Kauai Sea Tours


Whale Review-Whale Biology Part One



Whales, how many are there and how did they evolve to their modern form? There are 78 species of whales, dolphins and porpoises and the scientific name is Cetacean (pronounced se-TAY-shun) which comes from an ancient Greek word "ketos" meaning whale. All whales are mammals and they breathe air, give birth to live young and nurse their young with milk. There is amazing diversity from the largest adult Blue whale which is 20,000 times heavier than the smallest newborn Vaquita porpoise. Modern cetaceans carry with them remnants of their terrestrial (land) ancestry. If one examines the internal structure of a whale's side flipper-it resembles a huge hand complete with finger bones. Most whales also possess internal remnants of a functionless pelvic bone and hind leg bones. Whales evolved from hoofed land mammals about 50 million years ago.


What exactly is an ocean mammal, a whale? A whale is a mammal similar to a land mammal except that is lives in the water, specifically the ocean, which is very salty. So ocean mammals have evolved differently than land animals. Ocean mammals cannot breathe oxygen out of the water like fish. Ocean mammals, like whales, have to come to the surface to breath. Respiration is an exhausting activity and energetically expensive for mammals that have the same kind of lungs as human beings do (they're called ventilation lungs) except that whale lungs are extremely efficient. With each breath the whale takes, there is over 90% exchange of the content (carbon dioxide for oxygen) of its lungs, a respiratory rate 5-6 times more efficient than human lungs. The lungs of a humpback whale make up only 1-3% of their total body weight vs. 7% in a human.


How are whales able to grow to such large sizes? In a medium of water, the whale is able to grow to huge sizes. In fact, the Blue whale is almost twice the size of the largest dinosaur that ever lived on Earth. It averages 100 feet in length and can weigh from 120-150 tons. You can think of a Blue whale as being as long as 3 railroad cars and weighing as much as 1600 people or 30 elephants. Whales, especially the Humpback whale, have very thick layers of fat or blubber (6-8 inches) which keeps them warm in polar waters and helps them float. The fatty tissue provides enough buoyancy to offset the negative buoyancy of the whale's muscle and very light skeleton. The bones of a whale will actually float because they are filled with fat (which is quite different than the bones of a seabird which are filled with air). Whales don't have to worry about supporting their great weight because they are in a medium of water and between their very light bones and built in "fat life preservers" they are very buoyant. But if a whale is beached they have a limited amount of time (depending upon the size) before the mammal will be crushed by its own weight.


Besides the more efficient lungs that a cetacean has over a human being, what other features do they possess that enable some cetaceans i.e. Sperm whale to hold their breath for as long as 3 hours? The sperm whale, the cetacean with one of the most impressive of all underwater capabilities has been documented as diving over 12,000 feet (more then 2 miles) for as long as 3 hours. It seems that cetaceans are able to take more oxygen down with them than a human diver can. One factor in this performance is the cetacean's considerably greater volume of blood: up to 2-3 times more blood per unit of body weight than in human beings. The cetacean's blood also has a somewhat greater oxygen-carrying hemoglobin of the red blood cells) is responsible for the muscle's characteristic dark red color. Myoglobin is present in the muscles of terrestrial mammals too, but in much smaller amounts than cetaceans. In some cetaceans species more oxygen is carried in the muscles than in the animal's red blood cells. Another key factor for cetaceans is its highly developed vascular systems - the fast circulation which rapidly reloads the red blood cells with oxygen. This fast circulation is demonstrated by the faster heart rate when a whale comes to the surface to breath after an extended dive. The whale has a powerful heart and a circulatory system that features large networks of capillaries (retia mirabilia or wonderful nets) and large sinuses in the venous system. The ability to recharge red blood cells with oxygen fast constitutes the fundamental respiratory difference between cetaceans and terrestrial mammals, whose breathing is usually regular and whose blood flow is relatively smooth. For example, humpback whale exhales its breath at 300 miles per hour then inhales around 2,000 liters of air per minute.


Cool Facts:


The sea within us - a 155 pound human carries 16.5 quarts or a little over 4 gallons of salt water in his/her body. Some 3 quarts make up the blood plasma - the watery part of the blood flowing through veins and arteries. The rest serves as interstitial fluid in the spaces between all the cells of the body.


If we drained all the world's oceans how much salt would there be? There is enough salt in the oceans to cover all the continents of the earth in a layer of salt the height of a 50 story skyscraper (or 500 feet).

No way to get rich fast - There are 9 million tons of gold dissolved in the world's oceans - some 180 tons more than all the gold mined on earth throughout history.


Puzzler: How does the ATOC (Acoustic Thermometry of Ocean Climate) project work in measuring global warming? Hint: Sound travels faster in water than air because water is denser than air (4-5 times as dense depending on temperature and pressure). Thus, sound travels faster in cold water than in warm water because cold water is denser than warmer water, the molecules are moving faster in warm water and are farther apart. If the ATOC project "booms" sound from Hanalei Bay to Monterey Bay, California and the oceans are warming, will the sound travel faster or slower over time? Note if you think this is simple, the answer to this puzzler has been repeatedly misstated in the popular press because they don't seem to know these simple principles. (Answer will be given on next newsletter).


Coming next newsletter-Part Two of Whale Biology will review humpback whale facts.



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