Southern Elephant Seal Research Articles

Epidemiological data of an influenza A/H5N1 outbreak in elephant seals in Argentina indicates mammal-to-mammal transmission.

H5N1 high pathogenicity avian influenza virus has killed thousands of marine mammals in South America since 2022. Here we report epidemiological data and full genome characterization of clade 2.3.4.4b H5N1 HPAI viruses associated with a massive outbreak in southern elephant seals (Mirounga leonina) at Península Valdés, Argentina, in October 2023. We also report on H5N1 viruses in concurrently dead terns. Our genomic analysis shows that viruses from pinnipeds and terns in Argentina form a distinct clade with marine mammal viruses from Peru, Chile, Brazil and Uruguay. Additionally, these marine mammal clade viruses share an identical set of mammalian adaptation mutations which were also present in tern viruses. Our combined ecological and phylogenetic data support mammal-to-mammal transmission and occasional mammal-to-bird spillover and suggest multinational transmission of H5N1 viruses in mammals. We reflect that H5N1 viruses becoming more evolutionary flexible and adapting to mammals in new ways could have global consequences for wildlife, humans, and/or livestock.

Extreme fieldwork: flame-sealed capillaries versus frozen serums to estimate body composition of southern elephant seals (Mirounga leonina) using isotopic dilution

Extreme fieldwork: flame-sealed capillaries versus frozen serums to estimate body composition of southern elephant seals (Mirounga leonina) using isotopic dilution

CS-PHOC: weekly census counts of Southern Ocean phocids at Cape Shirreff, Livingston Island

Rapid climatic warming of the Antarctic Peninsula is driving regional population declines and distribution shifts of predators and prey. Affected species include Antarctic ice seals and the southern elephant seal, all of which rely on the peninsula region for critical stages of their life cycle. However, data collection is difficult in this remote region, and therefore long-term time series with which to identify and investigate population trends in these species are rare. We present the Cape Shirreff Phocid Census (CS-PHOC) dataset: weekly counts of phocids (crabeater, leopard, southern elephant, and Weddell seals) hauled out at Cape Shirreff, Livingston Island, during most austral summers since 1997. Data from these censuses were cleaned and aggregated, resulting in robust and comparable count data from 284 censuses across 23 field seasons. The CS-PHOC dataset, which is publicly available through the SCAR Biodiversity Portal, will be updated yearly to provide important information about Southern Ocean phocids in the Antarctic Peninsula.

Modeling climate influences on male survival in the highly polygynous southern elephant seal (Mirounga leonina)

AbstractThe Southern Ocean, its ecosystem, and inhabitants are vulnerable to climate‐mediated shifts in habitat conditions. These changes can affect marine predators in the long term through changes in the distribution, density, and quality of prey. To understand how these changes affect vital rates requires longitudinal studies integrating demography and environmental states. We analyzed 22 years of capture–mark–recapture data to quantify the influence of broad‐scale climate on the survival of male southern elephant seals from Macquarie Island, Tasmania, Australia. Weaning mass was incorporated as a quadratic predictor of survival to account for the known influence of maternal investment. First‐year survival was greatest for weaners weighing 160 kg. Subsequent developmental stages were grouped into juvenile, subordinate, and breeding adult states to reflect the known life history of individuals. We found increased juvenile and subordinate survival with positive values of the previous years' Southern Annular Mode. This is likely due to the northward shift of westerly winds increasing productivity and prey availability in the Sub‐Antarctic region. In contrast to females of this population, the Southern Oscillation Index did not affect male survival. In this highly polygynous mating system, sex‐dependent differences in foraging behavior may be causing the small number of successful breeding adult males to be less susceptible to external influences after reaching the minimum age and body size required to be socially competitive for mating. These extremely large bulls will breed with multiple females and thus make a disproportionate contribution to the gene pool of the next generation. Considering the susceptibility of males to climate influences is therefore highly relevant to assessing the future adaptive capability of the species.

New sightings of southern elephant seals (Mirounga leonina) in México: Citizen science and wildlife dispersion

New sightings of southern elephant seals (Mirounga leonina) in México: Citizen science and wildlife dispersion

Hunting tactics of southern elephant seals Mirounga leonina and anti-predatory behaviours of their prey

For air-breathing marine predators that must save energy during dives, the ability to adopt hunting tactics that minimise the risk of triggering an escape reaction from the prey is crucial for efficient foraging. Female southern elephant seals (SES) Mirounga leonina forage on small mesopelagic prey that they must hunt almost continuously to meet their high-energy requirements. Here we aimed at understanding how these large time-limited deep-divers can efficiently exploit their small-sized prey. To do so, we used data recorded by a new biologger, the sonar tag, deployed on SES during their post-breeding foraging trips. This tag combines an active acoustic sensor with ultra-high-resolution movement and bioluminescence sensors. This combination of sensors offers a unique opportunity to simultaneously describe SES hunting tactics and defence mechanisms of their prey. We analysed more than 5800 prey capture events in 9 SES and show that they adopt a ‘stalking’ hunting behaviour, allowing them to get as close as possible to their prey before attacking. The ability of SES to adopt stealth approach tactics, minimising the risk of initiating a flight reaction from their prey, might be a key factor in the success of this far-ranging generalist predator.

Occurrences and activities of New Zealand sea lions Phocarctos hookeri at non-natal Macquarie Island (1965–1980)

ABSTRACT The distribution of New Zealand sea lions is typically localised to New Zealand and its remote subantarctic islands. However, non-resident male sea lions were seen on Macquarie Island, 650 km from their nearest natal islands, in all months of all years from 1965 to 1980. The majority of the apparently opportunistic sightings were at the northern end of the island. Sightings increased from May to a September-October peak that was coincident with the cessation of breeding activities in the sea lions’ natal range and the period when resident gentoo and royal penguins, and fur and elephant seals aggregated for breeding, all of which are now confirmed prey for New Zealand sea lions on Macquarie Island. The long-term effect of predation pressure from New Zealand sea lions on resident species remains unmeasured. After sleeping, interacting with southern elephant seals was a core sea lion activity. Predation on seabirds and interactions with elephant seals increase the risk of cross-species disease transmission.

Evolution of the peroxiredoxin gene family: an antioxidant enzyme in the context of hypoxia-induced by aquatic mammals dives

Peroxiredoxins are a group of antioxidant enzymes that play a crucial role in eliminating hydrogen peroxide (H2O2) produced during cellular metabolism. In conditions such as tissue ischemia/reperfusion, H2O2 production is heightened. This scenario is recurrent in aquatic mammals, such as cetaceans and pinnipeds, when they perform breath-hold dives that lead to depletion of oxygen stores and cell hypoxia due to prolonged submersion. In such circumstances, peroxiredoxins are essential for regulating metabolism and preventing oxidative damage. Thus, our objective was to investigate evolutionary patterns of the peroxiredoxin gene family among aquatic mammalian species. Accordingly, we identified the number of ortholog and paralog genes among mammals, examining events of gene duplication, patterns of chromosomal distribution, and adaptive selection. We found that most subtypes of peroxiredoxins are characterized by single-copy genes with minimal missing data, with PRDX1, the most highly expressed subtype found in both the nucleus and cytoplasm, exhibiting an increase in gene copies in aquatic mammals, particularly in pinnipeds. The distribution of the copies was dispersed along the genome and the majority were retrocopies of the main coding sequence with little divergence among them. We also found evidence of positive selection in the PRDX3 gene, especially in a convergent mutation among two deepest-diving species, cuvier’s beaked whale and southern elephant seal in which the amino acid had radical physical-chemical property change, possibly affecting the protein function. These results suggest that the peroxiredoxin gene family has a role in the evolution of aquatic mammals by reducing oxidative damage intrinsic to diving behavior in these species. FAPESP - São Paulo Research Foundation. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Genomic Insights into Diving Adaptations of Extreme Pinniped Divers: A Comparative Study of Elephant and Weddell Seals

Extreme pinniped divers are extraordinary models to study adaptations to hypoxia/reoxygenation events derived from extreme fluctuations in oxygen levels during deep diving. We analyzed the evolutionary adaptations of the Weddell seal ( Leptonychotes weddellii) and the Northern and Southern elephant seals ( Mirounga angustirostris and M. leonina), which have exceptional diving abilities, reaching depths of over 1000 meters for extended periods up to 90 minutes. To understand the molecular mechanisms underpinning these remarkable adaptations, we conducted a comprehensive comparative genomic analysis of thirteen pinniped species. Our gene family evolution analyses revealed a significant loss of function in genes involved in the enzymatic degradation of glutathione, an endogenous antioxidant that our functional analysis have previously shown to increase rapidly in response to hypoxia exposure in primary cells derived from extreme divers, likely to protect cells against oxidative damage. We also detected adaptive signatures in pathways involved in the optimization of mitochondrial respiration, energy metabolism, DNA repair and cardiovascular regulation in these extreme divers. Notably the Weddell seal exhibited more genes under positive selection compared to the Elephant seals, possibly reflecting adaptations to extreme environmental pressures. Pathways enriched in Weddell seals include those related to fat metabolism, oxidative damage against hydrogen peroxide and membrane lipid remodeling. Our analysis sheds light on the remarkable genomic adaptations that enable extreme pinniped divers to tolerate oxygen fluctuations associated with deep diving while offering valuable insights into their unique physiological and biochemical strategies for overcoming the challenges posed by hypoxia and reperfusion damage. NSF OPP 2020664. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Sealing the deal - Antarctic fur seals' active hunting tactics to capture small evasive prey revealed by miniature sonar tags.

The ability of predators to adopt hunting tactics that minimise escape reactions from prey is crucial for efficient foraging, and depends on detection capabilities and locomotor performance of both predators and prey. Here, we investigated the efficiency of a small pinniped, the Antarctic fur seal (Arctocephalus gazella) at exploiting their small prey by describing for the first time their fine-scale predator-prey interactions. We compared these with those from another diving predator, the southern elephant seal (Mirounga leonina) that forage on the same prey type. We used data recorded by a newly developed sonar tag that combines active acoustics with ultrahigh-resolution movement sensors to study simultaneously the fine-scale behaviour of both Antarctic fur seals and prey during predator-prey interactions in more than 1200 prey capture events for eight female Antarctic fur seals. Our results showed that Antarctic fur seals and their prey detect each other at the same time, i.e. 1-2 s before the strike, forcing Antarctic fur seals to display reactive fast-moving chases to capture their prey. In contrast, southern elephant seals detect their prey up to 10 s before the strike, allowing them to approach their prey stealthily without triggering an escape reaction. The active hunting tactics used by Antarctic fur seals is probably very energy consuming compared with the stalking tactics used by southern elephant seals but might be compensated for by the consumption of faster-moving larger prey. We suggest that differences in manoeuvrability, locomotor performance and detection capacities and in pace of life between Antarctic fur seals and southern elephant seals might explain these differences in hunting styles.

Does the potential strength of sexual selection differ between mating systems with and without defensive behaviours? A meta-analysis.

The Darwin-Bateman paradigm predicts that females enhance their fitness by being choosy and mating with high-quality males, while males should compete to mate with as many females as possible. In many species, males enhance their fitness by defending females and/or resources used by females. That is, males directly defend access to mating opportunities. However, paternity analyses have repeatedly shown that females in most species mate polyandrously, which contradicts traditional expectations that male defensive behaviours lead to monandry. Here, in an extensive meta-analysis, encompassing 109 species and 1026 effect sizes from across the animal kingdom, we tested if the occurrence of defensive behaviours modulates sexual selection on females and males. If so, we can illuminate the extent to which males really succeed in defending access to mating and fertilisation opportunities. We used four different indices of the opportunity for sexual selection that comprise pre-mating and/or post-mating episodes of selection. We found, for both sexes, that the occurrence of defensive behaviours does not modulate the potential strength of sexual selection. This implies that male defensive behaviours do not predict the true intensity of sexual selection. While the most extreme levels of sexual selection on males are in species with male defensive behaviours, which indicates that males do sometimes succeed in restricting females' re-mating ability (e.g. elephant seals, Mirounga leonina), estimates of the opportunity for sexual selection vary greatly across species, regardless of whether or not defensive behaviours occur. Indeed, widespread polyandry shows that females are usually not restricted by male defensive behaviours. In addition, our results indicate that post-mating episodes of selection, such as cryptic female choice and sperm competition, might be important factors modulating the opportunity for sexual selection. We discuss: (i) why male defensive behaviours fail to lower the opportunity for sexual selection among females or fail to elevate it for males; (ii) how post-mating events might influence sexual selection; and (iii) the role of females as active participants in sexual selection. We also highlight that inadequate data reporting in the literature prevented us from extracting effect sizes from many studies that had presumably collected the relevant data.

1500-year reconstruction of Circumpolar Deep Water intrusion and its impact on southern elephant seal populations in King George Island, West Antarctic Peninsula

Circumpolar Deep Water (CDW) intrusion onto the continental shelf significantly affects basal melting of ice shelves, oceanographic and ecological processes in the West Antarctic Peninsula (WAP). Understanding the changes in CDW upwelling and its impacts on marine ecology during historical periods is urgent. Here, we presented a new reconstruction for the variability in CDW intrusion onto the WAP over the past 1500 years by using the cadmium (Cd) concentrations in southern elephant seal hairs collected from King George Island. In addition, multi-proxies including the abundance of seal hairs and TOC, TN, LOI, and bio-elements in the sediments were integrated to infer historical seal populations by using the Generalized Additive Models (GAMs). The overall trend of Cd concentrations was well consistent with those of primary productivity and sea ice, reflecting the contribution of CDW on regional oceanic environment and ecology. Notably, during a period of ∼900–500 yr BP, enhanced CDW intrusion allowed for increased regional marine productivity and decreased sea ice, and ultimately promoting an increase in seal populations. Enhanced CDW intrusion was possibly driven by southward shift and intensification of the Southern Hemisphere westerly wind. These results indicated that large-scale atmospheric circulation patterns were coupled with regional oceanic circulation and ecological processes of the Southern Ocean.

Lack of Highly Pathogenic Avian Influenza H5N1 in the South Shetland Islands in Antarctica, Early 2023.

In January 2023, an active surveillance initiative was undertaken in the South Shetland Islands, Antarctica, with the specific objective of ascertaining evidence for the presence of avian influenza, and specifically the highly pathogenic avian influenza virus subtype H5N1 (HPAIV H5N1). The investigation encompassed diverse locations, including Hanna Point (Livingston Island), Lions Rump (King George Island), and Base Escudero (King George Island), with targeted observations on marine mammals (southern elephant seals), flying birds (the kelp gull, snowy sheathbill and brown skua), and penguins (the chinstrap penguin and gentoo penguin). The study encompassed the examination of these sites for signs of mass mortality events possibly attributable to HPAIV H5N1, as well as sampling for influenza detection by means of real-time RT-PCR. Two hundred and seven (207) samples were collected, including 73 fecal samples obtained from the environment from marine mammals (predominantly feces of southern elephant seals), and 77 cloacal samples from penguins of the genus Pygoscelis (predominantly from the gentoo penguin). No evidence of mass mortality attributable to HPAIV H5N1 was observed, and all the collected samples tested negative for the presence of the virus, strongly suggesting the absence of the virus in the Antarctic territory during the specified period. This empirical evidence holds significant implications for both the ecological integrity of the region and the potential zoonotic threats, underscoring the importance of continued surveillance and monitoring in the Antarctic ecosystem.

From land to ocean: One month for southern elephant seal pups to acquire aquatic skills prior to their first departure to sea

Weaned southern elephant seals (SES) quickly transition from terrestrial to aquatic life after a 5- to 6-week post-weaning period. At sea, juveniles and adult elephant seals present extreme, continuous diving behaviour. Previous studies have highlighted the importance of the post-weaning period for weanlings to prepare for the physiological challenges of their future sea life. However, very little is known about how their body condition during this period may influence the development of their behaviour and brain activities. To characterise changes in the behavioural and brain activity of weanlings prior to ocean departure, we implemented a multi-logger approach combining measurements of movements (related to behaviour), pressure (related to diving), and brain electrical activity. As pups age, the amount of time allocated to resting decreases in favour of physical activity. Most resting (9.6 ± 1.2 h/day) takes place during daytime, with periods of slow-wave sleep representing 4.9 ± 0.9 h/day during the first 2 weeks. Furthermore, an increasing proportion of physical activity transitions from land to shore. Additionally, pups in poorer condition (lean group) are more active earlier than those in better condition (corpulent group). Finally, at weaning, clear circadian activity with two peaks at dawn and dusk is observed, and this pattern remains unchanged during the 4 weeks on land. This circadian pattern matches the one observed in adults at sea, with more prey catches at dawn and dusk, raising the question of whether it is endogenous or triggered by the mother during lactation.

Historical ecology of pinnipeds of the northern coast of the San Jorge Gulf (central Patagonia, Argentina) since the Late-Holocene

The northern coast of the San Jorge Gulf, Atlantic Patagonia, is recognised as a marine biodiversity hot spot and is designated as a priority conservation area. Among marine mammals, three species of pinnipeds inhabit the region. While South American sea lions ( Otaria flavescens) have a higher abundance and a larger number of colonies than South American fur seals ( Arctocephalus australis), a few individuals of the Southern elephant seal ( Mirounga leonina) reside in the region. Nevertheless, little is known about the abundance and distribution of these pinnipeds before the 18th century, when various extractive activities became widespread, including the unregulated exploitation of furs and oil. This study aims to examine whether the distribution and relative abundance of ancient pinnipeds differ from present-day populations. To achieve this, we conducted inter-specific identification of pinniped bone remains coming from archaeological assemblages dated from 6000 to 600 14C years BP and reviewed historical sources to contrast these retrospective data with modern ecological literature. The results suggest changes over time in the relative abundances of species within the pinniped community. The relative abundance of fur seals was greater than or equal to that of sea lions in most Late-Holocene pinniped assemblages. Additionally, fur seals have been recorded in historical and Late-Holocene periods in places where they are currently very rare. These findings are consistent with the higher relative abundance of fur seals recorded in other archaeological sites along the Patagonian coast, suggesting that modern distribution and abundance have been heavily affected by commercial hunting. This study contributes to a better understanding of the nature and magnitude of the anthropic impact on the marine ecosystem of the northern coast of the San Jorge Gulf. It also provides historical baseline information to strengthen conservation policies and restoration efforts.

A reconstruction of the marine mammal harvest by the Real Compañía Marítima through the analysis of historical sources (AD 1790–1804)

Humans have altered marine ecosystems over very long-time scales and historical data is often needed to understand the true magnitude of human impacts. The Southwest Atlantic Ocean has a long history of large-scale removal of marine vertebrates due to whaling, sealing, and fishing in the past three centuries. Historical catch records are crucial in assessing the conservation status of these historically over-exploited populations and setting suitable recovery goals. However, several gaps in the history of exploitation of many populations limit our ability to judge recoveries success. This study examines the history of the Spanish fishing company, the Real Compañía Marítima (Royal Maritime Company), and reconstructs its catches of marine mammals in Patagonia and on the north coast of the Río de la Plata. The analysis of a wide range of historical sources reveals that, between the years 1790 and 1804, the Company extracted less than 100 southern right whales Eubalaena australis, some 200,000 South American fur seals Arctocephalus australis and South American sea lions Otaria flavescens, and a few southern elephant seals Mirounga leonina. Although the Company’s whale catch is negligible compared to that of other nations in the same whaling grounds, the amount of fur seals and sea lions removed from the ecosystem deserves attention. This historical survey provides us with the first estimate of the catches made by the Real Compañía Marítima. However, these figures only represent a small part of the extractive activities that took place in the region and further research is encouraged to assess the true dimension of human impacts on Southwest Atlantic ecosystems. The incorporation of retrospective data into ecological studies can be laborious and may have inherent biases, but it also provides valuable information for comprehending modern ecosystems and formulating appropriate conservation plans.

Understanding the feeding ecology of the broadnose sevengill shark (Notorynchus cepedianus) in Patagonia, Argentina

The broadnose sevengill shark (Notorynchus cepedianus) is classified as Vulnerable by the IUCN, and its population in the Southwest Atlantic is declining. Despite some progress in understanding the ecological requirements of the sevengill shark, there are still several information gaps. Essential aspects of its trophic ecology, such as main prey items or key feeding grounds, remain uncertain and this information is essential for developing effective conservation strategies. Stable isotopes and spontaneous regurgitations were analyzed to describe the trophic ecology of sevengill sharks within a marine protected area (MPA) of Península Valdés in Patagonia, Argentina. Analysis of spontaneous regurgitations revealed that the southern elephant seal (Mirounga leonina) was the primary prey item (70%) for the sevengill shark, during abundance peaks of both species in the MPA. However, the stable isotope analysis indicated that the teleosts were the main prey item, and the overall contribution of the elephant seal to the diet of the sevengill shark was around 30%. In addition, the contribution of each prey group varied with the size of the individuals. The estimated trophic position was 4.43, placing the species among the apex predators of the region. This study confirmed the use of the MPA as an essential foraging ground and contributed to identifying its main prey items. Also, it reflects the need to expand conservation tools beyond this particular coastal protection.

Diminishing numbers of male southern elephant seals (Mirounga leonina Pinnipedia: Phocidae, Linnaeus, 1758) at the Vestfold Hills, East Antarctica (1957–2022)

Abstract A proportion of the southern elephant seal (Mirounga leonina) population that breeds in the Kerguelen Plateau region seasonally migrates between their natal sub-Antarctic islands and moult haul-out locations on the Antarctic coastline. Analyses of survey data collated for one moult location at the Vestfold Hills, East Antarctica, showed that there had been no appreciable change in the timing (phenology) of maximum seal arrivals between 1974 and 2022; however, the maximum number of seals moulting at that site had declined by ~90% over the same time interval. Spatial analyses showed rates of population change were survey area dependent, as seal numbers decreased most rapidly at haul-out areas closest to the permanently occupied Davis Station, suggesting that a relationship exists between seal numbers and human activities. The range of potential factors that contribute to population change for southern elephant seals moulting at the Vestfold Hills includes changes in status at primary source populations, one of which has not been surveyed since the 1990s, and species relocation. Should numbers of southern elephant seals in the Vestfold Hills continue to decrease at the current average rate of change (-7.78 seals/year) the species could vanish from the area by c. 2040.

Robustly estimating the demographic contribution of immigration: Simulation, sensitivity analysis and seals.

Identifying important demographic drivers of population dynamics is fundamental for understanding life-history evolution and implementing effective conservation measures. Integrated population models (IPMs) coupled with transient life table response experiments (tLTREs) allow ecologists to quantify the contributions of demographic parameters to observed population change. While IPMs can estimate parameters that are not estimable using any data source alone, for example, immigration, the estimated contribution of such parameters to population change is prone to bias. Currently, it is unclear when robust conclusions can be drawn from them. We sought to understand the drivers of a rebounding southern elephant seal population on Marion Island using the IPM-tLTRE framework, applied to count and mark-recapture data on 9500 female seals over nearly 40 years. Given the uncertainty around IPM-tLTRE estimates of immigration, we also aimed to investigate the utility of simulation and sensitivity analyses as general tools for evaluating the robustness of conclusions obtained in this framework. Using a Bayesian IPM and tLTRE analysis, we quantified the contributions of survival, immigration and population structure to population growth. We assessed the sensitivity of our estimates to choice of multivariate priors on immigration and other vital rates. To do so we make a novel application of Gaussian process priors, in comparison with commonly used shrinkage priors. Using simulation, we assessed our model's ability to estimate the demographic contribution of immigration under different levels of temporal variance in immigration. The tLTRE analysis suggested that adult survival and immigration were the most important drivers of recent population growth. While the contribution of immigration was sensitive to prior choices, the estimate was consistently large. Furthermore, our simulation study validated the importance of immigration by showing that our estimate of its demographic contribution is unlikely to result as a biased overestimate. Our results highlight the connectivity between distant populations of southern elephant seals, illustrating that female dispersal can be important in regulating the abundance of local populations even when natal site fidelity is high. More generally, we demonstrate how robust ecological conclusions may be obtained about immigration from the IPM-tLTRE framework, by combining sensitivity analysis and simulation.

Incidental pinnipeds at high latitudes of the Vestfold Hills, Prydz Bay, East Antarctica

AbstractSpecies distributions are predicted to change with future climate-associated ecosystem changes such that so-called ‘vagrant’ individuals may become established or re-establish in areas currently thought to be beyond their principle ranges. Survey data were collated for occurrences of pinniped (seal) species at very high latitudes of the Vestfold Hills, East Antarctica. Aside from Weddell seals (Leptonychotes weddellii) and southern elephant seals (Mirounga leonina), which aggregate annually at the Vestfold Hills to breed and/or moult, three other pinniped species were observed with the recession of the fast-ice edge. Leopard seal (Hydrurga leptonyx) occurrences increased with an increase in a seasonally abundant prey resource, and crabeater seals (Lobodon carcinophaga) were seen at a time that coincides with their moult period. Occurrences of sub-adult male Antarctic fur seals (Arctocephalus gazella) increase the known southward range for this species and may reflect population increases at source populations in the Kerguelen Plateau area. Although there were no direct sightings of Ross seals (Ommatophoca rossii), their presence close to the Vestfold Hills was detected by underwater passive acoustic monitoring. Sightings of obligate drift-ice species and sub-Antarctic fur seals may change at the Vestfold Hills with climate-mediated changes in sea-ice conditions.