No evidence for a role of MHC class II genotype in the chemical encoding of heterozygosity and relatedness in Antarctic fur seals.

Despite decades of research, surprisingly little is known about the mechanism(s) by which an individual's genotype is encoded in odour. Many studies have focused on the role of the major histocompatibility complex (MHC) owing to its importance for survival and mate choice. However, the salience of MHC-mediated odours compared to chemicals influenced by the rest of the genome remains unclear, especially in wild populations where it is challenging to quantify and control for the effects of the genomic background. We addressed this issue in Antarctic fur seals by analysing skin swabs together with full-length MHC DQB II exon 2 sequences and data from 41 genome-wide distributed microsatellites. We did not find any effects of MHC relatedness on chemical similarity and there was also no relationship between MHC heterozygosity and chemical diversity. However, multilocus heterozygosity showed a significant positive association with chemical diversity, even after controlling for MHC heterozygosity. Our results appear to rule out a dominant role of the MHC in the chemical encoding of genetic information in a wild vertebrate population and highlight the need for genome-wide approaches to elucidate the mechanism(s) and specific genes underlying genotype-odour associations.

Unraveling the gut microbiota of Mexican pinnipeds: the dominance of life histories over phylogeny.

Studying how phylogeny influences the composition and functions of microbiotas within animal hosts is essential for gaining insights into the connection between genetics, ecology, and health in the animal kingdom. However, due to limited comprehensive studies, this influence remains unclear for many wild mammals, including Mexican pinnipeds. We employed 16S rRNA gene deep-sequencing to investigate the impact of phylogeny on the gut microbiota of four pinniped species inhabiting Mexican shores: the Pacific harbor seal (Phoca vitulina richardii), the northern elephant seal (Mirounga angustirostris), the California sea lion (Zalophus californianus), and the Guadalupe fur seal (Arctocephalus philippii townsendi). Our results indicated that factors such as diets and shared life histories exerted more influence on microbiota composition than phylogeny alone. Notably, otariid species sharing similar life histories displayed greater microbiota similarity than phocids, which have distinct life histories and fewer microbiota similarities. Furthermore, harbor seals have more microbial similarities with the two otariid species than with elephant seals. Of particular concern, we observed a higher abundance of potentially pathogenic bacteria (e.g., Photobacterium damselae and Clostridium perfringens) in harbor seals and Guadalupe fur seals compared to other pinnipeds. This finding could pose health threats to these species and nearby human populations.IMPORTANCEPinnipeds in Mexico host microbial communities that remain understudied. While several factors can influence microbiota composition, the role of phylogenetic relationships among these pinnipeds remains unclear due to limited knowledge of the microbiota in certain species. This study aimed to fill this gap by characterizing the composition and function of the gut microbiota in the four pinniped species that occur in Mexico. Our analysis reveals that shared diets and life histories contribute to similarities in the composition of gut microbial communities. This study also highlights the potential differences in the metabolic capabilities and adaptations within the gut microbiota of pinnipeds. Understanding how phylogeny impacts microbial communities enhances our insights into the evolutionary dynamics of marine mammals.

Future climate-induced distribution shifts in a sexually dimorphic key predator of the Southern Ocean.

The response to climate change in highly dimorphic species can be hindered by differences between sexes in habitat preferences and movement patterns. The Antarctic fur seal, Arctocephalus gazella, is the most abundant pinniped in the Southern Hemisphere, and one of the main consumers of Antarctic krill, Euphausia superba, in the Southern Ocean. However, the populations breeding in the Atlantic Southern Ocean are decreasing, partly due to global warming. Male and female Antarctic fur seals differ greatly in body size and foraging ecology, and little is known about their sex-specific responses to climate change. We used satellite tracking data and Earth System Models to predict changes in habitat suitability for male and female Antarctic fur seals from the Western Antarctic Peninsula under different climate change scenarios. Under the most extreme scenario (SSP5-8.5; global average temperature +4.4°C projected by 2100), suitable habitat patches will shift southward during the non-breeding season, leading to a minor overall habitat loss. The impact will be more pronounced for females than for males. The reduction of winter foraging grounds might decrease the survival of post-weaned females, reducing recruitment and jeopardizing population viability. During the breeding season, when males fast on land, suitable foraging grounds for females off the South Shetland Islands will remain largely unmodified, and new ones will emerge in the Bellingshausen Sea. As Antarctic fur seals are income breeders, the foraging grounds of females should be reasonably close to the breeding colony. As a result, the new suitable foraging grounds will be useful for females only if nearby beaches currently covered by sea ice emerge by the end of the century. Furthermore, the colonization of these new, ice-free breeding locations might be limited by strong female philopatry. These results should be considered when managing the fisheries of Antarctic krill in the Southern Ocean.

La resposta al canvi climàtic en espècies amb dimorfisme sexual pot veure's dificultada per les diferències entre sexes respecte a les seves preferències d'ús de l'hàbitat i els seus patrons de moviment. L'os marí antàrtic (Arctocephalus gazella), és el pinnípede més abundant a l'Hemisferi Sud i un dels principals consumidors de krill antàrtic, (Euphausia superba), a l'Oceà Antàrtic. No obstant això, les poblacions que es reprodueixen al sector Atlàntic de l'Oceà Antàrtic estan disminuint, en part a causa de l'escalfament global. Els mascles i les femelles de l'os marí antàrtic difereixen considerablement en la seva mida corporal i ecologia tròfica, i es té poc coneixement sobre les seves respostes específiques al canvi climàtic. En aquest estudi hem utilitzat dades de seguiment per satèl·lit i models del Sistema Terrestre per predir els canvis en la idoneïtat de l'hàbitat per als mascles i les femelles d'os marí antàrtic de la Península Antàrtica Occidental sota diferents escenaris de canvi climàtic. Sota l'escenari més extrem (SSP5-8.5; temperatura mitjana mundial +4.4°C prevista per a 2100), les zones d'hàbitat idoni es desplaçaran cap al sud durant l'època d'hivernada (no reproducció), provocant una lleugera pèrdua d'hàbitat idoni. Tot i això, l'impacte serà més pronunciat per a les femelles que per als mascles. Aquesta reducció dels territoris d'alimentació durant l'hivern podria disminuir la supervivència de les femelles postdeslletades, reduint-ne el reclutament i posant en perill la viabilitat de la població. Durant l'època de cria, quan els mascles es troben majoritàriament en dejú a terra, els territoris d'alimentació idonis per a les femelles al voltant de les Illes Shetland del Sud romandran en gran part sense modificar-se, i n'emergiran de nous al mar de Bellingshausen. Com que les femelles d'os marí antàrtic es continuen alimentant durant la cria, els territoris d'alimentació de les femelles han d'estar raonablement a prop de la colònia de cria. Com a resultat, aquestes noves zones d'alimentació seran útils només si les platges properes, actualment cobertes de gel marí, emergeixen al llarg del segle. A més, la colonització d'aquests nous llocs de reproducció lliures de gel podria veure's limitada per la forta filopatria de les femelles. Aquests resultats haurien de tenir-se en compte en la gestió de les pesqueries de krill a l'Oceà Antàrtic.

Use of acoustic signals in Cape fur seal mother-pup reunions: individual signature, signal propagation and pup home range.

The Cape fur seal (Arctocephalus pusillus pusillus) is one of the most colonial mammals, with colonies of up to hundreds of thousands of individuals during the breeding season. During the lactation period, mothers and pups are regularly separated as females undertake multi-day foraging trips at sea. Mothers and pups use a mutual vocal recognition system to reunite after separation. Such communication is highly constrained by both high background noise and risk of individual confusion owing to the density of seals. This study aimed to experimentally assess the acoustic features relevant for mother-pup vocal identification and the propagation properties of their calls. Playback experiments revealed that mother and pup individual vocal signatures rely on both temporal and frequency parameters: amplitude and frequency modulations, timbre and fundamental frequency (f0). This is more parameters than in any colonial species studied so far. The combinational use of acoustic features reinforces the concept that both environmental and social constraints may have acted as selective pressures on the individual vocal recognition systems. Theoretical propagation distances of mother and pup vocalisations were estimated to be below the range of distances at which mother-pup reunions can occur. This suggests that Cape fur seals may have strong abilities to extract vocal signals from the background noise, as previously demonstrated in the highly colonial king penguin. Investigating the transmission of information throughout the propagation of the signal as well as the ability of the receiving individual to decipher vocal signatures is crucial to understanding vocal recognition systems in the wild.

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.

Niche partitioning and individual specialisation in resources and space use of sympatric fur seals at their range margin.

Ecological theory predicts niche partitioning between high-level predators living in sympatry as a mechanism to minimise the selective pressure of competition. Accordingly, male Australian fur seals Arctocephalus pusillus doriferus and New Zealand fur seals A. forsteri that live in sympatry should exhibit partitioning in their broad niches (in habitat and trophic dimensions) in order to coexist. However, at the northern end of their distributions in Australia, both are recolonising their historic range after a long absence due to over-exploitation, and their small population sizes suggest competition should be weak and may allow overlap in niche space. We found some niche overlap, yet clear partitioning in diet trophic level (δ15N values from vibrissae), spatial niche space (horizontal and vertical telemetry data) and circadian activity patterns (timing of dives) between males of each species, suggesting competition may remain an active driver of niche partitioning amongst individuals even in small, peripheral populations. Consistent with individual specialisation theory, broad niches of populations were associated with high levels of individual specialisation for both species, despite putative low competition. Specialists in isotopic space were not necessarily specialists in spatial niche space, further emphasising their diverse individual strategies for niche partitioning. Males of each species displayed distinct foraging modes, with Australian fur seals primarily benthic and New Zealand fur seals primarily epipelagic, though unexpectedly high individual specialisation for New Zealand fur seals might suggest marginal populations provide exceptions to the pattern generally observed amongst other fur seals.

Ninety years of change, from commercial extinction to recovery, range expansion and decline for Antarctic fur seals at South Georgia.

With environmental change, understanding how species recover from overharvesting and maintain viable populations is central to ecosystem restoration. Here, we reconstruct 90 years of recovery trajectory of the Antarctic fur seal at South Georgia (S.W. Atlantic), a key indicator species in the krill-based food webs of the Southern Ocean. After being harvested to commercial extinction by 1907, this population rebounded and now constitutes the most abundant otariid in the World. However, its status remains uncertain due to insufficient and conflicting data, and anthropogenic pressures affecting Antarctic krill, an essential staple for millions of fur seals and other predators. Using integrated population models, we estimated simultaneously the long-term abundance for Bird Island, northwest South Georgia, epicentre of recovery of the species after sealing, and population adjustments for survey counts with spatiotemporal applicability. Applied to the latest comprehensive survey data, we estimated the population at South Georgia in 2007-2009 as 3,510,283 fur seals [95% CI: 3,140,548-3,919,604] (ca. 98% of global population), after 40 years of maximum growth and range expansion owing to an abundant krill supply. At Bird Island, after 50 years of exponential growth followed by 25 years of slow stable growth, the population collapsed in 2009 and has thereafter declined by -7.2% [-5.2, -9.1] per annum, to levels of the 1970s. For the instrumental record, this trajectory correlates with a time-varying relationship between coupled climate and sea surface temperature cycles associated with low regional krill availability, although the effects of increasing krill extraction by commercial fishing and natural competitors remain uncertain. Since 2015, fur seal longevity and recruitment have dropped, sexual maturation has retarded, and population growth is expected to remain mostly negative and highly variable. Our analysis documents the rise and fall of a key Southern Ocean predator over a century of profound environmental and ecosystem change.

The influence of prey availability on behavioral decisions and reproductive success of a central-place forager during lactation.

Marine central-place foragers are increasingly faced with altered prey landscapes, necessitating predictions of the impact of such changes on behavior, reproductive success, and population dynamics. We used state-dependent behavioral life history theory implemented via Stochastic Dynamic Programming (SDP) to explore the influence of changes in prey distribution and energy gain from foraging on the behavior and reproductive success of a central place forager during lactation. Our work is motivated by northern fur seals (Callorhinus ursinus) because of the ongoing population decline of the Eastern Pacific stock and projected declines in biomass of walleye pollock (Gadus chalcogrammus), a key fur seal prey species in the eastern Bering Sea. We also explored how changes in female and pup metabolic rates, body size, and lactation duration affected model output to provide insight into traits that might experience selective pressure in response to reductions in prey availability. Simulated females adopted a central-place foraging strategy after an initial extended period spent on land (4.7-8.3 days). Trip durations increased as the high energy prey patch moved farther from land or when the energy gain from foraging decreased. Increases in trip duration adversely affected pup growth rates and wean mass despite attempts to compensate by increasing land durations. Metabolic rate changes had the largest impacts on pup wean mass, with reductions in a pup's metabolic rate allowing females to successfully forage at distances of 600+ km from land for up to 15+ days. Our results indicate that without physiological adaptations, a rookery is unlikely to be viable if the primary foraging grounds are 400 km or farther from the rookery. To achieve pup growth rates characteristic of a population experiencing rapid growth, model results indicate the primary foraging grounds need to be <150 km from the rookery.

Feeding morphology and body size shape resource partitioning in an eared seal community.

Body size and feeding morphology influence how animals partition themselves within communities. We tested the relationships among sex, body size, skull morphology and foraging in sympatric otariids (eared seals) from the eastern North Pacific Ocean, the most diverse otariid community in the world. We recorded skull measurements and stable carbon (δ13C) and nitrogen (δ15N) isotope values (proxies for foraging) from museum specimens in four sympatric species: California sea lions (Zalophus californianus), Steller sea lions (Eumetopias jubatus), northern fur seals (Callorhinus ursinus) and Guadalupe fur seals (Arctocephalus townsendi). Species and sexes had statistical differences in size, skull morphology and foraging significantly affecting the δ13C values. Sea lions had higher δ13C values than fur seals, and males of all species had higher values than females. The δ15N values were correlated with species and feeding morphology; individuals with stronger bite forces had higher δ15N values. We also found a significant community-wide correlation between skull length (indicator of body length), and foraging, with larger individuals having nearshore habitat preferences, and consuming higher trophic level prey than smaller individuals. Still, there was no consistent association between these traits at the intraspecific level, indicating that other factors might account for foraging variability.

Verminotic pneumonia in South American fur seal (Arctocephalus australis) in Southern Brazil.

Verminotic pneumonia caused by Parafilaroides spp. nematodes is an underreported disease in beached South American fur seals, with scant literature available on the characteristics of parafilaroidiasis, the nematode itself, as well as its occurrence in pinnipeds in Brazil. The present work aims to identify, describe and detail the histological features of the infection and molecular characteristics of verminotic pneumonia in the South American fur seal. Twenty-six specimens of Arctocephalus australis, found dead on the northern coast of Rio Grande do Sul in 2021, were analysed. These animals were identified and submitted to necropsy and histology. For the molecular identification of metastrongylids, lung fragments were subjected to DNA extraction, polymerase chain reaction targeting the Internal transcribed spacer 2 (ITS-2) gene and subsequent sequencing. In total, 12 animals presented with parasites in the lung parenchyma on histological evaluation, and only 1 showed a granulomatous lung lesion at necropsy. Microscopically, the nematodes were found mainly in the alveoli, associated with little or no inflammatory response, and they had morphological characteristics compatible with metastrongylids. Six ITS-2 gene quality sequences were obtained; after comparative analysis via BLAST, they showed similarity with sequences obtained from Parafilaroides sp. Therefore, verminotic pneumonia caused by Parafilaroides represents an important differential diagnosis of lung disease in South American fur seals found on the northern coast of Rio Grande do Sul.

B-cell small lymphocytic lymphoma in a free-ranging South American fur seal (Arctocephalus australis).

Lymphomas are malignant neoplasms of the hematopoietic system arising from lymphocytes with highly variable biologic behavior. B-cell small lymphocytic lymphoma (B-SLL) is a non-Hodgkin lymphoma infrequently described in domestic and wild animals. The present study describes a case of B-SLL in a free-ranging adult male Arctocephalus australis in Brazil. The main necropsy findings included poor body condition, generalized lymphadenomegaly, severe and diffuse splenomegaly, and multiple, white to yellow nodules in the kidneys and small intestine. Histologically, these organs were partially or totally effaced by neoplastic small lymphocytes arranged in sheets, with moderate anisocytosis and anisokaryosis and a low mitotic count. These cells diffusely immunolabeled for CD79α and CD20, and were negative for CD3. A diagnosis of multicentric B-SLL was established and to the authors' knowledge, it has not been previously described in this genus.

Phylogenomic Discordance in the Eared Seals is best explained by Incomplete Lineage Sorting following Explosive Radiation in the Southern Hemisphere.

The phylogeny and systematics of fur seals and sea lions (Otariidae) have long been studied with diverse data types, including an increasing amount of molecular data. However, only a few phylogenetic relationships have reached acceptance because of strong gene-tree species tree discordance. Divergence times estimates in the group also vary largely between studies. These uncertainties impeded the understanding of the biogeographical history of the group, such as when and how trans-equatorial dispersal and subsequent speciation events occurred. Here, we used high-coverage genome-wide sequencing for 14 of the 15 species of Otariidae to elucidate the phylogeny of the family and its bearing on the taxonomy and biogeographical history. Despite extreme topological discordance among gene trees, we found a fully supported species tree that agrees with the few well-accepted relationships and establishes monophyly of the genus Arctocephalus. Our data support a relatively recent trans-hemispheric dispersal at the base of a southern clade, which rapidly diversified into six major lineages between 3 and 2.5 Ma. Otaria diverged first, followed by Phocarctos and then four major lineages within Arctocephalus. However, we found Zalophus to be nonmonophyletic, with California (Zalophus californianus) and Steller sea lions (Eumetopias jubatus) grouping closer than the Galapagos sea lion (Zalophus wollebaeki) with evidence for introgression between the two genera. Overall, the high degree of genealogical discordance was best explained by incomplete lineage sorting resulting from quasi-simultaneous speciation within the southern clade with introgresssion playing a subordinate role in explaining the incongruence among and within prior phylogenetic studies of the family. [Hybridization; ILS; phylogenomics; Pleistocene; Pliocene; monophyly.].

Mutual mother-pup vocal recognition in the highly colonial Cape fur seal: evidence of discrimination of calls with a high acoustic similarity.

The Cape fur seal (Arctocephalus pusillus pusillus) is one of the most colonial mammal species in the world. Females exclusively nurse their pups for 9 to 11 months, during which they alternate frequent foraging trips at sea with suckling periods ashore. The survival of the pup thus depends on the ability of the mother-pup pair to relocate each other among thousands of individuals. Previous work has demonstrated identity information encoded in pup-attraction (PAC) and female-attraction (FAC) calls. Here, we investigated vocal recognition between mother and pup using playbacks of PAC and FAC performed during the breeding season at Pelican Point, Namibia. Both females and pups were able to specifically discriminate the voice of their pup or their mother from non-affiliated pup or mother. Females were able to memorize previous versions of their pup's calls (evidence of recognition up to 73 days after pup's calls recording). Vocal recognition was demonstrated in pups from 1- to 13-weeks old age. Females and pups did not respond differently to the non-filial or non-mother (for pups) stimulus even if it had a strong acoustic similarity with the filial or mother stimulus. This suggested that Cape fur seal mother-pup pairs have high perceptual and cognitive abilities, allowing individuals to identify kin's vocalizations in a very noisy and confusing environment.

Palaeoclimatic changes resulted in range expansion and subsequent divergence in brown fur seals, Arctocephalus pusillus.

Past climatic change as a driving force of marine diversification is still largely unclear, particularly for Southern Hemisphere species. Here, we present a case using the brown fur seal, Arctocephalus pusillus, assessing the geographical structure and demographic history using mitochondrial and nuclear data. Results show the two previously defined subspecies (one from Australia and the other from southern Africa) are phylogeographically distinct. Migration analyses based on nuclear data suggest the absence of migrants among the two genetically close assemblages. The demographic history of A. pusillus is characterized by a glacial population expansion (approx. 18 kya) in the southern African lineage, which coincides with time estimates of population expansion of prey species of seals. Approximate Bayesian calculations support an eastward dispersal event during the Last Glacial Maximum when sea levels were lower, followed by a postglacial divergence event, approximately 13 kya. The demographic history of the brown fur seal in the Southern Oceans provides support that recent palaeoclimatic changes could have facilitated expansions in some marine species and that postglacial sea-level rise may have acted as a dispersal barrier for species mostly confined to continental shelves.

Shifts in maternal foraging strategies during pregnancy promote offspring health and survival in a marine top predator.

The success of maternal foraging strategies during the rearing period can greatly impact the physiology and survival of dependent offspring. Surprisingly though, little is known on the fitness consequences of foraging strategies during the foetal period. In this study, we characterized variation in maternal foraging strategy throughout pregnancy in a marine top predator (South American fur seal, Arctocephalus australis), and asked if these shifts predicted neonatal health and postnatal survival. We found that during early pregnancy all pregnant females belonged to a single, homogenized foraging niche without evident clusters. Intriguingly though, during late pregnancy, individual fur seal mothers diverged into two distinct foraging niches characterized by a benthic-nearshore and a pelagic-offshore strategy. Females that shifted towards the benthic-nearshore strategy gave birth to pups with greater body mass, higher plasmatic levels of glucose and lower levels of blood urea nitrogen. The pups born to these benthic females were eight times more likely to survive compared to females using the pelagic-offshore foraging strategy during late pregnancy. These survival effects were mediated primarily by the impact of foraging strategies on neonatal glucose independent of protein metabolic profile and body mass. Benthic-nearshore foraging strategies during late pregnancy potentially allow for the greater maternal transfer of glucose to the foetus, leading to higher chances of neonatal survival. These results call for a deeper understanding of the balance between resource acquisition and allocation provided by distinct foraging polymorphisms during critical life-history periods, and how this trade-off may be adaptive under certain environmental conditions.

Myeloid and histiocytic sarcomas in subantarctic fur seals Arctocephalus tropicalis, Brazil.

Histopathological and immunohistochemical methods were used to diagnose round cell tumors in 2 subantarctic fur seals Arctocephalus tropicalis with marked anemia. Although wild-born, both individuals were placed under human care while juveniles in a Brazilian aquarium. Both pinnipeds were PCR tested for herpesvirus, and 1 was infected with otariid gammaherpesvirus 5 (OtHV-5), previously described in a subantarctic fur seal stranded in Brazil. Although some gammaherpesviruses can cause sarcomas and other neoplasms, it was not possible to definitively associate OtHV-5 with the neoplasm. To our knowledge, these are the first neoplasm records in subantarctic fur seals.

Survey of selected pathogens in free-ranging pinnipeds in Uruguay.

Marine mammals, regarded as sentinels of aquatic ecosystem health, are exposed to different pathogens and parasites under natural conditions. We surveyed live South American fur seals Arctocephalus australis and South American sea lions Otaria flavescens in Uruguay for Leptospira spp., canine distemper virus (CDV), Mycobacterium spp., Toxoplasma gondii, and Neospora caninum. Samples were collected from 2007 to 2013. The seroprevalence of Leptospira spp. was 37.6% positive, 50.9% negative, and 11.5% suspect for A. australis (n = 61) while for O. flavescens (n = 12) it was 67% positive, 25% negative, and 8% suspect. CDV RNA was not detected in any of the analyzed samples. Most animals tested seropositive to tuberculosis antigens by WiZo ELISA (A. australis: 29/30; O. flavescens: 20/20); reactivity varied with a novel ELISA test (antigens MPB70, MPB83, ESAT6 and MPB59). Seroprevalence against N. caninum and T. gondii was 6.7 and 13.3% positive for O. flavescens and 0 and 2.2% positive for A. australis respectively. To evaluate possible sources of infection for pinnipeds, wild rats Rattus rattus and semi-feral cats Felis catus were also tested for Leptospira spp. and T. gondii respectively. Water samples tested for Leptospira revealed saprofitic L. bioflexa. Pathogenic Leptospira were detected in the kidneys of 2 rats, and cats tested positive for T. gondii (100%). These results represent a substantial contribution to the study of the health status of wild pinnipeds in Uruguay.

Exploring fungal diversity in Antarctic wildlife: isolation and molecular identification of culturable fungi from penguins and pinnipeds.

AIMS: To survey the diversity of fungal species that may be cultured from Antarctic penguins and pinnipeds, and to test the in vitro susceptibility to triazole drugs of any medically important Aspergillus spp. isolates. METHODS: During an expedition to Argentinean Antarctic research stations at Potter Peninsula (South Shetland Islands) and Primavera Cape (Antarctic Peninsula) in February 2019, samples (n = 212) were collected from fur seals (Arctocephalus gazella), elephant seals (Mirounga leonine), leopard seals (Hydrurga leptonyx), Weddell seals (Leptonychotes weddellii) and crabeater seals (Lobodon carcinophaga) and gentoo penguins (Pygoscelis papua). Oral, nasal and rectal swabs and skin/hair brushings were collected from pinnipeds, and skin/feather brushings, cloacal swabs and moulted feathers from penguins. Samples were cultured on Sabouraud dextrose agar and/or potato dextrose agar plates and fungal isolates identified by morphological criteria followed by PCR amplification and DNA sequencing. Antifungal susceptibility of Aspergillus spp. isolates to triazoles was tested. RESULTS: Fungi from 21 genera were isolated from 121/212 (57.1%) samples obtained from pinnipeds and penguins. Among pinnipeds from Potter Peninsula (fur seals and elephant seals), the most frequent fungal species were Debaryomyces hansenii and Rhodotorula mucilaginosa, isolated from the oral, nasal and/or rectal mucosa, and Antarctomyces psychrotrophicus isolated from the skin/hair of all sampled individuals. Among pinnipeds from Primavera Cape (leopard seals, Weddell seals and crabeater seals), the most frequent fungal species were Naganishia adeliensis and Cryptococcus neoformans var. uniguttulatus, isolated from the nasal/oral mucosa of 4/33 (15.2%) and 5/33 (12.1%) animals, respectively. The most frequently isolated fungal species from gentoo penguins (Potter Peninsula), were Pseudogymnoascus pannorum and A. pyschrotrophicus, which both were isolated from skin/feathers of 7/15 (46.7%) birds, and Thelebolus microsporus, isolated from the cloacal mucosa and skin/feathers of 5/15 (33.3%) and 2/15 (13.3%) birds, respectively. Fungi that are potentially pathogenic to both humans and animals (Aspergillus fumigatus, Asp. flavus, Asp. versicolor, Candida parapsilosis and Microsporum canis) were isolated from 4/38 (10.5%), 1/38 (2.6%), 2/38 (5.3%), 4/38 (10.5%) and 2/38 (5.3%) sampled pinnipeds, respectively. Only non-azole-resistant isolates of Asp. fumigatus and Asp. flavus were identified. CONCLUSIONS: The fungal biodiversity in Antarctic pinnipeds and gentoo penguins was explored using standard mycological culture followed by PCR and DNA sequencing. The frequency of fungal carriage varied among animal species, sample type and location. This study constitutes an epidemiologic approach to monitoring of these marine animals for emerging fungal pathogens.

Evidence for an Allee effect in a declining fur seal population.

Allee effects play an important role in the dynamics of many populations and can increase the risk of local extinction. However, some authors have questioned the weight of evidence for Allee effects in wild populations. We therefore exploited a natural experiment provided by two adjacent breeding colonies of contrasting density to investigate the potential for Allee effects in an Antarctic fur seal (Arctocephalus gazella) population that is declining in response to climate change-induced reductions in food availability. Biometric time-series data were collected from 25 pups per colony during two consecutive breeding seasons, the first of which was among the worst on record in terms of breeding female numbers, pup birth weights and foraging trip durations. In previous decades when population densities were higher, pup mortality was consistently negatively density dependent, with rates of trauma and starvation scaling positively with density. However, we found the opposite, with higher pup mortality at low density and the majority of deaths attributable to predation. In parallel, body condition was depressed at low density, particularly in the poor-quality season. Our findings shed light on Allee effects in wild populations and highlight a potential emerging role of predators in the ongoing decline of a pinniped species.

Feel the beat: cape fur seal males encode their arousal state in their bark rate.

The cape fur seal is one of the most colonial mammal species in the world. Breeding colonies are composed of harems held by mature males (older than 10 years) with up to 30 females and their pups, while roaming subadult males (younger and socially immature) are kept away from bulls' territories. As in other pinnipeds, cape fur seals are highly vocal and use acoustic signals in all their social interactions. Males produce barks-short vocalizations always produced in sequences-for territorial defense, mating behaviors, and agonistic interactions. These calls convey information about the sex, age class, and individual identity. This study investigated whether motivational cues such as the arousal state can be encoded in territorial males' barks and whether these cues are decoded by listening sub-adult males. The rate (number of calls per unit of time) and fundamental frequency of barks were found to significantly increase during high arousal state interactions (i.e., male-male confrontation) compared to spontaneous barks. Playback experiments revealed that subadult males responded with a higher level of vigilance when territorial males' barks had a faster bark rate. This mechanism of decoding the bulls' arousal state from barks will likely constitute an advantage for both bulls and the subadult males, by avoiding or reducing physical conflicts, and thereby reducing energy expenditure and the risk of injury. This study is the first experimental evidence of cape fur seals' using vocal rhythmic patterns to modulate their social interactions.