We present the most recent data on the seasonal and spatial occupation of South American sea lions (Otaria flavescens) and fur seals (Arctocephalus australis) in the Wildlife Refuge of Ilha dos Lobos (WRIL) in southern Brazil throughout the year, based on aerial photographic counts. Thirty-one aerial photographic counts were conducted between July 2019 and November 2020 to assess monthly differences in the abundance of pinnipeds in the WRIL. The results were analysed using a generalized linear model. Spatial analysis was performed using kernel density. Subadult males of South American sea lion were the most abundant pinniped in the WRIL, followed by juveniles of South American fur seal. A juvenile of Southern elephant seal (Mirounga leonina) was also recorded. South American fur seals showed a marked seasonality, occurring only between July and October, while South American sea lions occurred year-round. Among the months analysed, September exhibited the highest mean abundance (mean 113.75; SD: ± 8.58), followed by August (mean 103.00; SD: ± 15.69). The pinnipeds were more often concentrated in the northern and central parts of the island. This study reinforces the importance of the WRIL as a haulout site for pinnipeds. Considering the seasonal occupation of the island by South American pinnipeds, monitoring is recommended prior to the development of activities in the area.

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.

Los índices de utilidad económica son aplicados en análisis zooarqueológicos desde hace más de cuatro décadas, lo que llevó al desarrollo de indicadores exclusivos para especies de mamíferos marinos. En Sudamérica se explotaron dos tipos de pinnípedos: Otaria flavescens y Arctocephalus australis; sin embargo, sólo para el primero fue derivado dicho índice. A partir de un individuo recolectado en el canal Beagle (Tierra del Fuego, Argentina) se presenta un índice de utilidad económica para A. australis basado en la medición de peso de carne para cada elemento o porción del esqueleto. Los resultados generales indican que O. flavescens presenta mayor desarrollo muscular en el sector de las costillas, mientras que los A. australis lo presentan en las vértebras cervicales. La aplicación del índice en conjuntos zooarqueológicos del canal Beagle con predominio de especímenes de A. australis ha mostrado un ajuste mejor respecto de las tendencias observadas previamente utilizando los valores generados para O. flavescens: (1) en el Segundo Componente de Imiwaia I (Holoceno medio) fue posible reconocer un perfil anatómico compatible con la selección de porciones de bajo valor económico; y (2) en Ajej I (Holoceno tardío) se identificó una tendencia similar, no identificada anteriormente.

We examined the skulls of Arctocephalus australis, Callorhinus ursinus and Otaria byronia with the objectives of (1) estimating the development and growth rates and comparing these parameters among the species; (2) describing the development for each linear measure, for each species and sex; (3) determining which variables are best correlated with age; (4) determining age of physical maturity. We employed traditional and geometric morphometric techniques to study the skulls. In A. australis and C. ursinus, skulls of females mature at about 6 years of age, and those of males at about 8 years. Otaria byronia matures later, at about 9 years. Using geometric morphometric data sets, the rate and constant of growth in A. australis did not differ between the sexes. Callorhinus ursinus and O. byronia showed rates significantly different between sexes concerning growth (and in the constant as well), but only O. byronia differed between sexes in both developmental model parameters (rates and constant). Comparisons between the growth and developmental models showed significant differences in slope and constant. In both treatments employed, a relationship between size and shape dimorphism could be inferred for the skulls of all three species. We conclude that rates or timing of growth and development evolves within a conserved spatiotemporal organization of morphogenesis.

Age is one of the most important life history parameters required to understand the dynamics of mammalian populations. Growth Layers Groups (GLGs) are incremental units of calcified tissue in the teeth (dentine and cementum), which represent a pattern of cyclical deposition that can be counted. However, the estimation of absolute age in GLGs demands a skull with teeth, the permission to destroy part of a tooth, equipment to cut the teeth, and experienced GLGs readers. In 1954 Sivertsen proposed an alternative method using cranial suture age (CSA) to establish age categories. However, there are no studies validating the CSA in relation to GLGs. Thus, this study examined whether there is a correlation between age categories proposed by the CSA and chronological age in years from GLGs of South American fur seals (Arctocephalus australis) (N = 52) and of South American sea lions (Otaria flavescens) (N = 37). 93% of the skulls of A. australis and 83.8% of O. flavescens corresponded accurately to the age in years estimated by each cranial suture age range. These results indicated the existence of high correspondence between the CSA and the GLGs age (r: 0.491 for A. australis and r: 0.675 for O. flavescens). However, an adaptation to Sivertsen's method is recommended: using only eight sutures (excluding the premaxillary-maxillary suture for CSA analysis, due to its late fusion), and updating the intervals for cranial sutures, that correspond to 16–32 = adults, 11–15 = young and 8–10 = pups.

The South American fur seal, Arctocephalus australis, was one of the earliest otariid seals to be exploited by humans: at least 6000 years ago on the Atlantic coast and 4000 on the Pacific coast of South America. More than 750,000 fur seals were killed in Uruguay until 1991. However, a climatological phenomenon—the severe 1997–1998 El Niño Southern Oscillation (ENSO)—was responsible for the decline of 72% of the Peruvian fur seal population due to starvation as a consequence of warming of sea-surface temperatures and primary productivity reduction. Currently, there is no precise information on global population size or on the species' conservation status. The present study includes the first bottleneck test for the Pacific and Atlantic populations of A. australis based on the analysis of seven microsatellite loci. Genetic bottleneck compromises the evolutionary potential of a population to respond to environmental changes. The perspective becomes even more alarming due to current global warming models that predict stronger and more frequent ENSO events in the future. Our analysis found moderate support for deviation from neutrality–equilibrium for the Pacific population of fur seals and none for the Atlantic population. This difference among population reflects different demographic histories, and is consistent with a greater reduction in population size in the Pacific. Such an event could be a result of the synergic effects of recurrent ENSO events and the anthropogenic impact (sealing and prey overfishing) on this population.

Southern fur seals Arctocephalus australis in Peru have declined gradually over the past decade, and declined dramatically (72%) as a result of low food availability during the severe El Niño in 1997–98. In 1999, seals abandoned some historically important breeding sites. This is particularly alarming because new sites were not colonized. Our objective was to examine how habitat features and human disturbance influenced whether sites were currently used, abandoned or apparently not used in the past by fur seals for breeding. Data were collected on 14 variables at 70 potential breeding sites at three guano reserves in Peru. Discriminant analysis revealed significant multivariate differences among sites currently used for breeding, abandoned sites and unused sites (F=5.97, P<0.00001), and the model classified 74% of sites correctly. Currently used sites were less likely to have human disturbance and more likely to have offshore islands, stacked rocks, tide pools and abundant shade. Separate discriminant analyses for each reserve produced similar results. Habitat associated with thermoregulation (e.g. shade or pools) may be more important to fur seals in Peru, which breed at lower latitudes and are at greater risk of overheating on land than other populations. Habitat with minimized human access may be especially important to seals in small populations in which individuals may perceive themselves as more vulnerable because of decreased vigilance and dilution effects. Seals in our study selected breeding habitat with stacked rocks, which create shade and tide pools for thermoregulation and make human access difficult; but pups might suffer higher mortality in this habitat. We hypothesize that fur seals in Peru may exhibit an Allee effect, whereby suitability of habitat varies with population abundance.