Manatee Brain

The brain of the adult manatee is about the size of a softball. The brain shown here is viewed from its left side. The spinal cord protrudes on the right of this picture and the olfactory bulbs (smell sense) are visible on the front (at the left) of the brain. The cerebral cortex is relatively smooth and unfissured, when compared to the cortex of a brain of relatively similar size, such as that of domestic cattle (zebu, see below). In the pages that follow, you will see external views of the manatee's brain from several different orientations. The pictures of external morphology will acquaint the viewer with he major sensory nerves, the major subdivisions of the whole brain, and indicate what externally visible features can be related to known characteristics of the manatee's behavior, social, emotional, and perceptual capabilities.

8 Standard Views	Left lateral	Right lateral	Dorsal	Rostral
8 Standard Views	Left dorsolateral	Right dorsolateral	Ventral	Caudal
View 10 Different Manatee Brains

We think that the relatively smooth cerebral cortex of of the sea cow (manatee) when compared with that of the land cow (zebu, shown here) indicates that the manatee has a fewer number and variety of cortical regions, which is reflected in the relatively simple perceptual and behavioral repertoires as well as in their relatively simple,casual and gentle mental, social, and emotional expressions. We believe this because manatees spend much of their life casually eating, and slowly moving around to find food, quiet places to rest, and seeking out streams We believe this because manatees spend much of their life casually eating, and slowly moving around to find food, quiet places to rest, and to seek out streams and bodies of water that allow them to keep warm (such as near the near electric power facilities).

Since the zebu is a land cow, and its brain is similar size to that of the manatee, we chose to discuss and compare the brain of this cow with that of the manatee in order to illustrate several behavioral, morphological, and ecological issues which we will discuss here.
Manatees navigate within the relatively smooth aquatic medium, and do not have to locomote over uneven surface terrains as do quadraped animals. Moreover, lacking hindlimbs, manatees do not have to create complex locomotor sequences over complex footscapes as do quadrapeds. Quadrapedial locomotion requires precise sensory-motor adjustments to land surfaces, as well as quick responses to sudden and strong gravitational forces which are continuously at play for standing and locomoting animals.

Manatees perceive environmental features mostly at close range, and the manatees distant environment is relatively simple and uniform and does not require complex sensory discriminative capacities, or complex sequential behaviors. The vision of manatees is relatively short range, their hearing is good and seems to focus mostly on listening, rather than rapid, orienting responses, scanning of the physical environment, or on producing and responding to elaborate vocal repertoires such as those exhibited by whales and porpoises.
These considerations as well as others (discussed in later sections) prompt us to view manatee cerebral cortex as being relatively smooth because of lack of complex areal differentiation and connectivity.

In contrast to the whales and porpoises, the vocal repertoires of manatees are relatively simple, and their vocabulary relatively small. Their social life is also relatively simple, they do not have complex social hierarchies and interactive social behaviors. Mother-infant behaviors are the most complex and long lasting, whereas courtship, sexual, and other social behaviors are relatively simple and brief. Behaviors that they do exhibit are relatively few, spatiotemporally simple, and stereotyped.

The manatee's most complex and elaborate sensory and motor capabilities involve the face, lips, and vibrissae, best seen in their interesting feeding and facial-oral exploratory activities involving the complex facial structures of their snout.

In pages that follow we will compare different structures in four mammals, two from the sea (manatee & seal) and two from land (cow & African lion), one each being a carnivore and one each a hervibore.