This is my favoritest one!
The Leopard Seal (Hydrurga leptonyx) can be found all along the coast of Antarctica, and sometimes as far north as the southern coasts of New Zealand, Australia, Tasmania, South America, South Africa, the Cook Islands, Lord Howe Island, and Tierra del Fuego. Like its namesake, the Leopard Seal is a powerful hunter - it is also called the sea leopard. It is the second-largest pinniped in Antarctica (after the southern elephant seal), and the orca is the only hunter in Antarctica more powerful than the Leopard Seal.
Unusually among pinnipeds, adult female Leopard Seals are larger than adult males. Females can grow almost to 12.5 feet (3.8 meters) in total body length, weighing 1,102 pounds (500 kg). Males are slightly smaller, growing to 10.8 feet in length, and weighing 661 pounds (300 kg). Their coats are gray, darker on their backs and lighter on their bellies, with individual patterns of light and dark spots. They have large (1 inch/2.5 cm) canine teeth like other carnivores, but their molars lock together to allow them a very versatile diet.
The diet of Leopard Seals is unique among pinnipeds in that they take the most warm-blooded prey of any other species. This includes different species of penguin (chinstrap, gentoo, emperor, adelie, rockhopper, and king), the pups of other seal species, squid, fish - and, surprisingly, krill. The configuration of their molars allows them to strain krill out of the water, and these tiny crustaceans actually make up the bulk of their diet during the winter, when other food sources can be scarce. They are powerful swimmers, and they use their fore-flippers to propel themselves forward with parallel movements. They are slow and ungainly on land, however.
In general, Leopard Seals are solitary hunters, gathering together in groups only during the mating season which occurs during summer of the Southern Hemisphere, between October and January. Leopard Seals are not very vocal, but females and males will call to each other during mating. Female Leopard Seals will nurse their pups for about a month, often digging a hole in the ice floes and protecting the pups until they are weaned. Not much is known about the seasonal movement of Leopard Seals, except that the more mature individuals tend to spend most of their time on the ice floes and in the Antarctic waters, while it is the juveniles that venture further north into the sub-Antarctic.
Leopard Seals are among the most dangerous to humans of all pinniped species, and there have been several recorded attacks on humans, including one fatality. They are territorial animals and will often stalk intruders. However, they have been observed engaging in unusual interactive behavior with divers as well, as was the case in 2006 when Paul Nicklen was offered a series of gifts of food by a Leopard Seal, possibly in an attempt to teach him how to hunt. Leopard Seals are considered to be a species of Least Concern by the IUCN, but as with other animals whose habitat include the arctic climate of the poles, they may be affected by the increasing effects of climate change.
Source for all images used in this post.