks, the chicks start to fledge. 

Scott took some video at two different rookeries. Watch (and listen!) here.

The chicks are huge

By age four, the offspring will have reached sexual maturity. They have an estimated life expectancy of 15-20 years.

Blue-eyed Shags usually forage alone or in small groups, feeding on fish, crustaceans, octopi, snails, worms, slugs and other invertebrates.

Two Shags resting between dives

On average, the Antarctic Shag dives as deep as 80 feet to feed on fish, sometimes going as far as 200 feet. They ingest smaller fish and invertebrates while underwater and bring larger fish to land to eat.

Parents ingest food and regurgitate it to feed chicks

Shags can't predict how much time is required to dive and capture prey. Once underwater, they look for prey and react based on the situation. If the Shag finds a fish but doesn't have enough oxygen, it will come back up to the surface, take in the largest amount of air possible and dive again to capture the prey.

Taking off

Typically, females consume more invertebrates while the males consume more fish. They are rarely prey for other species, although they there have been a few documented cases of predation by Leopard Seals and Brown Skuas. Many bird species prey on eggs and chicks.

A little wing-drying going on here

Shags can't fly with wet feathers and diving in the water can cause feathers to become waterlogged (fully saturated). 

But, unlike many other Cormorants, Blue-eyed Shags don’t stand with spread wings to dry feathers. Their dense plumage dries quickly and prevents icy waters from hitting the skin.

Unlike their Penguin rookery mates, Shags are known to be quiet. They do vocalize at breeding sites or when vulnerable. When threatened, the male makes an "aaark" call while the female will make a hissing call. During breeding, males honk. 

In my next post, we'll get back to our trip.

Yalour Islands

Trip date: December 30, 2023 - January 12, 2024