Occurrence of vagrant leopard seals, Hydrurga leptonyx, along the South African coast

Leopard seals inhabit the pack-ice rim of Antarctica, and they regularly haul out on Antarctic and Subantarctic islands. Occasionally, vagrants are sighted further north in South America, Australia, New Zealand, and very rarely in southern Africa and Oceania. Here we report on an observation made on the 15th of July 2010 of a single 3-m-long juvenile leopard seal at ‘Die Dam’in theWestern Cape, South Africa (34°45.772’S, 19°42.582’E). We searched historical records and found details of four observations of leopard seals along the coast of South Africa since 1946. All of these sightings were of juvenile animals. The relative scarcity of observations is a likely reflection of the great distance from Antarctica and the Subantarctic to South Africa.http://www.sawma.co.za/am2013ab201

Post-breeding at-sea movements of three central-place foragers in relation to submesoscale fronts in the Southern Ocean around Bouvetøya

At-sea behaviour of central-place foraging fur seals and penguins in the Southern Ocean is understudied during the latter stages of parental care and the subsequent pre-moulting period. This biologically important period is costly to investigate due to the risk (or certainty) of losing tracking instruments when the animals moult. Early in this period, parents must meet the increasing demands of larger, more mobile offspring that are still nutritionally dependent and then the parents must recover lost body condition prior to the onset of their annual moult. This study reports late-season, at-sea movement patterns of macaroni penguins, chinstrap penguins and adult female Antarctic fur seals from the subantarctic island Bouvetøya, in relation to remotely-sensed oceanographic features. Foraging trips differing significantly in direction and distance travelled compared to those performed earlier in the breeding season, coincide with the time when offspring would be expected to become independent. On these trips, macaroni penguins moved towards the Polar Front while chinstrap penguins and Antarctic fur seals moved southward. Individuals from all three species appeared to target submesoscale ocean features once they were presumed to have been released from the constraints of feeding their young and were able to travel greater distances from the colony.Norwegian Antarctic Research Expedition (NARE)http://journals.cambridge.org/action/displayJournal?jid=ANStm201

At-sea behaviour of three krill predators breeding at Bouvetøya—Antarctic fur seals, macaroni penguins and chinstrap penguins

Interspecific competition is an important structuring element in marine ecosystems, especially in the Southern Ocean which offers few prey choices to comparatively large predator populations. We present the first simultaneous observations of at-sea behaviour and attendance patterns of 3 synchronously breeding, central place, krill foragers at Bouvetøya—a small, isolated, sub-Antarctic island in the South Atlantic. Time depth recorders and satellite transmitters were deployed during the austral summer of 2007/2008 on 47 lactating Antarctic fur seals Arctocephalus gazella (AFS) rearing pups and on 20 macaroni Eudyptes chrysolophus (MAC) and 30 chinstrap Pygoscelis antarctica penguins (CHIN) rearing chicks. All 3 species showed a strong preference for the west side of the island, and their foraging ranges overlapped markedly. Solar elevation influenced the timing of departures from, and arrivals to, the island with markedly different patterns between the seals and the penguins. Diving patterns also showed significant differences among the 3 species, with the frequency of diving being higher at night for the AFS, while both penguin species dove more frequently during the day. But a common, vertical diel pattern occurred in all 3 species, with shallow diving occurring at night and deep diving during the day, consistent with the vertical migration of krill. MACs targeted 2 depth layers for feeding, including a deep prey layer at ~70 m, which was not exploited by AFSs and CHINs. The results suggest that there is potential for competitive overlap among these 3 krill predators at Bouvetøya, but that it is reduced via both spatial (horizontal and vertical) and temporal partitioning of foraging areas.The Norwegian Antarctic Research Expedition (NARE) programmehttp://www.int-res.com/journals/meps/meps-home/hj2013ab201

Confirmation of the occurrence of a second killer whale morphotype in South African waters

Killer whales Orcinus orca occur worldwide in a number of morphotypes that differ in size, pigmentation, acoustic behaviour, food type and genetics – some may indeed warrant subspecific or even specific status. Until recently, all killer whales in South African waters were referred to a single morphotype, Type A, but three individuals (two males and one female) that have stranded since 1969 differ in several respects from other killer whales examined from the region. Adult length is some 1–1.5 m smaller, appendages such as dorsal fin and flippers tend to be relatively larger, and tooth wear is excessive. Although dietary information is scant, one stomach contained the remains of several elasmobranchs, identified from a DNA subsample as blue sharks Prionace glauca, a dietary item that, if habitual, might account for the tooth wear. This morphotype, referred to here as ‘flat-toothed’ and which in several respects resembles the offshore form in the North Pacific and the Type 1 form in the North Atlantic, does not seem to have been recorded previously from the Southern Hemisphere.National Research Foundation, South Africahttp://www.tandfonline.com/loi/tams20hb201

Dispersal and dispersion of southern elephant seals at Marion Island

This study focused on the dispersal and dispersion of southern elephant seals, Mirounga leonina, at Marion Island in relation to their natal site, and to their site of first reproduction. Movements from the natal site to terrestrial haulouts used for reproduction, and between successive reproductive sites, were defined as dispersal, while movements from the natal site to sites used for purposes other than reproduction, were defined as dispersion. Some 33000 records collected over 12 years, of haul outs at 54 different sites of 5700 tagged seals, formed the database analysed. Both male and female seals were found to use sites closer to their natal site than expected, for reproductive, moult and winter haulouts. However, breeding seals used sites closer to their site of first reproduction than their natal site, on subsequent reproductive haulouts. No difference was found between the mean distances dispersed to moult sites and to winter haulout sites, but distances of dispersal were significantly less than distances of dispersion. Female seals dispersed further than males to reproductive sites, but no difference between the sexes was apparent for moult and winter dispersion. While the number of male seals hauling out to reproduce was too small to assess the effects of various factors on the dispersal of males, a number of factors influenced the dispersion of male seals, and dispersion and dispersal of female seals. These included age, isolation of natal site, anthropogenic disturbance, natal harem size and natal harem pre-weaning mortality. A number of hypotheses are proposed to explain the reasons behind the results found, and the direction of future research concerning the movements of southern elephant seals and their choice of terrestrial environment is suggested.Dissertation (MSc (Zoology))--University of Pretoria, 2006.ab2013Zoology and Entomologyunrestricte

Individual history of movement and the dispersal of southern elephant seals

While studies of dispersal note significant fidelity to natal site and to the site of first reproduction, few consider fidelity to other sites, and none have done so systematically. This study examined fidelity to all terrestrial sites within the study area during the course of its life, by a migratory marine predator, the southern elephant seal, Mirounga leonina. It also attempted to assess the role played by the winter haulout in terms of site fidelity. Finally it examined the influence of possible deterioration in spatial memory over time on site fidelity. The data used in this study were generated by a long-term mark-recapture programme conducted at subantarctic Marion Island. Although immature elephant seals of both sexes return to the vicinity of their natal sites, they appear to avoid popular breeding beaches, returning closest to the site previously used. At the first reproductive haulout, however, females return closer to their natal site than any other site, while males, although hauling out in the vicinity of their natal site, haul out closest to sites used in the year prior to the first breeding haulout. Subsequently, adults of both sexes breed closest to the breeding haulout of the previous year and moult closest to the moult haulout of the previous year. While males show greater site fidelity during the breeding season, there is no difference in site fidelity during the moult. Primiparous females show greater levels of site fidelity if recorded in the study site as an immature animal during either the winter or the moult haulouts. Also in female elephant seals, lower site fidelity is associated with an increase in the duration of period of absence from a site, and a lower number of visits to a site. Various factors related to site familiarity, social factors and anthropogenic disturbance may be responsible for the lack of strict site fidelity that is evident. Dispersal patterns may differ between the sexes due to differences in their life history. While purpose of the winter haulout by immature seals may be to increase familiarity with haulout sites, and thus site fidelity, the moult haulout also plays a role.Thesis (PhD)--University of Pretoria, 2013.Zoology and EntomologyUnrestricte

Vagrant subantarctic fur seal on the coast of Tanzania

An immature Subantarctic fur seal was sighted on Unguja Island, Zanzibar, Tanzania, in 2008. This is the most northerly record of a vagrant of this species. The nearest breeding colony is on the Prince Edward Islands, 4500 km distant. While it is likely that this is the natal site of the vagrant due to its proximity and population size, the actual location of origin is unknown. This is the second fur seal sighted in this area. A fur seal of unknown species was sighted on Pemba Island, 30 km north of the Unguja Island, in 2002. While the species of the latter animal could not be determined, it is likely also a Subantarctic fur seal

Intra-archipelago moult dispersion of southern elephant seals at the Prince Edward Islands, southern Indian Ocean

During three summer surveys at Prince Edward Island (PEI), southern Indian Ocean (2001, 2004 and 2008), 416 southern elephant seals Mirounga leonina were inspected for identification tags. In all, 42 seals that had been tagged as weaned pups at their natal site were found on Marion Island (MI), 38 of which could be individually identified by resighting their tag numbers. The majority of the MI-tagged seals were yearlings or subadults, and all but one were hauled out at PEI for the annual moult. The attendance rate of the known individuals at their natal island during the annual moult was only 40%, based on their resighting histories. This was significantly lower than the 77 ± 6% moult attendance rate estimated for a random MI population sample drawn from the same cohorts (based on 10 000 replications). Annual resight probabilities (considering all haulout phases) was 58% per annum for the MI seals seen at PEI, and 80 ± 4% for the simulation. Seasonal and annual absences of seals from MI violate the ‘homogeneity of capture’ assumption of mark–recapture models. When multiple sightings during any year are treated as a single sighting, resights during other haulouts (e.g. breeding) compensate only partially for absences during the moult. Therefore, mark–recapture studies undertaken in archipelagos should ideally include both marking and resighting of individuals on all islands which will allow discrimination between mortality and local migration

Intraspecific differences in the diet of Antarctic fur seals at Nyrøysa, Bouvetøya

Intraspecific differences in the diets of many species of pinnipeds are to be expected in view of the great differences in morphology, life history and foraging behaviour between the sexes of many species. We examined the diet of the Antarctic fur seal population at Bouvetøya, Southern Ocean to assess intersexual differences. This was made possible by the analysis of prey remains extracted from scats and regurgitations collected in areas used primarily by one or the other sex. The results indicate that both males and females feed primarily on Antarctic krill Euphausia superba with several species of fish and squid being taken, likely opportunistically given their prevalence. Significant differences were identified in the frequency of occurrence of otoliths in scats and the percentage numerical abundance of the major fish prey species in the diet. Adult males ate a smaller quantity of fish overall, but ate significantly more of the larger fish species. The greater diving capabilities of males and the fact that they are not limited in the extent of their foraging area by having to return regularly to feed dependant offspring may play a role in the differences found in the diets of males and females. Additionally, females might be more selective, favouring myctophids because they are richer in energy than krill. The absence of major differences in the diet between the sexes at this location is likely due to the high overall abundance of prey at Bouvetøya.This study was financed by the Norwegian Polar Institute (NPI) and the Norwegian Agency for Development Co-operation (NORAD). Further support was provided by the Mammal Research Institute of the University of Pretoria. We thank Bjørn Krafft, Ludvig Krag and Brian Flascas for their valuable assistance in the field. We are grateful to Bjørn Krafft, Iain Staniland and one anonymous reviewer for their comments and suggestions on the manuscript

Long-range migration of a chinstrap penguin from Bouvetøya to Montagu Island, South Sandwich Islands

We describe a long-range migration of a pre-moulting adult chinstrap penguin from Bouvetøya, a small relatively recently established colony, to the South Sandwich Islands, where large, established colonies of this species reside. The trip lasted around three weeks, covered ,3600 km, and the time of arrival was consistent with the annual moult. The bird did not travel along the shortest path or along a constant bearing, but instead followed what appeared to be a series of two or three rhumb lines of constant bearing. Small southward and northward deviations from the general path were consistent with local water currents. Travel speeds were high during daylight but decreased at night, suggesting that resting or opportunistic feeding occurred preferentially at night. While long-range winter migrations of chinstraps to feeding areas in the vicinity of distant colonies have been previously described, this is the first observation of such a trip during the period between breeding and moulting, and the first record of an individual actually arriving at one of these distant colonies. This has implications for understanding population structure and management of this important Southern Ocean predator