THE BOTTLENOSE PORPOISE IN CAPTIVITY
For two hundred years a porpoise fishery has been conducted in a
somewhat desultory manner at Cape Hatteras, North Carolina. The animal
which forms the basis of this industry is the bottlenose porpoise
(_Tursiops truncatus_), one of the commonest species of the Atlantic
coast, which is especially abundant at Hatteras during the winter.
The present fishery is owned by Mr. Joseph K. Nye of New Bedford,
Massachusetts, a gentleman who fortunately appreciates the opportunities
offered at Cape Hatteras for studying this porpoise and its life
history. Through his courtesy several live specimens were presented to
the New York Zoölogical Society and were transported to the New York
Aquarium under the direction of Dr. Charles H. Townsend, its Director.
Dr. Townsend deserves the greatest credit for his perseverance, after
several failures, in finally bringing to this city nine porpoises, four
of which lived seven months and one twenty-nine months in a circular
pool thirty-seven feet in diameter and seven feet deep, in the Aquarium.
This is a record which has never been equaled and, indeed, I am not
aware that any other aquarium of the world has a pool large enough to
contain a school of such lively ocean rangers.
[Illustration:
_Photo by Dr. C. H. Townsend._
“They are taken with a net of extra heavy twine, about 1,000 feet
long, which is placed about 200 yards outside the line of surf and
parallel with it.”
]
During the months these animals lived under Dr. Townsend’s eyes, he was
given an opportunity such as no other naturalist has ever had to study
and observe their habits and daily life. The results of his observations
have been published by the New York Zoölogical Society[17] and with Dr.
Townsend’s permission I am quoting in this chapter portions of his
interesting paper and republishing several of his photographs.
Footnote 17:
“The Porpoise in Captivity.” By Charles Haskins Townsend. _Zoölogica_,
Vol. I, No. 16.
Cape Hatteras is the only point in North America where a porpoise
fishery has ever been regularly conducted, and where such animals can
be taken near the shore and beached with drag seines. The Bottle-nosed
porpoise winters off our South Atlantic coast and is quite common in
the vicinity of Cape Hatteras during the fall, winter and spring
months. Schools of porpoises may be seen passing every day just
outside the surf.
They are taken with a net of extra heavy twine, about one thousand
feet long, which is placed about two hundred yards outside the line of
surf and parallel with it. At each end there is a boat in waiting,
ready to carry the haul lines directly ashore as soon as a band of
porpoises has passed between the net and the surf. After the lines
have been carried ashore the porpoises are considered fairly secure,
for they do not often attempt to cross the haul lines, and even when
they do, can usually be frightened back by having someone shake each
line continuously while it is being hauled in.
[Illustration:
_Photo by E. R. Sanborn._
“Thirty-three porpoises were beached in the haul of the seine which
provided our specimens.... Porpoises are valuable for their jaw oil,
hides and body blubber, the value of each being in the order given.”
]
It requires considerable time to bring the ends of the big seine to
the beach, but even then some of the porpoises may get away by leaping
over the net or attempting to dive under it. The former can be
prevented to some extent by sending a boat to the outer curve of the
net, which serves to keep the animals from charging against it. Some
of those that attempt to dive underneath become enmeshed and, being
air breathers, are soon drowned. Thirty-three porpoises were beached
in the haul of the seine which provided our specimens. The greatest
number taken in a single year appears to have been fifteen hundred.
Porpoises are valuable for their jaw oil, hides and body blubber, the
value of each being in the order given. The oil derived from the jaws
represents the greater part of the value, being worth ordinarily
twenty dollars a gallon, refined. It is extracted from the broad
posterior branches of the lower jaw, and is universally used for the
lubrication of watches, clocks and similarly delicate mechanisms. An
attempt was made at the Hatteras fishery to utilize the carcasses of
these animals for fertilizer, but, as the location is isolated, the
question of fuel for the furnace proved too serious and the project
was abandoned.
The Bottle-nosed Porpoise (_Tursiops truncatus_) is the only species
of porpoise that has ever been taken at the Hatteras fishery. Our
eight-foot specimens represent the average size. A number of animals
were measured in November, however, which exceeded nine feet in
length. The greatest length for this species at Hatteras is twelve
feet, but this is altogether unusual. Measurements and weights taken
in November show that a porpoise five and a half feet long weighs 100
pounds; six feet, 160 pounds; seven feet, 200 pounds; and eight feet,
300 pounds.
The movement of porpoises along the great beach which extends in a
general southwesterly direction from Cape Hatteras is usually close to
the surf. The bands appear to move in both directions. Residents of
Hatteras are of the opinion that the majority of those in the vicinity
of Hatteras Inlet move to the eastward, turning south from the Cape,
whence they gradually swing back to the mainland. They have not,
however, been followed away from the beach, and their winter movements
are not known with certainty.
Immediately after their capture at Hatteras, where they were brought
to land with a large drag-seine, the porpoises were placed for
twenty-four hours in a deep salt water pond just back of the ocean
beach. Here they had an opportunity to recover somewhat from the
fright of capture, and to rest in cool water. No chances whatever were
taken in the matter of temperature. On the beach their natural warmth
of body would no doubt have been greatly increased by the hot
sunshine.
The following day they were seined out of the pond and placed in the
shipping tanks, which were then hoisted on board a schooner and at
once filled with water. During the voyage through the fresh waters of
Pamlico Sound and the Great Dismal Swamp Canal, the water in the tanks
was changed whenever it became warm. After reaching the New York
steamer at Norfolk the cooling of the porpoise tanks en route was
greatly simplified by the use of the steamer’s salt water hose.
The shipping of porpoises alive is therefore a simple matter. The
adult animals readily stand transportation, while the young do not. If
carried in long, narrow boxes large enough to accommodate them without
rubbing, and if kept supplied with sufficient cold water to support
and cover them, they can be handled easily enough. There is probably
no reason why a porpoise, under such conditions, should not be carried
in a tank many times the two days’ journey from Hatteras to New York,
although on a journey by rail the changing of the water would be
difficult and expensive. While its temperature could be controlled by
the use of ice, the water carried without changing would be seriously
fouled, for two or three days. The question of food could be
disregarded for a few days without injury.
The captive porpoises are very lively and keep swimming day and night,
rising to blow usually with each circuit of the pool. Being kept in
shallow water, they probably breathe oftener than they would in deep
water. They often swim under water, belly up, like seals, but never
lie upon the bottom or bask at the surface as the latter do. Visitors
ask whether they ever rest—a question not easy to answer. If they do,
it is apparently without cessation of forward motion. Nevertheless
they are quieter at night when most of the lights are cut off, and do
not indulge in boisterous play.
For a time two of them habitually moved from left to right, while
three took the opposite course, but this practice soon became less
regular and is apparently breaking up. Sometimes the speed is slow,
but more often it is rather rapid. Occasionally they indulge in a bit
of racing that makes high waves, the water surging up to the coping of
the pool. A porpoise _speeding_ around the pool can make a
right-angled turn as quickly as a frightened fish, without lessening
speed.
When being fed all regularity of movement is abandoned, and they rush
in various directions to seize at the surface the fishes slowly thrown
into the pool. This continues for some time after feeding, until all
sunken scraps are gleaned from the bottom. All food is swallowed under
water. Frequently a porpoise will play with a dead fish, thrusting its
head clear of the water and throwing the fish from five to ten feet
away, when it is recovered and thrown again. Such play may last half
an hour, or until the fish is reduced to scraps too small to be
thrown. It is not uncommon for two or three of them to be engaged in
throwing fishes at the same time and the practice is becoming
habitual.
[Illustration:
_Photo by Dr. C. H. Townsend._
“Immediately after their capture at Hatteras ... the porpoises were
placed for 24 hours in a deep salt water pond, just back of the
ocean beach. Here they had an opportunity to recover somewhat from
the fright of capture, and to rest in cool water.... The following
day they were seined out of the pond and placed in the shipping
tanks, which were then hoisted on board a schooner and at once
filled with water.”
]
Several times a day they indulge in very active play, darting with
mock ferocity after each other, or leaping quite clear of the water
and striking with heavy splashes. They often swim on their backs, with
the jaws out of water, or on their sides repeatedly striking the
surface with the head. When leaping a favorite trick is to throw the
body around until the dorsal fin is forward, with a resulting splash
that sends the spray quite out on the floor. A high leap by one of
them is usually a signal that starts them all to leaping. Our fears
that they might leap quite out of the pool were unfounded; they are
clever enough to avoid the wall which surrounds them.
Another game is played by going around the pool with short dives, each
time striking the surface with the flat of the tail. When the pool is
entirely full of water their play is livelier than when the water
level is lowered. The increased depth gives them more confidence and
they often turn complete forward and backward somersaults.
The ordinary swimming motion of the tail is up and down, but, if
playfully charged by a companion, the porpoise seems to make a spurt
ahead by more or less side action of the tail. This is not easy to
determine, however, and may be more apparent than real, as the water
is too much disturbed by high speed dashes for accurate observation.
The animal undoubtedly relies upon its tail for propulsion, the
flippers or pectoral fins being brought into action in making turning
movements. Several of the porpoises have lately taken to swimming on
their backs, and the movement of the flippers and tail at such times
is easily seen contrasted with the white under parts. In swimming on
the back, however, there is considerable lateral action of the tail.
Frequently three or four of them will bunch together in the center of
the pool, rolling and rubbing against each other in a ball-like mass
suggestive of the tussling of puppies. This may at times mean that
they are merely scratching, as the single porpoise kept in the
Aquarium for two and a half months last summer frequently rubbed his
sides or back against the back of a large sturgeon kept in the same
pool. This injured porpoise indulged in no play and swam day and night
in the same circle from right to left, but always fed freely.
There is considerable mobility of the neck of the porpoise, an animal
lacking all outward appearance of a neck. The head can be turned down
at an angle of about 45 degrees to the body, and can be turned as far
sideways with equal readiness. These motions can be seen at feeding
time and when the animals are tossing fishes.
There is no evidence that the porpoise can see out of water. In
throwing a fish the head is often thrust well above the surface, but
the animal seems to be always intent on its plaything, entirely
disregarding the visitors leaning over the rail five or six feet away.
While a fish thrown into the water is promptly seized, the porpoise
pays no attention to a fish suspended by a thread two inches above the
surface. If the eyes of porpoises and other whales were fitted for
observation above the surface of the water, as are the eyes of seals,
they might long ago have learned to use them in the same way.[18]
Footnote 18:
I do not believe that because the porpoise would not seize a fish
suspended above the water, it is evidence that it could not see it.
Not being accustomed to take its food out of the water, the animal
probably did not know what the fish was. A wounded porpoise which I
kept alive for some time on a ship in the Pacific could see my hand
if it was brought within a few feet of its eyes. R. C. A.
Porpoises instantly recognize any change that may occur in connection
with the water level of the pool. The entirely noiseless opening of a
distant valve to lower the water is apparent to them and may stop
their play temporarily. A pool only thirty-seven feet in diameter does
not of course afford space for the high activity of which the porpoise
is capable. Nevertheless they often leap three feet or more clear of
the surface, sometimes striking the water forcibly enough to throw
spray thirty feet into the air. The visitor soon gets the impression
that they enjoy life even in captivity and their keepers, while always
vigilant as to their needs, have ceased to be concerned about their
safety, regarding them as almost domesticated animals.
[Illustration:
_Photo by E. R. Sanborn._
“The captive porpoises are very lively, and keep swimming day and
night, rising to blow usually with each circuit of the pool.”
]
The naturally sociable and gregarious habits of porpoises is evidently
not lessened by captivity. Sometimes they seize each other by the back
just behind the dorsal fin, but there are no tooth marks on any of
them and it is probably done in play. The indications are that they
are altogether amiable and inoffensive toward each other. The only
species of porpoise destructive to its kind is the well-known “Killer”
(_Orca gladiator_).
Our porpoises were observed mating in January, and again in March and
April. It is possible that they will breed in captivity if their lives
are not shortened by indoor life.[19]
Footnote 19:
Unfortunately all the female porpoises died at the time Dr.
Townsend’s paper was passing through the press. R. C. A.
Our porpoises were heavy feeders, the five consuming about ninety
pounds of fresh fish a day. This quantity of food has kept them in
good condition, apparently without loss of weight. For several days
after their arrival they would eat nothing, but at the end of a week
they began to take live fishes and, after having once started to feed,
it was not difficult to get them to take dead fish. A few days of
hunger brought them around, as it does in the case of the newly
captured seal or sea lion. Their principal food is herring and tomcod
purchased in the markets. The live crabs thrown to them at various
times were quickly seized and much tossed about, but were not eaten.
The keeping of porpoises in captivity has presented some difficulties
with the water supply, their excrement constantly discoloring the
water. The pool cannot be drained empty and cleaned, like those used
for seals, as stranded, and consequently frightened, porpoises beat
the ground with their tails so violently that they would be injured by
the daily emptying of the pool. The water is now being kept fairly
clear by carrying extra pipe lines to the pool and greatly increasing
the flow of water. The pool is supplied with brackish and rather
impure water pumped from New York Harbor, as it is not practicable to
supply it with pure sea water from the Aquarium’s large storage
reservoir, on account of the fact that porpoises would rapidly
discolor the stored sea water which is so important to the health of
the collection of marine fishes in the Aquarium.
The necessity of keeping them in the water of the Harbor, and
exhibiting them in a public exhibition room which has to be heated
during the winter makes it, of course, impossible to hold them under
entirely favorable conditions, yet they are undoubtedly doing well.
They could no doubt be kept for some time in fresh water, as is
sometimes done with seals and sea lions, but they would eventually
suffer from the lack of the salts contained in sea water. Porpoises,
perhaps of this species, frequently enter the fresh waters of Pamlico
Sound through the inlets southwest of Hatteras, and many species of
marine porpoises make long journeys into the fresh waters of rivers.