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Studying trophic feeding habits and their variation over time is crucial for understanding individual and population success. Although many generalist feeders' populations appear to use diverse trophic resources, they are often composed of individuals that specialize in only a subset of these resources, a phenomenon known as individual trophic specialization (ITS). The South American sea lion (SASL) (Otaria flavescens), widely distributed along the South American coast, is an opportunistic and generalist predator with a diverse diet, making it a good model for studying ITS. We aimed to estimate the diet composition and the degree of ITS among SASL females on Isla Arce, Argentina, over a period of three years (2012 to 2014). For that, we analysed stable isotopes (δ15N and δ13C) in vibrissae from 12 females. Over the three years studied, females from this colony primarily fed on pelagic prey. At the population level, the most commonly consumed prey varied between the Argentine anchovy (Engraulis anchoita) in 2012 and 2014 and the Patagonian squid (Doryteuthis gahi) in 2013. Consuming mostly pelagic resources throughout the year, unlike previous studies in nearby colonies, suggests the existence of different foraging strategies in lactating females. Although the prey contribution varied between years, the analysis indicated that SASL females breeding on Isla Arce show some degree of ITS, which could be a mechanism adopted by individuals to mitigate the potential competition given by sustained population increases. [ABSTRACT FROM AUTHOR]

Otaria flavescens has been one of the most heavily exploited pinnipeds during the last 200 years, with depletion of ~90% in some colonies. After the prohibition on sealing in South America, populations stabilized except for the Uruguayan population, which showed a constant decrease. The underlying causes of its decline are unknown. This study used genome-wide single nucleotide polymorphisms to assess the variability and connectivity of some of the most overexploited sea lion colonies in the Atlantic Ocean. Our results revealed low allelic richness, nucleotide diversity, and heterozygosity in the Uruguayan population and evidence of complete isolation from the Argentinean populations under study. In contrast, the Patagonian populations showed a high degree of connectivity, which could explain their recovery and high levels of diversity at present. Our study highlights the critical situation of the Uruguayan sea lion population, emphasizing the need for maintaining continuous conservation efforts in the region. [ABSTRACT FROM AUTHOR]

Although policymakers and stakeholders are beginning to acknowledge the importance of the marine biosphere in blue carbon services, the role of large marine vertebrates in the marine carbon and nitrogen cycle and especially in carbon sequestration has not yet been fully understood. Large marine vertebrates store only a small percentage of total oceanic carbon in their bodies, but they can provide important and lasting contributions to the oceanic carbon flux. The Península Valdés Biosphere Reserve in southwestern Argentina was partially established to conserve these large marine vertebrates, including the South American sea lion (Otaria flavescens) and southern right whale (Eubalaena australis). Three locations in Peninsula Valdés were sampling for the proximity of marine vertebrate populations in the area and the presence of salt marshes to assess the organic carbon (OC) and total nitrogen (TN) stocks in the top 1 m of sediment. Our work provides the first quantitative data on the OC and TN sequestered in the coastal sediments of Península Valdés and shows that this protected area contributes significantly to blue carbon by storing relevant quantities of OC (140 to 317 Mg OC ha-1) and nitrogen (7.3 to 22.9 Mg TN ha-1). Specifically, we found that salt marshes and terrestrial plants were the main C sources in each sediment core, but a non-negligible proportion (from 0.8 to 6.8% dry weight) of the OC stocks showed an isotopic signal from the large vertebrates that usually inhabit the area. Therefore, our results provide novel hypotheses about the potential contribution of large marine vertebrates as an OC vector in coastal systems and may serve as a basis for further investigation about their role into coastal blue carbon.

AbstractAccording to archaeological data, Otaria flavescens and Arctocephalus australis were exploited at the mouth of the Santa Cruz River by hunter-gatherers in the late Holocene. These studies suggest the past existence of reproductive colonies from where individuals of different ages were taken, highlighting the offspring available in the austral summer. This paper presents new information on sex, age, and season of death based on the study of teeth growth layers and rings recorded on canines of both species recovered in three archaeological sites located in Punta Entrada, on the southern bank of Santa Cruz River. The results confirm that otariids were captured in the austral summer and show that winter and spring were also important seasons. Prey included females, pups, and adult males captured according to the abundance of each age group at different seasons of the year. These data are in agreement with those obtained from other lines of evidence, such as osteometry and sclerochronology, which indicate this sector of the Patagonian coast was occupied recurrently to hunt otariids as one of the main resources taken by hunter-gatherers when visiting Punta Entrada at different times of the year. [ABSTRACT FROM AUTHOR]

We report here changes in bird assemblages over a 14-year interval at the Port of Mar del Plata, Argentina, and the adjacent beach before (PRE) and after (POST) South American Sea Lions Otaria flavescens increased at a local haul-out. Abundance and number of bird species were compared between periods, between sites (beach, sea lion rookery, and port sheds), and between breeding and non-breeding seasons of the birds' annual cycle. A total of 13 116 birds belonging to 15 species were recorded. Total bird abundance was higher during the POST period compared to the PRE period, regardless of the season. Larids occurred in all sampled areas but with higher abundance at Punta Mogotes beach. The Kelp Gull Larus dominicanus, Brown-hooded and Grey-headed gulls Chroicocephalus spp., and the Snowy Sheathbill Chionis albus dominated assemblages during the PRE sea lion increase period, while Kelp Gulls, Brown-hooded Gulls, and the South American Tern Sterna hirundinacea dominated the POST period. Variation in the numbers of birds may be related to changes in feeding opportunity related to increased human activity (e.g., fishery wastes) as well as expansion of the local rookery of South American Sea Lions, another food source. [ABSTRACT FROM AUTHOR]

Groups of male South American sea lions (Otaria flavescens; SSLs) congregate in harbours on the northern coast of Argentina. These groups are very dynamic, with a high degree of habituation to human activities and the ability to colonise different types of artificial substrates, making them an interesting subject for understanding individual association patterns and spatio-temporal variations in this species. In the present study, we recorded the associations between individual bleach-marked SSLs in the harbours of Mar del Plata (PM) and Puerto Quequén (PQ) on four different substrate types during four non-breeding seasons. We found that the association pattern differed between the harbours, with a well-differentiated social structure being evident in PM but very little social differentiation occurring in PQ. The observed social structure in PM may have resulted from passive habitat preference rather than genuine social behaviour, as the association pattern disappeared when SSLs moved to sandy beaches within the harbour. Given that these colonies are must-see tourist attractions but may have negative interactions with human activities, we recommend considering the association between SSLs and artificial habitats to design effective management strategies and reduce potential conflicts. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Biologia Marina y Oceanografía (RBMO) is the property of Universidad de Valparaiso, Facultad de Ciencias del Mar and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Punta María 2 es un sitio emplazado en la costa atlántica de Tierra del Fuego donde se recuperó el conjunto zooarqueológico de pinnípedos más abundante de dicho litoral hasta la fecha. En este trabajo presentamos la revisión de una submuestra de restos de otáridos sobre la que se desarrollan nuevos análisis osteométricos y de identificación de rasgos diagnósticos y cronograma de fusión. Así, a partir de la construcción de datos más ajustados de especies, sexo y edad, discutimos interpretaciones previas. Nuestros resultados señalan que las presas habrían sido mayormente individuos subadultos entre uno y tres años de edad, con predominio de Otaria flavescens sobre Arctocephalus australis, mientras que en los adultos la representación de especies fue más equitativa, indicando un uso oportunístico de los lobos marinos. Finalmente, se señala que el empleo conjunto de diferentes abordajes metodológicos resulta muy adecuado y promisorio para el análisis zooarqueológico de estos animales.

Mercury, a toxic metal released by various human activities, exerts environmental stress through its bioaccumulation and biomagnification, particularly in marine habitats. South American fur seals (Arctocephalus australis) and sea lions (Otaria flavescens) reproduce on the Atlantic coast of Uruguay. As top predators, they can accumulate toxic levels of mercury and are often used as sentinel species for monitoring ecosystem health. Fur seals prey on pelagic species, such as fish and squid, while sea lions consume coastal-benthic prey. We analyzed the total mercury concentration (THg) in hair and the trophic habits (δ13C and δ15N) of females from both species. The average THg concentration in adult female sea lions (30.5 ± 9.3 μg/g dry weight) was significantly higher than in fur seals (6.3 ± 2.5 μg/g dry weight). Additionally, the mean δ15N and δ13C values were significantly higher in sea lion (δ15N: 19.2 ± 0.6‰, δ13C: −13.8 ± 0.2‰) compared to fur seals (δ15N: 16.5 ± 0.5‰, δ13C: −15.5 ± 0.6‰). Our results suggest that different trophic levels and feedings areas affect the THg concentration in Uruguayan Otariids. Notably, at the intraspecific level, the THg concentration in sea lions increased with δ13C values, suggesting a link to coastal feeding habits. This indicates that coastal feeding behaviors, compared to feeding in pelagic environments, enhance mercury bioaccumulation in Otariids along the Uruguayan coast, with the discharge of freshwater from the Río de la Plata (one of the largest estuaries in South America) basin identified as a potential mercury source. THg concentrations found in female sea lion hair are the highest reported in Otariids globally. Mercury levels exceeded toxic thresholds observed in other mammals and could pose significant health risks. Our findings may explain why sea lions were particularly affected by the avian influenza outbreak in Uruguay compared to fur seals. Monitoring the declining sea lion population is crucial, making our results significant for integrated conservation and management strategies. [Display omitted] • Marine mammals are good sentinel species for monitoring Hg bioaccumulation. • Fur seals and sea lions prey on pelagic and coastal benthic species, respectively. • Hg accumulation in the hair of female sea lions was higher than in fur seals. • Hg levels in individual female sea lions rose with δ13C, indicating a link to coastal feeding habits. [ABSTRACT FROM AUTHOR]

Recent advances in unmanned aerial vehicle (UAV) technology have made them a popular and accessible tool for wildlife research. Despite their popularity, there are some concerns about their potential negative impacts due to the possibility of causing disturbance to the species being monitored. We assessed the potential behavioral disturbance of low altitude UAVs on South American fur seals (Arctocephalus australis) and sea lions (Otaria flavescens) on a haulout site in southern Brazil (Wildlife Refuge of Ilha dos Lobos (WRIL)) between October 2022 and August 2023. Behavioral responses of each individual toward the UAV were classified (no response, vigilant or movement) and individuals were also classified according to their species. The probability of individuals expressing each one of the three behaviors at each altitude was assessed by Binomial and Multinomial Mixed Models. We flew a small UAV (DJI Air 2S) vertically above 731 South American sea lions, including 131 adult males, 590 subadult males and 10 juveniles; and 121 South American fur seals, including one subadult, one juvenile and 119 yearlings. For sea lions, vigilant and movement responses represented only 7.70% and 0.36% of behaviors observed during vertical approaches. South American fur seals appeared less perturbed by UAV presence, as only 1.56% of observed behaviors were classified as vigilant, and no movement responses were observed during vertical approaches. Similar results were found during horizontal flights over these species. The most frequent behavior observed in both species was no response, with a probability higher than 0.89 during vertical and horizontal approaches with drones, even at lower altitudes. Based on these results, we recommend that due to their benefits and minimal impact on the studied species, UAV monitoring studies of South American pinnipeds be conducted at a minimum altitude of 30 m at non-breeding sites, especially at haulout sites. • First study to evaluate the potential behavioral disturbance of UAV on South American fur seals and sea lions in Brazil. • The most frequent behavior observe was no response. • South American fur seals are less disturbed by drones. • Only the non-response and alert behavior were noticed during horizontal approaches for both species, without movement. • Drones has showed benefit for collecting wildlife data with minimal impact. [ABSTRACT FROM AUTHOR]

Copyright of Relaciones de la Sociedad Argentina de Antropología is the property of Sociedad Argentina de Antropologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The estimation and monitoring of population trends are essential to understand the recovery and population dynamics of species that have been affected by humans. When population censuses are carried out for long periods of time, and especially if the species under consideration has wide distributional ranges, different working groups with different methods make these surveys. The aim of this work is to present methodological recommendations to carry out population censuses and abundance estimates of Otaria flavescens throughout its distribution. Our ultimate goal is that the present work will allow to systematize and standardize data gathering. In this way, the effort made will be comparable between areas and can be used in the long term to improve the knowledge and trend of recovering populations. [ABSTRACT FROM AUTHOR]

Aim: Many pinniped species have experienced drastic demographic changes due to their interaction with humans. Most studies, however, have failed to detect recent bottlenecks in otariids from genetic data. The South American Sea Lion Otaria flavescens have a long history of population changes associated with interglacial expansion and hunting to almost extinction. This study aimed at investigating these different demographic fluctuations integrating population genetics and phylogeographic approaches. Location: Pacific coast of South America. Methods: Eighty‐five samples from the Chilean coast were collected. Eight microsatellite loci were genotyped, and D‐Loop mitochondrial DNA (mtDNA) sequenced. Genetic diversity was assessed, and tests of recent genetic bottlenecks were performed. Past demographic changes were inferred based on neutrality tests, adjustment of a sudden expansion model and Bayesian skyline plots. The magnitude and timing of the different population size changes were further investigated through approximate Bayesian computation (ABC) of coalescent inferences. Results: The mtDNA shows relatively high diversity (h = 0.98 and π = 0.01) compared to most otariids, corroborates the divergence between Pacific and Atlantic populations, around 80,000 years ago (ya), and revealed a secondary contact zone in the Magellan strait. Microsatellite data support a second genetic discontinuity at 40°S, associated with post‐glacial colonization of Patagonia. ABC analyses confirmed that glaciation affected the effective population size (Ne) all along the Pacific Coast, between ~50,000 and 15,000 ya. A strong reduction of Ne was also inferred for the hunting period (73–66 ya from sampling). Main conclusions: O. flavescens shows clear signatures of susceptibility to climatic and anthropogenic disturbances and a spatial genetic structure that should be taken into account in the context of management and conservation policies. Yet, despite a recent history of demographic bottlenecks, the genetic diversity remains high, likely a consequence of the demographic dynamics in otariids, characterized by large and connected metapopulations. [ABSTRACT FROM AUTHOR]

In this article, we present the first results of the determination of season at death performed over eighteen South American sea lions (Otaria flavescens) teeth recovered at Cueva del Negro site (northern coast of the Santa Cruz Province, Patagonia, Argentina). Age and season of death was determined by growth-layer analysis on sea lion teeth. This analysis allowed us to suggest potential aboriginal hunting strategies regarding the capture of these pinnipeds. Our results indicate that sea lions were hunted between summer and early fall, more precisely between January and April. This would reflect a marked seasonality in relation to sea lion availability, which could be explained in terms of mobility and subsistence strategies of the human groups that inhabited the area. In this sense, our results are discussed taking into consideration paleodietary data and the existing archaeological studies.

This work aims to provide information regarding the behavioral ecology of the least studied of the two sheathbill species, the Snowy Sheathbill (Chionis albus), wintering in northern Argentina in a male South American Sea Lion (Otaria flavescens) haul-out. Data about bird abundances and time allocated to behaviors was gathered during the final stage of three consecutive non-breeding seasons. Significant differences were found in the abundance between and within seasons. Overall, sheathbills allocated most of their time to foraging, followed by resting and self-maintaining, with the least of the time allocated to agonistic behaviors. The results obtained by the authors demonstrated that the Snowy Sheathbill recurrently used the local sea-lion haul-out as a foraging ground, with steady numbers throughout the non-breeding seasons. [ABSTRACT FROM AUTHOR]

An 18-year-old captive born and neutered male South American sea lion (Otaria flavescens; Shaw, 1800) presented with intermittent gastrointestinal signs of disease (anorexia, reduced activity, vomit, and diarrhea). Over the course of 12 days, severe leukocytosis, signs of liver damage, and anemia developed, accompanied by rapid weight loss and physical deterioration. Ultrasonographic examination revealed hepatomegaly and reduction of liver vascularization with altered hepatic parenchyma along with ascites. Hemoculture results revealed no growth, and PCR tests from nasal, oral mucosa, and fecal swabs ruled out a Mycobacterium infection. Treatment consisted of antibiotics, anti-inflammatories, analgesics, probiotics, vitamin supplements, antitoxic and hepa-toprotective medication, supportive fluid therapy, and nutritional support. Medical condition of the animal did not improve despite the treatments, presenting as severe apathy (almost comatose), jaundice, oral hemorrhage, and melena. Thus, humane euthanasia was performed. On necropsy, major lesions were seen in the liver, confirming the ultrasonographic findings. Histopathology revealed a poorly demarcated hepatic epithelial neoplasia, metastasized to the lungs, spleen, and lymph nodes. Also, the presence of another neoplastic nodule at the level of the parathyroid made it difficult to define the primary tumor site. An immunohistochemical examination using a panel of antibodies (pan cytokeratin AE1/AE3, cytoker-atin 18 [CK18], and CK8, together with p-CEA, CD10, and vimentin) was used in an attempt to differentiate between hepatocellular carcinoma from cholangiocarcinoma and metastatic non-hepatic carcinoma. Results revealed that the tumor was of primary hepatic origin and metastasized to various organs, including the parathyroid which does not represent a usual site of metastasis. To our knowledge, this is the first case describing hepatocellular carcinoma with evidence of metastases to the lungs and parathyroid gland in a South American sea lion. [ABSTRACT FROM AUTHOR]

The conservation of marine animals, such as pinnipeds, is very difficult when their feeding areas overlap with fishing activity. During these interactions, they are often victims of firearm injuries that result in their death. For veterinarians and biologists investigating crimes against wildlife, the use of diagnostic imaging techniques is essential. Although computed tomography (CT) can be used to evaluate animals with skeletal trauma, digital radiography (DR) is a cheaper and more widely available diagnostic imaging technique. The objective of this study was to determine whether the presence and number of metal fragments in the skull of pinnipeds differed between DR and CT. Thirty pinniped skulls--19 South American sea lions (Otaria byronia) and 11 South American fur seals (Arctocephalus austra-lis)--with evidence of trauma and available DR and CT examinations were included in the study. The DR and CT images were evaluated by three independent observers--a veterinarian, a board-certified veterinary pathologist, and a board-certified veterinary radiologist. The detection of metal fragments in pinniped skulls with both imaging techniques was not different between the observers (p = 1.0), and it was not significantly different between DR (13/30) and CT (16/30) (p = 0.71). The number of metal fragments in pinniped skulls was also not significantly different between DR (6.6 ± 1.9) and CT (7.9 ± 1.7) (p = 0.37). Furthermore, there was excellent agreement between the three observers in the detection and number of fragments both for DR (kappa = 1.0; p < 0.0001) and for CT (kappa = 1.0; p < 0.0001), as well as between the two techniques (DR and CT: kappa = 0.802; p < 0.0001). This study showed that CT identified more skulls with metal fragments and an increased number of metal fragments as compared to DR; however, there were no significant statistical differences noted, suggesting that DR is just as useful as CT for the detection of metal fragments in pinniped skulls. Therefore, DR is a valid tool that can be used to investigate cases of projectile injuries against wildlife. [ABSTRACT FROM AUTHOR]

Populations of the South American sea lion (SASL, Otaria byronia) have been intensely exploited for leather and oil in different parts of its distribution range throughout the 19th and 20th centuries, generating large changes in abundance. In Patagonia, the SASL population was reduced by more than 90% of its original abundance, and it began to recover after sealing ended. The aim of this work was to assess changes in size and shape of the skull related to changes in population abundance during the last 100 years. Using geometric morphometry techniques, we analyzed 145 individuals (68 males and 77 females) from Patagonia. Skulls were classified by sex, time period (harvest vs. postharvest), and decades of individual's birth. Results indicated that there were differences in skull size but not in shape discriminated by time period. Moreover, individuals of the postharvest period showed a decrease in the skull size during the last two decades, coinciding with the recovery in population abundance. Our results suggest the existence of a density‐dependence response in somatic growth of SASL population of Patagonia. [ABSTRACT FROM AUTHOR]

Changes in the duration and frequency of foraging trips by female otariids may result in changes in the duration and frequency of lactation bouts and hence influence pup growth rate, unless females modify milk energy density and/or the total amount of milk delivered depending on the trip duration. To test this hypothesis on South American sea lions, we measured two attendance pattern components (foraging trip and haul-out duration) and three diving behaviour components of nursing females (dive time, bottom time and number of dives per h) at two different rookeries in Uruguay and Argentina, the composition and energy density of their milk, and the growth rate of their pups. Female foraging trip and haul-out durations depended on pup sex and weight, whereas milk energy density depended on female body mass and foraging trip durations. By contrast, the three dive variables were independent of female body mass or pup sex. Pup growth was also independent of the foraging trip and haul-out duration, with pup sex as the only significant variable. This suggests that individual differences in female foraging behaviour play a minor role in determining pup growth rates during the first three weeks after birth.

Background: The systematic of several marine diphyllobothriid tapeworms of pinnipeds has been revised in recent years. However, 20 species of Diphyllobothrium from phocids and otariids are still recognized as incertae sedis. We describe a new species of Diphyllobothrium from the intestine of California sea lions Zalophus californianus (Lesson) (type-host) and South American sea lions Otaria flavescens (Shaw). Methods: Zalophus californianus from the Pacific coast of the USA and O. flavescens from Peru and Argentina were screened for parasites. Partial fragments of the large ribosomal subunit gene (lsrDNA) and the cytochrome c oxidase subunit 1 (cox1) mitochondrial gene were amplified for 22 isolates. Properly fixed material from California sea lions was examined using light and scanning electron microscopy. Results: A total of four lsrDNA and 21 cox1 sequences were generated and aligned with published sequences of other diphyllobothriid taxa. Based on cox1 sequences, four diphyllobothriid tapeworms from O. flavescens in Peru were found to be conspecific with Adenocephalus pacificus Nybelin, 1931. The other newly generated sequences fall into a well-supported clade with sequences of a putative new species previously identified as Diphyllobothrium sp. 1. from Z. californianus and O. flavescens. A new species, Diphyllobothrium sprakeri n. sp., is proposed for tapeworms of this clade. Conclusions: Diphyllobothrium sprakeri n. sp. is the first diphyllobothriid species described from Z. californianus from the Pacific coast of North America, but O. flavescens from Argentina, Chile and Peru was confirmed as an additional host. The present study molecularly confirmed the first coinfection of two diphyllobothriid species in sea lions from the Southern Hemisphere. [ABSTRACT FROM AUTHOR]

Esta publicación describe el empleo de la tecnología RPA como método complementario durante el censo de lobos marinos chuscos (Otaria flavescens), en la Isla Chincha sur, Ica – Perú, como parte de las actividades programadas por el Instituto del Mar del Perú (IMARPE). Se llevó a cabo el mapeo de las colonias de estos pinnípedos y su posterior clasificación en entorno de Sistemas de Información Geográfico, con el objetivo de comparar los resultados obtenidos por conteo directo en el campo y el conteo de ortofotos generadas por RPA. Los valores totales de los conteos del método directo y de las ortofotos fueron 2300 y 2700 individuos, respectivamente. Si bien no se encontraron diferencias significativas entre ambos conteos, el conteo digital permitió obtener un mayor detalle del número de individuos correspondientes a las categorías crías y hembras. El uso de RPA constituye una herramienta que permite la georreferenciación de cada individuo y la posibilidad de hacer repeticiones del conteo, incluso por diferentes evaluadores.

La díada madre-hijo de Otaria flavescens normalmente dura alrededor de un año o menos, pero a veces pueden permanecer juntos por un período más largo, de hasta dos años. El reconocimiento madre-cría ya es mutuo antes de transcurridas 24 horas después del nacimiento y se realiza mediante señales acústicas y olfativas. Los machos subadultos reaccionan a los cachorros aislados y a sus vocalizaciones, atacándolos, mordiéndolos, sacudiéndolos y, a veces, matándolos.

Se presenta el análisis morfométrico de 38 elementos óseos de otáridos procedentes del sitio arqueológico P 133, desembocadura del río Santa Cruz, Patagonia austral. Los especímenes fueron recolectados en dos estratos de muestreo, uno sistemático (en cuadrículas de superficie y excavación, n = 28) y otro asistemático en una cuadrícula de superficie (n = 10). Se analizó la representación de especie, edad y sexo, considerando el estado de fusión y las variables métricas obtenidas sobre tres elementos óseos del miembro anterior no fusionados (húmero, radio y ulna) y uno fusionado (húmero), seleccionándose para ello los especímenes con buen estado de conservación. Los resultados indican un predominio de Otaria flavescens (88,57%), seguido de Arctocephalus australis (12%) entre los elementos no fusionados, mientras que los fusionados corresponden en su totalidad al húmero de esta segunda especie. En lo que se refiere a la edad ontogenética, los huesos no fusionados pertenecerían mayoritariamente a individuos neonatos, identificándose pocos elementos como cachorros de A. australis. Los especímenes fusionados fueron asignados a dos hembras y un macho adultos. Estos resultados complementan los obtenidos previamente en la localidad arqueológica de Punta Entrada, confirmando el aprovechamiento de crías de O. flavescens. A su vez, se amplían al identificar en este estudio a cachorros de A. australis, sugiriendo la posible existencia en esta localidad de apostaderos reproductivos de ambas especies, en el pasado. Se ofrecen así nuevos elementos para entender las relaciones entre humanos y pinnípedos en la costa de Patagonia austral durante los últimos 2000 años, cuya variabilidad aún no es suficientemente conocida.

Difference among colonies in the population structure of otariids can be driven by philopatry and/or by specializations in the foraging ecology of females. In northern Patagonia, the South American sea lion (SASL) shows some degree of spatial genetic structure among colonies from north and south zones. This study aims to explore the isotopic niche of SASL females in the last period of the pregnancy from different colonies of northern Patagonia and to consider whether the fine scale genetic spatial structuring is potentially related to variation in trophic resources. Stable isotope analysis was performed on 101 skin samples of newborn pups in 10 colonies, as a proxy for the feeding ecology of their mothers. Differences among colonies in the metrics studied revealed the plasticity of the species and support individual trophic specialization of SASL females at a small geographic scale. Also, significant differences were found in all isotopic metrics between the north and south zones. Several hypotheses were proposed to explain the differences in SASL females' isotope values (e.g., use of different foraging areas or prey, isotopic baseline variation). Nonetheless, further research is needed to better understand the relation between fine scale genetic structuring and the foraging ecology of SASL females. [ABSTRACT FROM AUTHOR]

The article offers information on the observation of killer whales in both hemispheres in the Eastern Tropical Pacific and mentions killer whales off Peru points to both oceanic and neritic distribution with predation observations targeting including Tursiops truncatus, Globicephala species, Arctocephalus australis, and Otaria flavescens. Topics discussed include a sighting of an adult male killer whale, photo-identification catalogs of killer whales, and resident fish eating.

Antarctophthirus microchir is a sucking louse species belonging to the family Echinophthiriidae and has been reported to parasitize all species of the subfamily Otariinae, the sea lions. Former studies on this ectoparasite mainly required fixation, immobilization, or death of host species and especially examinations of adult male sea lions are still very rare. Between March and May 2018, adult individuals of a unique "urban" bachelor group of South American sea lions (Otaria flavescens) living directly in the city of Valdivia, Chile, were studied regarding their ectoparasite infestation status. For first time, a non-invasive method in the form of a lice comb screwed on a telescopic rod and grounded with adhesive tape was used for sample taking process. Overall, during combing different stages of A. microchir were detected in 4/5 O. flavescens individuals, especially at the junction between the back and hind flippers. Our findings represent the first report of A. microchir infesting individuals of this synanthropic colony and fulfilling complete life cycle in a sea lion group despite inhabiting freshwater and in absence of females/pups. Our "telescopic lice comb apparatus" offers a new strategy to collect different stages of ectoparasites and a range of epidermal material, such as fur coat hair and superficial skin tissue for a broad spectrum of research fields in wildlife sciences in an unmolested and stress reduced manner. [ABSTRACT FROM AUTHOR]

Present study aimed to characterize gastrointestinal parasites and culturable bacteria from free-living South American sea lions (Otaria flavescens) inhabiting waters of Comau Fjord, Patagonia, Chile. Therefore, a total of 28 individual fecal samples were collected from sea lions within their natural marine habitat during several diving expeditions. Using classical parasitological techniques, study revealed infections with five different gastrointestinal parasite genera. In addition, bacterial cultures showed presence of at least 28 different bacterial genera. Referring to parasites, protozoan, and metazoan species were found with some of them bearing anthropozoonotic potential and/or pathogenic impact for these marine mammals. As such, four of identified parasite genera harbored zoonotic potential (i.e., Entamoeba, Balantidium, Diphyllobothrium, Anisakis) and one genus (Parafilaroides) represented a specific lungworm of marine pinnipeds. Proglottids from fecal samples showed high morphological homology to “Diphyllobothrium” scoticum (Rennie and Reid, 1912; Meggitt, 1924), which was found in Antarctic sea leopards (Hydrurga leptonyx; Phocidae), but contained eggs of smaller size. Molecular characterization revealed 97–100% identity to a new “Diphyllobothrium” species which was recently isolated from a Californian sea lion (Zalophus californianus; Otariidae) in San Francisco. As such, O. flavescens represents a new host record for this parasite species. Furthermore, potential zoonotic bacteria (i.e., Clostridium, Escherichia, Vibrio, Yersinia, Salmonella) were identified amongst others in O. flavescens indicating a reservoir role for these pinnipeds in marine ecosystem. Current data should be considered as a baseline study for future monitoring surveys on anthropozoonotic pathogens circulating in wild free-living sea lions and their possible impact on public health issues and marine wildlife.

Two species of ectoparasites were collected from a South American sea lion (Otaria flavescens) found stranded on the beaches of Chorrillos in Lima, Peru. The ectoparasites were identified as Antarctophthirus microchir (Phthiraptera) and Orthohalarachne attenuata (Acari). Some morphological characteristics are described in this report. The finding of these ectoparasites is the first records in Peru.

AbstractThe establishment of new pinniped colonies is a consequence of complex dynamics in which some colonies may transform from haul-outs into breeding sites. The aim of this article was to estimate the abundance of Otaria flavescens and Arctocephalus australis at two poorly known sites of Uruguay, the easternmost “Isla Verde-Islote Coronilla” (IV-IC) and the westernmost “Las Pipas” (LP). From June 2008 to June 2009 count from boats were conducted at LP, and aerial censuses at Isla Verde. At LP both pinniped species were recorded, and the abundance was maximum in July with a total of 202 animals.O. flavescens was present throughout the year, mainly adult males, while A. australis was only observed from June to October. LP is defined as a haul-out structure used as resting area, especially for O. flavescens. At IV-IC between 225 and 521 O. flavescens were recorded. The number of animals increased in Spring and Summer. Females were the most abundant category and pups were recorded in March. According to the age structure and the presence of pups, we propose it would have and incipient reproductive activity. This colony should be monitored in relation with its category as a marine protected area.

Fisheries interactions with non-target marine vertebrates are a worldwide problem. The impact of coastal bottom trawl fisheries on marine mammals has never been evaluated before in the Río de la Plata Estuary and the adjacent Atlantic Ocean. Our aim was estimating the bycatch per unit effort (BcPUE) and incidental mortality rates of marine mammals caused by the industrial coastal bottom trawl fisheries fleet. We evaluated the mortality of three species (i.e., franciscana dolphin Pontoporia blainvillei, South American sea lion Otaria flavescens, and the South American fur seal Arctocephalus australis); these species are facing conservation problems either at the regional or local scale. We conducted an onboard data collection program of marine mammals' bycatch involving crew members of 10 vessels (30%) of the Uruguayan coastal bottom trawl fleet between January 2009 and April 2012. A total of 102 marine mammal individuals were bycaught during 490 fishing trips involving 2,398 fishing days. Mortalities estimated for franciscana dolphin were the highest among the species affected, with values adding up to ~100 individuals for year (with scenarios of population decline in the area), followed by South American sea lion with ~77 individuals by year (0.8% of local population) and the South American fur seal with an annual mortality estimate of ~25 individuals (~0.02% of local population). BcPUE showed significant temporal variation, with franciscana dolphin BcPUE varying seasonally and those of otariids according to their breeding season. Our estimates of marine mammal bycatch by bottom trawl fisheries should constitute an important input for the sustainable management of fisheries and the conservation of marine biodiversity in the southwestern Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Acanthocephalans display a two-host life cycle that involves arthropods as intermediate hosts and vertebrates as definitive hosts. Some species also use paratenic hosts to bridge the trophic gap between both obligatory hosts. However, the relative role of these paratenic hosts in the transmission to definitive hosts has seldom been assessed quantitatively. We report on infection patterns of cystacanths of Corynosoma australe Johnston, 1937 in 20 common teleost species and the Argentine shortfin squid Illex argentinus (Castellanos) from the Patagonian shelf of Argentina. We also explore the role of different fish species in the transmission of C. australe to the most important definitive host in the area, i.e. the South American sea lion Otaria flavescens Shaw. Cystacanths of C. australe were found in all host species except Heliconus lahillei Norman, Merluccius hubbsi Marini and I. argentinus. In eight fish species, the prevalence of C. australe was > 50% and mean intensity > 4, i.e. Acanthistius patachonicus (Jenyns), Nemadactylus bergi (Norman), Paralichthys isosceles Jordan, Percophis brasiliensis Quoy & Gaimard, Prionotus nudigula Ginsburg, Scomber colias Gmelin, Raneya brasiliensis (Kaup) and Xystreurys rasile (Jordan). Two surveys on the trophic ecology of South American sea lions in the study area consistently found a generalist diet dominated by M. hubbsi, and data on the frequency of occurrence and number of other fish and cephalopod species in stomach contents strongly suggest that only R. brasiliensis may play a prominent role in the transmission of C. australe. This result raises interesting questions on the costs of paratenicity. [ABSTRACT FROM AUTHOR]

Context: As top predators, marine mammals play a key role consuming in different trophic levels and the trophic niche characterization may help to understand how species utilize and share resources. On the coast of the Río de la Plata and the South-west Atlantic, the South American sea lion (Otaria flavescens) and the franciscana dolphin (Pontoporia blainvillei) are two important predators. Aims: The present study investigated potential trophic overlap of both species by measuring stable carbon (δ13C) and nitrogen (δ15N) isotopes over two periods: historical (1959–79) and recent (2002–15) on the Uruguayan coast. Methods: Bone samples of P. blainvillei and O. flavescens were used to determine the isotopic niche using the Stable Isotope Bayesian Ellipses in R (SIBER) analysis. Key results: The isotopic niche did not overlap between species in any period. δ15N was higher in O. flavescens in both periods (20.29‰ ± 0.73 in the historical and 19.95‰ ± 1.0 in the recent period), indicating that it feeds at a higher trophic level than P. blainvillei. The δ13C was also significantly higher in O. flavescens than in P. blainvillei during the two periods (O. flavescens : –11.43 ± 0.6‰ historic, –12.72 ± 0.4‰ recent, and P. blainvillei : –12.69 ± 1.1‰ historic, –13.84 ± 1.3‰ recent). The isotopic niche areas of P. blainvillei in recent and historic periods confirmed they forage in 2 distinct environments, marine and estuarine, with low isotopic overlap. This overlap was higher in the recent period. Conclusions and Implications: O. flavescens and both P. blainvillei groups were segregated in both periods, with a higher overlap in the recent. These species appear to reduce competition by using different resources in the same coastal habitat. O. flavescens preferentially feeds on benthic fish and showed wider trophic amplitude in both periods, whereas P. blainvillei has a more coastal–pelagic diet and included a greater variability of resources in its diet. The differences between species trophic niches can still be detected after both marine mammals species abundance has declined and after the development of fisheries. We investigated the trophic overlap of two top predators, the South American sea lion and the franciscana dolphin between two periods of time including the development of fisheries and population declines. Trophic niches were segregated in both periods: sea lions preferentially feed on benthic fish whereas franciscana dolphins have a more coastal–pelagic diet. This approach enabled us to understand the trophic overlap, considering important changes in the ecosystem during the past 50 years. [ABSTRACT FROM AUTHOR]

Trichinella spp. from a sylvatic cycle has been found in several animal species such as pumas (Puma concolor), armadillos (Chaetophractus villosus), rats (Rattus norvegicus), and wild boars (Sus scrofa) in Argentina. Moreover, Trichinella infection has been detected in a wide range of marine mammals around the world, including polar bears (Ursus maritimus) and walruses (Odobenus rosmarus). Until the present time, Trichinella spp. infection has not been detected in marine mammals of South America. Samples from four South American sea lions (Otaria flavescens) found dead in Rio Negro, Argentina, were analyzed by artificial digestion, and in the case of one animal, Trichinella larvae were identified at the species level by nested multiplex PCR as Trichinella spiralis. This is the first report of a Trichinella species infecting marine mammals from South America. [ABSTRACT FROM AUTHOR]

In the last decades, an increasing fishing effort and a decreasing trend in fish catches have been observed in southern Brazil. Considering that marine mammals and fisheries usually compete for the same resources, it is reasonable to presume that the feeding ecology of these predators is affected by the current scenario. To evaluate this hypothesis, long-term variation in the diet of the South American sea lion (Otaria flavescens) relative to fisheries exploitation was analyzed for two periods (1993-2003 versus 2004-2014). The degree of overlap between the relative biomass of the sea lions’ diet and the target species of six types of local fishery was analyzed. An increase in prey overlap between sea lions and fisheries was observed in the more recent sampling period, along with an increase in prey diversity, richness, and niche breadth of the sea lions’ diet. These results suggest that the overfishing scenario could partly explain the modified feeding ecology of the sea lions. In this context, we recommend a review and better regulation of the current fishing effort in the region, which we believe will be an important step to maintain the fish stocks and minimize the impact of fishing on marine top predators. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Wildlife watching has become an important constituent of commercial tourism, and opportunities to encounter wildlife have proliferated and diversified. After regular tourist visits to a wildlife population, the intensity of behavioural responses to tourist approaches is expected to change due to diverse mechanisms, including habituation, sensitisation, social learning and population displacement. The village of Cabo Polonio (Uruguay, 34°24′S, 53°46′W) is small, but in summer, there is a massive influx of people, with more than 30 000 tourists entering Cabo Polonio in January alone. The rocky cape of Cabo Polonio is a haul-out site mainly occupied by South American fur seal ( Arctocephalus australis) males and South American sea lions ( Otaria flavescens). No monitoring or guided tours occurred at this continental colony. We examined changes in the intensity of behavioural responses of pinnipeds to tourist approaches at two temporal scales: (i) throughout a season, by comparing results from spring 2014 and summer 2015, and (ii) throughout the years, by comparing data from spring 1996 with those from spring 2014. We found that peopleś attitude and distance of approach influenced the animals' behaviour. The responsiveness of the pinnipeds almost tripled after two decades. We propose that the fence built in 1997 to protect the colony produced a paradoxical effect: instead of reducing the disturbance produced by tourists, it appears to increase it. This decrease in tolerance of tourism throughout the years goes against the argument that animals habituate to human presence after long-term exposure. [ABSTRACT FROM AUTHOR]

Colony formation is related to dispersal, philopatry, conspecific attraction, available suitable habitat, proximity and availability of food resources, and reproductive success. In this study we analyzed if female South American sea lions, (SASL, Otaria flavescens ), exhibit natal fidelity at a small geographic scale (between colonies of the same breeding area) in a context of a recovering population with population expansion and recolonization. We examined the mitochondrial genetic diversity and investigated spatial genetic structure, considering new and traditional colonies. We recovered 36 haplotypes (23 novel), with the contemporary presence of common and private haplotypes in each colony. AMOVA analysis indicated no population genetic structure, however F st , SAMOVA and AIS analyses suggested some level of genetic structure between northern and southern colonies. Therefore female SASL display different strategies when they choose where to breed: some are residents of -or return to- one particular colony whereas others disperse within the study area. In conclusion the recolonization of SASL may be the effect of weak female philopatry attenuated and/or interacting with other processes like site fidelity to near-by feeding grounds, breeding success, terrestrial habitat selection for breed and dispersal. [ABSTRACT FROM AUTHOR]

We analyzed the δ13C and δ15N values in the vibrissae of captive adult breeding South American sea lions ( Otaria byronia) fed at a constant diet and then used this information to analyze the change in stable isotope values along the vibrissae from wild individuals. The overall diet-to-vibrissa discrimination factor of the captive animals was 3.0‰ ± 0.1‰ for δ13C and 3.6‰ ± 0.1‰ for δ15N, but the stable isotope ratios fluctuated periodically despite constant diet. The δ13C and δ15N values of the captive male declined at the end of the breeding season, whereas the δ13C values of the female increased during the central part of pregnancy and the δ15N values peaked during lactation. The δ13C and δ15N values of adult wild specimens also fluctuated periodically and vibrissae growth rate (0.15 mm/d in both sexes) was slightly lower than in captivity (0.17 mm/d), assuming an annual periodicity for oscillations. Similarities in the amplitude of the cycles of captive and wild males suggested that fasting was probably the main source of periodic variability in the δ15N of wild males, whereas pregnancy and lactation were probably the main source of periodic variability for the δ13C of wild females. [ABSTRACT FROM AUTHOR]

Otaria flavescens (SASL) and Arctocephalus australis (SAFS) are endemic of South America. The aims were to assess Cd concentrations in red blood cells (RBC) and plasma from free living females of both species; and to establish metallothioneins (MT) levels in blood fractions and the possible relationship between MTs and Cd. Blood of fifteen SASL and eight SAFS females from Isla de Lobos were analyzed (years 2010–2011). All animals showed Cd levels above the detection limit. Cd concentrations on SAFS were higher than those of SASL, however, no significant differences were observed on metal concentrations between cell fractions by species. Metal levels were associated with a natural presence and ecological-trophic habits of the prey items. On SASL the MT concentrations between fractions were similar; whereas, SAFS plasma concentrations were higher than RBC. The results reported constitute the first information on Cd and MT blood levels in these species. [ABSTRACT FROM AUTHOR]

Conflicts between marine mammals and fisheries occur worldwide. Uruguay is an important breeding area of two pinniped species: the South American fur seal (Arctocephalus australis) and the South American sea lion (Otaria flavescens). Sea lions frequently interact with small-scale fisheries as their coastal feeding area coincides with the fishing zone used by coastal fisheries. In recent years, fishers have reported the presence of pinnipeds in small rookeries, Las Pipas and Isla de Flores, off the coast of Montevideo. The aim of this study was to assess the seasonal variability of both species at these two haulouts and to monitor their interactions with the small-scale fishery. We considered interactions to be when the presence of pinnipeds or predation or damages on catches were recorded during fishing operations. Between February 2013 and April 2014, six pinniped counts were made at each haulout; and between November 2013 and May 2014, 19 fishing events were monitored aboard fishing boats. Most animals in the colonies were adult males. The maximum number was recorded at Las Pipas in winter (160 animals). Sea lions were recorded throughout the year, while fur seals were only recorded in winter. In contrast, at Isla de Flores, only between 10 and 20 sea lions were recorded. Additionally, fishery catches were low (between 3 and 92 kg per fishing event). The catches per unit of effort were significantly higher in summer and autumn than in spring. However, catches did not differ significantly in the presence or absence of interactions. Sea lion predation varied from 0 to 1.72 kg per fishing event, averaging 2.37% of the potential catches. Interactions between sea lions and fishing operations were low in spring and summer, and the animals involved were mostly subadult and adult males. The fishing events with interactions and the abundance of pinnipeds were minimal in summer and maximal in autumn. In conclusion, the abundance of pinnipeds at the two haulouts can be explained by the reproductive cycles of these species, but also as a response of some animals to an increase in local food associated with the small-scale fisheries. [ABSTRACT FROM AUTHOR]