Mr. Van Arsdale

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Chapter 2: Cetaceans (Whales and Dolphins)

Classification of Whales and Dolphins

Mysticeti (Baleen Whales)

Description: Mysticeti, as a group, are the largest living animals that have ever existed on the Earth. Blue Whales, the largest, have an average adult length of 80 ft (24 meters,) and have been measured to 98 feet (30 meters.) It is impossible to weigh such and animal, but estimates have put the large ones near 190 metric tons. What gets lost in that size is how long and sleek these animals are. Blue whales are also some of the fastest swimming animals in the ocean, reaching 50 kilometers for hour for short distances. Baleen whales have large convex skulls with a nose shaped (double nostril) blow hole. One group known as the rorquals, have a pleated pouch on their ventral side that expands when feeding.

Feeding: Aside from their size, the mysticetis most distinctive feature is the baleen plates that hand down from their top jawbone. Whales use these plates to filter out small food items such as krill, herring, and plankton. It may seem strange that the largest animals on earth would feed on organisms that are frequently less than an inch long, but from an ecological perspective it makes perfect sense. Krill, copepods, and other types of plankton are some of the most abundant (by weight) forms of life on Earth. All baleen whales are filter feeders, but different whales use a variety of different strategies for capturing food. Some, like bowhead whales, will skim the surface of the water with mouths agape gathering small phytoplankton in their mouths. Some, like blue and fin whales will swim quickly into schools of prey gulping up tons at a time. Gray whales often feed by scraping the side of their heads along the bottom sucking up mouthfuls of sediment, filtering out the crustaceans living in the mud. Humpback whales have the most interesting feeding style of all. They feed in small groups producing nets of bubbles to entrap schools of fish. Click on any of the links to watch video of their feeding style.

Life Cycles: The life cycle of most baleen whales includes late reproductive maturity, long gestational periods, and calves every 3-4 years. Baleen whale mothers will nurse their calves for up to two years. Calving normally takes place in calm shallow seas at the end of long migrations. Most baleen whales feed in colder more nutrient rich waters. Click to watch a gray whale with her calf. Baleen whales are generally considered less social than their gregarious cousins the tooth whales, but they will form small feeding or mating groups. Baleen whales have a variety of courtship styles, they are can be highly competitive, often elaborate, and sometimes aggressive.  Male humpbacks, the most unique in this regard, participate in an annual "sing off" to attract potential female mates.

Behavior: Observing whales can be an exciting experience. This despite the fact that they spend much of their time underwater. Several behaviors can be observed when whale watching. Whales will often stick their heads out of the water to look around in a move called spy hopping. Sometimes they breach, leaping clear of the water. Whales may also slap their fins or flukes (tails) to make sound.

Odonticeti (toothed whales)

Description: With the noted exception of the sperm whale, the toothed whales are smaller than the baleen whales. They have highly developed brains and are aggressive predators. Toothed whales have concave skulls with a large bulbous organ called a melon, which they use to focus sound.

Feeding and Behavior: Toothed whales are defined by their social groups. Groups are typically large extended families led by a matriarchal head. Males, especially male sperm whales are more likely to be isolated into “male only groups." Smaller groups will often come together to form "super pods" for the purpose of mate selection. Dolphins and toothed whales are highly playful, puting on frequent aerial displays. Dolphins seem to enjoy riding the waves pushed by the front of boats in a behavior called bow riding

Feeding: As in all things, toothed whales feed in groups. Working collectively as unit, and are highly adapted hunters. Click to watch a video of a pod of killer whales attacking a much larger gray whale. Dolphins have been observed to coral fish into shallow areas and killer whales will sometimes beach themselves when going after pinnipeds or penguins. Toothed whales make extensive use of echolocation to locate, and in some cases, stun their prey. Click to listen to a sperm whale hunting. Their skills at hunting are so well adapted that large schools of tuna will often follow them. Some groups of toothed whales are migratory and others prefer to stay in local habitats. Toothed whales will often dive to great depths in the search for prey (particularly squid.) Sperm whales can dive to depths of three kilometers and stay down for over an hour.

Questions to Research

1. Using the Great Whales, by BBC.  Write the complete classification of one baleen whale and one toothed whale.


2. List in a chart a major behavioral, reproductive, and anatomical difference between baleen whales and toothed whales.


3. Watch the videos on baleen whale feeding strategies.  After watching them, describe each of the strategies (gulping, skimming, bottom feeding, and bubble netting) in a few sentences. In your description try to include their swimming motion as well as how they use their baleen. 


4. After watching some of the feeding behaviors on video.  Explain what is the purpose of the grooves on the bottom of a baleen whales belly.  If your still not sure you can check out Seaworld.org - Feeding Habits of Baleen Whales


5. Play the link to listen to a story about Right Whales. Although they are no longer hunted, explain what risks are these most endangered of whales are facing.


6. Use the following information and the long piece of paper you were given in class to create to scale (1 Meter= 1 Cm)drawings for the following 6 species. Your drawings can be very simple, but pay attention to the scale. [Human - 2 meters, Beluga - 4 meters, Blue Whale - 32 meters, Fin Whales - 27 meters, Sperm Whale - 20 meters,  Killer Whale - 9 meters.] If you are struggling to make the drawings, look up each species in Wikipedia. Finally just for fun. Type "blue whale skeleton" into google maps. Zone all the way in. Does this help understand how big these animals are?


7. In your own words describe what the following whale behaviors look like: Breaching, Spy Hopping, Fin Slapping, and bow riding.


8. Go to the website of the American Cetacean Society.  Check out the fact sheets located in the menu on the left.  Select one of the beaked or pigmy whales.  There is much less known about these groups of whales.   Describe two or things you learn about one of each.


9. Click on the link for Cook Inlet Beluga Whales.  This population is genetically distinct from other beluga whales and the population is now considered endangered.  Examine tagging maps from 1999-2002.  Is it likely that construction of a new bridge across Knik Arm would have an impact on them?  Please explain.


10. The baiji or Chinese river dolphin was one of the only cetaceans to have adapted to freshwater.  It is believed to have gone extinct in 2006.  Click here and identify why.