Title: Whale Primer, with Special Attention to the California Gray Whale
Author: Theodore J. Walker
Release date: January 15, 2019 [eBook #58695]
Language: English
Credits: Produced by Stephen Hutcheson and the Online Distributed
Proofreading Team at http://www.pgdp.net
With Special Attention to
THE CALIFORNIA GRAY WHALE
by
Theodore J. Walker
Published by
the
Cabrillo Historical
Association
1962
Produced in cooperation
with the National
Park Service
Copyright© Cabrillo Historical Association
1962
Second Printing 1965
Third Printing 1967
Fourth Printing 1969
Migration routes of the California gray whale. The Korean herd may now be extinct.
The WHALE PRIMER provides a brief introduction to one of nature’s most interesting creations, the whale. The principal star of the handbook is the California gray whale which in recent years has become a major tourist attraction in southern California. Notwithstanding the extreme interest, no concise interpretation of the migration has been prepared. Although there is a tremendous number of technical and popular writings about whales, there is still great mystery about them. Whales carry on practically their entire lives below the surface of the sea out of reach of man, so that most of our knowledge has been pieced together from the study of the bodies of slaughtered whales. The literature abounds in partial truths, misinterpretations and technicalities which confuse even the specialists. Many of the sources of information require translation.
Furthermore, many of these papers were published in journals of limited distribution. Others are long since out of print, and much of the primary historic records can be found by examination of records which exist only in one particular library. In the preparation of this manuscript, hundreds of books and over 4,000 papers were catalogued, of which the most important were available, and examined. The author was particularly fortunate to have Japanese and Russian friends who gave gladly of their time to insure coverage of these important papers.
The author deliberately made an extreme condensation of the facts in order to prevent the reader from being overwhelmed by details that merely obscure the broad picture. It is hoped that the reader will gain an awareness of the extreme mastery by whales of the marine environment. Other basic concepts of biology, which are clearly illustrated by the natural history of whales, are developed.
The intense interest and pleasure which the sight of the migrating whale creates clearly overshadows the brief monetary benefit that the whaling industry might gain from slaughtering it. We hope that you will be stimulated to join forces with those of us who feel that man should preserve those forms of life which add so much interest, beauty, and knowledge to man’s awareness.
The migration of the California gray whale is one of the most remarkable natural history events in the world today. The majority of these whales journey southward just off the shore of southern California and Lower California during January and February. Although a few early migrants may pass San Diego early in December, they are not abundant until Christmas. An occasional straggler can be sighted in March.
Only 20 years ago this species was so rare, that little hope was held that it could ever recover. Today the species appears out of danger, thanks to international cooperation among the whaling nations which stopped the slaughter of this truly unique whale. Now it is not at all unusual to see between 50 and 75 whales a day during the peak of the migration.
One of the finest locations for viewing this migration is the Cabrillo National Monument which commands an almost aerial view of the coastline. Here individual whales can be watched for at least 1 hour, as they hove into view from the north and at last recede to the southeast along the Silver Strand. The first and only public observatory for whales was established at the monument in 1951. The naturalist on duty not only keeps a plot of the whales passing by, but also helps visitors find their first whale. The observatory is one of the most popular wintertime attractions in southern California. With so many pairs of eyes on hand, it is not surprising that the count of whales is remarkably complete. There is no other marine animal which can be seen with such certainty in its natural element.
Migrating gray whales off Point Loma, Calif. Photograph by Burky Reeves.
Migrating gray whale passing San Diego, Calif. Courtesy Scripps Institute of Oceanography.
Migrating animals have always fascinated man who considered them harbingers of the seasons. Man continues to puzzle over the mysteries of how these animals are able to navigate so precisely and how they are able to maintain such timetables. Whereas other migrating animals pass broadly through an area, the California gray whales, at least on the final part of the route, are passing along just outside the surf zone, virtually single file! It is hard to realize that 3 months earlier these whales started off from their summer quarters in the Arctic Ocean and the Bering Sea, as well as along the shore of Siberia and Kamchatka en route to their winter quarters in the lagoons and harbors along the outer coast of Lower California. Between these two areas lie 6,000 miles of seemingly trackless ocean. With the advent of spring the whales must be on their way back again to their summer grounds.
Although all the large whales make such extensive travels, except the bowhead, only the gray whale spends so much time in sight of land. The other species are truly oceanic at all times, and never seem abundant because of the vastness of the oceans. Like the gray whale they congregate in polar seas during the summer months, moving into temperate and subtropical waters for the winter months. To this day, much of the migration route is unknown. Perhaps some day a scientist will attempt to trail a group of whales along the entire route. The tendency of the gray whale to hug the coast is manifest only within 600 miles of the destination. This may be a precautionary routing which prevents the whales from making their landfall south of the lagoons. Such an error in navigation would not only prolong the migration, but leave the whales on the horns of a dilemma—to swim on south or turn back?
One cannot help but be impressed with the remarkable utilization of time by the whales whose lives seem to be divided into two principal seasons, a summer feeding period and a winter period of reproduction. Each of these major activities is preceded by a tremendously long migration. Nearly half of every year must be devoted to this activity. Considering the extreme length of the migration, whales cannot wander aimlessly or carelessly. Whales which summer in the Antarctic continue to do so as do the whales in the Arctic waters, and only rarely does one pass through the wide belt of equatorial water to venture into the other hemisphere.
Once on the summer grounds the whales occupy themselves with feeding almost continuously during the long polar day. Even though the food is patchy, the whales seem to find it quickly, spending a minimum of time in search. By the onset of autumn, they are fat, and all the babies are weaned.
It is uncanny that the various species all manifest the instinctive reaction to vacate this region at the proper time, thus avoiding almost certain death by the freezing of the sea’s surface. Again the seeming miracle of aptness is evident, for the whales swim unerringly out of the dangerous areas toward warmer and calmer seas. Because of the extremely wide band of winter storms, whales must move at least below 30° latitude to be clear of the areas of stormy seas. Migration stops as soon as they are sufficiently clear of these. Whales then undertake the other essential link in the chain of life, reproduction. By spring the babies are strong enough and fat enough to accompany their mothers.
Whales do not feed extensively while migrating. For the most part there is not time enough, nor is the food plentiful enough to make it worth the effort. However, in the polar seas the whale’s food is plentiful enough to discolor the water. On close examination, the discoloration proves to be caused by thousands of tiny shrimps which are very slender and less than one-half inch in length. These creatures congregate in swarms near the surface to feed on microscopic plants known as diatoms. The whales need only swim back and forth through these cloudlike aggregations to fill their mouths quickly with water and shrimp. With each mouthful, the water is expelled between the jaws through a mat of fibers which hangs down from the upper jaw. The shrimps, which are retained on the mat, fall down onto the tongue and are swallowed. The work of pushing out several tons of water with each feeding is done by the tremendous tongue.
The fiber mats are the frayed inner side of enormous hornlike plates which grow down from the palate. The main body of each plate is placed edgewise to the outgoing water so that many plates are required to complete the mat which runs from the tip of the jaw to the corner of the mouth. These plates vary in size and stiffness from species to species. Some of the plates from the mouth of the bowhead whale are 12-14 feet in length, whereas in the finback whale the plates are 2-4 feet. There can be over 200 plates per side in the filtering structure. The frayed inner edge is constantly breaking off and the plates keep growing and fraying to provide the necessary thickness for the mat. Technically, these plates are called baleen. They were called whalebone by the whalers, and that is the name which is still used in commerce. The plates have no relationship to bones, nor could they be mistaken for them. The whalebone was assiduously collected and sold to be made into a variety of objects such as umbrella stays, corset stays, buggy whips and other articles which today are made of steel or plastic. There was a great demand for the product and a bowhead whale produced over a ton and one-half of whalebone valued back in the 17th century at over 400 English pounds, equivalent to about $10,000 today.
It has been observed that the coarseness and thickness of the baleen is suited to the size of the food which is filtered. For example, the rorqual or Sei whale, which feeds on tiny shrimp species, has a filtering surface which resembles fine wool. The blue whale, which feeds on the largest of shrimps and on fish, has the coarsest filter. Generally, fish occur only in the diets of the blue, finback and other rorqual which swim fast enough to engulf them. Here, the fish are weak-swimming, schooling fishes. The gray whale, unlike the other filter feeders, feeds on bottom-frequenting crustaceans known technically as amphipods. These organisms, occurring principally in shallow water, keep the gray whales close to the shores of Siberia and Kamchatka.
In order for a whale to be able to exist on a 3 to 4 month feeding period, it must have not only ample food, but time in which to collect it. Although the whales may not all be far enough north to have a 24-hour day, there is enough twilight to let them feed the clock around. In order to take advantage of the prodigious amounts of food available, whales have a huge four-chambered stomach. It is not at all uncommon to find 5 to 10 wheelbarrow loads of shrimp in the stomach. No one yet knows how fast the food passes through the alimentary tract.
The shrimps on which the whales thrive are not uniformly concentrated, but occur at special places where oceanographic processes have enriched the surface waters with cold, nutrient-rich, subsurface water. The principal oceanographic action which enriches the water at the surface is called upwelling. It can be induced by a number of physical conditions. One of the best places to look for upwelling is along the edge of the polar icecaps and along the junction of strong currents. Upwelling is one of the ways nature refertilizes the surface waters which are otherwise deficient in nutrients. Whenever the ocean surface is fertilized, the microscopic plants begin to grow and multiply, discoloring the water to a brownish or reddish color. If the subsurface waters continue to be pumped to the surface, the growth continues and a rich ocean pasture results. The animals which begin to crop this are the shrimps, and when they have thrived and reproduced, there are enough for the whales. The other all-important factor in the fertility of the polar seas is the length of day, which provides ample time for the sun’s energy to be entrapped by plants. By autumn, the days have shortened and night begins to predominate. At this time the microscopic plants stop growing and form resting stages which protect them through the long winter.
The whale has made such efficient use of its summer feeding period that it is fat enough to live the other 8 months without danger of starvation. Whales might be thought of as huge natural tankers carrying enough oil to provide for long periods of active fasting. Unlike those mammals which avoid starvation by winter hibernation, the whale is able to migrate away from inhospitable seas into warmer waters where they can then reproduce and care for the new young. The strain on the mother at this time must be considerable for her baby grows at a prodigious rate. It has been calculated that a blue whale baby grows about 10 pounds per hour, gaining a ton every 9 days.
Although there are at least nine species of filtering whales, each seems to be dependent on a different kind of shrimp which are seldom found together. This prevents the various species of whales from being in constant competition with each other. However, no one altogether understands why there is no competition. Of course, structurally a species may be more suited to feeding on one kind of food. The porosity of the filter plate, which varies, may account for this. The actual shape and size of the head varies from species to species and this may be related to improving the efficiency of feeding. Right whales have heads which are very large, permitting a large intake of water and the accommodation of a tremendous set of filters. These whales have heads which are enlarged both in width and length. In fact, the head may account for nearly one-third of the total body. The rorqual group are more streamlined and have proportionately smaller heads. To make up for this limitation, the floor of the mouth is pleated on the outside which permits the floor to balloon out like a huge scoop each time the mouth is filled.
The right whales, incidentally, were so named by the early whalers to apply to those species which were suitable for whaling. The majority of whales were not molested because they sank as they died, or they were fast-moving, wary species which could not be approached with the whaler’s lance.
Infra-red photograph of gray whale reveals heat of the spout and also indicates the double source of the spout. Photograph by T. J. Walker.
To appreciate fully the biology of whales, one must know that their ancestors were terrestrial mammals. It is indeed impossible to account for all the steps which were necessary for this difficult reentry of the oceans. However, the fossil records for whales are numerous and permit at least a partial reconstruction of the evolutionary steps. Whales have obtained not only complete mastery of this difficult habitat, but also they have spread out to crop a variety of marine foods. Biologists have generally dramatized the earlier conquest of land by marine organisms, leaving the more recent and perhaps more difficult reentry of the marine world by whales to go unnoticed.
Not only have whales become completely aquatic, but they have been able to eliminate nearly all the design features which were necessary for life on land. Only the retention of air breathing remains, and this does not seem to be much of a hardship. There has been a great improvement in the conservation of oxygen so that really long dives are possible. The subtlety of this accomplishment is only partially understood by scientists. Apparently, diving mammals are able to shut down those bodily activities which contribute little to the diving mission. These activities can go on later when oxygen is available. It is also normal to incur an oxygen debt by borrowing from stockpiles present in the tissue fluids and muscles. After a long dive a whale will idle at the surface in order to completely free the body of the excess carbon dioxide, and to pay back the oxygen debt. The greater the debt the longer the surfacing, and the greater the number of breaths which must be taken.
When a whale surfaces to breathe, the act of exhaling is called “blowing.” Whenever a whale has been submerged for a normal dive, the air in the lungs becomes saturated with moisture from the blood. The exhalation of this spent air is accomplished very quickly by forcing the air out under pressure by the diaphragm, and the sudden expansion of the expelled air produces sufficient cooling to condense the moisture. This cloud or fog is the most conspicuous feature of a surfaced whale, particularly when the spout is 10 to 15 feet in height. Within a minute’s time the fog is usually scattered and heated enough to disappear. The duration of the spout depends principally on the temperature of the surrounding air, the amount of moisture condensed from the breath and the local surface wind. At the higher latitudes air temperatures are low enough that the spout may persist for several minutes. It is possible to recognize some of the whale species by the form and size of the spout.
Inhalation is accomplished very quickly. The breathing act is generally both visible and audible. The release of air produces a very loud “whoosh” which can be heard for quite a distance on a quiet day. The nostrils are called blowholes. In order to facilitate breathing, they have been moved from the tip of the snout to the top of the head (with the exception of the sperm whale), to prevent waves from flooding the lungs. During diving, the pressure of the water operates on the nostril in such a way as to close the nostril from the outside so that regardless of depth there can be no leak. The natural buoyancy of the animal exposes enough of the head to keep the nostrils clear of the waves.
The nostrils communicate directly to the lungs rather than share a portion of the throat as is customary in other air-breathing vertebrates. This means that the whale’s mouth and throat can be full of water without danger of flooding the lungs, and that it is unnecessary to empty such a spacious cavern prior to breathing. Furthermore, it is unlikely that a whale could keep his mouth closed enough to prevent flooding through the baleen because there is no upper lip over this device.
Although a whale can be sighted by the telltale spout, a frightened whale may elude detection by exhaling just before surfacing, so that nothing more than a foamy patch is produced. Under these situations the whale does not expose the usual amount of buoyant head, but only the nostrils. A disturbed whale can dive, and then surface a mile or two away, or it may not move at all, preferring to hide on the bottom or among rocky reefs or in the kelp. The California gray whale was judged by whalers to be the most wary and elusive of them all.
The most essential features needed for the successful invasion of the marine habitat were those necessary for efficient propulsion. Fish, eons before, had solved the hydrodynamic equations necessary for movement through such a resistive medium. This solution required a streamlined form with a tail for propulsion, placed at the very end of the body. Extra fins were employed for maneuvering and for balancing. Whales, too, have reached the same solution, and man, when he finally develops sufficient highspeed submarines, will employ the same solution, namely streamlining. As a consequence, all whales look alike, differing principally in the degree of streamlining, color or size. In a whale’s streamlined body there can be no sharp discontinuities to accommodate the head, the neck, the trunk, and lastly the tail. Instead these features must grade imperceptibly one into the other. The only allowable discontinuity is the end of the tail which is expanded into fanshaped lobes to function like a propeller.
Gray whale rolled over on side during courtship. Note outline under water of tail and tailflukes. Courtesy Scripps Institute of Oceanography.
These features, called tail flukes, are driven up and down in contrast to the tail of a fish which is driven sidewise. Whales have long banks of muscle along either side of the backbone which attach to the tail flukes by means of tendons. This makes it unnecessary to disturb the streamlined form by bending the hind part of the trunk as is necessary when fish drive with their tails. It also makes it possible to devote a great deal more muscle to the task. The power developed by these muscles is prodigious, capable of driving a 100-ton body through the water at speeds up to 20 knots. Wounded whales can smash a 20-foot whaleboat to bits with a single slap of the tail.
The hind limbs which were useful on land have been eliminated and all that persists are vestigial bones or cartilages which are buried deep below the surface of the body. The forelimbs have undergone reduction and modification into flippers which assist in the turning and diving. The flippers are useful in other ways, providing a platform on which the baby may stay when danger threatens. They are also useful during courtship and mating, but not for combat. The toothless whales do not have too much to fight with. They may strike an adversary with the powerful tail flukes, and during courtship the males jostle and bump each other.
Whales are almost completely hairless, save for a few bristles on their heads. Certainly the elimination of hair has improved streamlining, and has reduced the frictional drag. Furthermore, continuously wet hair could not have been of much value in keeping the whale warm. It is also possible that a hairy whale would have been very much bothered by skin parasites which would have flourished in the quiet water between the hairs. However, if this prompted the loss of hair, it was in vain for now the streamlined bodies of humpbacks and right whales are marred by large encrusting barnacles. It is surprising that the barnacles do not completely cover the whales. Perhaps they are scraped off on the bottom, or they cannot flourish during the long migration or in plankton-impoverished waters of the winter quarters. At any rate the parasites are kept partially under control so that much of the streamlined surface is unblemished.
If the physical properties of water forced upon whales a common shape, they did at least, by the buoyant effect, free the animals of the need for structural and muscular developments to support themselves against the pull of gravity. Free of this structural problem, whales were able to evolve into the largest mammals which the world has ever known. As they became larger, they had to shift in their feeding to slower and less maneuverable prey. It would appear that the porpoises, which feed on the rapid-swimming, elusive fishes, are small in order to catch their prey. The whales, which have specialized to feed on the jet propelled squids, were able to evolve into much larger whales because they could capture the squid either by stealthy approach or by sucking the squid into the mouth, thus counteracting its jet.
Tailflukes extended for deep dive. Courtesy Scripps Institute of Oceanography.
Whales are known technically as cetaceans (pronounced seh-TAY-shuns); so also are the various porpoises and dolphins which are mostly eaters of fish. These are certainly the most numerous of all the cetaceans, making up in numbers for their small size (6 to 8 feet). A few species range between 20 and 30 feet. Porpoises and dolphins congregate around schools of fish. Therefore fishermen are constantly on the lookout for a sight of them. Since not infrequently the porpoises break the surface of the water, leaping completely clear as if for a look around, they are not difficult to locate. Porpoises and dolphins can be seen most frequently in coastal waters where fish are most abundant. The porpoise and dolphin families contain a great many species and it is beyond the scope of this treatise to differentiate or name them all. However, these families include such unique forms as the killer whale, narwhal, white whale (or beluga as it is known to the Eskimos), and the pilot or black whale. Generally one associates cetaceans with the ocean, so it may come as a surprise to find that four dolphin species live in such major rivers as the Amazon, La Plata, Ganges, and the Yangtze.
In dolphins, the mouth protrudes beyond the head as a beak or snout, and in porpoises, the front of the head is blunt or gently rounded. It is impossible to avoid confusion if one uses common names to separate the various whales. Even though the word whale properly covers all the kinds, to some it connotes only the larger species. Such a distinction is wholly arbitrary, and cannot properly differentiate the natural groupings of whales to which zoologists have assigned technical names. It would be impossible to summarize the variety of common names which many of the species have acquired through the centuries. The only solution to this is to refer to the whales by the technical names which connote relationship. (For readers who desire this differentiation, a brief listing of the groups and representatives of each are provided in an appendix.)
BALEEN WHALES
TOOTHED WHALES
The bottlenose whales are nearly toothless, feeding on squid like their close relatives, the sperm whales. Porpoises and dolphins possess many sharp conical teeth on both the upper and lower jaws, although the narwhal which is related to them, breaks the rule by being toothless save for the tusklike canine of the male. In this instance either the right or left tooth elongates to produce an 8-foot spear. The other tooth does not break the gum, and this is the condition found in the female where both are rudimentary and not evident. The bottlenose whales have but a single pair of teeth in the lower jaw, and their relatives, the sperm whales, have 18-28 conical teeth per side on the lower jaw, and these when fully grown may be 8 inches in length. Pockets are provided in the toothless gum of the upper jaw to accommodate the teeth when the mouth is closed.
The decline in the number of teeth in the sperm and bottlenose whales is thought to be the elimination of structures which are no longer useful. Whereas a porpoise’s long mouth, bristling with sharp teeth, insures the hooking and retention of a slippery active fish, a small mouth with a few teeth is adequate to crush and slurp down the squid and the weak-swimming fishes of the abyssal depths.
The sperm whale is the largest of the squid feeders, reaching 60 feet. There is a diminutive counterpart, the pygmy sperm whale, which reaches 13 feet. It is exceedingly rare, whereas the sperm whale is abundant in temperate and tropical seas. The beaked whales complete the groups specialized for feeding on squid. Besides the modification of the mouth, all these whales are noted for their ability to dive to great depths where their food abounds. Not only can they dive to great depths, but they can stay submerged for long periods—up to an hour? Sperm whales have been found entangled in the submarine cables which were known to be on the bottom at a depth of 3,000 feet. It is clear that such feeding habits have opened up vast areas of the oceans to these species.
The whalebone whales seem to have undertaken two different lines of specialization in feeding: The right whales developed an enormous head with a very large filter plate, whereas the rorquals are much more streamlined with a small filter plate. The ability of the latter to gather food is insured by the pleated throat. The right whales lack a dorsal fin and are decidedly less streamlined. The rorquals have a dorsal fin. There are two species which do not exactly fit in either group. The humpback whale appears to be like the rorquals in that it has a pleated throat and a suggestion of a fin. It is however, a very bulky slow swimming species. The California gray whale, apparently, is intermediate between the two groups and may be thought to be a survivor of the ancestral stock from which both groups differentiated. It has neither a pleated throat nor a fin. The gray whale, like the right whale, has been slow to recover from whaling. It is likely that the populations were never very large. Only the rorquals seem to have the numbers needed for large whaling operations.
As whales extended their operations into the icy waters of polar regions or into the cold waters of the ocean depths, they had to develop means of keeping warm. Anyone who has attempted to swim in cold water knows how quickly one loses his body heat and becomes chilled. Whales minimize the heat loss by accumulating a thick layer of fat just below the surface of the skin. The fatty layer, called blubber, not only keeps the whale warm, but it also provides for food storage. It has already been stressed how important it is for whales to survive long periods without eating, so it is likely that the two specializations arose together.
There are, however, extensive areas of the whale which cannot be blanketed with fat and these are the flippers and the large tail flukes. It has been observed that the blood going into these structures gives up its heat not to the outside but to the veins which parallel and surround the arteries. By this anatomical feature most of the heat which would otherwise be lost to the water, is recaptured by the veins which deliver the heat back into the body. Of course, this means that the tissues of the tail flukes and flippers function at temperatures much lower than those found within the body. Here we find that nature was using the principal of the heat exchanger long before man discovered it or put it to work in air conditioning.
Whales are so well insulated that they stay quite warm 24-36 hours after death. Whalers must process the whales quickly, for otherwise, at the elevated body temperature, decomposition proceeds most rapidly and ruins much of the meat. It is possible that the baleen-bearing whales do not cross the warm equatorial waters because they overheat. No one has yet determined whether the newborn young have a sufficient layer of fat to protect them from the cold water, and it has been suggested that whales calve in temperate waters to prevent the babies from being chilled. However, there are species like the narwhal and the white whale which calve in Arctic waters.
Another aspect to the extensive deposits of fat is that these tissues are lighter than water and help counteract the heaviness of the whale’s body so that with the assistance of the lungs neutral buoyancy is achieved. The fat is accumulated in between the muscle strands, and in fact, in every available nook and cranny.
Much of this fat is drawn upon for food. Whenever a whale is existing on its fatty tissue, acetone is one of the waste products which must be eliminated in the breath. This pungent material makes the breath very strong and noticeable at these times. Certainly among whales, there is no stigma attached to being fat or having halitosis.
Ordinarily fatty tissues only accumulate when there is a surplus of food over the needs of the animal. You might suspect that whales would need to stockpile fat first, in order to remain warm and buoyant, and that growth would be curtailed and accomplished last. However, studies on the growth of whales show that the efficiency of food gathering is so high and food so plentiful, that growth not only continues but at a tremendous pace.
Whales mature sexually between their third and seventh years. Toothed cetaceans attain sexual maturity later than filter-feeding whales. A blue whale is sexually mature at 5 years, whereas porpoises require at least 7 years. Most filtering whales are sexually mature in 2 or 3 years. Whales are not fully grown at sexual maturity, but they continue to grow for years. In most mammals growth stops with sexual maturity. Female whales generally can be expected to produce a baby every other year, for the gestation period is approximately one year. Babies are nursed for about 9 months. At birth the baby is completely formed and active, but lacking baleen, must nurse. A blue whale baby at birth weighs approximately 8 tons, about 1/12th of the weight of the mother. The mother provides the baby with 50 gallons of milk a day. Since the nursing is done under water, and the baby must surface frequently to breathe, the act of nursing is very brief. Muscles in the breasts of the mother force the milk into the baby’s mouth in large amounts. The baby will double its length in 7 months, which averages to a daily weight gain of 220 pounds. During all this time the mother must fatten for the winter ahead, and perhaps continue to grow herself.
It is not known for certain how long a whale may live after completing its growth. At the present time, commercially important species seldom attain physical maturity before being captured. Many whales which are captured are measured for scientific study. Such measurements also keep the whalers from taking undersized juveniles. Whales apparently do not live to be very old. Fifty years appears to be the best current estimate of a life span.