Tucuxi dolphins (Sotalia fluviatilis), which range from the Amazon Basin to the tropical coast of Central America and the temperate waters of southern Brazil, face many environmental challenges. A recent study of home range size in Baía Norte, southern Brazil, provides a model for tucuxi conservation and future research on the species.
Earthwatch-supported scientist Dr. Paulo Flores and his colleague Mariel Bazzolo (both of the International Wildlife Coalition, Brazil) reported their findings in the Latin American Journal of Aquatic Mammals. The most surprising result was that tucuxi home ranges in the study area were extremely small, averaging from 13 to 15 square kilometers depending on the analysis method.
Apparently females and males have an extensively overlap in home ranges areas, and their home range sizes do not present significant differences," said Flores, principal investigator of Earthwatch's Dolphins of Brazil project from 2001 to 2004. "Core areas are totally within the federally protected area created to conserve the species."
Flores and colleagues helped to create the Environmental Protection Area of Anhatomirim (EPAA), located at the study site in Baía Norte, in 1992. Although federally protected, Flores found that the local tucuxi population still felt the impacts of habitat loss, pollution, fish stock depletion, and incidental bycatch by commercial fisheries.
"Here in EPAA, the marine tucuxis could be more easily protected if the existing law was followed by educated people, and enforced upon those not so well educated," said Flores. "Also, a buffer zone should be created to ensure protection outside this protected area, where the tucuxi home ranges extend. Further protection in the area would also benefit other marine mammals, such as the rarely seen franciscana (Pontoporia blainvillei), the most endangered dolphin in Brazilian waters."
As the first study to present home range estimates for the marine tucuxi, Flores' findings provide a minimum area for protecting other populations. Although any generalization is difficult in such a socially complex and intelligent animal, ranging from tropical to temperate waters, the findings offer valuable guidance for further research and conservation efforts.
Earthwatch teams working in Baía Norte with Flores made a significant contribution to collecting the data reported in the paper. "Moreover, their enthusiasm and support while in the water, for long periods on occasions, have inspired us as well," said Flores.
For more information, see "Home ranges and movement patters of the marine tucuxi dolphin, Sotalia fluviatilis, in Baía Norte, southern Brazil." Paulo A.C. Flores and Mariel Bazzolo. Latin American Journal of Aquatic Mammals 3(1): 37-52, January/June 2004.
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