The Southern Ocean Exchange: porous boundaries between humpback whale breeding populations in southern polar waters.

Humpback whales (Megaptera novaeangliae) are a cosmopolitan species and perform long annual migrations between low-latitude breeding areas and high-latitude feeding areas. Their breeding populations appear to be spatially and genetically segregated due to long-term, maternally inherited fidelity to natal breeding areas. In the Southern Hemisphere, some humpback whale breeding populations mix in Southern Ocean waters in summer, but very little movement between Pacific and Atlantic waters has been identified to date, suggesting these waters constituted an oceanic boundary between genetically distinct populations. Here, we present new evidence of summer co-occurrence in the West Antarctic Peninsula feeding area of two recovering humpback whale breeding populations from the Atlantic (Brazil) and Pacific (Central and South America). As humpback whale populations recover, observations like this point to the need to revise our perceptions of boundaries between stocks, particularly on high latitude feeding grounds. We suggest that this "Southern Ocean Exchange" may become more frequent as populations recover from commercial whaling and climate change modifies environmental dynamics and humpback whale prey availability.

Homophily around specialized foraging underlies dolphin social preferences.

Individuals often associate socially with those who behave the same way. This principle, homophily, could structure populations into distinct social groups. We tested this hypothesis in a bottlenose dolphin population that appeared to be clustered around a specialized foraging tactic involving cooperation with net-casting fishermen, but in which other potential drivers of such social structure have never been assessed. We measured and controlled for the contribution of sex, age, genetic relatedness, home range and foraging tactics on social associations to test for homophily effects. Dolphins tended to group with others having similar home ranges and frequency of using the specialized foraging tactic, but not other traits. Such social preferences were particularly clear when dolphins were not foraging, showing that homophily extends beyond simply participating in a specific tactic. Combined, these findings highlight the need to account for multiple drivers of group formation across behavioural contexts to determine true social affiliations. We suggest that homophily around behavioural specialization can be a major driver of social patterns, with implications for other social processes. If homophily based on specialized tactics underlies animal social structures more widely, then it may be important in modulating opportunities for social learning, and therefore influence patterns of cultural transmission.

Lacaziosis-like disease in Tursiops truncatus from Brazil: a histopathological and immunohistochemical approach

ABSTRACT: Cetacean lacaziosis-like disease or lobomycosis-like disease (LLD) is a chronic skin condition caused by a non-cultivable yeast of the order Onygenales, which also includes Lacazia loboi, as well as Paracoccidioides brasiliensis and P. lutzii, respectively responsible for lacaziosis and paracoccidioidomycosis in humans. Complete identification and phylogenetic classification of the LLD etiological agent still needs to be elucidated, but preliminary phylogenetic analyses have shown a closer relationship of the LLD agent to Paracoccidioides spp. than to L. loboi. Cases of LLD in South American cetaceans based on photographic identification have been reported; however, to date, only 3 histologically confirmed cases of LLD have been described. We evaluated multiple tissue samples from 4 Tursiops truncatus stranded in the states of Santa Catarina (n = 3) and Rio Grande do Sul (n = 1), southern Brazil. Macroscopically, all animals presented lesions consistent with LLD. Hematoxylin-eosin, periodic acid-Schiff, Grocott's methenamine silver, and Mayer's mucicarmin stains were used for histological evaluation. Microscopically, numerous refractile yeasts (4-9 µm in diameter) were observed in skin samples (4/4), and for the first time in dolphins, also in a skeletal muscle abscess (1/4). Immunohistochemistry using anti-P. brasiliensis glycoprotein gp43 as a primary antibody, which is known to cross-react with L. loboi and the LLD agent, was performed and results were positive in all 4 cases. We describe 3 new cases of LLD in cetaceans based on histopathology and immunohistochemistry. This is the first report of LLD in the muscle of cetaceans.

The structure of a bottlenose dolphin society is coupled to a unique foraging cooperation with artisanal fishermen.

Diverse and localized foraging behaviours have been reported in isolated populations of many animal species around the world. In Laguna, southern Brazil, a subset of resident bottlenose dolphins (Tursiops truncatus) uses a foraging tactic involving cooperative interactions with local, beach-casting fishermen. We used individual photo-identification data to assess whether cooperative and non-cooperative dolphins were socially segregated. The social structure of the population was found to be a fission-fusion system with few non-random associations, typical for this species. However, association values were greater among cooperative dolphins than among non-cooperative dolphins or between dolphins from different foraging classes. Furthermore, the dolphin social network was divided into three modules, clustering individuals that shared or lacked the cooperative foraging tactic. Space-use patterns were not sufficient to explain this partitioning, indicating a behavioural factor. The segregation of dolphins using different foraging tactics could result from foraging behaviour driving social structure, while the closer association between dolphins engaged in the cooperation could facilitate the transmission and learning of this behavioural trait from conspecifics. This unique case of a dolphin-human interaction represents a valuable opportunity to explore hypotheses on the role of social learning in wild cetaceans.

Seasonal variations in spatial usage by the estuarine dolphin, Sotalia guianensis (van Bénéden, 1864) (Cetacea; Delphinidae) at its southern limit of distribution.

The use of space by the resident population of estuarine dolphins (Sotalia guianensis) in Norte Bay, southern Brazil was studied by boat surveys between 2000 and 2003. Data such as the geographical position and group size was collected at 5-minute intervals using focal-group sampling. The distribution and seasonal and daily group home-ranges were estimated using a GIS (Geographic Information System) environment. The dolphins did not use the area homogeneously, restricting their activities to a well-defined area located in the western part of the bay, while the use of the eastern part was not observed. A discrepancy between the Environment Protection Area of Anhatomirim, created especially to protect this population and the distribution of the dolphins was observed. Seasonal group home-range varied both qualitatively and quantitatively among the four consecutive seasons analyzed. The dolphins tended to use a larger area in cold seasons, when apparently the abundance of major prey items is lower. Core areas of intense use were identified, and also varied seasonally. These core areas may be regarded as critical habitats and require special legislation and control. The mean daily group home-range did not differ statistically among seasons. The present study corroborates a spatially strict residency pattern of the estuarine dolphin in highly productive coastal ecosystems.

Seasonal variations in spatial usage by the estuarine dolphin, Sotalia guianensis (van Bénéden, 1864) (Cetacea; Delphinidae) at its southern limit of distribution

The use of space by the resident population of estuarine dolphins (Sotalia guianensis) in Norte Bay, southern Brazil was studied by boat surveys between 2000 and 2003. Data such as the geographical position and group size was collected at 5-minute intervals using focal-group sampling. The distribution and seasonal and daily group home-ranges were estimated using a GIS (Geographic Information System) environment. The dolphins did not use the area homogeneously, restricting their activities to a well-defined area located in the western part of the bay, while the use of the eastern part was not observed. A discrepancy between the Environment Protection Area of Anhatomirim, created especially to protect this population and the distribution of the dolphins was observed. Seasonal group home-range varied both qualitatively and quantitatively among the four consecutive seasons analyzed. The dolphins tended to use a larger area in cold seasons, when apparently the abundance of major prey items is lower. Core areas of intense use were identified, and also varied seasonally. These core areas may be regarded as critical habitats and require special legislation and control. The mean daily group home-range did not differ statistically among seasons. The present study corroborates a spatially strict residency pattern of the estuarine dolphin in highly productive coastal ecosystems.

A utilização espacial pela população residente de botos-cinza, Sotalia guianensis, na Baía Norte de Santa Catarina, Sul do Brasil, foi estudada por meio de saídas de barco realizadas entre 2000 e 2003. Dados como posição geográfica (GPS) e tamanho de grupo foram obtidos utilizando-se o método de grupo focal. A distribuição e a área de vida diária e sazonal do grupo foram estimadas por um SIG (Sistema de Informações Geográficas). O uso do espaço pelos botos foi heterogêneo, restringindo suas atividades a uma área bem definida, localizada na parte oeste da baía, enquanto a utilização do lado leste não foi observada. Observou-se uma discrepância entre a distribuição dos botos e a Area de Proteção Ambiental de Anhatomirim, criada especialmente para proteger esta população. A área de vida sazonal do grupo variou tanto qualitativamente como quantitativamente nas quatro estações do ano consecutivas estudadas. Os botos tenderam a utilizar uma área maior nas estações frias do ano, quando a abundância de suas presas potenciais parece ser menor. Identificaram-se áreas de maior concentração de indivíduos, que também tiveram variação sazonal. Estas áreas de concentração podem ser consideradas hábitats críticos e exigem controle e legislação especial. Não houve uma diferença sazonal significativa nas áreas de vida diária do grupo de botos nas diferentes estações do ano estudadas. Os resultados deste trabalho apontam para um padrão de residência espacialmente restrita de S. guianensis em ecossistemas costeiros de grande produtividade.