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.
Buoyancy
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.
Food Storage
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.
Sexual Maturity
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.