Feeding ecology of the amazonian manatee (Trichechus inunguis) in the mamirauá and amanã sustainable development reserves, Brazil

Abstract

The Amazonian manatee (Trichechus inunguis) is an exclusively herbivorous freshwater mammal. Between 1994 and 2008, 230 fecal and 16 stomach content samples from wild Amazonian manatees were obtained. The material was collected during both dry and wet seasons in the sustainable devel-opment reserves of Mamirauá (MSDR) and Amanã (ASDR) from floodplain and terra firme and igapó (not subject to long-term flooding) habitats, respec-tively. Species constituting the diet of the Amazonian manatee were identified through a comparative anal-ysis with a reference collection of epidermis from 69 plant species of potential consumption by the spe-cies. Forty-nine plant species were identified in the species' diet. In the MSDR, 32 plant species were found-18 during the dry season and 28 during the wet season. In the ASDR, 48 species were identified of which 40 occurred in both periods. A total of 30 new species were added to the Amazonian mana-tee diet known to date. The species that were found most frequently in the material were Hymenachne amplexicaulis, Oryza grandiglumis, Paspalum repens, Azolla caroliniana, and Limnobium spongia. Poaceae was the family with the greatest frequency of occurrence (91.5%). Plant species most consumed present emergent or floating habits. There was a dif-ference in the composition of plant species found in manatee feces between the dry and wet seasons (p = 0.0002) but not between floodplain and igapó. Results show that the Amazonian manatee feeds on a great variety of plant species during the wet and dry season alike, and both in floodplain and igapó envi-ronments. Therefore, food availability alone does not represent a determining factor to explain the seasonal migration of the species.