Leopard Seal

Leopard seals are the second-largest species of seal found in the pack-ice region of the Antarctic and sub-Antarctic. They have dark spots all over their slender gray body, making them resemble their feline namesake. 

They have a strikingly large skull with massive jaws and are earless, like all true seals. They are one of the most formidable predators, responsible for wiping out emperor penguins and other seals from their ecosystem. 

Description

Length: 2.4 to 3.5m (7.9 to 11.5 ft) 

Weight: Male –  Approx. 300 kg (661 lbs)  Female – Approx. 500 kg (1100 lbs)

Body and coloration:

They have a distinctively long and muscular body counter-shaded in a ventrally light and dorsally dark pattern. Also, the dark flecks on their gray coat resemble those of a leopard.

Besides having a disproportionately large skull that lacks external pinnae, these sea creatures also boast long front flippers with edgy claws and unusually sharp pointed molars.

Distribution and Habitat

They spend most of their time in the frigid waters of the Antarctic pack ice, between 50°S and 80°S latitudes. However, during autumn and winter, they disperse northward through the Southern Ocean to sub-Antarctic regions, including Heard and Macquarie Islands and other southern countries like New Zealand. 

Diet

Leopard seals mostly feed on Antarctic krill. They also actively hunt birds like Emperor penguins and warm-blooded mammals like Wedell, Southern Fur, and Crabeater seals.

Behavior

1. Leopard seals primarily lead a solitary life, gathering only around December and January, the ideal season for them to mate and reproduce. Around this time, the males are notably vocal underwater. They use five recognized calls to attract potential mates and assert their territory, which includes the high double trill, medium single trill, low double trill, low descending trill, and a hoot with a single soft trill. 
2. They are experts in hunting penguins. A leopard seal patrols around the edges of the ice with its body completely submerged in water. It patiently waits for a penguin to jump in search of food or to lose its footing and fall. It then quickly grabs its feet and keeps lashing its body against the surface water till the skin peels off. This wild flailing enables them to tear the flesh off their prey since they lack teeth for slicing it.

Lifespan

They can thrive up to an impressive 26 years in their natural habitat.

Reproduction and Life Cycle

The breeding in leopard seals is polygynous, where a single male mates with multiple females in one season. Males attain sexual maturity between 3 and 6 years, while females reach this stage during 2 to 7 years. 

After mating in December and January, the male abandons his partner. It could take several months for an egg to fertilize, and the subsequent delayed implantation ensures that the pups are born when they are more likely to survive. The expectant mother digs a circular hole in the ice, thus building a safe home before the arrival of her baby. 

The females give birth to a single pup on the ice floes, following a gestation period of about 270 days. The pups are generally born around late October and November, weighing about 66 pounds. These newborns have an average body length of 120 cm. Over the next four weeks, the mother tenderly nurses her baby and prepares them for the weaning stage.

Predators

Since leopard seals themselves are apex predators, they are always on top of the Antarctic food chain. However, their only known natural predator is the orca or the killer whale.

Adaptations

1. They have a thick layer of fat under the skin called the ‘blubber,’ which keeps them insulated from frigid Antarctic conditions.
2. The short hair called ‘whiskers’ on their snout helps them sense movements underwater.
3. They have ‘lophodont’ teeth, with transverse ridges on their molars that help them grind their food. These molars are arranged in an interlocking pattern that enables ‘filter-feeding’. As the seals swim, the seawater passes through their teeth, trapping tiny krill in between. 
4. They have very long canines (up to 2.5 cm), enabling a firm grip on prey like large fishes and penguins. 
5. The presence of myoglobin in their blood helps them retain oxygen in their muscles for a longer period, thereby reducing the need to swim to the surface for air. 

Conservation Status

Based on the latest assessment by IUCN (2015), leopard seals have been listed under the ‘Least Concern’ category of the Red Data List, with about 18,000 mature individuals reported in the wild.

However, the gradual melting of pack ice due to global warming seriously threatens their population, potentially leading to the complete loss of their habitat and prey and an eventual breakdown of the Antarctic ecosystem. Hence, they are protected under the Convention for the Conservation of Antarctic Seals (1972) and the Antarctic Treaty.