Cetaceans

"Cetacean" is the word for all mammals, which includes whales, dolphins and porpoises.
The term cetacean comes from the Greek ketos, meaning "sea monster” an from the Latin cetus meaning "a large sea animal,"
Cetaceans are mammals who are adapted to life in the water.
Over 80 species of whales, dolphins and porpoises on Earth, from the small Hector's dolphin (39” long) to the huge blue whale (100 ft long)
Cetaceans are further divided into two groups: baleen whales and toothed whales.
Pronunciation: "Suh-tay-shun"

Evolution of whales
Cetaceans are thought to have evolved from hooved land mammals that lived about 50 million years ago.

http://www.robins-island.org/dolphins_evolution.php

Types of Cetaceans: according to how they feed

Mysticetes (baleen whales)

• include species such as the blue whale, fin whale, right whale and humpback whale.
  
• have hundreds of comb-like plates of baleen hanging from their upper jaw.
• feed by gulping large amounts of water containing hundreds or thousands of fish or plankton, then forcing the water out in between the baleen plates, leaving the prey inside to be swallowed whole
• 14 baleen whale species

Odontocetes (toothed whales)

• include the sperm whale, orca (killer whale), beluga and all of the dolphins and porpoises.
• these animals have cone-shaped or spade-shaped teeth
• usually capture one animal at a time and swallow it whole.
• feed mostly on fish and squid, although some orcas prey on other marine mammals.
• 72 different species

Cetacean Characteristics

• Are mammals, which means they are endothermic (commonly called warm-blooded)
• Their internal body temperature is about the same as a human's.
• They give birth to live young and breathe air through lungs just like we do. They even have hair.
• Unlike fish, which swim by moving their heads from side-to-side to swing their tail, cetaceans propel themselves by moving their tail in a smooth, up-and-down motion.
• Some cetaceans, such as the Dall's porpoise and the orca (killer whale) can swim faster than 30 miles per hour.

Breathing & Insulation

• When a cetacean wants to breathe, it has to rise to the water surface and exhale and inhale out of the blowholes located on top of its head.
• When the cetacean comes to the surface and exhales, you can sometimes see the spout, or blow, which is the result of the warm air in the whale's lungs condensing upon reaching the cool air outside.
• Whales do not have a coat of fur to keep warm, so they have a thick layer of fat and connective tissue called blubber underneath their skin.
• This blubber layer can be as much as 24 inches thick in some whales.

Senses & Diving

• Whales have a poor sense of smell, and depending on where they are, they may not be able to see well underwater.
• They have excellent hearing. They do not have external ears, but have tiny ear openings behind each eye. They can also tell the direction of sound underwater.
• Whales have collapsible rib cages and flexible skeletons, which allows them to compensate for high water pressure when they dive.
• They can also tolerate higher levels of carbon dioxide in their blood, allowing them to stay underwater for up to 1 to 2 hours for large whales.

Difference Between Dolphins & Porpoises:

Dolphins

• Dolphins have cone-shaped teeth
• Dolphins usually have a pronounced “beak,”
• Dolphins generally have a very curved or hooked dorsal fin
• Dolphins are larger than porpoises

Porpoises

• Porpoises have flat or spade-shaped teeth
• Porpoises do not have a beak.
• Porpoises have a triangular dorsal fin.
• Porpoises are generally smaller than dolphins.

Do Whales Sleep?

Whales are voluntary breathers, meaning they think about every breath they take.
A whale breathes through the blowholes on top of its head, so it needs to come up to the water surface to breathe. That means the whale needs to be awake to breathe.

How's a whale going to get any rest?

Unlike us, whales "sleep" by resting one half of their brain at a time.

While one half of the brain stays awake to make sure the whale breathes and alerts the whale to any danger in its environment, the other half of the brain sleeps.
We humans are involuntary breathers, meaning we breathe without thinking about it and have a "breathing reflex" that kicks into gear when we're sleeping or are knocked unconscious.
Whales do not appear to have REM (rapid eye movement) sleep that is characteristic of humans. This is the stage in which most of our dreaming occurs.

Where do cetaceans sleep?

Captive dolphins have been known to rest at the bottom of their pool for a few minutes at a time.

Large baleen whales such as humpbacks resting at the surface for sometimes half an hour at a time. These whales take slow breaths that are less frequent than a whale that's active. They are so relatively motionless on the surface that we refer to this behavior as "logging," because they look like giant logs floating on the water.

Do Whales Have Hair?

Whales are mammals, and one of the characteristics common to all mammals is the presence of hair. There are over 80 species of whales, and hair is only visible in some. Some of the larger baleen whales have visible hair. Eg.

• Humpback whale, which has golf ball-sized bumps on its head. Within each of these bumps, called tubercles, there is a hair follicle.
• Right whale, which has hairs on its chin and upper jaw,
• Bowhead whale, which has hairs on its lips, chin, snout and behind its blowhole.
• Baleen whales also have hairlike structures in their mouth called baleen, which is made of keratin, a substance found in hair and nails.

How do whales and dolphins swim?

Cetaceans use their tail to swim. Unlike fish, the tail of whales, dolphins and porpoises lies in an horizontal plane and it is moved up and down rather than from side to side. Muscles actively work when the tail is raised, while they rest (or almost completely rest) when the tail is lowered.

How do whales and dolphins communicate?

Cetaceans communicate mainly by producing a wide range of sounds, such as clicks, moans, creaks, squeaks, etc. Unlike mysticetes (baleen whales), most odontocetes (toothed cetaceans) also produce whistles, and their clicks plays a central role in a mechanism known as echolocation - an extremely powerful bio-sonar that allow them to detect other members of their group, prey, predators and also investigate the physical features of the aquatic environment.
Mysticeti (baleen whales) do not seem to use echolocation.

Whale Fun Facts

• Sperm Whales have the largest brain on the planet. It may weigh 20lbs.
• Fin whale is one of the fastest whales. They can swim over 20 miles per hour for short periods.
• Blue whale is the largest whale. They may grow up to 100 feet and weigh as much as several elephants.
• Harbor porpoise is one of the smallest whales. They grow to only about 5 feet in length.
• Killer whales are the largest dolphins. They get their name because they sometimes eat other, larger whales.
• A humpback whale may eat up to a ton of food every day.
• Whales can't breathe through their mouths. The mouth is connected directly to the stomach. They breathe through their blow holes, which go to the lungs.
• Sperm whale can hold its breath for at least an hour.
• The voice of the blue whale is one of the deepest voices on the planet. It is so powerful that it can travel for perhaps a 100 miles underwater.
• Blubber on a whale which lives in very cold water may reach up to 20” thick.
• Whales do not spout water. They are letting out air from their lungs.
• A new born baby blue whale may weigh two tons and be 25 feet long.
• Some whales do not have teeth. They have baleen. The largest baleen is that of the bowhead whale, whose baleen may be up to 10 ft long.
• There is a toothed whale which only has two teeth.
• Narwhales have one tooth hidden under the gums, but in the males the other tooth sticks out from their head like a tusk, which may grow to be 8 feet long.