Meet Mr. Porpoise - Ceta-Base

All during rliis period the babj was receiving nourishment
from her parent. In the eleventh week, how-
ever, she again swallowed small mullet. During tin-
next three weeks the amount of fish consumed rose to
about ten pounds. The young one, however, fre-
quently attempted to nurse until the fourteenth week.
The second nursing porpoise to be studied in the
tanks was captured with her mother in July, 1939.
About a month after capture, the female appeared to
go dry. The young one, however, made frequent at-
tempts to obtain milk. For a ten-day period the little
one went apparently without nourishment and lust
much weight. Finally she started eating a few fisb a
day, but swallowed them with considerable effort.
Within a week she was eating up to ten pounds per
day and was competing successfully with the adult
porpoises. At this writing, she is healthy and filling
out rapidly.
The portion of the brain devoted to receiving
sensations of sound, we learn, is particularly well
developed in the porpoise. It is extremely interesting,
therefore, to watch the behavior of an animal whose
principal concept of his surroundings comes to him
through his auditory apparatus.
The auditory apparatus has been considerably
modified in the case of these sea-going mammals. No
outer ear is visible on the head of the porpoise. If we
look closely, however, in the region a few inches be-
hind and lower than the eye, we notice an almost in-
visible opening, the rudiment of the auditory canal.
In the case of the animal we are watching, it is scarcely
large enough to permit the entrance of a toothpick.
Water is an excellent conductor of sound. This
closure of the auditory canal, therefore, does not im-
pair the animal's sense of hearing, as sound vibrations
are carried directly to the bones of the skull. The por-
poise is interested principally in the sounds trans-
mitted through water, and has been able to close his
external auditory canal without endangering his
survival.
The importance that this sense of hearing plays in
feeding has been particularly interesting. The first
porpoise to be captured and placed in the tanks here
in March, 1938, showed no interest whatsoever in
dead fish that were presented to him. Accidentally,
however, it was discovered that if the fish hit the
water broadside, with a splash, it was immediately
taken by the porpoise. Thereafter, fish were slapped
on the surface several times and were then thrown to
the porpoise in such a manner that they landed broad-
side on the water. The significance of this discovery
is interesting because we know that here in the murky
inland waters of the Florida coast, mullet frequently
leap clear of the water to land on the surface with a
splash. The possibility is offered, therefore, that the
J let.
The importance that sound plays in the life
porpoise lias ] (-d to much discussion about the
of communication among whales, dolph
siderable reference- have been made in literature to
or calls uttered bj ing mammals.
particularly, when harpooned oi
OVeries made at Marine Studio- with
porpoises was that the animals are capa
A sharp whistling sound was clearly evident in the
corridors surrounding the circular tank after the first
bottle-nosed dolphin was introduced. The sound was
-0011 noted to be caused by the 1 air from the
blowhole. Subsequent observations led to the :
tion that the sharp whistling sound made by porpoises
was possiblj similar in origin.
During the first week or two of captivity all of the
specimens whistled constantlj and swam about the
tank nervously. Afterthey became acclimated, bow ever,
the whistling was heard less frequently and appar-
ent [j served as a method of communication. I
mals made this sound less frequently during the day-
light than at night.
Apparently the animals used variations in this whis-
tling sound to indicate different emotional states.
L sually when one or several of the animals w ere chas-
ing a live fish, they would be whistling excitedly.
When any disturbing object, such as a net. was pres-
ent, this was also true. This sound was transmitted
well through water and was heard distinctly in the
corridors surrounding our tanks above the scuffling
of feet and the chatter of voices.
A\ hen it was necessary to move two porpoises, the
original mother and daughter, from the rectangular
tank into the circular one, a very clear example of the
function of the sound was obtained. The parent was
netted first and moved through the shallow connecting
tank into the circular. The water level was then
lowered in order to catch the young one. The two
animals remained in their respective tanks close to the
wire mesh gates that separated them from each other,
the young one whistling madly and the parent fre-
quently answering her. As soon as the water level in
the two tanks dropped low enough, so that the con-
necting tank was dry, and the watery, and therefore
sound-conducting connection between the two tanks
was severed, the parent left her position at the gate
and swam about the whole tank, even showing some
interest in chasing live fish. The young one persisted
in whistling as loudly as ever although the parent
never whistled again after she was unable to hear the
young one. Within a short time the young one was
captured and placed in the tank with its parent, where
they joyfully renewed their life together.
MEET MISTER PORPOISE J 9