Otaria byronia (de Blainville, 1820)
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https://doi.org/ 10.5281/zenodo.6604474 |
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https://doi.org/10.5281/zenodo.6604531 |
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persistent identifier |
https://treatment.plazi.org/id/965C87FE-1E57-5643-99B4-94FD886EFE74 |
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Diego |
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scientific name |
Otaria byronia |
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South American Sea Lion
French: Otarie a criniere / German: Mahnenrobbe / Spanish: Le 6n marino de Sudamérica
Other common names: South American Sealion, Southern Sea Lion
Taxonomy. Phoca byronia de Blainville, 1820 View in CoL ,
“I'ile de Tinian,” Northern Mariana Islands.
Taxonomy of O. byronia has been a matter of debate because it has also been referred to as O. flavescens , named by G.
Shaw in 1800, based on a specimen of uncertain species identity and location of origin. The location of origin of Byron’s specimen, given as Tinian, has been doubted by most authors, and it is widely assumed that it was mislabeled and originated in the Falkland Islands (= Malvinas) or from another location where the expedition stopped in southern South America. However, the identity of the specimen as a South American Sea Lion is unquestioned, and thus Byron's specimen has precedence as the first representative ofthis species to be collected and described. O. byronia in the Atlantic Ocean appear to be a genetically isolated population. Monotypic.
Distribution. South America, from S Brazil to Cape Horn and the Falkland Is in the Atlantic, and N to N Peru in the Pacific. View Figure
Descriptive notes. Total length 260 cm (males) and 200 cm (females); weight up to 300-350 kg (males) and 144 kg (females). Newborns are 75-85 cm and 11-15 kg. Dental formula 13/2, C 1/1, PC 6/5 (x 2) = 36. South American Sea Lions are heavy, robust otariids that display a high degree of sexual dimorphism. Muzzle is wide and squared off, and large nose is upturned, conspicuously so in males, whose jaws extend beyond muzzle. Small ear pinnae are not prominent. Males are easily distinguished by enlarged neck and mane reaching from head to chest. Females and subadult males lack manes. Foreflippers have some hair on dorsal surfaces, but hair does not extend to rounded tips. Otherwise, flippers, including undersides, are covered with dark leathery skin. First digit is the longest and curves back. Cartilaginous rods in hindflippers lengthen toes, and first and fifth are longer than three middle digits. Similar to foreflippers, hindflippers have hair on upper part closest to body, but otherwise they are covered in dark leathery skin. Coat of the South American Sea Lion is mainly golden to buff, with varying tints. As they age, males usually darken to a browner color. Mane and abdomen can retain pale hues, and some males never darken, permanently retaining paler female color pattern. Face color on males can make them appear somewhat masked. Newborns are black on upper parts and paler on belly and chest. They molt after 1-2 months to a deep brown, which lightens during their first year.
Habitat. Mainly coastal, with marine habitat over continental shelf and slope and occasionally in deep pelagic zone. South American Sea Lions may also be found in freshwater habitats such as rivers and near glacier melt water. Predators include sharks, Killer Whales (Orcinus orca), and Leopard Seals (Hydrurga leptonyx, and potentially Pumas (Felis concolor) on land. Killer Whales are well known for their ability to capture juvenile South American Sea Lions on the beach at Valdes Peninsula, Argentina, partially beaching themselves to grab their prey. Vampire bats have been observed lapping blood from flippers of dozing South American Sea Lions.
Food and Feeding. The extremely varied diet of the South American Sea Lion is composed of several species offish, invertebrates, pinnipeds, and birds. Key prey species include hake, herring, elephantfish ( Callorhinchidae ), anchovy ( Engraulidae ), grenadier ( Macrouridae ), sardines ( Clupeidae ), cusk-eels ( Ophidiidae ), butterfish ( Stromateidae ), lobster krill, squid, octopus, jellyfish, and gastropods. An analysis of stomach contents of individuals killed in fishing nets revealed that males ate primarily mid-water prey and females focused more on bottom-dwelling species. Small numbers of male South American Sea Lion routinely kill and eat South American Fur Seals ( Arctocephalus australis ), especially targeting juveniles. Research has shown that c¢.17% of attacks on fur seals are successful. In the Falkland Islands, South American Sea Lions have been known to kill juvenile Southern Elephant Seals (Mirounga leonina). They also eat several species of penguins.
Breeding. The South American Sea Lion has the same general polygynous breeding system as described for the New Zealand Sea Lion ( Phocarctos hookert). For South American Sea Lions, breeding season is in December-March. Males and pregnant females begin to arrive at the rookery in mid-December, and maximum numbers are reached in January. Males at most rookeries will physically dominate females to the point of hauling them off the beach into territories. Non-territorial subadult males may forcibly herd South American Fur Seals as they attempt to copulate with them, often resulting in the death of the fur seals. Territorial behavior has proven to be quite different for rookeries in Peru. Unlike other species of sea lions that hold fixed territories or defend females (as is true for Australian Sea Lions, Neophoca cinerea ), male South American Sea Lions at the Ballestas Islands off Peru lined up along the shoreline where females pass as they come and go during foraging trips, or where they go to cool off from high temperatures in the desert environment. Males also needed to remain near the water to thermoregulate, so they are unable to restrain female movements. Females moved freely, chose their mates, and copulate on the beach—a “lek-like” breeding system. In general, after arriving at rookeries, females give birth within 2-3 days and then enter estrus six days later. They nurse young for 2-3 days before leaving on theirfirst feeding trip at sea, and they return for nursing bouts that usually last two days. Weaning occurs when young are 8-10 months old. Some females extend care to yearlings. A census of young born in Peru revealed that mortality ranges from a level of 13% in a normal weather year to complete failure (100% mortality) during an El Nino event when food is scarce. Gestation is c¢.12 months. Females attain sexual maturity at c.4 years of age, and males are mature at 5-6 years. Life span is ¢.20 years.
Activity patterns. South American Sea Lions are seen singly or rafting in groups when at sea. They may aggregate near feeding seabirds and cetaceans. Studies of lactating females reveal that their typical dives are 19-62 m and last 2-7 minutes, with a maximum dive depth of 175 m and duration of 7-7 minutes. A dive depth of 250 m is the expected limit for the South American Sea Lion. Two males tracked at sea made 600 km journeys that lasted 5-6 days before they hauled out. Although diving behavior has not been studied in males, the tagged males spent their time primarily in water 50-100 m deep.
Movements, Home range and Social organization. South American Sea Lions are nonmigratory, but some individuals travel considerable distances from colony sites after breeding. Rookeries on the Falkland Islands are deserted during harsh southern winters, but most rookeries retain some residents throughout the year. South American Sea Lions breeding at Valdes Peninsula, Argentina, relocate to Uruguay in the nonbreeding season. Lactating females adjust their movements and nursing patterns depending on food supply. During EI Nino events in Peru, when food resources are scare close to the colonies, they spend more time feeding at sea and less time ashore with offspring. Vagrants reach Bahia, Brazil (13° S) in the Atlantic Ocean and the Galapagos Islands west of mainland Ecuador in the equatorial Pacific Ocean.
Status and Conservation. Classified as of Least Concern on The IUCN Red List (as O. flavescens ) Total population of the South American Sea Lion is 250,000-280,000 individuals, with ¢.100,000 individuals in mainland Argentina and c.6000 in the Falkland Islands. There are 90,000-100,000 individuals in Chile, ¢.60,000 individuals in Peru, and c.12,000 individuals in Uruguay. Depending on locale, numbers are increasing or decreasing, and many colonies are still recovering from earlier hunting pressure. Native people hunted South American Sea Lions long before commercial sealers arrived from Europe in the 16™ century. Harvesting for hides and oil led to dramatic reductions in numbers. In southern Patagonia, the population of South American Sea Lions is estimated to be only 15% of what it was in the 1940s. In the Falkland Islands, the population may be a mere 20% of earlier levels, falling from ¢.30,000 individuals in the 1960s to ¢.15,000 in the 1980s and ¢.3000 by the 1990s, possibly due to the local trawlnet fisheries. The South American Sea Lion is bycatch in fisheries throughout their distribution, despite legal protections. It has benefited from creation of reserves at rookeries, particularly in Argentina, although enforcement is weak at the more remote sites. Natural cycles in productivity of the marine environment can have profound effects on survival of young, and frequent El Nino events that develop in the Pacific Ocean may put the Peruvian population of South American Sea Lions at risk. It was devastated by the 1997-1998 El Nino, dropping from c.144,000 individuals to ¢.28,000 individuals. The 2003-2004 El Nino reduced the population from ¢.80,000 individuals to ¢.60,000 individuals, during which time production of offspring fell 48%. Currently, this population is showing signs of recovery.
Bibliography. Alonso et al. (2000), Berta & Churchill (2012), Campagna (1985, 2008b), Campagna & Le Bouef (1988a, 1988b), Campagna, Cappozzo & Le Bouef (1988), Campagna, Le Bouef & Cappozzo (1988), Campagna, Werner et al. (2001), Cappozzo & Perrin (2009), Cassini & Fernandez-Juricic (2003), Crespo et al. (1997), Fernandez-Juricic & Cassini (2007) , Harcourt (1993), Jefferson et al. (2008), Reijnders et al. (1993), Rice (1998), Rosas et al. (1993), Schiavini et al. (2004), Sepulveda & Oliva (2005), Sepulveda et al. (2012), Shaw (1800), Soto & Trites (2011), Soto et al. (2004, 2006), Thompson et al. (2005), Tunez et al. (2007), Vaz-Ferreira (1981), Werner & Campagna (1995).
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