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.
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
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
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.