Australian Sea Lion
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The Australian sea lion (''Neophoca cinerea''), also known as the Australian sea-lion or Australian sealion, is a species of
sea lion Sea lions are pinnipeds characterized by external ear flaps, long foreflippers, the ability to walk on all fours, short and thick hair, and a big chest and belly. Together with the fur seals, they make up the family Otariidae, eared seals. ...
that is the only endemic
pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely range (biology), distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammal, marine mammals. They comprise the extant taxon, extant family (biology ...
in Australia. It is currently
monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...
in the genus ''
Neophoca ''Neophoca'' is a genus of the family Otariidae (sea lions and fur seals) of order Carnivora Carnivora is a Clade, monophyletic order of Placentalia, placental mammals consisting of the most recent common ancestor of all felidae, cat-like ...
'', with the extinct
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...
New Zealand sea lion ''
Neophoca palatina ''Neophoca palatina'', the Pleistocene New Zealand sea lion, is an extinct species of pinniped known from a nearly-complete adult male skull found at Ōhope Beach on the North Island in 1937. It was found in a stratum from the late Castlecliff ...
'' the only known congener. With a population estimated at around 14,730 animals, the Wildlife Conservation Act of Western Australia (1950) has listed them as “in need of special protection”. Their Conservation status is listed as
endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and in ...
. These pinnipeds are specifically known for their abnormal breeding cycles, which are varied between a 5-month breeding cycle and a 17-18 month aseasonal breeding cycle, compared to other pinnipeds which fit into a 12-month reproductive cycle. Females are either silver or fawn with a cream underbelly and males are dark brown with a yellow mane and are bigger than the females.


Distribution

Australian sea lions are sparsely distributed across their range which reaches from the Houtman Arbrolhos Islands (28°S, 114°E) in
Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...
along the southern Australian coast to
The Pages The Pages is an island group in the Australian state of South Australia consisting of two small islands and a reef located in Backstairs Passage, a strait separating Kangaroo Island and the Fleurieu Peninsula. The island group has been loca ...
Islands (35°46’S, 138°18’E) in
South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...
. 66 breeding colonies have been identified: 28 in Western Australia and 38 in South Australia. Most breeding colonies exist on offshore islands, with the exception of
Point Labatt Point Labatt is a headland located on the west coast of Eyre Peninsula in the Australian state of South Australia about south by east of Streaky Bay. It is notable as one of the largest Australian mainland breeding sites for Australian sea li ...
in South Australia, Baxter Cliffs (west of
Twilight Cove Twilight Cove is situated at the end of the Baxter Cliffs on the south coast of Western Australia on the Great Australian Bight coastline. It has had other names, including ''Malbinya''. The local Aboriginal language for the area (known as Willi ...
) in Western Australia, and the
Bunda Cliffs The Bunda Cliffs, also known as the Nullarbor Cliffs, are a coastal scarp on the southern coast of Australia, extending from the western coast of South Australia to the south-eastern corner of Western Australia. Geography The Bunda Cliffs ex ...
,
Great Australian Bight The Great Australian Bight is a large oceanic bight, or open bay, off the central and western portions of the southern coastline of mainland Australia. Extent Two definitions of the extent are in use – one used by the International Hydrog ...
, which straddles the border between the two states. Forty-two percent of the total known population occurs at the three largest colonies east of Port Lincoln: Seal Bay (on Kangaroo Island's south coast), The Pages and
Dangerous Reef Dangerous Reef is an island and reef system located in the Spencer Gulf in the Australian state of South Australia about east-southeast of the city, Port Lincoln. It is the southernmost member of the Sir Joseph Banks Group. It has been the s ...
(in Spencer Gulf). The species' breeding range has contracted as the population has fallen. Now extinct breeding colonies existed in Bass Strait, particularly on Clarke Island and adjacent islands in the
Furneaux Group The Furneaux Group is a group of approximately 100 islands located at the eastern end of Bass Strait, between Victoria and Tasmania, Australia. The islands were named after British navigator Tobias Furneaux, who sighted the eastern side of ...
. The Abrolhos Island breeding colony is believed to be much smaller today than it was prior to European settlement. Kangaroo Island's north and east coasts and islands near
Perth Perth is the capital and largest city of the Australian state of Western Australia. It is the fourth most populous city in Australia and Oceania, with a population of 2.1 million (80% of the state) living in Greater Perth in 2020. Perth i ...
and Albany hosted now-extinct breeding colonies.


Phylogeny

The Australian sea lion is a
pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely range (biology), distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammal, marine mammals. They comprise the extant taxon, extant family (biology ...
, most closely related to other species of sea lions and
fur seal Fur seals are any of nine species of pinnipeds belonging to the subfamily Arctocephalinae in the family '' Otariidae''. They are much more closely related to sea lions than true seals, and share with them external ears (pinnae), relatively l ...
s making up the family Otariidae. These mammals use their flippers to propel themselves in water and can walk on land with their flippers. Australian sea lions share distinct features with other sea lions. These include short fur, short flippers and a bulky body.


Communication

In pinnipeds, mothers and pups are frequently separated throughout nursing and are thus expected to have evolved an efficient individual recognition system. Consequentially, in Australian sea lions, as in many social mammals, mothers and their offspring can identify each other. Individual recognition produces mutual benefits by avoiding misdirected maternal care and therefore energy expenditure for mothers, and the risk of injury for young approaching unrelated, potentially dangerous, adult females. Individual recognition can be accomplished with a combination of several sensory modalities, including olfaction, vision, and audition. The use of olfactory cues as a close range recognition mechanism allows mothers to further confirm their pup's identity. In contrast to recent olfactory studies in pinnipeds which showed the presence but not a natural function of olfaction in pinnipeds, the present study shows that wild Australian sea lions use their olfactory abilities in a functional manner, by discrimination between the scents of their own offspring and a non-filial pup. However, in a dynamic, crowded colony, the acoustic channel seems to be the most reliable modality. For pinnipeds, neither visual nor olfactory cues are likely to be the primary modality for mother–pup recognition. Male Australian sea lions were observed producing three different call types: a barking call, a bleating call and a female-like call. The predominant call type produced by males of all ages was the barking call. The barking call of Australian sea lions was similar in structure to the barking calls described in some other species of otariid in that it was a short sound produced repetitively in a series. Mature Australian sea lion males were found to emit the barking call in almost all social interactions, despite the existence of at least three call types in their vocal repertoire, plus a guttural threat and growl. While Australian sealions have a reputation for curiosity and playfulness during interactions with humans, their bite (albeit rare) can require hospitalisation.


Diet

Australian sea lions have been described as opportunistic, benthic foragers. Limited stomach content and faecal analyses have identified a wide variety of prey in the diet of the Australian sea lion, including teleost fish, squid, cuttlefish, octopus,
shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachi ...
s (including Port Jackson sharks),
Southern rock lobster ''Jasus edwardsii'', the southern rock lobster, red rock lobster, or spiny rock lobster, is a species of spiny lobster found throughout coastal waters of southern Australia and New Zealand including the Chatham Islands. It is commonly called '' ...
, other small crustaceans and Little penguins. Regurgitate and stomach samples from Australian sea lions at Seal Bay contained hard parts consisting predominantly of benthic taxa. This supports previous evidence that this species forages primarily on neritic, benthic prey, many of which are non-migratory. For the cephalopod component of the Australian sea lion diet, octopus and giant Australian cuttlefish made up the greatest biomass of prey taxa. Although the Australian sea lion feeds off seasonally available prey such as semelparous cephalopods, it also exploits prey species that are available throughout the year, such as Southern rock lobster and many fish species. Observations from the 1930s in Western Australian noted that Australian sea lions seemed to be subsisting on little penguins during the summer, and that their regular diet didn't compete with commercial fisheries. Also in the 1930s, the animal was described informally as "rather fond of penguins". They were known to feed on little penguins in the 1960s.


Predators

Adult Australian sea lions are eaten by
Great white shark The great white shark (''Carcharodon carcharias''), also known as the white shark, white pointer, or simply great white, is a species of large Lamniformes, mackerel shark which can be found in the coastal surface waters of all the major ocean ...
s and are occasionally killed by other animals such as stingrays. Pups are vulnerable to attack by other smaller shark species.


Breeding behaviour

As of 2020, 66 breeding colonies have been identified: 28 in Western Australia and 38 in South Australia. The animals breed on at least 50 islands, 27 in
Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...
and 23 in Southern Australia. Prior to a study that took place from 1987 to 1992, thirty-one of the 50 islands were undiscovered, as well as 19 more islands considered additional breeding grounds. On the basis of surveys conducted primarily in 1990, about 70% of the population was in Southern Australia and 30% in Western Australia. Pup production was estimated at 2,432 for these 50 islands in 1990. In 1994 and 1995 another 10 breeding colonies were recorded on the mainland in the
Great Australian Bight The Great Australian Bight is a large oceanic bight, or open bay, off the central and western portions of the southern coastline of mainland Australia. Extent Two definitions of the extent are in use – one used by the International Hydrog ...
region, only producing 161 pups. Reproduction is yielding fewer and fewer pups per breeding season. The four largest colonies, on
The Pages The Pages is an island group in the Australian state of South Australia consisting of two small islands and a reef located in Backstairs Passage, a strait separating Kangaroo Island and the Fleurieu Peninsula. The island group has been loca ...
Islands, at Seal Bay on
Kangaroo Island Kangaroo Island, also known as Karta Pintingga (literally 'Island of the Dead' in the language of the Kaurna people), is Australia's third-largest island, after Tasmania and Melville Island. It lies in the state of South Australia, southwest ...
, and at
Dangerous Reef Dangerous Reef is an island and reef system located in the Spencer Gulf in the Australian state of South Australia about east-southeast of the city, Port Lincoln. It is the southernmost member of the Sir Joseph Banks Group. It has been the s ...
, produced 42% of the total pup numbers; they are at the eastern end of the range, east of
Port Lincoln Port Lincoln is a town on the Lower Eyre Peninsula in the Australian state of South Australia. It is situated on the shore of Boston Bay, which opens eastward into Spencer Gulf. It is the largest city in the West Coast region, and is located a ...
. The breeding cycle of the Australian sea lion is unusual within the
pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely range (biology), distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammal, marine mammals. They comprise the extant taxon, extant family (biology ...
family. It is a 17.6- to 18-month cycle and is 'not' synchronised between colonies. However, census data collected since 1973 shows that breeding events shift forward in time to 13.8 days earlier every 18 months. The duration of the breeding season can range from five to seven months and has been recorded for up to nine months at Seal Bay on
Kangaroo Island Kangaroo Island, also known as Karta Pintingga (literally 'Island of the Dead' in the language of the Kaurna people), is Australia's third-largest island, after Tasmania and Melville Island. It lies in the state of South Australia, southwest ...
. Bulls do not have fixed territories during the breeding season. The males fight other males from a very young age to establish their individual positions in the male hierarchy and during the breeding season, dominant males will guard females for the right to breed with her when she comes into
oestrus The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. Estrous cycles start after sexual maturity in females and are interrupted by anestrous ...
. A female comes into season for about 24 hours within 7 to 10 days after she has given birth to her new pup. She will only look after the new pup and generally fights off the previous season's pup if it attempts to continue to suckle from her. Male Australian sea lions are also known to kill young as an act of defence of territory. Australian sea lions also practice
alloparental care Alloparenting (also referred to as alloparental care) is a term used to classify any form of parental care provided by an individual towards young that aren't its own direct offspring. These are often referred to as "non-descendant" young, even th ...
, in which an adult may adopt the pup or pups of another. This might take place if the original parents die or are for some reason separated from them. This behaviour is common and is seen in many other animal species such as the elephant and
fathead minnow Fathead minnow (''Pimephales promelas''), also known as fathead or tuffy, is a species of temperate freshwater fish belonging to the genus ''Pimephales'' of the cyprinid family. The natural geographic range extends throughout much of North Amer ...
.


Population

In 2010, an estimated 14,730 Australian sea lions existed. By 2014, the population had dropped to an estimated 6,500 and continues to decrease. The population is listed as Endangered on the IUCN Red List of Threatened Species. The Australian sea lion population is naturally disadvantaged when compared to other pinnipeds in Australia. Its long and complicated breeding cycle, the high site fidelity of females, and high mortality rates all make the species more vulnerable to extinction. Jones Island, west of Eyre Peninsula in South Australia is one of the few sites where the population is not decreasing. In 2019, it was declared a "prohibited area" to eliminate human disturbance to the colony while landed. In 2018, aerial drones were being used to search for, discover and measure colonies of Australian sea lions along the Nullarbor Plain. Previously, surveying these areas was limited to the use of binoculars and peering down 60 metre high cliffs to view the rocks below.


Interactions with humans

Australian sea lions should only be approached in the company of a park ranger. They may exhibit defensive behavior including biting. Sea lions have historically been captured from the wild and held in captivity in various zoos and aquaria, including
Marineland of South Australia Marineland of South Australia was a public aquarium and wildlife park in West Beach, South Australia that opened in 1969 and closed permanently in 1988. Exhibits Exhibits included local species such as the Australian pelican, Little penguin, Aus ...
.


Hunting

Sea lions were heavily hunted following European settlement which greatly reduced their numbers. Large-scale hunting ceased in the 1920s, but some killing and trade in "hair seal" skins continued. No baseline population data exists, but the species population and range have both decreased. Sea lions on Dangerous Reef were shot and butchered for use as shark bait during the 1960s and 1970s. Between 1964 and 1975, conservationist Valerie Taylor saw the colony there reduce from over 200 animals to between 60 and 80 animals based on her own population counts in both years. She described noticing the difference in the animals response to humans from her early visit in the 1960s to her follow up in the 1970s, when the animals on both Dangerous Reef and Hopkins Island demonstrated fear of humans. In the 1980s, Australian sea lions were entangled in gill nets, after which fishers shot them and used them as shark bait. Major threatening processes in the 20th and 21st centuries were primarily interactions with commercial fishing gear and illegal shooting. Entangled animals can sometimes be found and treated successfully. Secondary threats include: marine fish aquaculture (including loss of habitat, entanglement and direct killing), disease, pollution, oil spills and noise, particularly from seismic surveys, construction, or marine operations.


Illegal shooting

Illegal shootings have been reported in both South Australia and Western Australia. Dead animals with gunshot wounds have been found at Cheynes Beach, Albany, near Port Wakefield in South Australia and at other locations. Some killings have led citizens to start petitions demanding thorough investigation. The shooting of a male Australian sea lion which had hauled out at Port Macdonnell in 2013 by government employees without a prior veterinary assessment was criticised by animal rescue workers and the general public. In March 2021, a male Australian sea lion was shot and killed with a
longbow A longbow (known as warbow in its time, in contrast to a hunting bow) is a type of tall bow that makes a fairly long draw possible. A longbow is not significantly recurved. Its limbs are relatively narrow and are circular or D-shaped in cross ...
at Bales Beach, Kangaroo Island.


Shark fishery

Australian sealions are caught as bycatch by the Southern and Eastern Scalefish and Shark Fishery. Following the closure of the Commonwealth gillnet fishery in southern Spencer Gulf in 2001, pup production increased at Dangerous Reef (within Spencer Gulf) and that population began to recover. Researchers estimated that while the fishery was operating, 374 Australian sea lions were killed by the fishery each breeding cycle. While most sealion bycatch occurred close to breeding colonies, some occurred as far as 130 kilometres away. In 2011, Humane Society International lobbied for the trigger figure for the closure of the fishery of 104 Australian sea lion deaths to be lowered. Some Australian sealions have drowned after becoming entangled or trapped in Southern rock lobster pots and gear. Commercial fishers have also illegally shot and killed Australian sealions which they believed were competing with their fishery.


Long lactation period

The transition for young mammals from dependence on milk to independent foraging can lead to increased risk of natural mortality. The Australian sea lion demonstrates one of the longest lactation periods in pinnipeds and pups begin diving before they are weaned. Australian sea lion adults work hard to forage at the seabed, demonstrating high field metabolic rates, and spending 58% of time at sea diving and 35% of time at sea on or near the bottom. Juveniles spend 67% of time at sea diving and 44% of time at sea on or near the bottom. Although many air-breathing vertebrates dive well within their estimated limit of oxygen stores, Australian sea lion adults and juveniles appear to operate close to their physiological maximum. The prolonged dependency period could provide extensive opportunities for foraging lessons, while the extreme diving behaviour required in the Australian sea lions' environment might necessitate it. Alternatively, it has hypothesised that female harbour seals accompanying pups demonstrate reduced foraging efficiency, and hence, the metabolic demands of foraging for Australian sea may preclude lactating females from performing suboptimal dives with their young. This becomes a preventative measure to maintain a population and avoid a complete extinction. However, as a result of small population size, small breeding colony size, low reproductive rate, exposure to human activities, and evidence of population declines in some areas, Australian sea lions have recently been listed as threatened and vulnerable.


Conservation status & management

The protection of breeding habitat for the Australian sealion has been a conservation priority since the early 20th century. In 1909, field naturalists lobbied for the protection of three critical breeding sites for the Australian sea lion: Dangerous Reef, The Pages and the Casuarina Islets off Kangaroo Island. In 1918, the South Australian parliament debated the Birds and Animals Protection Bill, and the Legislative Council agreed that it would protect Australian sea lions from harm covering waters of Spencer Gulf, St Vincent Gulf, the
Investigator Strait Investigator Strait is a body of water in South Australia lying between the Yorke Peninsula, on the Australian mainland, and Kangaroo Island. It was named by Matthew Flinders after his ship, HMS ''Investigator'', on his voyage of 1801–1802 ...
,
Backstairs Passage The Backstairs Passage is a strait in South Australia lying between Fleurieu Peninsula on the Australian mainland and Dudley Peninsula on the eastern end of Kangaroo Island. The western edge of the passage is a line from Cape Jervis on Fleurieu ...
and to the mouth of the
Murray River The Murray River (in South Australia: River Murray) (Ngarrindjeri: ''Millewa'', Yorta Yorta: ''Tongala'') is a river in Southeastern Australia. It is Australia's longest river at extent. Its tributaries include five of the next six longest ...
. The introduction of the South Australian ''
National Parks and Wildlife Act 1972 Protected areas of South Australia consists of protected areas located within South Australia and its immediate onshore waters and which are managed by South Australian Government agencies. As of March 2018, South Australia contains 359 sepa ...
'' prohibited the killing of Australian sea lions statewide. In 2005, the Australian sea lion was listed as Vulnerable under the Commonwealth ''
Environment Protection and Biodiversity Conservation Act 1999 The ''Environment Protection and Biodiversity Conservation Act 1999'' (Cth) is an Act of the Parliament of Australia that provides a framework for protection of the Australian environment, including its biodiversity and its natural and cult ...
'' and is similarly listed in each state across its range (South Australia and Western Australia). On 11 June 2013, the Recovery Plan for the Australian sea lion (''Neophoca cinerea'') was adopted by the Minister for Sustainability, Environment, Water, Population and Communities. The plan considers the conservation requirements of the species across its range and identifies the actions to be taken to ensure its long-term viability in nature and the parties that will undertake those actions. In November 2014, the species was assessed by the
International Union for the Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natura ...
as Endangered.


Captive breeding

Some zoos and aquariums are participating in captive breeding programs. In 2006 it was reported that at least 41 pups had been born and raised in captivity since 1981. The species has been kept in aquaria since at least as early as 1965. In 2015, an Australian sea lion juvenile was captured at Bletchley near Strathalbyn in South Australia, and was going to be considered for holding in captivity.


Fisheries Management

The Australian Fisheries Management Authority Commission finalised an Australian Sea Lion Management Strategy which came into force on 30 June 2010. This included closures of waters around colonies, seasonal closures, increased observation of sea lion activity and trials of modified fishing techniques and equipment. The strategy was designed to meet the commission's obligations under the ''Fisheries Management Act 1991'' and the ''Environment Protection and Biodiversity Conservation Act 1999.'' The strategy was expected to significantly reduce the impact of fishing in the Southern and Eastern Scalefish and Shark Fishery (SESSF) on Australian sea lions and enable the recovery of the species, including all sub-populations.
Southern rock lobster ''Jasus edwardsii'', the southern rock lobster, red rock lobster, or spiny rock lobster, is a species of spiny lobster found throughout coastal waters of southern Australia and New Zealand including the Chatham Islands. It is commonly called '' ...
fisheries in both South Australia and Western Australia use pots which feature special collars designed to prevent Australian sea lions from entering the pots or spikes which act as a deterrent.


Ecology

Australian sea lions defecate nutrient-rich faeces which may provide an important nutrient source for coastal ecosystems. Metagenomic analysis of the bacterial consortia found in the faeces of Australian sea lions found very high levels of nutrient cycling and transport genes which may break down the nutrients defecated by sea lions into a bioavailable form for incorporation into marine food webs. Diving behaviours indicate that the Australian Sea Lions worked extremely hard to exploit the benefits of their surrounding habitats. The Australian sea lion exceeds the limit (calculated aerobic dive limit) on 79% of dives. Australian sea lions spend 58% of time at sea diving and demonstrate high field metabolism, which allows the sea lions to maximise their time spent at or near the benthos, with 61% of each dive and 35% of their time at sea being spent at the deepest 20% of the dives. When diving, these animals are spending 57.9% of their time at sea spent at depths greater than or equal to 6 m, which can be considered as continuous diving. Seasonal variability in foraging energetics and dive behaviour is likely to be sensitive to regional oceanography, the maintenance costs of female sea lions and their offspring, and the distribution and behaviour of their prey. The Australian sea lion exhibits strong site fidelity, with a foraging range of at most 300 km from their colony. Australian sea lions sometimes travel inland during tumultuous weather, and have been known to travel up to 9.4 km from the ocean.


See also

* '' Uncinaria sanguinis'', a hookworm parasite of the Australian sea lion.


References


Further reading

* "Saving Australia's sea lion population" (2019). The University of Sydney. https://sydney.edu.au/news-opinion/news/2019/11/08/saving-australia-sea-lion-population-vet-science.html *Marcus, Alan David (2015). Hookworm infection in the Australian sea lion (''Neophoca cinerea''). PhD thesis. The University of Sydney. http://hdl.handle.net/2123/13606. *Shannon Leone Fowler (2005). Ontogeny of diving in the Australian sea lion. Ph.D. thesis. University of California, Santa Cruz. * {{Taxonbar, from=Q744392 Neophoca Endemic fauna of Australia Mammals of New South Wales Mammals of South Australia Mammals of Victoria (Australia) Mammals of Western Australia Mammals described in 1816 Pinnipeds of Australia