Southern elephant seals (Mirounga leonina) are the largest of all seals with males reaching 4-5 m in length and 3 500 kg in weight. Females are much smaller at 2-3 m in length and only 500 kg in weight. Southern elephant seals are coloured rusty grey-brown and are covered with thick blubber. Mature males have a large 'trunk', or proboscis which is used to amplify their vocalisations and, together with their bulk, gives rise to their name 'elephant' seal. They often appear cumbersome and indifferent to humans yet, despite their awkwardness, the speed with which they can move their bulk makes them potentially dangerous if harassed.

Southern elephant seals are the deepest diving seal in the world. Females have been recorded diving as deep as 1600m with dive durations of up to two hours.

Southern elephant seals once bred in Tasmania on King Island but were wiped out by the sealing industry. There have been several births of elephant seals recorded in Tasmania. On Maatsuyker Island there have been two recordings of elephant seals giving birth with a pup born in 1977 and one in 1998. Around the coast of mainland Tasmania, there have been four records of females with pups including one at Strahan on the west coast in 1958 when a cow gave birth in the main street; one near St Helens on the east coast in 1977; one in southern Tasmania at Dover in October 2000; and one at Mable Bay, Bruny Island in October 2001.

Their diet consists mainly of squid.

Each year in Tasmania an average of eight elephant seals are reported. The age of the animals visiting our shores varies from  yearling animals (one year old) to animals of 16 or more years of age.

Often people mistake the elephant seal for a sick or shot fur seal. The genital area is unfortunately mistaken by many people for a gun shot wound. Elephant seals have bloody-looking mouths, which is perfectly normal for this species but often alarms people who have not seen the species before.

The closest breeding area of elephant seals is Macquarie Island. Here, there is an estimated population of 86,000 animals. However, the population is declining at a rate of 2.5% per annum.