Size is the dominant characteristic one thinks of when whales are discussed. Many whale species are staggeringly enormous. The blue whale, for example, can grow to 100 feet long, about the height of a 10-story building, and can weigh as much as 150 tons (300,000 lbs). Its heart alone is the size of a small car, and there's enough room on its tongue for 50 people. It is the largest known animal in Earth's history.Despite their monumental proportions, whales are mammals, just like us--warm-blooded, air-breathing creatures--but spend their entire life in the ocean. They feed their young milk and have some (although very little) hair. Their bodies resemble the streamlined form of a fish, while the forelimbs or flippers are paddle-shaped.(Source: How Stuff Works)
More than speculation, evidence supports the hypothesis whales evolved from land dwelling creatures with legs to the body type they have today. Over the course of millions of years, the "land whale" spent less time on firm soil and more time in the water, thus eliminating the need for legs. Fossil remnants of whale-like creatures with legs so small they couldn't possibly support the animal's weight, have been found by paleontologists.(Source: How Stuff Works)
Whales belong to the order cetacea, which includes whales, dolphins and porpoises. Whales are divided into two suborders: baleen and toothed whales. Baleen whales have a comb-like fringe, called a baleen, on the upper jaw, which is used to filter plankton, as well as small fish and crustaceans. They are the largest species of whale. Toothed whales have teeth and prey on fish, squid, other whales and marine mammals. They sense their surrounding environment through echolocation--like a one ounce bat does!(Source: Defenders of Wildlife)
Beneath the skin lies a layer of fat called blubber. It serves as an energy reservoir and also as insulation. Whales breathe through blowholes, located on the top of the head so the animal can remain submerged. Baleen whales have two blowholes, while toothed whales have one.(Source: Defenders of Wildlife)
Whales live in all the world's oceans, though their range is specific to their species.
Whales swim forward by flexing their tails up and down, instead of side to side as with most fish. To change direction they move their flippers, similar to the way an airplane steers. If a dorsal fin is present, it helps stabilize the whale's body as it swims.
Many whales, especially baleen whales, tend to migrate long distances from their cold-water feeding grounds to warm-water breeding grounds each year. They travel alone or in groups, or pods, on their annual migrations. Toothed whales often hunt in groups, migrate together and share young-rearing duties.
Most whales are quite active in the water. They jump high, or breach, out of the water and land back in the water. They also thrust their tails out of the water and slap the water's surface, which is believed to be a warning of danger nearby. Whales also communicate with each other using lyrical sounds. These sounds are extremely loud depending on the species and can be heard for many miles. (Source: Defenders of Wildlife)
Because of their environment (and unlike many animals) and because they need to breathe air by coming to the water's surface, whales are conscious breathers, meaning they decide when to breathe. All mammals sleep, including whales, but they cannot afford to fall into an unconscious state for too long, since they need to be conscious to break the surface in order to breathe. Marine biologists have determined that whales get around this problem by letting only one-half of the brain sleep at a time. It is possible for a whale to drown!
Diet: The species of whale will determine its diet--from microscopic plankton to large marine mammals.(Source: How Stuff Works)
Breeding & Reproduction: The mating season varies depending on the specific species. Gestation is minimally nine (9) months up to 15 months, again depending on the species. Offspring is generally one (1) calf no matter which species. The calf is nursed for along time, promoting a bond between mother and young. While this strategy of reproduction spawns few offspring, it provides each with a high probability of survival. This slow reproductive rate means that any substantial whale hunting may have a detrimental effect on whale populations.
High on the scale of infant mortality are human-created circumstances: ship strikes and entanglements, naval testing employing loud sonic disturbances, climate change, and whale hunting by countries where it has not been banned.(Source: Defenders of Wildlife)
(Source: Merck Manual, Veterinary Manual)
Pneumonia - witnessed in captive marine mammals
Many times necropsies performed by marine biologists on dead whales are analyzed for causation, with nothing definitive being confirmed