CHAPTER XXIV
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.
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.
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.
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.
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]
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.
“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]
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.
