Social organization of marine Tucuxi dolphins, Sotalia guianensis, in the Cananeia Estuary of southeastern Brazil

Social organization is an important component of the population biology of a species that influences gene flow, the spatial pattern and scale of movements, and the effects of predation or exploitation by humans. An important element of social structure in mammals is group fidelity, which can be quantified through association indices. To describe the social organization of marine tucuxi dolphins (Sotalia guianensis) found in the Cananeia estuary, southeastern Brazil, association indices were applied to photo-identification data to characterize the temporal stability of relationships among members of this population. Eighty-seven days of fieldwork were conducted from May 2000 to July 2003, resulting in direct observations of 374 distinct groups. A total of 138 dolphins were identified on 1-38 distinct field days. Lone dolphins were rarely seen, whereas groups were composed of up to 60 individuals (mean +/- 1 SD = 12.4 +/- 11.4 individuals per group). A total of 29,327 photographs were analyzed, of which 6,312 (21.5%) were considered useful for identifying individuals. Half-weight and simple ratio indices were used to investigate associations among S. guianensis as revealed by the entire data set, data from the core study site, and data from groups composed of <= 10 individuals. Monte Carlo methods indicated that only 3 (9.3%) of 32 association matrices differed significantly from expectations based on random association. Thus, our study suggests that stable associations are not characteristic of S. guianensis in the Cananeia estuary.

Skin diseases in Guiana dolphins (Sotalia guianensis) from the Paranagua estuary, Brazil: A possible indicator of a compromised marine environment

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Feeding associations between Guiana dolphins, Sotalia guianensis (Van Bénèden, 1864) and seabirds in the Lagamar estuary, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Group size and composition of Guiana dolphins (Sotalia guianensis) (Van Bénèden, 1864) in the Paranaguá Estuarine Complex, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Guiana dolphins (Sotalia guianensis) displaying beach hunting behavior in the Cananéia Estuary, Brazil: social context and conservation issues

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Guiana dolphins, Sotalia guianensis (Cetacea: Delphinidae), in the Paranaguá Estuarine Complex: insights on the use of area based on the photo-identification technique

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Taxonomic status of the genus Sotalia: Species level ranking for tucuxi (Sotalia fluviatilis) and costero (Sotalia guianensis) dolphins

Dolphins of the genus Sotalia are found along the Caribbean and Atlantic coasts of Central and South America and in the Amazon River and most of its tributaries. At present, the taxonomy of these dolphins remains unresolved. Although five species were described in the late 1800s, only one species is recognized currently (Sotalia fluviatilis) with two ecotypes or subspecies, the coastal subspecies (Sotalia fluviatilis guianensis) and the riverine subspecies (Sotalia fluviatilis fluviatilis). Recent morphometric analyses, as well as mitochondrial DNA analysis, suggested recognition of each subspecies as separate species. Here we review the history of the classification of this genus and present new genetic evidence from ten nuclear and three mitochondrial genes supporting the elevation of each subspecies to the species level under the Genealogical/Lineage Concordance Species Concept and the criterion of irreversible divergence. We also review additional evidence for this taxonomic revision from previously published and unpublished genetic, morphological, and ecological studies. We propose the common name costero for the coastal species, Sotalia guianensis (Van Beneden 1864), and accept the previously proposed tucuxi dolphin, Sotalia fluviatilis (Gervais, 1853), for the riverine species.

Feeding habits of Guiana dolphins, Sotalia guianensis, from south-eastern Brazil: New items and a knowledge review

This study presents new information on feeding habits of Guiana dolphins, Sotalia guianensis, in south-eastern Brazil, together with new regression equations to evaluate the weight and length of fish from otoliths, showing an overview on the knowledge about this species-diet in this area. Eighteen stomach contents had been analysed and compared to 180 samples collected in another eight feeding studies. The analysed specimens were either incidentally caught in gillnets used in coastal waters by the fleet based in the Cananéia main harbour (25°00âS 47°55âW), south of São Paulo State, or found dead in inner waters of the Cananéia estuary between 2003 and 2009. Based on the index of relative importance analysis, the most important fish species were the banded croaker, Paralonchurus brasiliensis. Doryteuthis plei was the most representative cephalopod species. Stellifer rastrifer was the most important fish species observed in dolphins in inner estuarine waters and P. brasiliensis in recovered dolphins from coastal waters. Loliguncula brevis is the only cephalopod species reported from dolphins found in inner estuarine waters up to date. Doryteuthis plei was the most important cephalopod species observed in coastal dolphins. When considering other feeding studies, the most representative fish family in the diet of S. guianensis was Sciaenidae, which is mainly represented by demersal fishes. The main preys of S. guianensis are abundant in the studied areas, which may indicate an opportunistic feeding habit. The majority of them are not the most important target species by the commercial fishery in south-eastern Brazil. © 2012 Marine Biological Association of the United Kingdom.

Identificação e análise das áreas domicilares do boto-cinza, Sotalia guianensis (Van Bénéden, 1864), no estuário de Cananéia, São Paulo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Home ranges of Guiana dolphins (Sotalia guianensis) (Cetacea: Delphinidae) in the Cananeia estuary, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Análises moleculares como ferramentas voltadas ao estudo do boto-cinza (Sotalia guianensis) na região do Lagamar de Cananéia

Dentre os mamíferos marinhos presentes na costa brasileira, Sotalia guianensis (subordem Odontoceti, família Delphinidae) é um dos mais comumente encontrados, possuindo ampla distribuição pela América do Sul e Central. Pelo fato de apresentar hábito costeiro, esta espécie encontra-se diretamente relacionada com impactos de origem antrópica tais como poluição, pesca acidental ou degradação de habitats. Somado a estes fatores, a falta de informações relatada pela IUCN surge como outro ponto de preocupação, visto que não se sabe de fato qual o grau de conservação dessa espécie. Por este motivo o presente estudo pretende avaliar características populacionais existentes nos grupos de S. guianensis na região do Lagamar de Cananéia, litoral sul de São Paulo, utilizando-se de microssatélites. Para tanto, aspectos referentes à diversidade genética, grau de parentesco e fluxo gênico entre áreas estuarinas e de mar aberto foram considerados. A amostragem é composta por 22 tecidos oriundos de indivíduos de mar aberto e 11 estuarinos, coletados entre os anos de 1996 e 2009. O material foi amplificado por PCR utilizando-se de oito locos específicos para a espécie. O presente estudo concluiu que a diversidade genética (número de alelos, riqueza alélica, heterozigosidade esperada e observada) ocorrente no grupo de estudo é considerada como moderada quando comparada a outras populações de S. guianensis estudadas. Após a retirada dos locos com indício da presença de alelos nulos, a população mostrou-se em equilíbrio de Hardy-Weinberg, como revelado também pelo valor de FIS. Corroborando com o nível de diversidade genética encontrado, foram avaliados baixos índices de parentesco, sem diferenças significativas entre os grupos em comparação (estuário e mar aberto), bem como entre os sexos, indicando a ausência de dispersão sexo assimétrica... (Resumo completo, clicar acesso eletrônico abaixo)

Estimativa de abundância do Boto-Cinza, Sotalia Guianensis, no complexo estuarino-lagunar de Cananéia (SP): gerando subsídios para a carta SAO

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The Gonads of the South American Dolphins, Inia geoffrensis, Pontoporia blainvillei, and Sotalia fluviatilis

The appearances of the gonads are described in males and females of 18 Inia geoffrensis, 11 Pontoporia blainvillei, and eight Sotalia fluviatilis from South America. Males of I. geoffrensis become sexually active at a length of about 228 centimeters, females at 175 to 180 centimeters. Length at birth is 76 to 80 centimeters; parturition occurs from about July to September in the upper Amazon. Males of P. blainvillei are still sexually immature at a length of 128.5 centimeters, females become sexually active at a length of 137 centimeters. Off Uruguay, pregnant females have fetuses 6 centimeters in length in February and 61 centimeters in October. Males of S. fluviatilis are sexually active at a length of 148 centimeters, females at 140 centimeters. Gonad weights and details of corpora lutea and albicantia are given. Corpora albicantia appear to persist as in other cetaceans. The ovaries of I. geoffrensis are relatively bulky with the corpora enclosed in the ovarian substance and not pedunculated as in P. blainvillei and S. fluviatilis in which the right ovary is poorly developed.

Timing of ontogenetic changes of two cranial regions in Sotalia guianensis (Delphinidae)

Despite the fact that heterochronic processes seem to be an important process determining morphological evolution of the delphinid skull, previous workers have not found allometric scaling as relevant factor in the differentiation within the genus Sotalia. Here we analyzed the skull ontogeny of the estuarine dolphin S. guianensis and investigate differential growth and shape changes of two cranial regions the neurocranium and the face in order to evaluate the relevance of cranial compartmentalization on the ontogeny of this structure. Our results show that, even though both cranial regions stop growing at adulthood, the face has higher initial growth rates than the neurocranium. The rate of shape changes is also different for both regions, with the face showing a initially higher, but rapidly decreasing rate of change, while the neurocranium shows a slow decreasing rate, leading to persistent and localized shape changes throughout adult life, a pattern that could be related to epigenetic regional factors. The pattern of ontogenetic shape change described here is similar to those described for other groups of Delphinidae and also match intra and interspecific variation found within the family, suggesting that mosaic heterochrony could be an important factor in the morphological evolution of this group. (C) 2012 Deutsche Gesellschaft fur Saugetierkunde. Published by Elsevier GmbH. All rights reserved.