With a spotted coat and fearsome reputation, the Leopard Seal (Hydrurga leptonyx) is sometimes referred to as a sea leopard. Though rationale for its scientific name comes from a description of it as a ‘small-clawed’ ‘water worker’. The species is found in Antarctica, all around the subcontinent, and as far north as the sub-Antarctic, with individuals even reaching temperate latitudes on occasion. H. leptonyx are abundant as well as widely distributed, and thus are classed as a Least Concern species. Estimated population size = 35,500.
H. leptonyx are a large true seal (males ♂ up to 3.3 m long/ 450 kg, females ♀ up to 3.8 m/ 600 kg). They have long, slender flippers at the front and back, and are noticeably more lithe and streamlined in body shape than most other phocids. Their long neck, wide, flat head, and powerful, broad muzzle give them an almost reptilian appearance, that is unique amongst the pinniped clade. Sharp, carnivorous teeth are visible with a characteristic mouth gape, while the molars lock together, enabling the seal to sieve seawater for small prey items. The eyes are comparatively small and well apart on either side of the head. Coloration of the coat is dark grey to black on top, with a paler ventral section, and they appear silvery or even bluish when wet. They are invariably spotted, as referred to above, mostly on the undersides and particularly on the front of the muscular neck.
Unlike most other pinnipeds, H. leptonyx is an apex predator in parts of its range. Well known for preying on large birds and mammals such as penguins, smaller seabirds and juveniles of other seal species, they are quite a formidable hunter, doing so in the water, and also known to drag prey from the edge of land into the water. Shaking of the head from side to side breaks the neck of their prize, and they will then consume it in chunks. However, besides this, during seasons where young animals are not available, they will regularly eat fish, squid and krill. Krill in particular are thought to be a very important component during winter months. It is likely juvenile H. leptonyx also stick to smaller prey.
Sexual maturity – males ♂ 4.5-6 years old/ females ♀ 3-4 years old.
H. leptonyx are thought to be promiscuous or polygynous breeders, and solitary the rest of the time. Males do not haul out while the females are birthing, and it is presumed mating takes place underwater. Data on H. leptonyx breeding strategies is limited, but after a probable 9 month gestation period, soft-coated pups are born in a similar colour to the adult, between September and January (austral summer). Pups are thought to suckle for approximately 1 month, and there is evidence that at the end of this period, the pup may accompany the mother to sea in order to be taught to hunt. The adults will moult around January/ February. The lifespan of H. leptonyx is likely around 26 years.