Prehensile use of perioral bristles during feeding and associated behaviors of the Florida manatee (Trichechus manatus latirostris)

The use of perioral bristles (modified vibrissae) by 17 captive Florida manatees and approximately 20 wild manatees was analyzed. Captive manatees were fed six species of aquatic vegetation normally eaten in the wild (four freshwater species and two seagrasses). Inanimate objects were placed in the holding tanks with manatees at Lowry Park Zoological Gardens (Tampa, FL) to determine the degree to which perioral bristles were used in exploration and to define the range of manipulative behavior. In addition, behavioral observations were made on the use of perioral bristles during social interactions with conspecifics. Observations were recorded using a Hi8-format video camera. Florida manatees possess an unusually large degree of fine motor control of the snout and perioral bristles. The large and robust perioral bristle fields of the upper lip were used in a prehensile manner during feeding. Bristle use by manatees feeding on submerged vegetation differed from that seen during feeding on floating vegetation. Other behavioral use of the perioral bristles shows variation depending upon the situation encountered. The degree of plasticity of perioral bristle use supports our hypothesis that the vibrissal-muscular complex of the Florida manatee has evolved to increase the efficiency of grazing and browsing on aquatic vegetation and to fully maximize the potential of the manatee as a generalist feeder. The manipulative and sensitive nature of the manatee snout is likely a manifestation of a complex sensory and motor system which has evolved for marine mammal aquatic herbivores living in shallow turbid habitats.