The Wildlife of South Georgia – Seals

Title image: Oli Prince

South Georgia is home to some incredible wildlife. Join us for this mini-series as Rachel Davies, volunteer writer, introduces us to some of the animals that call South Georgia home. In this first instalment, we will be focusing on the different seals that frequent the island –  some calling it home, some coming to feed, and others returning each year to give birth. 

Southern Elephant Seal, Mirounga leonina

Two main species of seal breed in large numbers on South Georgia. The largest being the southern elephant seal, which is actually the largest seal species in the world, with males able to reach a weight of a whopping 4000 kilograms! Males of this species can be readily identified by their large, trunk-like snout, used to amplify their vocalisations, particularly during the breeding season. Females are smaller than males, and they lack the enlarged snout. They can also be told apart from other seal species by the lack of patterning on their coat. Their coat ranges from a yellowish to grey/brown colour, and pups are born almost black. There are over 400,000 southern elephant seals on South Georgia each year.

For much of the year, southern elephant seals spend their time at sea foraging for food, and they will often travel large distances to reach plentiful feeding grounds. When the breeding season begins however, they come ashore. This offers a fantastic opportunity to see large colonies of this fascinating animal.

Bulls (males) kick off the breeding season by arriving on South Georgia in late August to early September when they establish dominance and fight for territories. Pregnant cows (females) arrive from September to November, with pups being born within ten days of their arrival. Pups weigh approximately 45 kilograms at birth and cows will nurse their pups for about three weeks, during which time their weight usually triples. Mating occurs a few days before pups are fully weaned, with each bull mating with numerous females.

The end of the breeding season sees the departure of southern elephant seals from South Georgia, with most leaving by the end of November. Pups leave on average at eight to ten weeks old.

 

Antarctic Fur Seal, Arctocephalus gazella

The other seal species that breeds in large numbers on the island is the Antarctic fur seal. These are the smallest species of seal you are likely to encounter on South Georgia, with males only reaching a maximum of 133 kilograms and females less than a third of this weight. Unlike other species which use blubber to keep warm, this species uses fur. The thick coat is usually darker in males, a dark brown or steel grey, and paler in females, often a lighter grey or brown. Pups have very dark fur. In addition to their small size, thick fur and colouration, this species also has visible ears which help to identify it against other species seen on South Georgia. There are over three million Antarctic fur seals on South Georgia each year- roughly 98% of the global population!

The breeding season starts in October, with bulls fighting for territory. They then spend their days defending their patch until the cows arrive later in the year, typically late November through to January. Cows give birth a few days after their return to small pups, weighing in at a tiny three to seven kilograms. Mating takes place long before weaning, typically only a week after giving birth. Males will again mate with numerous females. The females stick around as pups will suckle for up to four months before being ready to wean. Freshly weaned pups will spend several years feeding and resting on land, until they reach sexual maturity.

 

Weddell Seal, Leptonychotes weddelli

A third species, the Weddell seal, is also known to breed on the island, though in much smaller numbers. This species typically breeds on fast ice – a type of ice that is usually attached to the coast. However, some individuals have been known to live on subantarctic islands and there is a small breeding colony at Larsen Harbour in South Georgia. They are another large seal species, yet there is little size difference between the sexes, unlike the other species mentioned here, where the male is always larger than the female. They have long bodies, with short fore-flippers and a small head, with a short, wide snout. They have no visible ears, and their coat is mottled grey to brown, with a white underbelly.

Although this species usually favours giving birth and weaning on fast ice, the colony found on South Georgia is unique as they favour snow-covered beaches instead. The breeding season takes place between September and November. Pups weigh approximately 30 kilograms and cows will nurse for around 6 weeks, with the pup’s weight quadrupling during this period.

At the end of the breeding season, the seals do not disperse, staying close to their home at South Georgia year-round.

 

Leopard Seal, Hydrurga leptonyx

Most leopard seals will be found around the Antarctic pack ice, hunting and breeding; however, some individuals choose to frequent subantarctic islands. Because of this, the leopard seal can be seen at Bird Island, which is located just off the north-west tip of South Georgia. They are large animals with a long, stream-lined body and they lack of an external ear. Leopard seals can be told apart from other species by their coat, which is spotted with grey, black, and white fur. In fact, their coat is so distinctive that individuals can be identified based on their unique fur patterns!

Although Leopard Seals do not visit the island to breed, they make the most of the feeding opportunities. They have an unusual feeding behaviour as they are the only seal known to regularly hunt warm-blooded prey. They actively hunt penguins and pups from many of the other seal species found around South Georgia.

 

Crabeater Seals, Lobodon carcinophagus

Another visitor to the island is the crabeater seal. Like the leopard seal, most crabeater seals are found around Antarctic pack ice but some will visit subantarctic islands like South Georgia.

Crabeaters are a medium to large sized seal with a long body and a dog-like snout. They are typically a silvery-grey colour, and they often become paler with age. They are often seen with extensive scarring- usually as a result of attacks from predators like leopard seals, and from fighting during the breeding season.

Despite their name, this species does not eat crabs, instead they specialise in eating Antarctic krill – and they have a sieve-like tooth structure for doing this.

Regardless of the time of year you visit, you will always be treated to wonderful wildlife encounters around, and on, the island. In the next blog in the series, we will be looking at the other marine mammals that can be seen around South Georgia.

 

References

• Antarctic and Southern Ocean Coalition. [online] Available at: https://www.asoc.org/.
• BirdLife DataZone [Online]. Available at: https://datazone.birdlife.org/site/factsheet/south-georgia-mainland-islands-islets-and-stacks.
• Burton, R. (2015). The Weddell seals of Larsen Harbour, South Georgia: a unique but apparently declining colony. Polar Record, 51(6), pp.667–671. doi: https://doi.org/10.1017/s0032247414000953.
• Higher Predators – Bird Island – Seal monitoring – British Antarctic Survey [Online]. Available at: https://www.bas.ac.uk/project/higher-predators-long-term-science/higher-predators-bird-island-seal-monitoring/.