By Kara Hoglund
Geographic Range
Australian sea lions are found on islands offshore of Australia. They range from western Australia to islands in southern Australia. The largest populations are found on Kangaroo Island and Dangerous Reef (near Port Lincoln) in southern Australia. The smallest numbers are found on the west coast of southern Australia and in Western Australia. Some live in Tasmania as well, but these are few in number. They once bred in the Bass Strait, but the entire population was wiped out by the sealing industry. (Tasmania Parks and Wildlife Service, 2000)
Biogeographic Regions:
australian 
(native ); indian ocean (native ); pacific ocean (native ).
Habitat
(98.4 ft)
(131.2 ft)
Australian sea lions are non-migratory , so they live and breed on sandy beaches near their birth site in relatively large colonies. The greatest distance recorded for a tagged animal has been 300km from its birth site (Jefferson, 1993). During times of tumultuous weather, they will often travel inland to seek shelter in dunes and coastal vegetation (Riedman 1990). Unlike many pinnipeds, Australian sea lions are very capable out of the water, and have been found as far as 9.4 km inland (Nowak, 1999). Many have been found at the tops of cliffs as high as 30 meters, as they are also excellent climbers.
In the water, Neophoca cinerea has been seen at depths up to 40 meters (Nowak, 1999). (Jefferson, Leatherwood, and Webber, 1993; Nowak, 1999; Riedman, 1990)
These animals are found in the following types of habitat:
temperate ; terrestrial ; saltwater or marine .
Terrestrial Biomes:
desert or dune .
Physical Description
(231 to 660 lbs; avg. 445.5 lbs)
(5.9 to 8.2 ft; avg. 7.05 ft)
At birth, pups are roughly 60 to 70 cm and weigh approximately 6.5 to 8 kg. Their pelage is initially chocolate brown, but is replaced by adult-like fawn colred fur by the age of two months. Australian sea lions are sexually dimorphism, with a significant difference in the size of females and of males. As an adult, males grow to about 2.5 m and weigh 300 kg. Females grow to a length of about 1.8 m and weigh approximately 105 kg. Females reach sexual maturity at around 3 years of age, whereas males usually do not mature until they are 6 years of age or older. Males darken even further as they mature, and go through a transition phase where they have spots on their chests.
Australian sea lions have a large head with a long, narrow, and tapered muzzle. The skull has a sagittal crest approximately 30 mm in height. Males display a much larger head than females and juveniles, as well as significantly broader shoulders. Their pinnae, or ears, are incredibly small and lie close to the head. Juveniles are a dark brown with a pale crown and a dark facial mask. Subadult males and females display a coat that is fawn to silvery-gray on top and tan to pale yellow on the bottom. Mature males are dark brown with a cream-colored crown and nape, and a paler chest and throat area. (Jefferson, Leatherwood, and Webber, 1993; Nowak, 1999; Ridgway, 1972)
Some key physical features:
endothermic ; homoiothermic; bilateral symmetry .
Sexual dimorphism: male larger.
Reproduction
Because the breeding interval is oddly spaced, the breeding season steadily shifts throughout the calendar year.
The mating system of this sea lion is polygynous. A male secures a breeding territory on the beach and actively defends it against other males though ritualized posturing and aggressive confrontation. The male leaves his territory to feed in the ocean for a few hours at a time. Upon his return, he may have to battle to regain his territory.
Males keep several females on their territories. If the female strays, the male will aggressively herd her back, sometimes entering another male's territory to do so. (Nowak, 1999)
Males have been seen killing pups, although presumably not their own. Defense of territories may be an indirect mechanism of paternal care for young.
There is some evidence of cooperative breeding (See Behavior) in which females care for pups other than their own. (Nowak, 1999)
Mating systems:
polygynous ; cooperative breeder .
Australian sea lions have a breeding cycle of approximately 17.6 months. These non-annual cycles are affected by some unknown factor, not by environmental influence as previously thought (Higgins, 1993). Some females do not produce young in consecutive breeding seasons (Nowak, 1999). Births can occur over a period of 4-6 months in any colony of N. cinerea, making births highly unsynchronized.
When the breeding cycle begins, males copulate with harems of four or five females at a time (Ridgway, 1972). Males also have the ability to herd the females into mating groups, a feature rare in other species of sea lion (Riedman, 1990).
Females enter estrous about 6 days after giving birth, and are mated by the male at this time. There is some debate in the literature about the ensuing gestation period. Pinnipeds typically experience a delay in implantation of about three months, followed by an eight or nine month placentation. Because N. cinerea experiences a much longer interbirth interval, it is clear that this species differs from the typical pinniped pattern. Some investigators think that Australian sea lions experience a longer than average dely in implantation of the blastocyst, amounting to 10-11 months, and a normal length pregnancy (8-9 months). Others think there is a more typical pinniped length delay in implantation (5-6 months) and a longer than average placentation (over 12 months). (Nowak, 1999)
Young are typically weaned just before the birth of subsequent offspring, at 15-18 months. However, females have been seen nursing pups of different ages at the same time. (Nowak, 1999; Ridgway, 1972; Riedman, 1990)
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous ; delayed implantation .
Female N. cinerea come to shore about two days before they give birth in order to establish a natal site. After giving birth to a pup, the female will stay at the natal site for approximately 10 days before returning to the sea to forage. She will return to land every couple of days to nurse her young, staying with the pup for about 33 hours at a time. A mother uses both vocal and scent communication to locate and identify her pup.
As pups grow up, they often form small groups and swim in shallow rock pools before they venture into the ocean with their mothers.
Females care for their own young, nursing them until about 26 days before giving birth to their next pup. Some mothers have been seen nursing both a yearling and a newborn pup. There are reports of females being aggressive to pups other than their own, but there are also some reports of females taking care of groups of pups. This makes it difficult to determine how much cooperative care of young there might actually be, although it is clear that some cooperative care occurs. Altricial at birth, pups are able to follow their mothers both on land and into the sea at approximately 3 months of age.
No specific male parental care has been reported for N. cinerea, but by maintaining territories, fathers may protect their offspring from other males of the species. (Nowak, 1999)
Parental investment:
altricial ; pre-fertilization (provisioning, protecting: female); pre-hatching/birth (provisioning: female, protecting: female); pre-weaning/fledging (provisioning: female, protecting: female).
Lifespan/Longevity
Information on longevity in this species is not available.
Behavior
Australian sea lions are among some of the only pinnepeds that display “fostering behavior.” This is a form of altruism, as a female will nurse and protect the young of others at her own expense. In some cases, they will even adopt the young of others if the mother is killed. Some females living in the Seal Bay region have even displayed “babysitting behavior,” where a female will protect an entire group of pups even if they are not her own. When she gets tired, another female takes her place (Riedman, 1990). However, it should be noted that there are also reports of females showing agonistic behavior toward pups that are not their own (Nowak, 1999). It may be speculated that the familial relationship between females affects their behavior toward pups.
Males, on the other hand, are not at all protective of the pups, and will often engage in infanticide. They can sometimes be seen viciously attacking pups, often biting or shaking them to death (Bruemmer, 1994). Males will also sexually harass groups of females, and engage in play behavior with other males. Another behavior members of the species exhibit is the practice of swallowing gastroliths (small stones). It is believed that they do this in order to balance their weight when diving for food (Riedman 1990). (Bruemmer, 1994; Nowak, 1999; Riedman, 1990)
Key behaviors:
natatorial ; motile ; sedentary ; territorial ; social ; dominance hierarchies .
Food Habits
Australian sea lions feed on a small number of fishes (which include whiting, rays, and small sharks), squid, cuttlefish, and fairy penguins (Eudyptula minor). The main diet of N. cinerea consists of blue-throated wrasse (Notolabrus tetricus) and octopus (Achtel, P., personal communication). They concentrate on shallow-water benthic prey, and usually dive for food at depths no greater than 37 meters (Riedman, 1990). (Riedman, 1990)
Primary Diet:
carnivore (eats terrestrial vertebrates, piscivore , molluscivore ).
Animal Foods:
birds; fish; mollusks.
Predation
- great white sharks (Carcharodon carcharias)
- humans (Homo sapiens)
One of the predators of the Australian sea lion is the great white shark (Carcharodon carcharias), especially near the Dangerous Reef region of the Port Lincoln area (Riedman, 1990). Fishermen also occasionally kill them accidentally by entangling them in their nets (World Conservation Monitoring Centre, 2000). Historically, the population was greatly reduced due to sealing (Jefferson, 1993). (Jefferson, Leatherwood, and Webber, 1993; Riedman, 1990; World Conservation Monitoring Centre, 2000)
Ecosystem Roles
This species is probably a component of control on fish and penguin populations.
Economic Importance for Humans: Negative
Fishermen often see them as a nuisance as they rob fishing nets and rock lobster traps. (Jefferson, Leatherwood, and Webber, 1993)
Economic Importance for Humans: Positive
The beauty and docility of Australian sea lions draws tens of thousands of tourists to Seal Bay on Kangaroo Island every year. (Goldie, 1998)
Ways that people benefit from these animals:
ecotourism .
Conservation Status
Australian sea lions are fully protected within Australia. They were listed as “rare” in the 1994 IUCN Red List of Threatened Animals. They have been recently removed from this list, and the population has remained stable at around 10,000 animals (World Conservation Monitoring Centre, 2000). Harvesting of this species is not allowed, and a permit is required for research or capture for zoos (Toorn, 1999). (Toorn, 1999; World Conservation Monitoring Centre, 2000)
Other Comments
In the past, there have been times of great fluctuation in the population numbers of Australian sea lions. The main reason suspected for the decrease in numbers was parasites such as hookworm. Other factors such as environmental disturbance, male aggression, human harassment, injuries from fishing gear, and competition for resources with the New Zealand fur seal, may all have played a part in their population decline (Goldie, 1998).
Other common names for Australian sea lions are hair seal, white-necked hair seal, white-capped hair seal, and counselor seal (Riedman, 1990). (Goldie, 1998; Riedman, 1990)
For More Information
Find Neophoca cinerea information at
Contributors
Kara Hoglund (author), University of Wisconsin-Stevens Point.
Chris Yahnke (editor), University of Wisconsin Stevens Point.
