How can you tell a male from a female sea lion?
A full-grown, male sea lion (a bull) has brown hair, a blonde mane and can weigh up to 350kg. Females and juveniles are ash grey on top with cream underbellies. A full-grown female will weigh up to 100kg.
How long do they live?
Australian sea lions have a life span of between 17 and 25 years.
Males mature between eight and nine years of age, and females from three years. The long period between birth and reaching maturity is one of the reasons for the slow population growth of the Australian sea lion.
Australian sea lions are quite agile on land, they use their front flippers to prop themselves up. Their back flippers help them to ‘walk’ on land. In the water the back flippers act as a rudder to steer. They are very social animals and when not feeding out at sea, they spend time resting and sunbaking on sandy beaches and rocks.
What do they eat?
The Australian sea lion feeds along the continental shelf, most in depths of 20 – 100m. They feed from the sea floor, catching creatures such as octopus, cuttlefish, small rays, sharks and rock lobster.
Do they eat penguins?
As opportunistic feeders, sea lions have been known to eat seabirds, but they hunt mainly on the sea floor rather than catching surface-dwelling animals such as penguins.
Do they compete with fur seals for food?
No, fur seals and sea lions are not in direct competition for food. Fur seals mostly feed from the middle of the ocean where they take fast moving fish. Sea lions are bottom feeders and eat cuttlefish, mullet and small rays.
Where do they feed?
When feeding, male sea lions will travel up to 100km and females up to 70km from their breeding colony. These trips average about 3 days and in that time a sea lion will dive 900‑1200 times.
Where are Australian sea lions found?
Sea lions are unique to South Australia and Western Australia. Their total population is less than 12 000, with 85 percent in South Australia and the other 15 percent in Western Australia.
Large colonies exist at Dangerous Reef in the Spencer Gulf, Seal Bay on Kangaroo Island and The Pages. There are smaller colonies on the West Coast and in the Great Australian Bight.
In South Australia, there are 39 breeding colonies. Most are very small and some of these are at risk of becoming extinct because each breeding colony is a closed population. Female sea lions practice what is called ‘philopatry’, meaning they return to the same breeding colony throughout their lives, and their pups do the same. Therefore Australian sea lion colonies don’t tend to mix – making each breeding site a closed population.
This makes the Australian sea lion unlikely to expand its range or recolonise breeding sites that have already become extinct.
Breeding and raising their young
During the breeding season, mature bulls fight for access to females. They become aggressive and territorial, defending females from other males.
Timing of the birth of pups is not the same at each colony. Females can fall pregnant from the age of three and gestation time is 17.6 months – the longest of any seal species.
Are their numbers decreasing?
Australian sea lions were hunted heavily during the 19th century for their leather and oil. The population has never returned to its pre-hunting levels.
The colony at Seal Bay is declining, though it still has more than 800 animals. The Pages colony is stable. Dangerous Reef is the only sea lion colony that is increasing in size.
There are regular surveys of sea lion populations. The surveys are invaluable as a comparison between seasons and a barometer of how the populations are faring.
What are the biggest threats to Australian sea lions?
Entanglement in marine debris and fishing gear pose the main threat to sea lions. Up to 80 percent of this debris comes from the land, including rubbish dumped by beach visitors.
Other threats include big sharks (such as great white sharks), being struck by boats, human disturbance, pollution, and overfishing which reduces access to prey.
The major causes of death in sea lion pups are accidental crushing by adults (particularly fighting juvenile males), and deliberate attacks by sub-adult males. It is normal for one third of sea lion pups to die before weaning.
What is the conservation status of the Australian sea lion?
The Australian sea lion is listed as threatened (vulnerable) nationally (Environment Protection and Biodiversity Conservation Act 1999) and in South Australia (National Parks and Wildlife Act 1972).
In Western Australia it is listed as specially protected fauna (Wildlife Conservation – Specially Protected Fauna – Notice 2003)