First Evidence for Adoption in California Sea Lions

Demographic parameters such as birth and death rates determine the persistence of populations. Understanding the mechanisms that influence these rates is essential to developing effective management strategies. Alloparental behavior, or the care of non-filial young, has been documented in many species and has been shown to influence offspring survival. However, the role of alloparental behavior in maintaining population viability has not been previously studied. Here, we provide the first evidence for adoption in California sea lions and show that adoption potentially works to maintain a high survival rate of young and may ultimately contribute to population persistence. Alloparental behavior should have a positive effect on the population growth rate when the sum of the effects on fitness for the alloparent and beneficiary is positive

Bycatch of franciscana dolphins Pontoporia blainvillei and the dynamic of artisanal fisheries in the species' southernmost area of distribution

Na Argentina, a toninha é um dos cetáceos mais vulneráveis devido às capturas por rede de pesca artesanal. O presente estudo teve como objetivo estimar as capturas acidentais no sul da província de Buenos Aires, através de entrevistas aos capitães de barcos de pesca artesanal, entre os anos 2006-2009. As capturas foram reportadas para redes de emalhe e de camarão; com as mais altas frequências entre outubro e fevereiro, a 5 km da costa e 10-20 m de profundidade. A mortalidade acidental média anual estimada foi de 107 golfinhos (IC 95% = 87-129), 92 em redes de emalhe (IC 95% = 73-112) e 15 em redes de camarão (IC 95% = 8-25), com uma captura de 0,029 golfinhos/km de rede de emalhe (IC 95% = 0,023-0,036) e 0,024/rede de camarão (IC 95% = 0,012-0,035). As flutuações anuais responderam principalmente às diferenças nos dias de pesca. Considerando o último levantamento estimativo feito para o norte costeiro da província, estima-se uma mortalidade entre 360-539 golfinhos/ano em toda a província de Buenos Aires. Esses valores correspondem de 2,5-3,7% da abundância populacional da Argentina; o que traria como consequência um declínio populacional da espécie, tornando-se fundamental encontrar alternativas de pesca para a área.In Argentina, the franciscana dolphin is one of the most vulnerable cetaceans regularly entangled in coastal artisanal fishery nets. The aim of this paper is to estimate the species' incidental mortality on the Southern coast of Buenos Aires province through interviews with the captains of artisanal fishing vessels, in the period 2006-2009. Franciscana bycatch was reported for gillnets and shrimper gear all year round but it occurred more frequently between October and February, at 5 km offshore and 10-20 m depth. The estimated mean annual incidental mortality was 107 dolphins (CI 95% = 87-129), 92 caught in gillnets (CI 95% = 73-112) and 15 in shrimpers' gear (CI 95% = 8-25) with a capture per unit effort of 0.029 dolphins per km of gillnet (CI 95% = 0.023-0.036) and 0.022 per shrimpe r's net (CI 95% = 0.012-0.035). Annual fluctuations were due to differences in the number of gillnetting fishing days. If mortality estimates for the Northern coast are also taken into account, values attain a maximum of 360-539 dolphins bycaught in the entire Buenos Aires province, representing 2.5-3.7% of the species' abundance in Argentina. This will inevitably lead to the decline of franciscana dolphin populations in the near future unless alternative fishing grounds are identified and alternative gearadopted

Weak Polygyny in California Sea Lions and the Potential for Alternative Mating Tactics

Female aggregation and male territoriality are considered to be hallmarks of polygynous mating systems. The development of genetic parentage assignment has called into question the accuracy of behavioral traits in predicting true mating systems. In this study we use 14 microsatellite markers to explore the mating system of one of the most behaviorally polygynous species, the California sea lion (Zalophus californianus). We sampled a total of 158 female-pup pairs and 99 territorial males across two breeding rookeries (San Jorge and Los Islotes) in the Gulf of California, Mexico. Fathers could be identified for 30% of pups sampled at San Jorge across three breeding seasons and 15% of sampled pups at Los Islotes across two breeding seasons. Analysis of paternal relatedness between the pups for which no fathers were identified (sampled over four breeding seasons at San Jorge and two at Los Islotes) revealed that few pups were likely to share a father. Thirty-one percent of the sampled males on San Jorge and 15% of the sampled males on Los Islotes were assigned at least one paternity. With one exception, no male was identified as the father of more than two pups. Furthermore, at Los Islotes rookery there were significantly fewer pups assigned paternity than expected given the pool of sampled males (p<0.0001). Overall, we found considerably lower variation in male reproductive success than expected in a species that exhibits behavior associated with strongly polygynous mating. Low variation in male reproductive success may result from heightened mobility among receptive females in the Gulf of California, which reduces the ability of males to monopolize groups of females. Our results raise important questions regarding the adaptive role of territoriality and the potential for alternative mating tactics in this species

Predation of Otaria flavescens over artisanal fisheries in Uruguay: opportunism or prey selectivity?

Interactions between pinnipeds and fisheries have become an increasingly important topic for fisheries and pinniped management. In particular, the predatory behavior on fisheries is a cause of concern in many places because seals frequently opt to take fish from fishers' gear rather than searching and caching their own food. Sea lion prey selectivity on artisanal fisheries catches was analyzed, with the aim of determining if the predatory behavior was opportunistic or selective. Data were collected through direct observations of sea lion predation onboard during routine fishing trips at four fishing ports on the Uruguayan coast (Buceo, Piriápolis, La Paloma and Cabo Polonio), during two time periods (winter and spring-summer) in 1997/1998. The proportion of the most consumed fish and those most caught by the fishery was analyzed. An odds ratio was calculated as a selection index, using the number of prey items consumed by sea lions, and those caught by the fishery. Two general predatory strategies are apparent, one at the two fishing ports located on La Plata River estuary (Buceo and Piriápolis) and the second at the other two localities on the Atlantic Ocean coast. In the first strategy, the most consumed prey were the same most caught by the fishery (Macrodon ancylodon and Urophycis brasiliensis), suggesting an opportunistic behavior. However, at La Paloma and Cabo Polonio sea lions preyed mostly upon species which were not the main for the fishery (Cynoscion guatucupa in La Paloma, and Mustelus schmitti in Cabo Polonio) and exhibited selections and rejections of other species. Preferences and rejections however, represented small proportions of sea lion consumption and of the fishery catch. Seasonal differences in prey consumption and catches, as well as in selections and rejections were also evident. In some cases prey selections were reversed between both time periods. There was no evidence of an important conflict between sea lions and artisanal fisheries because the most selected species were not the most important for the fishery

Overlap between pinniped summer diet and artisanal fishery catches in Uruguay

The similarity of the trophic ecology of Arctocephalus australis and Otaria flavescens in Uruguay was studied to help understand a possible trophic competition between the two species and its relation with artisanal fisheries. Dietary data for both pinnnipeds together with artisanal fisheries catch data were analyzed to estimate the overlap in prey species and sizes. Diet overlap was very high (Colwell and Futuyma overlap index, C = 0.80), with three fish species (Anchoa marinii, Cynoscion guatucupa, and Trichiurus lepturus) comprising more than 90% of the total number of individuals consumed by both species. In addition, the length of these three fish prey taken by fur seals and sea lions was similar, suggesting a large overlap not only in species but also in the size of prey ingested. The main difference between the two pinniped diets was that O. flavescens showed a more diverse diet than A. australis. Concerning pinniped fisheries interactions, a low level of overlap was observed between the diet of each pinniped and artisanal fisheries catches (C = 0.22 for O. flavescens, and C = 0.09 for A. australis). Possibly, sea lion diet is broader than artisanal fisheries catches. Length comparisons for C. guatucupa, the only species well represented in both pinniped species diet and fisheries catches, indicated that individuals taken by the latter were larger than those consumed by the pinnipeds. However, the use of different age classes of the same resource, at different times or spatial locations do not imply less intensity of the interaction

Sexual foraging segregation in South American sea lions increases during the pre-breeding period in the Río de la Plata plume

Stable carbon and nitrogen isotopes in skin and bone of South American sea lionsfrom Brazil and Uruguay were analysed to test the hypothesis that trophic overlap between the sexes is lower during the pre-breeding season than throughout the rest of the year. The isotopic values of skin and bone were used to infer the trophic relationships between the sexes during the pre-breeding period and year round, respectively. Prey species were also analysed to establish a baseline necessary for interpreting the stable isotope ratios of skin and bone. Standard ellipse areas, estimated using Bayesian inference in the SIBER routine of the SIAR package in R, suggested that males and females used a wide diversity of foraging strategies throughout the year and that no differences existed between the sexes. However, the diversity of foraging strategies was largely reduced during the pre-breeding period, with all the individuals of each sex adopting similar strategies, but with the two sexes differing considerably in stable isotope values and the ellipse areas of males and females not overlapping at all. Nevertheless, the results revealed a general increase in the consumption of pelagic prey by both sexes during the pre-breeding period. The progressive crowding of individuals in the areas surrounding the breeding rookeries during the pre-breeding period could lead to an increase in the local population density, which could explain the above reported changes.Fil: Drago, M.. Universidad de la Republica. Centro de Estudios Interdiciplinarios Uruguayos; UruguayFil: Franco Trecu, V.. Universidad de la República. Facultad de Ciencias; UruguayFil: Zenteno, L.. Universidad de Barcelona; EspañaFil: Szteren, D.. Universidad de la República. Facultad de Ciencias; UruguayFil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Riet Sapriza, F. G.. Universidad del Uruguay. Facultad de Ciencias; UruguayFil: de Oliveira, L.. Study Group of Aquatic Mammals of Rio Grande do Sul; BrasilFil: Machado, R.. Study Group of Aquatic Mammals of Rio Grande do Sul; Brasil. Universidade Federal do Rio Grande do Sul; BrasilFil: Inchausti, P.. Universidad de la Republica. Centro de Estudios Interdiciplinarios Uruguayos; UruguayFil: Cardona, L.. Universidad de Barcelona; Españ

Sexual foraging segregation in South American sea lions increases during the pre-breeding period in the La Plata River plume

Stable carbon and nitrogen isotopes in skin and bone of South American sea lions from Brazil and Uruguay were analysed to test the hypothesis that trophic overlap between the sexes is lower during the pre-breeding season than throughout the rest of the year. The isotopic values of skin and bone were used to infer the trophic relationships between the sexes during the pre-breeding period and year round, respectively. Prey species were also analysed to establish a baseline necessary for interpreting the stable isotope ratios of skin and bone. Standard ellipse areas, estimated using Bayesian inference in the SIBER routine of the SIAR package in R, suggested that males and females used a wide diversity of foraging strategies throughout the year and that no differences existed between the sexes. However, the diversity of foraging strategies was largely reduced during the pre-breeding period, with all the individuals of each sex adopting similar strategies, but with the two sexes differing considerably in stable isotope values and the ellipse areas of males and females not overlapping at all. Nevertheless, the results revealed a general increase in the consumption of pelagic prey by both sexes during the pre-breeding period. The progressive crowding of individuals in the areas surrounding the breeding rookeries during the pre-breeding period could lead to an increase in the local population density, which could explain the above reported changes

Sexual foraging segregation in South American sea lions increases during the pre-breeding period in the La Plata River plume

Stable carbon and nitrogen isotopes in skin and bone of South American sea lions from Brazil and Uruguay were analysed to test the hypothesis that trophic overlap between the sexes is lower during the pre-breeding season than throughout the rest of the year. The isotopic values of skin and bone were used to infer the trophic relationships between the sexes during the pre-breeding period and year round, respectively. Prey species were also analysed to establish a baseline necessary for interpreting the stable isotope ratios of skin and bone. Standard ellipse areas, estimated using Bayesian inference in the SIBER routine of the SIAR package in R, suggested that males and females used a wide diversity of foraging strategies throughout the year and that no differences existed between the sexes. However, the diversity of foraging strategies was largely reduced during the pre-breeding period, with all the individuals of each sex adopting similar strategies, but with the two sexes differing considerably in stable isotope values and the ellipse areas of males and females not overlapping at all. Nevertheless, the results revealed a general increase in the consumption of pelagic prey by both sexes during the pre-breeding period. The progressive crowding of individuals in the areas surrounding the breeding rookeries during the pre-breeding period could lead to an increase in the local population density, which could explain the above reported changes