Leopard seals are very vocal in the breeding season, and their calls tend to be soft and lyrical. Males sing underwater for up to 13 hours a day in the breeding season, from late October to early January, and male leopard seal calls are believed to function in mate attraction. Researchers analysed the songs of 26 individual male leopard seals recorded in the Eastern Antarctic pack ice. The male songs use the same alphabet of five sounds, common across the population, and what makes each male's song different is the order and structure of the sounds, not the sounds themselves. The predictability of leopard seal songs was compared with human nursery rhymes. Leopard seals mate in December and early January, and they are believed to mate in the water.

What a leopard seal eats changes with the season and with how much of each food is nearby. Leopard seals eat penguins, fish and squid, and they also eat the pups of other kinds of seals. Krill is an important food for leopard seals, and they catch most of their food in the water. Penguins are an important part of the diet of some leopard seals in late January and February. Leopard seals are ambush hunters, and they often wait underwater near an ice shelf for penguins entering the water. They are the only members of the seal family that regularly eat other seals, and one leopard seal captured near Sydney had eaten a fully grown platypus. A leopard seal has unusual teeth for straining krill from the water.

Leopard seals live mostly on and around the pack ice of Antarctica, in Antarctic and sub-Antarctic waters, and they usually live alone. Some leopard seals migrate north to Heard Island to feed on penguins and seal pups there, and in winter, young leopard seals from the south visit Macquarie Island, and some travel far north of Antarctica, and sightings include Tasmania. Leopard seals are much more agile in the water than on ice, and they can swim at up to about 40 km/h (25 mph) in short bursts. They haul out, which means they come out of the water, on ice and on land, often preferring ice floes near shore when they are available. A leopard seal has a slender body, and its long front flippers, which are almost one-third of its body length, are designed for speed.

Leopard seal births in the records occur between September and December. A mother leopard seal gives birth to a single pup on the sea ice after a nine month pregnancy, and a female is at least six years old when she does. Pups are usually born on the ice in November and December, and a newborn pup weighs about 30 kilograms or more, and it is nursed for about four weeks, while pups have the same markings and proportions as adults, but a softer, longer and thicker coat. Once weaned, leopard seal pups start hunting krill. Sources differ on when leopard seals mature: females at 3 to 7 years and males at 2 to 6 years in one, males at 3 years and females at 2 in another. Leopard seals may live for 26 years or more.

Words to know

• vocal: making many sounds
• lyrical: like a song
• analysed: studied closely
• alphabet: set of letters