The leopard seal (Hydrurga leptonyx), also referred to as the sea leopard, is the second largest species of seal in the Antarctic. It is only smaller than the southern elephant seal, and is the only member of the genus Hydrurga. Together with the Ross seal, the crabeater seal and the Weddell seal, it forms the tribe of Lobodontini seals.
The leopard seal was first described by French zoologist Henri Marie Ducrotay de Blainville in 1820. The name of the seal’s genus, hydrurga, means “water worker” and leptonyx in its scientific name is the Greek for “thin-clawed”.
This seal eats a wide range of prey including cephalopods, other seals, sharks, krill, birds and fish. Its only predator is the killer whale. The leopard seal is a solitary animal throughout most of its life, and is known for being quite aggressive. They are very vocal animals, and can “sing” underwater which helps them to find a mate during the breeding season.
Leopard seals are listed as Least Concern on the IUCN Red List. Their estimated population ranges from 220,000 to 440,000 individuals. Because their only predator is the killer whale, it is thought that their biggest threat is global warming.
Leopard Seal Characteristics
Leopard seals are the second species of seal in the Antarctic. Females are larger than males, growing up to 3.8 meters in length and weighing around 500 kg. Males can grow up to 3 meters in length and weigh approximately 300 kg.
The leopard seal is known for its long and slender body, which is very muscular, that helps it to move through the sea with ease. They have very large front flippers that are used to steer themselves through the water column, making them hydrodynamic. They are also covered in a thick layer of blubber that helps to keep them warm while in the cold temperatures of the sea. This layer of blubber also helps to streamline their body making them more agile while hunting.
They have a dark grey back, a silvery grey underside, and dark and light spots throughout the entire body, which is what gives them the name of leopard seal.
These seals have a long snout with a large head, which is well-designed for catching and handling prey. They have very large jaws with sharp front teeth. Their back teeth, molars, lock together in a way that allows them to sieve krill from the water. They also have short and clear whiskers.
Leopard seals, like “true” seals, do not have external ears or pinnae, but possess an internal ear canal that leads to an external opening. It is thought that their hearing is similar to humans in air, but can also be used underwater to help them track their prey.
Leopard Seal Lifespan
In the wild, leopard seals have a relatively long lifespan considering the conditions they live in, and can live up to 26 years old.
Leopard Seal Diet
The leopard seal eats a variety of different foods. While younger leopard seals eat mostly krill, squid and fish, with krill often making up 45% of their diet, adult leopard seals eat various penguin species and seal species.
Leopard seals eat krill by suction, straining them through their grooved teeth. However, when hunting penguins, these seals do not possess the right teeth necessary to slice their prey into manageable pieces. To get around this, they flail the prey from side to side until it tears and rips into smaller pieces. These two different methods of eating prey show how adaptable the leopard seal is to their environment, and shows how they likely survive so long in the harsh waters.
When hunting penguins, the seals swim around the waters near the edges of the ice, almost completely submerged, waiting for the penguins to enter the water. It grabs the penguins by its feet, and then vigorously shakes and beats the penguin against the surface of the water repeatedly until the penguin is dead.
Leopard seals are primarily shallow divers but they do dive deeper than 80 meters in search for food. They are able to complete these dives by collapsing their lungs and re-inflating them at the surface.
Leopard Seal Behavior
Leopard seals are primarily solitary creatures, except during mating and nursing. Outside of these times, where they spend more time on the ice, they spend the majority of their time in the water. They use their large fore flippers to help propel themselves through the water at speeds of up to 40 kph (25 mph).
While the ends of a leopard seal’s mouth are permanently curled upward, creating the illusion of a smile, leopard seals are actually known for being quite aggressive. They have even been known to kill humans.
Young penguins seals can often play with their food. They may seek out penguins or young seals, and, as the penguin or seal swims to the shore, the leopard seal will cut them off and chase them back into the water. They may do this over and over again until the penguin successfully makes it to shore or succumbs to exhaustion. Scientists do not know the reason for the leopard seals doing this, especially as they may not even eat the animal, but it is thought this might be so the young seals can sharpen their hunting skills.
Vocalization are also thought to be important in leopard seal breeding, since males are much more vocal around this time. Around the austral summer, males produce loud calls (153 to 177 dB re 1 μPa at 1 m) for many hours each day. They hang upside down and rock from side to side under the water while singing. Their singing can be split into two categories: vocalizing and silencing, in which vocalizing is when they are making noises underwater, and silencing noted as the breathing period at the air surface.
Scientists have identified five distinctive sounds that male leopard seals make, which include: the high double trill, medium single trill, low descending trill, low double trill, and a hoot with a single low trill. These are thought to be for both territorial and breeding purposes.
Females will often use vocal calls to signal to their young, particularly if they have just got back from a forage for food.
Leopard Seal Reproduction
Little is known about leopard seal reproduction, because they live in areas in which humans do not reside. Leopard seals are polygynous, meaning that males mate with multiple females during the mating period. The mating period usually takes place from December to January, shortly after the pups from the previous season are weaned when the female seal is in estrus.
Mating takes place in the water. After breeding takes place, the implantation of the fertilized egg can be delayed by up to three months, ensuring the pup will be born in the spring or early summer when it is more likely to survive. This process is known as delayed implantation or embryonic diapause, and it is common in seal species. The gestation period is usually around 274 days.
Pups are born on ice floes and kept in small snow holes that the female leopard seals dig out during their pregnancy. Here the mother nurses the pup and eventually teaches it how to hunt in the water.
Leopard seal pups weigh around 66 pounds at birth and are usually weaned from their mother at around 6 months old. The male plays no part in raising the young.
Female leopard seals reach sexual maturity before males, between the age of three and seven, while males reach sexual maturity between six and seven. Females usually produce one pup per year.
Leopard Seal Location and Habitat
Leopard seals are predominately found in the circumpolar region of the Antarctic ice pack, between 50˚S and 80˚S. They are pagophilic (“ice-loving”) and most leopard seals remain within the pack ice throughout the year. They may also be seen on the subantarctic islands if there is enough ice substrate.
Matrilineal groups made up of mothers and pups often move further north in the austral winter to sub-antarctic islands and the coastlines of the southern continents to provide care for their pups.
Leopard seals are seen much more often in the water than they are on land. Their prey is often in the surface waters of the ocean, so this is primarily where they reside.
Leopard Seal Conservation Status
Leopard seals are listed as Least Concern on the IUCN Red List. Their population is thought to be between 220,000 and 440,000 individuals and, because they are an apex predator, they are nor really threatened in their environment. The biggest threat to these animals is climate change and global warming, and changes to their habitat as a result of this.
Leopard Seal Predators
Leopard seals are apex predators, meaning they are at the top of the food chain. The only predator they have is the killer whale, although very few leopard seals are actually eaten by these whales.
Leopard Seal Importance
As an apex predator, the leopard seal is very important to its ecosystem. It helps to keep populations of other animals in check by feeding on them.
Tribe Of Lobodontini Seals
Alongside the leopard seal, the other members of the true seal tribe Lobodontini, known collectively as the antarctic seals or lobodontin seals, are the Ross seal, the crabeater seal and the Weddell seal.
The Ross Seal
The Ross seal (Ommatophoca rossii) is the only species of the genus Ommatophoca and is the smallest, least abundant and least well known of the Antarctic pinnipeds. It is characterized by its disproportionately large eyes which can measure up to 7 cm in diameter, which is where it gets its name from.
Ross seals are brachycephalic, as they have a short broad muzzle and have the shortest fur of any other seal. They reach a length of about 1.68 to 2.09 m (5.5 to 6.9 ft) and weight of 129 to 216 kg (284 to 476 lb). They are colored dark-brown in the dorsal area and silvery-white beneath.
They eat primarily squid and fish and are preyed on by killer whales and leopard seals.
The Ross seal is relatively unknown and is considered to be the least common pack ice seal. Its population is estimated to be around 130,000 individuals. It almost never leaves the Antarctic Ocean, with the very rare exception of stray animals found around subantarctic islands.
The Crabeater Seal
The crabeater seal (Lobodon carcinophaga), also known as the krill-eater seal, is the most abundant seal species in the world. They are estimated to be as many as 75 million individuals in Antarctica.
Its scientific name translated as “lobe-toothed (lobodon) crab eater (carcinophaga)”, refers specifically to the finely lobed teeth adapted to filtering their small crustacean prey, which is thought to be the reason for their success and abundance in their environment. Despite their name, crabeater seals do not eat crabs. They are preyed on by leopard seals.
Crabeater seals measure an average length of 2.3 m (7.5 ft) and weigh an average of around 200 kg (440 lb). These seals are covered mostly by brown or silver fur, with darker coloration around their flippers. The color fades throughout the year, and recently molted seals appear darker than the silvery-white crabeater seals that are about to molt. Their bodies are generally more slender than other seals, and their snout is pointed.
Crabeaters are the most gregarious of the Antarctic seals and have been seen in swimming groups of several hundred individuals.
The Weddell Seal
The Weddell seal (Leptonychotes weddellii) measures about 2.5 to 3.5 m (8 ft 2 in to 11 ft 6 in) long and weigh 400 to 600 kg (880 to 1,320 lb) and have a bulky body and short fore flippers relative to their body length. This seal varies from bluish-black to dark gray dorsally and to light gray/silver ventrally, and grows a thin fur coat around its whole body except for small areas around the flippers.
Weddell seals are named when it was discovered in the 1820s during expeditions led by British sealing captain James Weddell to the area of the Southern Ocean now known as the Weddell Sea.
They eat an array of fish, bottom-feeding prawns, cephalopods and crustaceans, and hunt in different parts of the water column depending on prey availability. They have also been known to hunt seals. At sea or on pack ice, they are prey for killer whales and leopard seals, which prey primarily on juveniles and pups.