Neophoca cinerea (Peron, 1816)
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publication ID |
https://doi.org/ 10.5281/zenodo.6604474 |
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DOI |
https://doi.org/10.5281/zenodo.6604526 |
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persistent identifier |
https://treatment.plazi.org/id/965C87FE-1E56-5645-9C2D-93CE8810F747 |
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treatment provided by |
Diego |
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scientific name |
Neophoca cinerea |
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Australian Sea Lion
French: Otarie d/Australie / German: Australien-Seelowe / Spanish: Le 6n marino de Australia
Other common names: Australian Sealion, Counselor Seal, Hair Seal, White-capped Sea Lion, White-necked Sea Lion
Taxonomy. Otaria cinerea Péron, 1816 View in CoL ,
“N. de I'lle Decres,” Kangaroo Island, South Australia, Australia.
This species is monotypic.
Distribution. S Australia, from Houtman Albrolhos Is in C Western Australia E along the coast to SE South Australia, including Kangaroo I. View Figure
Descriptive notes. Total length minimum 250 cm (males) and 130-180 cm (females); weight minimum 200-300 kg (males) and 61-105 kg (females). Newborns are 60-70 cm and 6.4-7.9 kg. Dental formulal3/2,C1/1,PC5/5 (x2) = 34, rarely1 3/2, C 1/1, PC 6/5 PC (x 2) = 36. Australian Sea Lions are sexually dimorphic, with adult males having 2-5-3-5 times the weight and 1-2 times the length of females. In both sexes, head is relatively wide and long, larger in males, with muzzle tapering to a blunt rhinarium (nose). Eyes are set well apart, and short ear pinnae lay close to side of head. Males have moderate forehead, produced by sagittal crest that lies toward back of skull, and they have conspicuously large neck, chest, and shoulders. Foreflippers have some hair on dorsal surfaces, but it does not extend to rounded tips. Otherwise,flippers, including undersides, are covered with dark leathery skin. First digitis the longest and curves back. Cartilaginous rods in hindflippers lengthen toes, and first and fifth digits are longer than three middle digits. Similar to foreflippers, hindflippers have hair on upper part closest to body, but they otherwise are covered in dark leathery skin. Coat color of females and juveniles is yellowish-tan to light gray above, and buff to light yellow below, with diffuse dividing line from side of neck down to base of foreflippers and back along sides. Pattern on face varies, with pale color of chest extending higher to include muzzle, often surrounding eyes, and even reaching ear pinnae. Some female Australian Sea Lions are darker over their entire bodies, showing little color contrast. Males darken as they age, developing dark spots on chest as the first sign. Males grow mane of guard hairs that reaches from head to shoulders. Their body is dark brown, with a buff crown and nape that fades into darker body color on back of neck, but pale crown contrasts sharply with face color, giving them an appearance of wearing dark masks. Males that are not fully mature can show a transition pattern with pale circles surrounding eyes. Newborns are deep brown to gray-black but become grayer with age. They may also show a pale crown, giving the impression of having dark facemasks. First molt begins at 8-10 weeks, after which their coat resembles that of a female.
Habitat. Over continental shelf and coral reefs of the Houtman Albrolhos Islands. Australian Sea Lions preferred breeding sites on sandy or rock-strewn beaches. Predators include great white sharks (Carcharodon carcharias) and potentially Killer Whales (Orcinus orca).
Food and Feeding. There is scant information about the diet of the Australian Sea Lion, but lactating females forage diurnally, mainly for bottom-dwelling species. They consume fish such as whiting, Australian salmon (Arripis sp.), rays, and small sharks, and squid,cuttlefish, and small crabs. They also prey on penguins, seabirds, and even small sea turtles and are known to steal lobsters from traps.
Breeding. Although Australian Sea Lions have a breeding system that shares somefeatures typical for sea lions, they are unique among otariids in having no synchronized annual breeding cycle. Females give birth every 17-18 months, and timing of births at nearby rookeries may be completely different. Young can be born at any time of year, with females in the same rookery giving birth over 5-7 months. Rather than defending a well-defined, fixed area of land or water,as other species of sea lions do, male Australian Sea Lions maintain a territory around individual females, excluding other males and physically restraining and chasing females to prevent their departure until they have entered estrus. Like all sea lions, the female Australian Sea Lion begins estrus soon after giving birth and usually copulates with the male guarding her. After conception, development of the fertilized egg is suspended at the blastocyst stage and then resumes a few months later by implanting in the uterus. In other species of sea lion, this delayed implantation allows short gestation to synchronize to an annual breeding cycle. In the case of Australian Sea Lions, delayed implantation precedes a 14month developmental gestation, the longest for any pinniped. Female Australian Sea Lions enter estrus 7-10 days after they give birth. After copulating, the male moves on, finding and guarding another female, repeating the pattern until hunger drives him to leave the beach to find food at sea. This breeding system is termed “sequential polygyny.” Males defend their territories vocally (guttural clicks, growls, and barks), with postural displays, and by fighting. Males take no role in parenting and are, in fact, a serious dangerto offspring. Males will attack and toss young, or trample them accidentally when challenging rivals. Females care for their young continuously for the first 9-10 days and then leave them to go on foraging trips at sea. Young are left alone or join a group of other unattended neonates. Young play near the splash zone or in tide pools, and when they are c¢.2 months old, they begin to swim on their own. Over the following five months, lactating females make a series of 2day foraging trips, followed by nursing bouts ashore that average 1-2 days. Weaning occurs at 15-18 months of age, usually about a month before the female is ready to give birth again. Some females may extend care of their young for a year past weaning and can be seen with a newborn and ajuvenile. Lactating females tolerate only their own young and act aggressively toward others. Pregnancy rates of mature females are ¢.71%. Female Australian Sea Lions are sexually mature at 4-5-6 years of age and males at c.6 years. Average age of breeding females is c.11 years, but there is a record of one female giving birth when she was 24 years old. Females live for a maximum of 26 years and males for 21-5 years.
Activity patterns. Australian Sea Lions are powerful swimmers and have been observed “porpoising,” leaping in low arcs across the water when traveling at high speed. They often reach their regular feeding destinations by swimming along the sea bottom. Studies of the diving behavior of lactating females revealed they achieve depths of 41-83 m during dives that last 2:2—4-1 minutes. Maximum depth recorded was 105 m, and the longest dive lasted 8-3 minutes.
Movements, Home range and Social organization. Australian Sea Lions are non-migratory, remaining near their natal rookeries throughout most oftheir lives. They are Australia’s only endemic pinniped, breeding at more than 70 island sites and several rookeries on the continent. Sixty percent of all births occur at only five rookeries. Maximum distance traveled by a tracked Australian Sea Lion was ¢.250 km. Molecular studies support their tendency toward site fidelity, showing genetic differences even among rookeries located relatively close to each other. Vagrant Australian Sea Lions have seen in eastern Australia as far north as New South Wales.
Status and Conservation. Classified as Endangered on The IUCN Red List. Total population of the Australian Sea Lion is estimated at 13,790 individuals, with 80% in South Australia and 20% in Western Australia. This number is assumed to be much lower than the historical level. Aboriginal Australian people hunted Australian Sea Lions for food and other uses before commercial European sealers arrived in the 18" and 19" centuries and extirpated sea lions from Tasmania and the Bass Strait. Despite protections, the extant population has not fully recovered or reoccupied its original distribution, and it is small and genetically fragmented. Due to extreme breeding-site fidelity, most rookeries are essentially subpopulations with their own unique lineages. Fragmentation may be a result of fisheries pressure because bycatch in gill nets remains a significant threat, especially for small subpopulations. As long as bycatch rates remain elevated, declines of Australian Sea Lions are predicted for most rookeries. Fishing gear and marine debris entangle 0-2-1-3% of the population. The Environment Protection and Biodiversity Conservation Act of 1999 extends legal protection to all Australian pinnipeds, but widespread measures to safeguard Australian Sea Lions from fisheries conflicts have not been implemented. Population stability was achieved for colonies at Dangerous Reef and Pages Islands in South Australia after fisheries were closed. In contrast, lack of gillnet closures off Kangaroo Island continuesto stress the island’s Seal Bay colony, which isstill declining. Sea lion watching has developed as a tourist industry and is regulated at rookeries and parks to minimize harassment during breeding periods.
Bibliography. Campbell, Chilvers et al. (2006), Campbell, Gales et al. (2008), Costa & Gales (2003), Dennis & Shaughnessy (1996), Gales & Costa (1997), Gales et al. (1994), Goldsworthy & Gales (2008b), Goldsworthy & Page (2007), Higgins (1993), Higgins & Gass (1993), Jefferson et al. (2008), Ling (1992, 2009), Ling et al. (2006), Lowther et al. (2011), Mcintosh et al. (2012), Page et al. (2004), Pitcher, Ahonen et al. (2011), Pitcher, Harcourt et al. (2011), Reijnders et al. (1993), Rice (1998), Shaughnessy et al. (2007), Tripovich et al. (2008), Walker & Ling (1981b).
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