Close Window

Abstract ID: 314

Seasonal habitat use of the Amazonian manatee: a conservation perspective

We studied the environment and movements of the Amazonian manatee Trichechus inunguis in the mid-river Solimões region to show that males have seasonal home ranges, and suggest why. We analyzed Landsat-TM/ETM+ images of different flood pulse phases and a 10 year average-hydrograph of Lake Mamirauá, and generated a bathymetric model of the water bodies where manatees were tracked. We classified the images distinguishing areas covered by macrophytes (main food), forest and open-water to create 'maps' for habitat analyses. During the low-water floodplain lakes may dry-out or become isolated, and potential predators (ex. Caymans Melanosuchus niger) aggregate in them. In contrast, lake Amanã offers larger and safer aquatic space for manatees because of its smaller water level variation, larger size, flat bottom and lower predator concentration. We then calculated home ranges of 10 males tracked with VHF telemetry and used general linear models to contrast habitat content of ranges in floodplain lakes with that in river Japurá and lake Amanã. We tested differences in the mean quantity and proportion of area covered by food during high-water, as well as in seasonal reduction in flooded area. We demonstrate that during high-water males remain in floodplain lakes in association with macrophytes (R2=98.62%, p=0.001), which compositional analysis indicates they select (F(2;5DF)=7.56; p=0.04). We then show that the greatest reduction in flooded area occurs in ranges in floodplain lakes (R2=98.76%, p=0.001) and suggest how direct and indirect consequences of space reduction explain why males migrate to lake Amanã to spend the low-water. Based on analysis of the flooding dynamics of river Solimões' via radar classifications (Hess et al., 2003), we show that during the high-water the best manatee habitats occur in white-water floodplain lakes and hypothesize that ria lakes are the main low-water shelters. We discuss how the spatial superposition between good manatee habitat and the more densely human populated areas is of importance for conservation, and suggest future steps.

Session:  Biodiversity - Modeling biodiversity, present and future. (B)

Presentation Type:  Oral

Close Window