Perhaps one of the most endearing qualities of the
dolphin is its apparent smile. Actually this is not a smile at all, but is a fixed design of their head, a hydrodynamic adaptation
to a life swimming in water. It is not a facial expression; in fact, the dolphin (unlike human beings with their greater
than 40 facial muscles) has no facial muscles with which to form an expression. Thus, the dolphin spends no time focusing
on facial expression (whereas human beings focus on facial expression as a major way in dealing with each other). The dolphin’s
upper jaw and signature under-bite with projecting lower jaw bone (a single lower jaw bone is common to all mammals) houses
its sharp teeth. Unlike most other mammals, the dolphin's teeth are undifferentiated. In other words, there are no specialized
teeth for biting, cutting, and grinding. The dolphin's teeth are all the same shape and function in the same manner.
They begin to appear at about 3 months of age and are fully erupted at 5 months. These permanent,
non-replaceable, conical teeth are interlocking. 18-26 are distributed on each of the upper and lower jaw sides to total
80-100 in number. The dolphin's teeth are arranged in a configuration that functions as an antenna to receive incoming echolocation
clicks and make it easier for the animal to pinpoint the exact location of an object.
An accurate determination of a dolphin's age can be made by counting
the growth rings lying with each tooth. Each growth ring represents one year of life. Unfortunately, the dolphin's teeth are
permanent and this determination would typically be possible only in a necropsy (animal autopsy) setting by sectioning the
tooth. Their teeth are not used for chewing. They act as defensive weapons and aid in gripping objects. The dolphin swallows
its food whole, head first to avoid the resistance of scales and operculum slits catching in its throat.
In the following video the trainer has the unenviable task of trying to feed three hungry dolphins at the same
time. Note how they swallow their food whole, without chewing. He must keep each animal in its correct "position" to make
sure each animal receives food from its own individually labeled canister. In this way he can assure the specific diet weighed
out for each animal is properly distributed.
These teeth are also used in another interesting manner – discipline. Dolphins, within their pods or social
groups, develop a discipline hierarchy. An animal establishes its dominance through “raking” other animals
as a control mechanism. Raking is the scratching of another’s skin with these sharp teeth. It is called raking
because the marks left on the skin appear as if made with a garden rake. The marks are superficial and appear to present no
risk to the animal being disciplined. When the skin is raked, dark scar tissue is formed, which later turns white. These
scars remain visible for some time, but will eventually be shed in the normal process of skin replacement. Raking is
a very common practice between dolphins and seems to provide messages such as, “Behave yourself”, “Don’t
do that”, “Stop bothering me”, “Get in line”, "I'm in charge here", etc. Attempts of subdominant
animals to rake dominant ones have been also observed, but are less common.
The male dolphin pictured below was previously kept with a number of other males in a facility as a "feeder dolphin"
where it was fed by the public. In such a situation, he and his pool-mates competed aggressively for available feeding opportunities.
This is apparent by the number of rake marks seen around the eyes and on top of the body, as well as the force with which
it appears they were applied. The degree to which this captive dolphin is raked is more typical of dolphins seen in the
wild.
Raking is more common with males, as they are more aggressive than females. Aggressiveness in males
is required in order to be more successful in obtaining desirable females with which to mate. In the following video
three males are seen in an aggressive raking episode, The dominant animal is chasing the other two males attempting to remain
"in charge" by raking. At one point one male is even temporarily driven out of the water by the aggression of the dominant
male raking him.
Site Content
Understanddolphins.com contains information condensed from a number of reputable technical sources,
peer reviewed journal articles, and respected dolphin research facilities, as well as from my personal experiences and
observations as a dolphin VIP Tour Guide and Educator.
I have made every attempt to support the information presented in this site with video and still
photographic images. On a regular basis I plan to produce more of these images and will continue to update the site with these
as well as with any new and scientifically verified information which becomes available.
