Weddell Seal | Meet Antarctica’s Southernmost Mammal

Leptonychotes weddellii

Weddell seals are the most southerly dwelling mammals on the planet—adapted to life deep within the frozen continent. Named after British sealing captain James Weddell in the 1820s, these seals are built for polar survival. They have a large rotund body with a patchwork of silvery tones, helping them to camouflage in their environment. On first sighting you might even find yourself questioning is that a rock or seal? Until you see their endearing round faces framed with soulful eyes and a permanent smile; making them one the most photogenic pinnipeds in the Antarctic. 

Physical characteristics

Pinnipeds, or seals are classified into two main families, Weddell seals belong to the phocids, also known as true or earless seals. Unlike their Otariidae cousins the eared seals, Weddell seals lack visible ear flaps, and move very differently. Whilst these seals are highly adapted to their semi-aquatic lifestyle, they struggle on land due to their inability to draw their hind flippers underneath their bodies, which prevents them from supporting their weight effectively, making them appear very cumbersome.

Weddell seals exhibit sexual dimorphism, with females being slightly larger than males. In terms of appearance, both sexes share a similar physique, characterized by a streamlined, rotund body that can span up to 1 meter in width. Their striking coloration includes a counter-shaded pattern, darker dorsally and lighter ventrally, with individual variations. Despite their size, they have relatively small heads, large eyes, and a distinctive upturned mouth creating the illusion of a permanent smile. They have a number of sensitive vibrissae (whiskers) that enable them to detect vibrations in the water—an essential adaptation for hunting in near-darkness.

Living so far south, an ice hole is a Weddell seals lifeline, they have unique dentition with canines and incisors that stick out in order to create and maintain their holes in the ice. These ice holes are utilised for breathing, feeding, moulting and also to give birth. 

It can be challenging at times to distinguish Weddell and crabeater seals. Weddell seals are often described as having cat-like features, while crabeater seals are noted for their dog-like appearance with slightly longer snouts. 

• Size: 2.5 – 3.5m 

• Weight: 300-600kg   

• Dive Depth: > 900 meters

• Dive Duration: up to 96 minutes

• Life Expectancy: approx. 25 years

Habitat and distribution

Weddell seals are primarily found in Antarctic waters, ranging from the edge of the fast ice to the boundary of the pack ice. They are the second most abundant true seal species in Antarctica, surpassed only by the crabeater seal. Social by nature, Weddell seals often form colonies and exhibit strong site fidelity. Considered non-migratory, they typically remain close to their home ranges and rarely venture into open, ice-free waters.

A unique exception exists in South Georgia, where a small breeding colony estimated at fewer than 100 individuals, inhabits an ice-free area within Larsen Harbour, at the island's southern end. Isolated from the rest of the species, this population is especially notable as pups here are born on land rather than on ice.

Despite their record for being the most southerly dwelling of all mammals; they have occasionally been sighted far beyond their typical range with appearances recorded in New Zealand and southern Australia. Remarkably, in 2015, a Weddell seal was documented on Trindade Island, Brazil. This remains the northernmost documented sighting of the species to date.

Weaning generally coincides with the austral summer, when sea ice becomes more dynamic and prey availability increases. Following weaning, the mother returns to sea to feed and replenish her blubber reserves. Typically, by January, young seals start their independent lives under the sea ice when they disperse from their natal sites.

Conservation Status

The International Union for Conservation of Nature (IUCN) classifies Weddell seals as 'Least Concern,' due to their large population size and widespread distribution around the Antarctic continent. The current population trend is unknown and was last assessed in 2014 with an estimate of 300,000 mature individuals.

Despite their stable status, Weddell seals face several threats, largely driven by environmental changes and human activities. One significant concern is the impact of fisheries operating in Antarctic waters, particularly those targeting the Antarctic toothfish, a key component of their diet. Overfishing can reduce prey availability; although these fisheries are regulated by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), ensuring sustainability and ecosystem balance, the potential ecological impacts of long-term commercial harvesting remain under close scrutiny and are continually monitored. 

The effects of global climate change on Weddell seals are unknown; increasing temperatures impact the presence and distribution of the Sea ice habitat which will likely cause issues for this southerly dwelling mammal. Given that there is a small population of Weddell seals in South Georgia that breed on land, this indicates the species can colonise different environments, however, the extent of this flexibility is still uncertain.

Where to see them in the wild

The Antarctic Peninsula is an exceptional place to observe these endearing seals. Often seen hauled out on ice floes or resting along the beaches, your chances of spotting these remarkable pinnipeds are high across various locations on the Peninsula, for example Neko Harbour, Cuverville Island, Mikkelsen Harbour, and Paradise Bay.

Areas teeming with icebergs offer an ideal setting for spotting Weddell seals on ice floes. Transiting through the Lemaire Channel is a breath-taking experience, this narrow passage is incredibly picturesque with towering peaks on either side, often like a millpond it can be the perfect place for spotting whale blows too. 

Pleneau Island often referred to as an “Iceberg Graveyard” is at the southern end of the Lemaire Channel, here the currents lead to a traffic jam of icebergs in the shallow waters; creating an extraordinary opportunity to marvel at the myriad of icebergs, while keeping an eye out for Weddell seals in the water and resting on the ice.

Responsible wildlife viewing

At Secret Atlas, minimising our impact on wildlife is a priority; we follow guidelines set by the International Association of Antarctic Tour Operators (IAATO), maintaining a minimum distance of 5m (15ft) from seals on land and in water. This distance may be altered based on the situation, and your expedition guides will provide guidance.

For more on IAATO’s wildlife watching guidelines click here.

Fun facts

• Weddell Seals are extremely efficient divers, storing some of the highest levels of oxygen in their bodies compared to any other pinniped.

• Weddell seals have an impressive vocal repertoire, including trills, buzzes, chirps, trills and more—some of which sound like sci-fi sound effects underwater.

• Weddell seals can slow their heart rate down to just a few beats per minute during deep dives, conserving their oxygen enabling them to stay underwater longer.

• Weddell seals have a nictitating membrane; this third transparent eyelid acts like a shield protecting their eyes while diving in cold, icy waters. 

• Weddell seals can swim at speeds of around 10km per hour.

• Weddell seals are the most studied pinniped species in Antarctic waters.