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Article Evaluations

• Article topic: Leopard Seals
  • This article did a good job outlining the basic characteristics of Leopard seals
  • However, certain sections are lacking information, or are shorter than previous sections (ex. Description section)
  • Also, there are some minor spelling errors, and lack of resources (could use more research and published scientific literature)
  • There is also a lack of their feeding and mating habits mentioned in this article
  • It just kind of seems "half done" in the sense of some of the information provided in the article
  • There could be improvements made to this article by including: a section on future scientific discoveries/research being done on Leopard seals, a section on their diet/feeding patterns, more information included in the Life History Section and Description section, and add some more reputable sources to the article

Article:

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). The leopard seal is classified within the kingdom Animalia, phylum Chordata, class Mammalia, order Carivora, suborder Pinnipedia, family Phocidae, and genus Hydrurga, which evolved from either bears or musteloids. Its closest relatives are the Ross seal, crabeater seal and the Weddell seal, which together are known as the tribe of lobodontini seals. Leopard seals share homologous features with the other lobodontine seals; the pups are born with a gray, brown, or grayish-brown pelage. It is in the tribe of Lobodontini seals, and is the only species in the genus Hydrurga. The name hydrurga means "water worker" and leptonyx is the Greek for "small clawed". It is second only to the killer whale among Antarctica's top predators.

Characteristics:

he 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 are their counter-shaded coats. A counter-shaded coat is when the dorsal side of the coat is darker, than ventral side. So, in leopard seals they have a silver to dark gray blended coat that make up its distinctive "leopard" coloration that make a spotted pattern. Whereas, the ventral side of the coat are 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 vibrissae that are used for sensory input of their environment. Since, leopard seals have an enormous gape relative to their body size- scientists have a clear understanding of their dentition. The front teeth are sharp like those of other carnivores, but its 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, however, they do have an internal ear canal that leads to an external opening. Their hearing in air is similar to that of a human, however; scientists have noted that the leopard seals external pinnae in conjunction with their vibrissae are used to locate, and navigate the hydrodynamic turbulence of tracking prey.

Distribution:

The leopard seal lives in the cold waters surrounding the Antarctic continent; however, some sightings can range as far north as southern coasts of Australia, New Zealand, South America, and South Africa. However, higher densities of leopard seals are seen in the Western Antarctic than in other regions respectively. Most leopard seals remain restricted 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 matrineal 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 think because of safety concerns for the pups. As for the male leopard seals they can be seen hunting alone in the icy antarctic waters along the packed ice on other marine mammals, like penguins. The estimated population of this species ranges from 220,000 to 440,000 individuals, which from a conservation status puts leopard seals at a "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 however has made them available to acoustic surveys, which has allowed researchers to gather most of what is known about this marine animal.

Behavior-

Acoustic Behavior:

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.

Breeding Behavior:

A sexually active female (ages 3-7) can give birth to a single pup during the austral summer on the floating ice flows of the Antarctic pack ice, with a sexually active male (ages 6-7). The mating season is takes place from November to December, where the gestation period is between 9 to 11 months. 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 the care taking of the pup, and goes back to its solitary lifestyle after the breeding season.

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.

Foraging Behavior:

The leopard seal is second only to the killer whale among Antarctica's top predators. 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.

Attacks on Humans:

Leopard seals are potentially highly dangerous towards humans, but attacks are rarely reported. Examples of aggressive behaviour, stalking and attacks have been documented. Notable incidents include:

• A large leopard seal attacked Thomas Orde-Lees (1877–1958), a member of Sir Ernest Shackleton's Imperial Trans-Antarctic Expedition of 1914–1917 when the expedition was camping on the sea ice. The "sea leopard", about 12 ft (3.7 m) long and 1,100 lb (500 kg), chased Orde-Lees on the ice. He was saved only when another member of the expedition, Frank Wild, shot the animal.
• In 1985, Scottish explorer Gareth Wood was bitten twice on the leg when a leopard seal tried to drag him off the ice and into the sea. His companions managed to save him by repeatedly kicking the animal in the head with the spiked crampons on their boots.
• In 2003, a leopard seal dragged snorkeling biologist Kirsty Brown of the British Antarctic Survey nearly 200 ft (61 m) underwater to her death, in what was identified as the first known human fatality from a leopard seal.

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.

Conservation:

From a conservation standpoint, the only known predators of the leopard seals are killer whales and sharks. Based on their sub polar environment in the antarctic, they have a specific niche in which they can survive. So, it is important to researchers that the polar ice caps don't diminish overtime by human involvement, like global warming. In the wild, leopard seals can live up to 26 years old.