Papers by Alexandra Costa
Morphometric characteristics of the periotic -timpanic bone complex in the middle ear of cetacean... more Morphometric characteristics of the periotic -timpanic bone complex in the middle ear of cetaceans, are effective characteristics in evaluating systematics. However, they have not been used for studies of geographic variation regarding dolphins of the genus Sotalia. This study aimed to compare the periotic -timpanic of Sotalia guianensis from four distinct locations, considered here as different operational taxonomic units, Amapá/Pará (AM/PA), Maranhão/Piauí (MA/PI), Ceará (CE), and Rio de Janeiro (RJ), using 21 morphometric measurements. Multivariate analysis showed significant distinction mainly between the units of northern (AM/PA and MA/PI) and south-eastern (RJ) Brazilian coast. The timpanic bone showed variation, reaching larger sizes in the Brazilian south coast unit, corroborating current molecular data on the geographic variation of S. guianensis.
The objective of the present study was to analyze the distribution of manatees, dolphins and sea ... more The objective of the present study was to analyze the distribution of manatees, dolphins and sea turtles off northea stern Brazil through aerial surveys, relating them to specific habitats and human activities, with emphasis on marine protected areas (MPAs). Surveys were conducted between January and April 2010 at 150 m altitude and 140 km h À1 , using two independent observ ers. Strip trans ects were flown in a zigzag pattern. Transects covered 4026 km in more than 27 flight hours. A total of 36 sightings of manatees (Trichechus manatus manatus , 41 individuals), 28 of dolphins (Delphinidae, 78 individuals, including 10 Sotalia guianensis ) and 256 of sea turtles (Cheloniidae, 286 individ uals) were recorded. Manatees and sea turtles displayed solitary habits, while dolphins were commonly seen in groups. Manatees were positivel y correlated with sea turtles, probably due to their preference for sheltered shallow habitats with favorable conditions for foraging and resting. Furthermo re, manatees showed a positive relationship with mangrove estuaries, and medium-sized coastal cities probably due to the intense urban development in many estuarine areas. Manatees and sea turtles were also positively correlate d with boats, showing a severe threat for these species. Density of manatees was significantly higher within MPAs with preserved mangrove estuaries than in non-protecte d areas, while dolphins and sea turtles were observed in high densities MPAs with coral reefs. The elevated density of these organisms shows the vital importance of protecting and adequately managing unique ecosy stems to ensure a sustainable future for the populations of severely threatene d species.
RESUMO: A costa norte do Brasil representa uma nova fronteira para o avanço do conhecimento sobre... more RESUMO: A costa norte do Brasil representa uma nova fronteira para o avanço do conhecimento sobre a fauna de mamíferos aquáticos. A ausência de dados pretéritos sobre os mamíferos aquáticos nessa região e a própria dificuldade logística de monitoramento resultou, até muito recentemente, numa lacuna de conhecimento. A fim de reverter este quadro, o Projeto Piatam vem incentivando a formação de grupos de pesquisa sobre mamíferos aquáticos da costa amazônica. Como resultado dos esforços recentes, foi reunido um conjunto relevante de informações inéditas ou complementares sobre as 22 espécies de mamíferos aquáticos registradas até o momento na região. Destacam-se as áreas de ocorrência do peixe-boi-marinho no litoral dos Estados do Maranhão, Pará e Amapá, as quais poderiam garantir a manutenção destas populações criticamente ameaçadas. Merece destaque ainda a ocorrência do boto-cinza em toda costa amazônica e sua problemática de interação com a pesca artesanal e o comércio de peças anatômicas. Sugere-se uma ampla campanha de conscientização e a promoção de campanhas educativas visando uma nova tomada de atitude em relação aos mamíferos aquáticos e seus hábitats, respeitando os valores tradicionais e o conhecimento etnoecológico das comunidades costeiras.
This study reviews and updates information on cetacean strandings in the state of Ceará, Brazil (... more This study reviews and updates information on cetacean strandings in the state of Ceará, Brazil (02830 0 S 41815 0 W-04830 0 S 36845 0 W), comprising 573 km of coastline. In the years 1992-2005, there were 252 cetacean stranding events, representing 19 species: three species of Balaenopteridae, three Physeteridae, two Kogiidae, two Ziphiidae and 11 Delphinidae. Three species comprised the majority (78.9%) of stranding events: estuarine dolphin, Sotalia guianensis (61.9%); sperm whale, Physeter macrocephalus (10.3%); and rough-toothed dolphin, Steno bredanensis (6.7%). There was an increasing trend in the number of cases reported in the first five years with a highest frequency achieved in 1996. Stranding events occurred throughout the year, with the lowest frequency occurring in the autumn (March-May). Approximately 4% of the events were attributed to natural causes while 24.6% were human-related, mainly incidental captures. Meat removal for human consumption or bait was recorded in 6.7% of events. In the study area, Sotalia guianensis, P. macrocephalus and Steno bredanensis were the most abundant cetacean species, whereas Lagenodelphis hosei, Pseudorca crassidens, Orcinus orca, Kogia sima, Mesoplodon europaeus, Balaenoptera acutorostrata and Balaenoptera bonaerensis are probably rare in the area.
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Papers by Alexandra Costa