Marine Ecology

Leopard seal

Content Cover Image

leopard seal. Source: Dave Mobley/NOAA

The Leopard seal (scientific name: Hydrurga leptonyx) is one of nineteen species of marine mammals in the family of true seals. Together with the families of eared seals and Walruses, True seals form the group of marine mammals known as pinnipeds.

Leopard seals are the second largest species of true seal), second only to Elephant seals. This species is near the top of the food chain and will attack Crabeater seals, Fur seals and Penguins.

Physical Description

caption Leopard seal. Source: Yan Ropert-Coudert/WoRMS/Encyclopedia of Life
Conservation Status

Scientific Classification

Kingdom: Animalia (Animals)
Phylum:--- Chordata
Class:------ Mammalia (Mammals)
Order:-------- Carnivora (Carnivores)
Family:-------- Phocidae (True Seals)
Genus:--------- Hydrurga
Species:-------- Hydrurga leptonyx (Blainville, 1820)

Adult Leopard seals reach 2.4 -3.4 meters in length, with females being characteristically slightly larger than males. The body is massive but streamlined, with a very large head and long broad foreflippers.

Leopard seals swim with long, powerful, simultaneous strokes of the forelimbs, unlike most other phocids which propel themselves by means of side-to-side strokes of the hindlimbs. Colouration is dark above giving way to silvery pale on the sides and below, with varying degrees of spotting.

In addition to having well developed canines, the cheek teeth of the leopard seal consist of three tubercles or lobes, similar to those of the crabeater seal, Lobodon carcinophagus. These complex teeth allow the leopard seal to filter krill from the water.

Reproduction

Males are thought to be serially polygynous. Male leopard seals reach sexual maturity around their fourth year, females in their third. Mating occurs in the water from November to February. Gestation lasts around 11 months, but implantation seems to be delayed for about two months. Parturition occurs from September to January, with the concentration of births in October and November.

The female gives birth to a single pup weighing about 30 kg and about 160 cm long. Lactation can persist for up to four weeks. The pup's coat is soft and thick, dark grey above with a dorsal stripe, pale on the sides and with black spots below. Males do not seem to participate in parental care.

Behavior

The leopard seal is primarily a solitary species. Individuals of different age groups are often segregated in separate areas. Mature animals normally occur on the outer fringes of the pack ice. Young animal disperse to sub-Antarctic islands during the winter, and it is debated whether or not these movements are migrations or periodic dispersals due to intraspecific competition.

Leopard seals are capable of producing a variety of vocalizations, which have been correlated with different body movements and postures. The vocalizations have been associated with intraspecific agression, female receptivity, and males searching for mates.

caption Distribution of Leopard seal. Source: Mikko Thiessen

 

Distribution

Leopard seals are most common in the polar and subpolar waters of the Southern Hemisphere, along the coast of Antarctica and on most sub-Antarctic islands. Some individuals can be found on the coasts of South Africa, southern Australia, Tasmania, New Zealand, Lord Howe Island, the Cook Islands, Tierra del Fuego, and the Atlantic coast of South America.

Habitat

Leopard seals are most common in Antarctic and sub-Antarctic waters, along the outer edges of the pack ice, hauling out on ice and land.

Predators

There are few natural predators of leopard seals. They are top carnivores in Antarctic ecosystems. However, the Leopard seal may occasionally be taken by orcas (Orca orcinus) or large sharks.

Food Habits

The diet of the leopard seal is quite variable, and it is the only pinniped in which warm blooded vertebrates make up a large portion of the diet. Crabeater seals and fur seals (in the genus Arctocephalus) often bear scars from leopard seal attacks. Prey has been estimated at 45 percent krill, 35 percent seals, 10 percent Sphenisciformes, and 10 percent fish and cephalopods, but proportions will vary along with age, seasonal abundance of food, and location. A Leopard seal will often patrol in the near shore coastal waters waiting for young Gentoo penguins to enter the Antarctic waters for the first time; in many cases, the young Gentoo will be taken within minutes after its first entry into these sea waters. Leopard seals have also been known to scavenge the carrion of whales and other seals.

Conservation Status

Leopard seal populations are abundant in preferred habitat, and the species is not directly exploited by man, other than some taking for scientific research. Leopard seals, especially young, seasonally depend on krill, but are less competitive than other krill-feeding species.Leopard seals could, therefore, be one of the first species adversely affected by commercial krill fisheries. The species is currently rated as Lower Risk/Least Concern by the International Union for the Conservation of Nature.

Further Reading

  1. Hydrurga leptonyx (Blainville, 1820) Encyclopedia of Life (accessed May 9, 2010)
  2. Leopard seal, Seal Conservation Society (accessed May 10, 2010)
  3. Hydrurga leptonyx, IUCN Red List of Threatened Species (accessed May 10, 2010)
  4. The Pinnipeds: Seals, Sea Lions, and Walruses, Marianne Riedman, University of California Press, 1991 ISBN: 0520064984
  5. Encyclopedia of Marine Mammals, Bernd Wursig, Academic Press, 2002 ISBN: 0125513402
  6. Marine Mammal Research: Conservation beyond Crisis, edited by John E. Reynolds III, William F. Perrin, Randall R. Reeves, Suzanne Montgomery and Timothy J. Ragen, Johns Hopkins University Press, 2005 ISBN: 0801882559
  7. Walker's Mammals of the World, Ronald M. Nowak, Johns Hopkins University Press, 1999 ISBN: 0801857899
  8. Leopard seal, MarineBio.org (accessed May 10, 2010)

 

Glossary

Citation

Saundry, P. (2011). Leopard seal. Retrieved from http://www.eoearth.org/view/article/154220

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