The leopard seal (Hydrurga leptonyx), also referred to as the sea leopard, is a long and muscular seal native to the Southern Ocean of Antarctica and southern Patagonia. It is the second largest species of seal in the Antarctic (after the southern elephant seal). It is the same length as, but half the weight of, a walrus. Its fur coat is countershaded, being silver on the bottom and dark gray on the top, and is distinctive for its leopard-like pattern of dark spots. The leopard seal is an apex predator, with massive jaws, and teeth which are 2.5 cm (1 in) long. It feeds on a wide range of prey including its fellow pinnipeds, cephalopods, krill, fish, and birds, particularly penguins. Its only natural predator is the orca. It uses its hearing and whiskers to track prey underwater. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal, and the Weddell seal, which are all Antarctic seals of the tribe Lobodontini.
Research history and taxonomy Henri Marie Ducrotay de Blainville, a French zoologist, described the leopard seal in 1820 from a stuffed specimen from the collection of one M. Hauville, in Le Havre. The skin that produced this work of taxidermy was sourced from "the southern seas", that he ascertained to be from around the Falkland Islands. Blainville describes the specimen as "beautiful", 7-8 pieds long (7–8 ft (2.1–2.4 meters) long) and elongated, the form and features of the head resembling the "phoque moine" or monk seal, with a small number of whiskers short and simple in shape. Blainville was not able to find the ear opening. The "anterior" limbs are falciform, consisting of five fingers which decrease in size from the first to the fifth, tipped with very small claws, with that of the thumb not being "terminal". The hindlimbs are very distal (far back) and close to the short tail; these also consist of five digits, though in contrast to the forelimb, the middle toe is the shortest, with the rear flippers forming a "swallowtail". The skin he examined was described as yellow-white with a brownish dorsum; this is evidently a result of the skin discoloring, as taxidermies degrade over time. He thought that this new species, Phoca leptonyx, must correspond to the animal that "navigators of austral seas" named the "sea calf". Blainville found it comparable to a specimen he refers to as the "third skull" he examined and described in the same work, possessing the same number and shape of the incisors. This skull, unlabeled and thus of unknown locality, was noted as fresher and more bleached than the second skull he examined, being 10-12 pouces long. At first glance, he found that the skull had significant resemblance to the skull of the "phoque commun" or common seal, moreso than the previous two; though this skull was of bigger dimensions, was not as flattened nor narrowed post-orbitally, and notably had a well developed sagittal crest and enlarged nasal fossae. The robust molars of this skull possesses two roots and three cusps, pointed and prominent with the central cusp being the tallest. Five molars were present on each side of the jawbone, after the robust canines, and the two incisors, the outer pair of incisors resembling the shape of the canines. The genus Hydrurga was erected by Johannes von Nepomuk Franz Xaver Gistel in 1848.
Description
The leopard seal has a distinctively long and muscular body shape when compared to other seals. The overall length of adults is 2.4–3.5 m (7.9–11.5 ft) and their weight is in the range 200 to 600 kilograms (440 to 1,320 lb), making them the same length as the northern walrus but usually less than half the weight. They are covered in a thick layer of blubber that helps to keep them warm while in the cold temperatures of the Antarctic. This blubber also helps to streamline their body making them more hydrodynamic, and thus able to hunt down swift prey. A seal's body condition can be ascertained through blubber thickness, along with general girth, weight, and length measurements. The leopard seal is sexually dimorphic, with females being up to 50% larger. In the wild, leopard seals can live up to 26 years. It is perhaps best known for its massive jaws, which allow it to be one of the top predators in its environment. The seal's canine teeth are up to 2.5 cm (1 in) long. These and the incisor 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. This characteristic is shared with the other species in the tribe Lobodontini such as the crabeater seal, and is the trait that gives the tribe its name.
As "true" seals of the family Phocidae, they do not have external ears or pinnae, but possess 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. The whiskers are short and clear. Their 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 (family Otariidae) The pelage is counter-shaded; consisting mainly of a blend of silver and dark-gray, with a distinctive spotted leopard-like pattern on the dorsum, and a white to light gray color ventrally.
Distribution
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