Arctocephalus forsteri

The species can "porpoise" out of the water when travelling quickly at sea.[1] They can dive deeper and longer than any other fur seal.[5] Females can dive for about 9 minutes and to a depth of about 312 metres, and can dive deeper and longer in autumn and winter. Males can dive for about 15 minutes to a depth of about 380 metres.[1] On average, the species typically only dives for 1–2 minutes.[5] When they dive for food they dive deeper during the day but shallower at night, because during the day their prey typically migrates to deeper depths and migrates back up during the night.[5]

Lactating females alter their dive patterns in order to regularly care for their young. Dives are shorter, from around 9 minutes down to 5 minutes. Several longer trips may be taken at first to find patches of prey. The shorter dives then utilise these patches. Due to the differences in diving pattern between males and females, there is very little inter-sexual competition for food sources. Males typically forage over continental shelf breaks in deeper water, while females typically utilise the continental shelf as foraging grounds. It is believed that differences in diving abilities and depths could be the cause of some sexual dimorphism between males and females.[10]

Diving behaviour by the pups begins in the months leading up to weaning, when the pups are nursing less. The pups begin to dive from the age of 6–10 months, yet weaning is known to occur between the ages of 8 and 11 months, so the young pups do not have much time to learn to forage. The pups need to progressively develop nocturnal diving skills while they still have their mothers' milk to fall back on if dives are unsuccessful. Age, physiological development, and experience are important factors for success in hunting and contribute to the development of the pups' diving ability and behaviour. This transitional period when young pups are becoming nutritionally independent while their foraging efficiency is rather low, is a time of high risk, and mortality can be very high. Based on scat samples, it has been found that the pups start by eating cephalopods and eventually making their way to fish, but this may just be a result of prey availability during different times of the year.[11]

Males vocalise through a bark or whimper, either a guttural threat, a low-intensity threat, a full threat, or a submissive call. Females growl and also have a high-pitched pup attraction wail call.[1] Pup-attraction calls allow communication from longer distances. Once together, females use olfactory recognition to confirm the pup as their own.[12] In males, the full neck display is a non-combative posture that functions as a threat to surrounding males by which they are able to assess each other's dominance status.[12]

Arctocephalus forsteri near Kaikoura, New Zealand

Females mature between 4 and 6 years old, and males mature between 8 and 10 years old.[1] These seals are polygynous.[1][5] Males obtain and guard territory in late October before females arrive.[1] Often females mate only once a year, and this usually occurs eight days postpartum for about 13 minutes on average. Females have a delayed implantation of the fertilised egg, so that implantation on the uterine wall does not occur for 3 months.[5] Gestation occurs for 9 months[5] Females are more aggressive near the time of birth, and do not like to be approached right after birth.[8] Females will continue to reproduce until their death which is on average between 14 and 17 years of age.[5]

Females first arrive on the shore between November and January,[1] just a few days before giving birth, and stay close to the birth site for up to ten days. When they are close to labour they become very restless and irritable. When beginning labour, which can last as much as five hours, they lie down and toss their head in the air, straining forward on their fore flippers, lifting their hind quarters, or moving laterally, before slowly lowering their head down, a process they repeat until they finally give birth. In one study, observations of the actual birth, starting from when the pup was first seen, found an average of 2 minutes for a head-first delivery, but an average of 6.5 minutes if the pup came out tail first. Immediately after birth the mother begins frequently sniffing the newborn pup to better identify when she has to find it after a trip out to sea. Pups are fairly mature at birth, and within 60 minutes they start suckling for about 7 minutes. Eventually the suckling can exceed 33 minutes.[8]

The mothers may take from 45 minutes to 3 days before leaving the pups to swim, and 6–12 days to go on longer feeding trips. Even then the mothers tend to not leave the pups for longer than 2 days. When the pups are about 21 days old they have been seen to congregate into little pods while their mothers are away. When the females return they only feed their own pups, and have been seen to be hostile toward pups that are not their own.[13]

Female seals have been documented to have a gradual increase in trips for feeding throughout lactation. It has been found that mothers who have sons made longer foraging trips then the mothers who had daughters during the lactation period. When observing growth patterns in the male and female pups within two cohorts, it is recognised that the growth patterns are similar, however the males grow faster and are weaned off nursing heavier in some years.[14] Suckling can occur for about 300 days. Pups start to eat solid food just before weaning,[5] and are eventually weaned around September, when they disperse.[8][5]

Pup mortality has been attributed to both natural factors and human interaction. The biggest natural cause of death for pups is starvation, followed by suffocation in the amnion, stillbirth, trampling, drowning, and predation.[15] Human factors include the handling of pups, tagging, and human presence in general.[15]

In Australian Commonwealth waters, Arctocephalus forsteri is protected under the Environment Protection Biodiversity Conservation (EPBC) Act 1999 under which it is listed as a protected marine species.[22] The species is also protected within the jurisdictions of the following Australian states:

The species received protection by the creation of a 16 million hectare Marine Park located on the eastern side of Macquarie island in 2000. The Tasmanian government has also extended to Macquarie Island Nature Reserve by 3 nautical miles surrounding the island.[20]

In New Zealand, the species is protected by the Marine Mammals Protection Act 1978, which works to conserve marine animal species; it specifies that all wild Pinnipeds cannot be touched or fed.[1]