What is a Whale, Anyhow?
Whales are mammals just like horses, dogs, cats and humans. All mammals have lungs, breathe air, have warm blood, bear live young, and the females have mammary glands which produce milk to feed their young. Most mammals also have legs and hair or fur.
About 65 million years ago the ancestors of today’s whales are believed to have lived on land… not in the sea. These early whale ancestors were animals that looked much like modern wild dogs in Africa. It is thought that the availability of food on land became scarce (remember, 65 million years ago marks the cretaceous-tertiary boundary, the time when most of the dinosaurs went extinct due to an asteroid striking the Earth near the Yucatan Peninsula in Mexico) and so the modern-whale-ancestors took to the ocean in search of food.
As these ancient whale ancestors spent more and more time in the ocean they gradually became adapted to life in the sea. The changes that they underwent during this evolution are very well documented. In fact, the fossil record of whales from 65 million years ago to now is one of the most complete fossil lines known to science!
Modern whales still have “vestigial” traces of their land ancestry. For example, the skeletal structures of some whales still have the bones of hind legs, a pelvis, fingers, and some species of whale still have hair (mostly on their heads).
Over the centuries, as whales gradually moved from the land back into the sea (remember life began in the sea), incredible adaptations in their anatomy occurred. The muscles of the upper rear legs have become a powerful tail stock, enabling some whales to swim at speeds of over 35 miles per hour. At the end of the tail evolved a pair of horizontal “flukes” (together forming the animal’s tail) that propels the whale forward by moving up and down through the water.
A whale’s nostrils (now called a “blowhole”) have migrated from the front to the top of the animal’s head which means very little of the whale has to be raised out of the water when the whale surfaces to breathe. This enables the whale to continue swimming as it breaths, rather than having to stop, turn vertical in the water, and surface for air.
The forelimbs of whales evolved into flippers of varying length, and retain a bone structure similar to a human arm and hand (with an ulna, radius, carpals, metacarpals, and phalanges or “finger bones”). The flippers themselves are used by the whales for balance when swimming, to make sudden changes in direction, to concentrate prey, and even to help cool the whales off. By pumping blood into the long, thin flippers the blood is cooled off by surrounding seawater before returning to the whale’s body!
So how do whales get the fresh water they need to survive? Well, they get fresh moisture in one of two ways: The first is through the food that they eat. The fish themselves are laden with fresh moisture. The second way is through the metabolization of their fat or “blubber” layer. When the whales metabolize fat water is released as a by-product and the whales can re-absorb that water. Whales also don’t have sweat glands (in fact their skin has no pores at all) and so they don’t lose water through their skin due to perspiration. Perspiration (aka “sweating”) is the number one way that we or any other terrestrial (land-dwelling) animal loses water so whales simply use what water they do get much more efficiently. In fact, they only need about half as much fresh water per pound of body weight as humans.
The length and number of the baleen plates inside a whale’s mouth can indicate the kind of food that the whale prefers to eat. Generally speaking, the larger the prey, the shorter and fewer the baleen plates. That makes sense when you think about it… whales that eat relatively large fish such as herring or mackerel (5 to 9 inches long) need only have short baleen plates (or a smaller filter). Minke and Fin whales are good examples of this as they have baleen plates that rarely exceed 3 feet in length and number between 600 and 900 on average.
However whales such Right whales that eat only tiny, flea-sized crustaceans called “copepods” must have a giant filter to capture enough food to survive. The baleen of Right whales can be 14 feet long and number well over 1,000 individual plates!
Different baleen whale species have developed many different feeding strategies depending upon the exact type of food that they eat and places like Stellwagen Bank and Jeffrey’s Ledge are good places to observe these various strategies in action.
Today all whales, dolphins, and porpoises belong to the same order of mammals called the “cetaceans“. There are approximately 78 species of cetaceans in the world today. The exact number varies depending on which authority you talk to and how whether-or-not they consider some species, such as Common dolphins or Minke whales, to be one or more-than-one species.
The order cetacea is divided into three major groups: the “odontocetes” or “toothed-Whales”, the “mysticetes” (from the Greek word for “mustache”) or “baleen whales,” and the now extinct “archaeocytes“.
The odontocetes comprise the dolphins, porpoises, Orca or “Killer whales” (which are technically dolphins), Sperm whales and all other extant whales with teeth.
The mysticetes comprise all whales that have “baleen” in their mouths instead of teeth. These include such well-known species as the Right whale, Finback whale, Minke whale, Sei whale, Bowhead, Gray whale, and many people’s favorite, the Humpback whale.
The Odontocetes or toothed whales are the largest families of cetaceans and they are usually quite small in size by whale standards. The vast majority of toothed whales are either dolphins or porpoises that rarely exceed 14 or so feet in length. The only “great” whale (or whale over 30 feet in length) that has teeth is the Sperm whale like the one made famous in Herman Melville’s novel “Moby-Dick”. (By the way, the story of Moby dick is based on the true story of the sinking of the whaling ship “Essex” that left the port of Nantucket in the late 1800’s in search of Sperm whales. The Essex and her crew sailed all the way down the east coast of North and South America, around Cape Horn, and up into the tropical Pacific, only to be rammed and sunk by an enraged male Sperm whale… but that’s just the beginning of the crew’s ordeal. If you want to know more read “In The Heart of The Sea” which chronicles not only the sinking of the Essex but also her crew’s struggle to reach civilization after being set adrift in the middle of the Pacific. I don’t want to ruin the story for you… but let’s just say they got REALLY hungry;-)
All of the odontocetes possess the amazing ability to “echolocate”. That is, they can send out blasts of sound and then listen for the echoes of those sounds to locate prey much like a bat flying through the night sky looking for insects. Once a prey item is located, a toothed whale will zero in on one individual fish (or squid, etc) and consume their prey one at a time.
The mysticetes or “baleen whales” are fundamentally quite different from the toothed whales. All of the baleen whales are quite large, ranging in size from the 21 foot Pygmy right whale all the way up to the biggest of all animals… the giant Blue whale. The largest Blue whale ever recorded was an 114-foot female taken in the Southern Ocean and processed at a whaling station on South Georgia Island.
The structure of the feeding mechanism inside a baleen whale’s mouth is one of the most curious in nature. Instead of teeth, they have a curious substance called “baleen” which allows them to filter small fish or plankton from the sea. Many of the very large baleen whales need to eat up to 3,000 pounds of food each day in order to sustain themselves. To do this they cannot afford to take just one fish at-a-time like the toothed whales do. To catch that amount of fish they have to target entire schools of fish at once and capture hundreds of pounds of fish in each mouthful.
But these whales have a problem. Remember that whales are mammals, just like us, and just like us they can’t drink seawater. The ocean is, on average, about 3.5% dissolved salt and when a mammal such as a dog, cat, human, or a whale drinks seawater the salt pulls moisture from its body tissues and causes dehydration. Drinking too much seawater can be fatal for for any mammal… even a whale. (That’s why the crew of the Essex couldn’t drink the seawater when they were lost at sea!)
So how do baleen whales catch entire schools of fish without drinking a lot of sea water in the process? They do it by straining or filtering their food from the water using plates of “Baleen” (which was called “whale-bone” by the early whalers, although it’s not actually comprised of bone tissue). These “baleen plates” are made of “keratin,” the same protein that makes up your finger nails (and toenails, and hair, and horses hooves, and scales on snakes, and the Exo-skeleton of insects). An adult baleen whale has between 600 and 1,200 individual baleen plates that are suspended only from the upper jaw of the animal and together they form a giant straining wall through which water can easily escape but the fish cannot.
When a baleen whale is feeding it will dive beneath the surface and most likely listen for schools of fish beneath the surface (although the truth is no one knows for certain how baleen whale find fish in the dark depths of the ocean). Once a dense school of fish is located the whale will open up its enormous mouth and take in hundreds of gallons of fish and seawater at one time. The whale will then close its mouth almost all the way and, by constricting its throat muscles and forcing its tongue up to the roof of its mouth, it will squeeze the water out through the baleen plates. The water flows out through the narrow gaps between the plates very easily but the fish are too big to fit out and so they are left trapped inside. Now the whale can just kick its head back and swallow the fish whole and doesn’t have to worry about drinking an excessive amount of salt water. Their kidneys are slightly better adapted for salt intake than ours, but not by very much so it important to filter as much of the salt water out as possible. It is the baleen that allows them to do this quite efficiently.