South American fur seal

Arctocephalus australis is a fur seal of the family Otariidae described by Zimmermann in 1783 ^[1]. In Peru it is called «lobo marino fino» ^[2]. It is one of the 2 otariid species that breed in the country, and the animals of Peru and northern Chile belong to a subspecies that has not yet been named ^[3]. The IUCN Red List classifies the species as Least Concern in its current assessment ^[4], and Peru's 2014 official list of threatened wildlife places it in the Endangered category ^[5].

For a fur seal it has a fairly sturdy body. The muzzle is moderately long, flat on top and pointed, and the nose reaches past the mouth; the forehead is noticeable, the ears are long and easy to see, and the whiskers of adults are creamy white ^[6]. Adult males are bigger than females, with a thicker neck and heavier shoulders, and they grow a mane of longer hairs over the head and shoulders ^[6].

Adult females and subadults are dark brown to greyish black on the back and lighter underneath, with a pale band around the lower neck; as they age, males darken and turn a more even colour ^[6]. Adult males reach 1.9 m in length and weigh 120 to 200 kg, females measure about 1.4 m and weigh 40 to 50 kg, and newborn pups weigh 3.5 to 5.5 kg and measure 60 to 65 cm ^[6]. Pups are dark at birth ^[6].

Similar species

• Otaria byronia: It has a short, broad, deep and slightly upturned muzzle and small ears held close to the head, whereas Arctocephalus australis has a longer, pointed muzzle and long, prominent ears ^[6].

It lives from central Peru, around the southern tip of the continent, to southern Brazil, and also around the Falkland Islands; it is thought to use mainly coastal, continental shelf and slope waters, although there are records more than 600 km from shore ^[6].

In Peru it is found from Isla Mazorca (11° 20′ S) to Ilo (17° 42′ S), plus a small isolated colony on Isla Foca in the north ^[3]. IMARPE's surveys from 2016 to 2019 checked 30 localities along the coast, and the species turned up at least once in 19 of them ^[3]. The southern coast, between 15° and 18° S, held more than 90 % of the animals counted, while Isla Foca, the only colony in the northern zone, held about 0.4 % ^[3].

Its colonies form mainly on rocky shores ^[7]. Populations of the genus living at low latitudes favour beaches with tide pools, wet rocks, caves, shade and exposure to the wind, which let them regulate their temperature where heat is constant ^[3]. In Peru they have been seen to choose breeding sites with less human disturbance or that are hard for people to reach ^[3].

The breeding season runs from mid-October to mid-December ^[6]. In Peru, 90 % of births happen within 40 days towards the end of November, and at that time the number of animals ashore comes closest to the real population; IMARPE runs its surveys in that season, in November and December ^[3].

Between 2016 and 2019 pups were seen every year at 7 localities, and yearly production was 1322 pups in 2017, the lowest year, and 2090 in 2018, the highest ^[3]. Punta San Juan contributed on average 51.4 % of the country's pups and Punta Coles 24.6 % ^[3]. In those surveys, females and juveniles together made up 62.5 % of the animals recorded, pups 20.5 % and adult and subadult males 7 % ^[3].

In Peru far more pups die in their first weeks than in other fur seal populations: between 31 % and 49 % during the first month, whereas elsewhere the maximum is 20 % ^[8]. In 1987 and 1988, on a high-density beach, pup mortality rose with the number of females ashore, and so did fighting among them, pushed to high levels by crowding together with the females moving around the colony to regulate their temperature ^[8].

It feeds on small schooling fish and on invertebrates such as cephalopods, crustaceans and gastropods ^[6]. In Peru its main prey is the Peruvian anchoveta (Engraulis ringens), as it is for Otaria byronia ^[9]. Its population grows more slowly than that of Otaria byronia, possibly because it copes worse with high temperatures and depends more on anchoveta; when anchoveta is scarce during El Niño there are abortions and females die, which cuts pup production ^[3].

Males of Otaria byronia prey on the pups of this species. In 1987 and 1988, on a low-density beach, they took between 5.0 % and 8.3 % of all pups, against 0.2 % on a crowded beach, where males of Arctocephalus australis drove off 58.8 % of the attackers ^[8].

In animals found dead at Punta San Juan, the respiratory mite Orthohalarachne attenuata was present in 3 of 32 individuals examined and caused moderate to severe inflammation of the pharynx; the hookworm Uncinaria sp. was present in 6 of 32, inflamed the gut and was the cause of death of 2 pups ^[10].

Its global category is Least Concern ^[4]. In Peru it is classified as Endangered, and the regulation that lists it prohibits the hunting, capture, possession, trade, transport and export for commercial purposes of the species included ^[5]. Hunting of sea lions and fur seals has been banned along the whole Peruvian coast since Ministerial Resolution N.° 0013-96-PE, and the species is listed in Appendix II of the Convention on Migratory Species and in Appendix II of CITES ^[3].

The 1997-1998 El Niño cut the Peruvian population by 66 % in 2 years ^[3]. The 2016, 2017, 2018 and 2019 surveys counted 9727, 8115, 8289 and 7770 animals ^[3], a drop of 20.1 % from the first to the last, steepest at 17° S, at 28.3 % ^[3]. Those figures amount to 34.6 % of the 1996 count: the population has not regained the abundance or the distribution it had before the 1997-1998 El Niño ^[3].

IMARPE lists among the causes of the decline pollution, the degradation or loss of habitat, badly planned tourism, targeted hunting, and fishing and gathering, and shows as an example a juvenile photographed at Punta Atico in 2018 with a neck laceration caused by an entangled raffia bag ^[3]. In the San Fernando National Reserve and south of Marcona, the presence of people collecting seaweed on the beaches would be harming the colonies ^[3]. As early as 1993 it was reported that the species dies in incidental catches and through poaching across its range, especially in Peru ^[6].

In the San Fernando National Reserve, the population of this species stayed stable during the period in which the 2023 avian influenza hit Otaria byronia hard ^[7].

Not medical advice. For a sting, a poisoning or an allergy, seek medical care.

At Punta San Juan, in 2011 and 2012, domoic acid, a neurotoxin produced by harmful algae, was found in the faeces of 25 % of the fur seals of this species tested (11 of 44), and okadaic acid in 42 % of those tested in 2012 (5 of 12); saxitoxin was not confirmed in any animal ^[9]. Across the animals of this species and of Otaria byronia sampled there, domoic acid peaked at 533 ng/g, far below the values reported in pinnipeds with neurological symptoms of poisoning, and none showed signs of neurotoxicity ^[9].

In November 2010, 29 adult females from Punta San Juan were examined: there was no sign of contact with canine or phocine distemper viruses or with 5 serovars of Leptospira interrogans, but 37.9 % tested positive for Mycoplasma, 53.7 % were positive or doubtful for marine Brucella and 85.7 % carried antibodies against phocine herpesvirus PHV-1 ^[11]. The authors fear that a population with so little previous contact with pathogens could suffer disease outbreaks ^[11]. In whiskers and serum from this species and from Otaria byronia, sampled at that same site between 2011 and 2019, the concentrations of aluminium, arsenic and lead point to environmental pollution possibly affecting the health of both ^[12].

SERFOR warns that a stranded sea lion or fur seal can be very dangerous even if it looks weak or calm, and that it may react aggressively ^[13]. Anyone who has to handle one must wear gloves and protect themselves from diseases spread by bites or by contact with body fluids ^[13]. A pup alone on the beach should not be returned to the sea, because it may be waiting for its mother, who has gone out to feed, and any handling must be left to specialised staff only ^[13].

Native peoples, especially those of the Tierra del Fuego region, relied heavily on pinnipeds for food and skins; exploitation of this species by Europeans goes back to the sixteenth century, and hunting for its skin and oil was very intense in the late eighteenth and early nineteenth centuries in many parts of its range ^[6].

Sea lions and fur seals are a priority target of the master plan of the Paracas National Reserve, which also highlights their cultural value for the visitors who come to watch them; among their threats, the plan names interaction with fishing, pollution, illegal capture and bad tourism practices ^[2].

SERFOR's 2026 technical criteria allow sea lions and fur seals to be watched from land or from boats, without touching, feeding or scaring them, and do not allow swimming or diving with them in open water ^[14]. From a boat, the approach must be from the side and at 4 knots at most, no closer than 30 m to the nearest animal, with at most 2 boats at a time and 20 minutes per spot, and never in front of breeding areas ^[14].

In the 2016 to 2019 surveys, the largest colonies were Punta San Juan (37.2 % of the animals), Punta Coles (24.8 %), Punta Atico (12.2 %) and the San Fernando National Reserve (10.6 %), all on the southern coast ^[3]. On the central coast, the haul-outs of the Paracas peninsula stood out, with about 61 % of the animals in that zone ^[3].

Inside the Paracas National Reserve, a 2020 report counted 1166 individuals on Isla San Gallán, Punta Lagarto, Punta Lechuza, Punta Arquillo, Punta Sacasemita and Isla Independencia ^[2]. The cliffs of Punta Lagarto and Lechuza, where the species breeds and rests, lie in a strict protection zone where people and vehicles may not enter or pass through ^[2].

In the San Fernando National Reserve, 2084 individuals were estimated in April 2014 ^[7].