Hydrurga leptonyx

(Blainville, 1820) - Leopard seal

Distinctive Characteristics

Leopard seals have a sinuous body and massive head and jaws. Because of the shape of the head, they appear almost reptilian. Females grow slightly longer and heavier, but not enough to allow the sexes to be distinguished in the field based on size. The long body is thin overall, thickest through the shoulders and upper chest. There is no trace of a forehead. The head is widest at the eyes, which appear small and set both far apart and well back from the end of the muzzle. The nostrils are on top of the muzzle, just back from the wide rounded end. The lower jaw is massive, wide, and deep, as are the throat and neck. The vibrissae are clear to pale, generally quite short and inconspicuous. Leopard seals have an enormous gape. The very long (almost one-third of the body length) foreflippers are broad and otariid-like. They are completely furred and each digit bears a short terminal claw. The first digit is long and massive, creating a thick strong leading edge.

Leopard seals are basically countershaded. The darker top is silver to dark grey, and it blends along the midsides and neck at about the level of the eyes with the paler undersides, which are light grey. There is a swath of lighter colour on the upper lip. Leopard seals are spotted to varying degrees, usually most noticeably on the sides and belly. Pups have essentially the same markings and proportions as adults, although their coat is softer, longer, and thicker. Dense constellations of spots may occur without any pattern or symmetry. One area where dense clusters of spots normally occurs is around the insertions of the foreflippers.

The dental formula is I 2/2, C 1/1, PC 5/5. The canine teeth are very long (up to 2.5 cm) and sharply pointed. The remaining teeth are complex and multi-lobed, somewhat resembling those of crabeaters.

Can be confused with

When seen well, leopard seals are unmistakable. At a distance, however, they might be confused with crabeater or Weddell seals. Of these, the crabeater is the most likely candidate for confusion. To rule out other species, note the size and shape of the head, overall coloration, and length of the foreflippers.


Adults usually reach 3 m and weigh 270 to 450 kg. Very large females may reach 3.6 m and 500 kg. Pups are born at about 1 to 1.6 m and around 30 to 35 kg.

Geographical Distribution

Leopard seals are widely distributed in the polar and subpolar waters of the Southern Hemisphere, from Antarctica north, and regularly reach warm temperate latitudes as vagrants. They are found throughout the pack ice zone, where their abundance is greatest. They haul-out on ice and land, often preferring ice floes, when available.

Biology and Behaviour

Little is known of breeding behaviour. Pups are born on the ice from September to January, with a peak in November to December.

At sea and on the ice, leopard seals tend to be solitary. They float at the surface, and crane their neck high to view objects of interest. Sounding in this species is commenced either by sinking or rolling forward. Swimming is most often accomplished with long, powerful, coordinated sweeps of the foreflippers, rather than the side-to-side strokes of the hindflippers typical of most phocids. Leopard seals mostly sleep or are otherwise inactive when out of the water, but will move in a serpentine slithering manner across ice, and will toboggan like penguins.

Leopard seals are probably best known for their habits of preying upon penguins. The diet is actually quite varied and changes with seasonal and local abundance of prey. Leopard seals will consume krill, fish, squid, penguins, and young seals, and will occasionally scavenge from carcasses of whales. Most prey is caught in the water.


Leopard seals are only taken in small numbers for scientific research and have never been the target of more than minor commercial activities.

IUCN Status

Insufficiently known.