Part 2

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.

Evolution of Whales

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.

Breathing Adaptations

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.

Swimming Adaptations

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.

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.

Whale Types

Porpoises and Dolphins

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.)

BLUE WHALE (SULPHUR-BOTTOM WHALE) FIN-BACK WHALE (COMMON RORQUAL) GREENLAND RIGHT WHALE (BOWHEAD WHALE) BLACK RIGHT WHALE SEI WHALE HUMP-BACKED WHALE (unlabelled in picture) CALIFORNIA GRAY WHALE LITTLE PIKED WHALE (LESSER RORQUAL) PYGMY RIGHT WHALE The Sperm Whale is given here for size comparison only.

SPERM WHALE BOTTLE-NOSE WHALE KILLER WHALE PILOT WHALE (BLACKFISH) CUVIER'S BEAKED WHALE FALSE KILLER WHALE TRUE'S BEAKED WHALE NARWAL WHITE WHALE (BELUGA) PYGMY SPERM WHALE BOTTLE-NOSE DOLPHIN COMMON DOLPHIN COMMON PORPOISE

Squid Eaters

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.