Cetaceans

Whales, Dolphins, and Porpoises

• Cetaceans are named after Cetus, a sea monster in Greek mythology both Perseus and Heracles needed to slay
• Cetus is also a constellation in the sky
• Examples: blue whale, humpback whale, killer whale (orca), beluga whale, dolphins

• Cetaceans are the largest group of marine mammals

• Largest group of marine mammals
• Spend entire lives in the water
• There are 90 different species of Cetaceans

• 85 are marine
• 5 are freshwater dolphins

• Whales and dolphins are not fish

• Anatomy of a cetacean

• Shape

• Streamlined

• Fins

• Pectoral fins (Flippers) used for steering
• Most have a dorsal fin

• Blowholes (for respiration)

• Cetaceans have a blowhole (single or double) on the top of their heads

• Function as nostrils
• inhale and exhale air ONLY through their blowholes
• They do not blow water out of their blowholes

• **CETACEANS CANNOT BREATHE THROUGH THEIR MOUTHS**

• The blowhole is connected to the trachea
• The mouth does not
• This prevents food from going into the cetaceans’ lungs

• Nasal Plug

• Prevents water from getting into the blowhole
• Contracts when diving underwater
• Opens when surfacing

• Fluke (Tail)

• Separated into lobes
• Separated by a notch
• Made of cartilage
• Propels animal forward by moving up and down
• Flukes differ from species to species

• In some species, flukes are so unique researchers can use them like fingerprints to ID individuals.

• Diving

• While diving, cetaceans reduce their oxygen use by lowering their heart activity and blood circulation
• Individual organs receive no oxygen during this time.
• Some average dive times:

• Dolphins: 8-10 mins
• Sperm whales: 60-90 mins
• Bottlenose whales: 2 hours

• Sleeping

• Cetaceans practice unihemispheric slow-wave sleep (USWS)
• This means they sleep with one side of their brain at a time
• They can still breathe and swim to avoid predators

• Toothed vs. Non-Toothed Whales

• Toothed whales

• Have teeth
• Have one blowhole
• Generally smaller than Baleen whales
• Predators: find, chase, capture prey                  

• swallow prey whole

• Use echolocation
• Examples of toothed whales: Orca, Beluga, Pilot Whale, Sperm Whale, Narwhal

• Echolocation

• Works as a navigation system and can detect objects in the water.
• Sends out signals called “Ultrasounds” from their nasal passage
• How it works: Signal bounces off objects and returns to give a clean “Sound-picture” of the object's size, shape and location

• Melon

• A mass of fat/wax found in the forehead of toothed whales.
• Acts as an acoustic lens for echolocation and communication
• Different size/shape in all species

• Non-Toothed Whales

• Have series of baleen (whalebone) plates in gums along each side of upper jaw
• Baleen feeding behavior

• Eat plankton or small schooling fish like krill
• Use baleen to strain food from water

• Two blowholes
• Travel alone or in small groups
• Biggest: Blue Whale (90 ft)
• Smallest: Pygmy right whale (15-20 ft)
• Whales sing
• Examples: Minke whale. blue whale, humpback whale,

• Dolphins vs. Porpoises

Characteristic	Dolphin	Porpoise
Beak	Pointed snout	Blunt snout
Dorsal Fin	Wave shaped	Triangular
Teeth	Pointed and cone-shaped	Flat with upper edges that are circular and sharp
Size	Up to 12 feet	Up to 7 feet
Lifespan	40-60 years	8-10 years
Melon	Present	Absent
Groups	Large pods of 12+	Small groups of ~4
Human Relations	Friendly to	Shy of (hide)