Trichecus manatus is a large aquatic, coastal and estuarine, browsing, diurnal herbivore. These 1000 pound mammals have an ellipsoidal submarine appearance, with a large, mobile snout, with a upper lip divided into two mobile prehensile pads containing large clusters of protrusive bristles. The flexibly mobile forelimbs are oval flippers with 3 nails rather than claws on the digits. Hindlimbs are absent and the tail is flattened dorsoventrally into a fluke. The eyes are small with tiny lids and a nictitating membrane. The nares are dorsal and closeable during submersion.

These animals have an estimated life span of 30 years, live in family groups of 2-20, are gently social, have casual movement patterns while feeding, migrating, being social, or when resting or sleeping. They are rarely vigorously active except when suddenly disturbed or injured. They do not exhibit rapid body movements, or agile or complex whole-body responses to stimuli. Even their courtship and mating behaviors are mildly intense. Their oro-facial browsing and feeding activities are the most complex, detailed, focused and deft of all their behaviors. The orofacial structures of the proboscis are anatomically differentiated (Fig. X) and have prominent sensory and motor innervation. Much of their waking life is spent in feeding activities, which is apparently associated with their relatively low metabolic rate and large gastrointestinal system, as well as the relatively low nutritional value of the aquatic plants which are their food source.

The forelimb flippers are active in touching, pulling and guiding food to the mouth and are also used in scratching, wiping and in social contacts. Hind limbs are absent and the tail is broadened and flattened dorsoventrally as a fluke, the movements of which play a major role in forward propulsion as well as in adjustments of posture, tilt, yaw and roll. The eyes are relatively small, having minimal movement; and visually guided behavior is relatively simple and slow. There is no pinna, but the external ear canal is present, but tiny, as in porpoises. Olfactory inspired behaviors are not apparent, and ingestion and rejection are presumably guided largely by somatic sensation, although gustation is also likely prominent. The manatee's vocal repertoire is relatively simple. A major emphasis of this report will be to identify neuroanatomical features of the manatee's brain that appear to be correlated with sensory-motor features of its behavioral repertoire.