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Title: Number, seasonal movements, and residency characteristics of river dolphins in an Amazonian floodplain lake system
Authors: Martin, Anthony Richard
Silva, Vera Maria Ferreira da
Keywords: Floods
Water Levels
Animals Movement
Floodplain Lake Systems
Seasonal Migration
Community Structure
Seasonal Variation
Site Fidelity
Water Level
Amazon River
South America
Western Hemisphere
Inia Geoffrensis
Issue Date: 2004
metadata.dc.publisher.journal: Canadian Journal of Zoology
metadata.dc.relation.ispartof: Volume 82, Número 8, Pags. 1307-1315
Abstract: The size and structure of a community of Amazon river dolphins or botos, Inia geoffrensis (de Blainville, 1817), was investigated using boat surveys and long-term observations of recognisable animals. Year-round, some 260 botos occurred in or near the 225-km2 Mamirauá várzea floodplain lake system, of which half were permanent residents by our definition. Seasonal variation in water levels influenced distribution between habitats but not the overall number of botos. Ninety percent of marked botos encountered within the lake system were permanent residents. There appeared to be a cline in site fidelity between those that always live in or near the system and those that visit at intervals of years. We estimated that 270 botos were "significant users" of the lake system (i.e., occurred within it for sufficient periods in a year to be observed at least once) and that many others visited for short periods. Individuals moved many tens to hundreds of kilometres along the rivers, but there was no broad-scale seasonal migration. The boto population of the central Amazon, at least, may be structured on the basis of floodplain lake systems, with extensive animal movement between systems. We estimate that 13 000 botos occur in the 11 240 km2 Mamirauá Sustainable Development Reserve, which covers an estimated 11%-18% of várzea habitat in Brazil.
metadata.dc.identifier.doi: 10.1139/Z04-109
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