Opportunistic carnivory by Florida manatees (Trichechus manatus latirostris)

The Florida manatee (Trichechus manatus latirostris) is one of the most endangered marine mammals in the US To protect this species, it is important to understand the feeding ecology to define critical habitats. Manatees generally are considered to be strictly herbivious mammals that only incidentally consume animal species. This concept is based on the preponderence of freshwater vegetation, seagrasses, and algae that is found in most stomach content and fecal analyses. In the present study, manatees were observed feeding in areas of the Indian River Lagoon in Vero Beach and Fort Pierce, Florida, USA during June to August 2001. Most manatees were observed to be feeding on seagrasses and algae; however, on two occasions, manatees were observed apparently preferentially consuming invertebrates that were attached to a dock. Although some fibrous algae were present on the dock structure, the majority of biomass present was made up of invertebrates. Manatees were heard crunching invertebrate shells and seen pulling animals, such as tunicates, into their mouths. These observations suggest that manatees actively, rather than incidentally, consume invertebrates in some cases.