The leopard seal (Hydrurga leptonyx), also referred to as the sea leopard, is the second largest species of seal in the Antarctic (after the southern elephant seal). Its only natural predators are the killer whale. It feeds on a wide range of prey including cephalopods, other pinnipeds, krill, birds and fish. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal and the Weddell seal, which together are known as the tribe of lobodontini seals. The name hydrurga means "water worker" and leptonyx is the Greek for "small clawed".
|Size compared to a 6ft human|
|Hydrurga leptonyx range map|
French zoologist Henri Marie Ducrotay de Blainville described the leopard seal in 1820.
The leopard seal has a distinctively long and muscular body shape, when compared to other seals. This species of seal is known for its massive head and jaws that allow it to be one of the top predators in its environment. A notable key feature of leopard seals is its counter-shaded coat. A counter-shaded coat is when the dorsal side of the coat is darker than ventral side. Leopard seals have a silver to dark gray blended coat that makes up its distinctive "leopard" coloration with a spotted pattern, whereas the ventral side of the coat is paler in color—ranging from white to light gray. Females are slightly larger than the males. The overall length of this seal is 2.4–3.5 m (7.9–11.5 ft) and weight is from 200 to 600 kilograms (440 to 1,320 lb). They are about the same length as the northern walrus, but usually less than half the weight.
Another notable characteristic of leopard seals are their short clear whiskers that are used to sense their environment. Leopard seals have an enormous mouth relative to their body size. The front teeth are sharp like those of other carnivores, but their molars lock together in a way that allows them to sieve krill from the water, in the manner of the crabeater seal. Since leopard seals are "true" seals, they do not have external pinnae, but they do have an internal ear canal that leads to an external opening. Their hearing in air is similar to that of a human, but scientists have noted that leopard seals use their ears in conjunction with their whiskers to track prey under water.
Leopard seals are pagophilic, "ice-loving" seals, which primarily inhabit the Antarctic pack ice between 50˚S and 80˚S. Sightings of vagrant leopard seals have also been recorded on the coasts of Australia, New Zealand, South America, and South Africa. In August 2018 an individual was sighted in Geraldton on the west coast of Australia. Higher densities of leopard seals are seen in the Western Antarctic than in other regions. Most leopard seals remain within the pack ice throughout the year and remain solitary during most of their lives with the exception of a mother and her newborn pup. These matrilineal groups can move further north in the austral winter to sub-antarctic islands and the coastlines of the southern continents to provide care for their pups. While solitary animals may appear in areas of lower latitudes, females rarely breed there. Some researchers believe this is due to safety concerns for the pups. Lone male leopard seals hunt other marine mammals and penguins in the packed ice of antarctic waters. The estimated population of this species ranges from 220,000 to 440,000 individuals, which puts leopard seals at "least concern". Although with an abundance of leopard seals in the antarctic, they are difficult to survey by traditional visual techniques because they spend long periods of time vocalizing under the water during the austral spring and summer when visual surveys are carried out. This trait of vocalizing underwater for long periods has made them available to acoustic surveys, allowing researchers to gather most of what is known about them.
Leopard seals are very vocal underwater during the austral summer. The male seals produce loud calls (153 to 177 dB re 1 μPa at 1 m) for many hours each day. While singing the seal hangs upside down and rocks from side to side under the water. Their back is bent, the neck and cranial thoracic region (the chest) is inflated and as they call their chest pulses. The male calls 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. Adult male leopard seals have only a few stylized calls, some are like bird or cricket-like trills yet others are low haunting moans. However, 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 cadence of calls are believed to be a part of a long range acoustic display for territorial purposes, or the attraction of a potential mate. The leopard seals have age-related differences in their calling patterns, just like birds. Where the younger male seals have many different types of variable calls – the adult male seals have only a few, highly stylized calls. Each male leopard seal produces these individual calls, and can arrange their few call types into individually distinctive sequences (or songs). The acoustic behavior of the leopard seal is believed to be linked to their breeding behaviour. In male seals, vocalizing coincides with the timing of their breeding season, which falls between November and the first week of January; captive female seals vocalize when they have elevated reproductive hormones. Conversely, a female leopard seal can attribute calls to their environment as well; however, usually it is to gain the attention of a pup, after getting back from a forage for food.
Since leopard seals live in an area difficult for humans to survive in, not much is known on their reproduction and breeding habits. However, it is known that their breeding system is polygynous, meaning that males mate with multiple females during the mating period. A sexually active female (ages 3–7) can give birth to a single pup during the summer on the floating ice floes of the Antarctic pack ice, with a sexually active male (ages 6–7). Mating occurs from December to January, shortly after the pups are weaned when the female seal is in estrus. In preparation for the pups, the females dig a circular hole in the ice as a home for the pup. A newborn pup weighs around 66 pounds and are usually with their mother for a month, before they are weaned off. The male leopard seal does not participate in taking care of the pup, and goes back to its solitary lifestyle after the breeding season. Most leopard seal breeding is on pack ice.
Five research voyages were made to Antarctica in 1985, 1987 and 1997–1999 to look at leopard seals. They sighted seal pups from the beginning of November to the end of December, and noticed that there was about one pup for every three adults, and they also noticed that most of the adults were staying away from other adults during this season, and when they were seen in groups they showed no sign of interaction. Leopard seal pups mortality rate within the first year is close to 25%.
Vocalization is thought to be important in breeding, since males are much more vocal around this time. Mating takes place in the water, and then the male leaves the female to care for the pup, which the female gives birth to after an average gestation period of 274 days.
Research shows that on average, the aerobic dive limit for juvenile seals is around 7 minutes, which means that during the winter months juvenile leopard seals do not eat krill, which is a major part of older seals' diets, since krill is found deeper during this time. This might occasionally lead to co-operative hunting. Co-operative hunting of leopard seals on Antarctic fur seal pups has been witnessed, which could be a mother helping her older pup, or could also be female-male couple interactions, to increase their hunting productivity.
Its only natural predators are the killer whale and possibly the elephant seal. Its canine teeth are 2.5 cm (1 in). It feeds on a wide variety of creatures. Young leopard seals probably eat mostly krill, squid, and fish. Adult seals probably switch from krill to more substantial prey, including king, adelie, rockhopper, gentoo, emperor, and chinstrap penguins, and less frequently, Weddell, crabeater, Ross, and young southern elephant seals. Leopard seals have also been filmed eating fur seal pups.
Around the sub-Antarctic island of South Georgia, the Antarctic fur seal (Arctocephalus gazella) is the main prey. Other prey include penguins and fish. Antarctic krill (Euphausia superba), southern elephant seal (Mirounga leonina) pups and seabirds other than penguins have also been taken as 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. It kills the swimming bird by grabbing the feet, then shaking the penguin vigorously and beating its body against the surface of the water repeatedly until the penguin is dead. Previous reports stating the leopard seal skins its prey before feeding have been found to be incorrect. Lacking the teeth necessary to slice its prey into manageable pieces, it flails its prey from side to side tearing and ripping it into smaller pieces. Krill meanwhile, is eaten by suction, and strained through the seal's teeth, allowing leopard seals to switch to different feeding styles. Such generalization and adaptations may be responsible for the seal's success in the Antarctic ecosystem.
Leopard seals' heads and front flippers are extremely large in comparison to other phocids. Their large front flippers are used to steer themselves through the water column making them extremely agile while hunting. They use their front flippers similarly to sea lions (otariids) and leopard seal females are larger than males. They are covered in a thick layer of blubber that helps to keep them warm while in the cold temperatures of the Antarctic. This layer of blubber also helps to streamline their body making them more hydrodynamic. This is essential when hunting small prey items such as penguins because speed is necessary. Scientists take blubber thickness, girth, weight, and length measurements of leopard seals to learn about their average weight, health, and population as a whole. These measurements are then used to calculate their energetics which is the amount of energy and food it takes for them to survive as a species. They also have incredible diving capabilities. This information can be obtained by scientists by attaching transmitters to the seals after they are tranquilized on the ice. These devices are called satellite-linked time depth recorders (SLDRs) and time-depth recorders (TDRs). Scientists attach this device usually to the head of the animal and it records depth, bottom time, total dive time, date and time, surface time, haul out time, pitch and roll, and total number of dives. This information is sent to a satellite where scientists from anywhere in the world can collect the data.This is how we are currently learning so much about leopard seals diet and foraging habits. With this information we are able to calculate and better understand their diving physiology. They 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. This is possible by increasing surfactant which coats the alveoli in the lungs for re-inflation. They also have a reinforced trachea to prevent collapse at great depth pressures.
The leopard seal is bold, powerful and curious. In the water, there is a fine line between curiosity and predatory behaviour, and it may 'play' with penguins it does not intend to eat. There are also records of leopard seals attacking divers. Paul Nicklen, a National Geographic magazine photographer, captured pictures of a leopard seal bringing live, injured, and then dead penguins to him, possibly in an attempt to teach the photographer how to hunt.
Leopard seals are top order predators presenting a potential risk to humans. However, attacks on humans are rare. Examples of aggressive behaviour, stalking and attacks have been documented. Notable incidents include:
Leopard seals have shown a predilection for attacking the black, torpedo-shaped pontoons of rigid inflatable boats, necessitating researchers to equip their craft with special protective guards to prevent them from being punctured.
From a conservation standpoint, the only known predators of the leopard seals are killer whales and sharks. Because of their limited subpolar distribution in the Antarctic, they may be at risk as polar ice caps diminish with global warming. In the wild, leopard seals can live up to 26 years old. Leopard seal hunting is regulated by the Antarctic Treaty and the Convention for the Conservation of Antarctic Seals (CCAS).
Acrophoca longirostris, sometimes called the swan-necked seal, is an extinct genus of Late Miocene pinniped. It was thought to have been the ancestor of the modern leopard seal, however it is now thought to be a species of monk seal.Australian National Antarctic Research Expeditions
The Australian National Antarctic Research Expeditions (ANARE ann-AR-ee) is the historical name for the Australian Antarctic Program (AAp) administered for Australia by the Australian Antarctic Division (AAD).Chinstrap penguin
The chinstrap penguin (Pygoscelis antarcticus) is a species of penguin which inhabits a variety of islands and shores in the Southern Pacific and the Antarctic Ocean. Its name derives from the narrow black band under its head which makes it appear as if it were wearing a black helmet, making it easy to identify. Other common names include ringed penguin, bearded penguin, and stonecracker penguin, due to its loud, harsh call.Christine Muller-Schwarze
Christine Muller-Schwarze (also Müller-Schwarze), a German-born psychologist from Utah State University, was the first American scientist to work on the Antarctic mainland.Crabeater seal
The crabeater seal (Lobodon carcinophaga) is a true seal with a circumpolar distribution around the coast of Antarctica. They are medium- to large-sized (over 2 m in length), relatively slender and pale-colored, 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 accessing their prey. They are by far the most abundant seal species in the world. While population estimates are uncertain, there are at least 7 million and possibly as many as 75 million individuals. This success of this species is due to its specialized predation on the abundant Antarctic krill of the Southern Ocean, for which it has uniquely adapted, sieve-like tooth structure. Indeed, 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. Despite its name, crabeater seals do not eat crabs. As well as being an important krill predator, the crabeater seal is an important component of the diet of leopard seals (Hydrurga leptonyx), which consume about 80% of all crabeater pups.Earless seal
The earless seals, phocids or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae . They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae. Seals live in the oceans of both hemispheres and, with the exception of the more tropical monk seals, are mostly confined to polar, subpolar, and temperate climates. The Baikal seal is the only species of exclusively freshwater seal.East Antarctica
East Antarctica, also called Greater Antarctica, constitutes the majority (two-thirds) of the Antarctic continent, lying on the Indian Ocean side of the continent, separated from West Antarctica by the Transantarctic Mountains. It lies almost entirely within the Eastern Hemisphere and its name has been accepted for more than a century. It is generally higher than West Antarctica and includes the Gamburtsev Mountain Range in the centre.
Apart from small areas of the coast, East Antarctica is permanently covered by ice. The only terrestrial plant life is lichens, mosses and algae clinging to rocks, and there are a limited range of invertebrates including nematodes, springtails, mites and midges. The coasts are the breeding ground for various seabirds and penguins, and the leopard seal, Weddell seal, elephant seal, crabeater seal and Ross seal breed on the surrounding pack ice in summer.Hydrurga Rocks
The Hydrurga Rocks (64°8′S 61°37′W) are a group of rocks lying east of Two Hummock Island, in the Palmer Archipelago, Antarctica. They were photographed by the Falkland Islands and Dependencies Aerial Survey Expedition, 1955–57, and were named by the UK Antarctic Place-Names Committee in 1960 after Hydrurga leptonyx, the leopard seal.Janjucetus
Janjucetus is an extinct genus of cetacean, and a basal baleen whale (Mysticeti), from the Late Oligocene around 25 million years ago (mya) off southeast Australia, containing one species J. hunderi. Unlike modern mysticetes, it possessed large teeth for gripping and shredding prey, and lacked baleen, and so was likely to have been a predator that captured large single prey animals rather than filter feeding. However, its teeth may have interlocked, much like those of the modern-day filter feeding crabeater seal (Lobodon carcinophaga), which would have allowed some filter feeding behavior. Its hunting behaviour was probably similar to the modern day leopard seal (Hydrurga leptonyx), probably eating large fish. Like baleen whales, Janjucetus could not echolocate; however, it did have unusually large eyes, and so probably had an acute sense of vision. The only specimen was found on the Jan Juc beach, where the remains of the extinct whales Mammalodon, Prosqualodon, and Waipatia have also been discovered.Leopard (pattern)
A leopard pattern is a spotted color pattern, particularly in the hair coat or skin of animals, but can also describe spotting patterns in plants and fabrics. The term refers to the black and gold spotted coat of the leopard cat, but is used to describe many color combinations that result in spots scattered randomly across the skin or hair coat of other animals.
Examples of animals with coloring patterns termed leopard include many great cats in the genus Panthera, the leopard frog, the "leopard" spotting pattern in the Appaloosa and Knabstrupper breeds of horses, the leopard seal, insects such as the giant leopard moth, and fish species such as the leopard darter, leopard shark, and the leopard eel. Examples of plants that use the term include the leopard lily, and the leopard flower.
The Lp (leopard complex) gene is responsible for the leopard color pattern in horses, which not only produces a spotted coat color but also causes mottling of the skin, a white sclera around the eye, and striped hooves. Horses with the Lp gene may be spotted all over, or may have concentrations of spots in various patterns.Lobodontini
The true seal tribe Lobodontini, collectively known as the lobodontine seals, consist of four species of seals in four genera: the crabeater seal (Lobodon carcinophaga), the leopard seal (Hydrurga leptonyx), the Weddell seal (Leptonychotes weddelli), and the Ross seal (Ommatophoca rossii). All lobodontine seals have circumpolar distributions surrounding Antarctica. They include both the world's most abundant seal (the crabeater seal) and the only predominantly mammal-eating seal (the leopard seal). While the Weddell seal prefers the shore-fast ice, the other species live primarily on and around the off-shore pack ice. Thus, though they are collectively the most abundant group of seals in the world, the combination of remote range and inaccessible habitat make them among the least well studied of the world's seals.Pinniped
Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic marine mammals. They comprise the extant families Odobenidae (whose only living member is the walrus), Otariidae (the eared seals: sea lions and fur seals), and Phocidae (the earless seals, or true seals). There are 33 extant species of pinnipeds, and more than 50 extinct species have been described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage (descended from one ancestral line). Pinnipeds belong to the order Carnivora and their closest living relatives are believed to be bears and the superfamily of musteloids (weasels, raccoons, skunks, and red pandas), having diverged about 50 million years ago.
Seals range in size from the 1 m (3 ft 3 in) and 45 kg (99 lb) Baikal seal to the 5 m (16 ft) and 3,200 kg (7,100 lb) southern elephant seal, which is also the largest member of the order Carnivora. Several species exhibit sexual dimorphism. They have streamlined bodies and four limbs that are modified into flippers. Though not as fast in the water as dolphins, seals are more flexible and agile. Otariids use their front limbs primarily to propel themselves through the water, while phocids and walruses use their hind limbs. Otariids and walruses have hind limbs that can be pulled under the body and used as legs on land. By comparison, terrestrial locomotion by phocids is more cumbersome. Otariids have visible external ears, while phocids and walruses lack these. Pinnipeds have well-developed senses—their eyesight and hearing are adapted for both air and water, and they have an advanced tactile system in their whiskers or vibrissae. Some species are well adapted for diving to great depths. They have a layer of fat, or blubber, under the skin to keep warm in the cold water, and, other than the walrus, all species are covered in fur.
Although pinnipeds are widespread, most species prefer the colder waters of the Northern and Southern Hemispheres. They spend most of their lives in the water, but come ashore to mate, give birth, molt or escape from predators, such as sharks and killer whales. They feed largely on fish and marine invertebrates; but a few, like the leopard seal, feed on large vertebrates, such as penguins and other seals. Walruses are specialized for feeding on bottom-dwelling mollusks. Male pinnipeds typically mate with more than one female (polygyny), although the degree of polygyny varies with the species. The males of land-breeding species tend to mate with a greater number of females than those of ice breeding species. Male pinniped strategies for reproductive success vary between defending females, defending territories that attract females and performing ritual displays or lek mating. Pups are typically born in the spring and summer months and females bear almost all the responsibility for raising them. Mothers of some species fast and nurse their young for a relatively short period of time while others take foraging trips at sea between nursing bouts. Walruses are known to nurse their young while at sea. Seals produce a number of vocalizations, notably the barks of California sea lions, the gong-like calls of walruses and the complex songs of Weddell seals.
The meat, blubber and fur coats of pinnipeds have traditionally been used by indigenous peoples of the Arctic. Seals have been depicted in various cultures worldwide. They are commonly kept in captivity and are even sometimes trained to perform tricks and tasks. Once relentlessly hunted by commercial industries for their products, seals and walruses are now protected by international law. The Japanese sea lion and the Caribbean monk seal have become extinct in the past century, while the Mediterranean monk seal and Hawaiian monk seal are ranked endangered by the International Union for Conservation of Nature. Besides hunting, pinnipeds also face threats from accidental trapping, marine pollution, and conflicts with local people.The NewZealand Story
The NewZealand Story (ニュージーランドストーリー, Nyū Jīrando Sutōrī) is a 1988 arcade game developed and published by Taito. The game's concept and setting were inspired from a holiday trip in New Zealand by one of Taito programmers. The player controls Tiki (ティキ), a kiwi who must save his lover Phee Phee (ピューピュー) and several of his other kiwi chick friends who have been kidnapped by a large blue leopard seal. While avoiding enemies, the player has to navigate a scrolling maze-like level, at the end of which they release one of Tiki's kiwi chick friends trapped in a cage. In 2005, the arcade game received a remake for the Nintendo DS under the title, New Zealand Story Revolution.Tracey Rogers
Tracey Rogers is a marine ecologist at the University of New South Wales who studies how mammals survive changing environments.USS Sea Leopard (SS-483)
USS Sea Leopard (SS-483), a Tench-class submarine, was the only ship of the United States Navy to be named for the leopard seal. Her keel was laid down by the Portsmouth Navy Yard on 7 November 1944. She was launched on 2 March 1945 sponsored by Hon. Margaret Chase Smith, United States Congresswoman from Maine, and commissioned on 11 June 1945 with Commander Robert E. M. Ward in command.
Extant Carnivora species