South American Sea Lion (Otaria flavescens)

The South American Sea Lion, also known as the Southern Sea Lion or the Patagonian Sea Lion, is, as its name suggests, found exclusively in South America. Its range extends from the northernmost coast of Peru, all the way down the west of the continent, and then from southern Brazil in the east, downwards. This includes the Falkland Islands. The species has some controversy regarding its latin name, and there are two schools of thought amongst scientists. Both Otaria flavescens and Otaria byronia are currently acceptable and in use, but for the purposes of this website we will be using O. flavescens as the earliest descriptor available, pending further decisions on the taxonomy. ‘Flavescens’ may make reference to their yellowish orange colouration. Generally doing well as a species, O. flavescens are categorised as Least Concern. Estimated population size = 445,000.
O. flavescens are large, powerful, eared seals (males up to 2.8 m long/ 350 kg, females up to 2.2 m/ 144 kg), that show remarkable sexual dimorphism, as is usual in sea lions. The males are twice the weight of the females, and appear huge as a result of their enormous shaggy manes that develop with maturity. It is not hard to see why the name ‘sea lion’ came about when you view these males! The females too, are bulky, but more lithe and streamlined. Fore flippers in both are large and broad, whereas hind flippers are relatively short, and heads are proportional, with heavy faces and long pale whiskers. Both sexes are chocolatey dark brown in colour, though the mane of the males will often be tinged with a rusty orange colour, and the females too can look almost yellowish or buff.
Feeding behaviour:
O. flavescens are a highly adaptable predator that will take on a wide range of food in their diet. It has been shown that in different locations the diet will take advantage of species available locally, and that they can also adapt to a changing environment by varying their habits. Pre-breeding, there can be a difference in feeding strategy in males and females, with males disappearing offshore to forage in pelagic waters, and females concentrating on the coastal and benthic areas. That being said, some of the most widely found prey items associated with O. flavescens include: fish (hake, cusk-eel, anchovy, croaker, sculpin, grunt, herring, jack mackerel and snake mackerel), cephalopods (octopus and squid), crustaceans (squat lobster), gastropods, polychetes, sponges and tunicates. In addition, a small percentage of male individuals regularly take South American Fur Seal pups and juveniles, and there have been known to be predation attacks on young Southern Elephant Seals as well as penguins and sea turtles.
Breeding behaviour:
Sexual maturity – males 4-7 years old/ females 4-5 years old.
The mating system for this species is polygynous, with males on average mating with between 3 and 10 females.  There has been noted to be some variation in the beach structure across different locations to account for differing environmental conditions, and this may include males displaying and aggressing for dominance of a territory, males defending and dominating individual females in oestrus, and males ‘lekking’ on the shoreline for female attention. These different tactics can coexist on the same beach. Breeding takes place in summer, with gestation lasting 1 year, and pups born from mid-December through to early February. The young pups are born black with paler undersides and often tinges of rust or reddish-brown. After a couple of months this coat will moult into a dark brown juvenile fur which gradually becomes paler with age. They enter the water after only 3-4 weeks, and will be confident swimmers but the time they have their second coat. Mothers nurse continuously for the first 7 days, before returning to the sea for short foraging trips, and during this time, groups of pups may gather together at the rookeries. Weaning generally occurs by 8 months to a year, but it is not unusual for lactation to continue for much longer, even alongside that of the next year’s pup. Moulting normally mostly takes place in the autumn, after completion of the breeding season. O. flavescens are thought to live around 20 years.
The species is not currently split into subspecies. There is some evidence that the Atlantic and Pacific animals are sufficiently genetically differentiated to warrant it, however further research is needed.

Photos: (1) Natalie Pozo (2, 3) Kayleigh Jones

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