Marine Mammals

Kingdom Animalia

Phylum Chordata

Class Mammalia

General Characteristics

Endotherms: “warm-blooded” or able to maintain a constant temperature through their metabolism

Viviparous: embryo receives nutrients and oxygen through the placenta (exceptions: platypus and akidna)

Mammary glands: produce milk for newbornHair: at some point in their lives they have

hair/fur.Blubber: thick layer of fat to keep warm

Class Pinnipedia (Pinnipeds)

Seal, Sea Lions and WalrusesPredators: feed mostly on squid and fishBodies are streamlined and adapted for

swimmingPaddle-shaped flippersRelated to dogs and cats

Seals

Family Phocidae: True Seals Lack ear flaps (pinnae) Fore-flippers are short and have claw on

each of the fine digits Hind-flippers cannot be rotated forward Swim with powerful strokes of rear

flippers Use only fore-flippers on land

Harbor Seal

Adults to left

Juvenile below

Harp Seal

Harp Seal

Elephant Seal

Largest pinnipeds20 ft long 4 tons

Sea Lions and Fur Seals

Eared seals= have pinnaeLong, hairless or only partially haired fore-

flippers with splayed digitsLarge hind flippers; can rotate beneath the

bodySwim mostly with fore-flippersCan sit on land with head and neck

raised.

California Sea Lion

Sea Lion Diagram

Fur Seals

Stellar Sea Lion

Walruses

Distinct pair of protruding tusksFeeds mostly on bottom invertebrates,

particularly clamsStiff whiskers act as feelersTusks used in defense and anchor on to

ice

Walrus

Sea Otter

Order CarnivoraSmallest marine mammalsWeighs 60 to 80 lbsLacks a layer of blubberDense fur to keep warmNeed to eat 25-30% of weight per dayEat urchins, abalone, mussles, crabs

Manatees and Dugongs

Order SireniaRelatives of the elephantsAlso known as a sea cowHerbivoresPrefer warm water

Manatee

•15 feet and 3,000 lbs

•Grayish in color

•Tail is broad and rounded

•3 species

•Found in Florida, South America and West Africa

Distribution

Dugong

•10 feet and 600 lbs

•Tail resembles a whales

•One species

•Found in Australia

Order Cetacea

Order Cetacea

Three suborders:Archaeoceti- “ancient whales”; all extinct

Mysticeti- “mustached whales”

Odontoceti- “toothed whales”

1. Suborder Mysticeti (Baleen Whales)

Filter feeders, eat plankton & small fishBaleen plates- made from protein, comb/

strain planktonLargest whales- 150 tons; heart the size

of a compact car; Blue whale: 103 ft.Two blowholes, create a v-shape

Baleen Plates

a. Family Balaenidae (Right Whales)

Slowly swim at the surfaceMany (more than 200) relatively short

baleen platesNo throat pleats4 species; N & S Right Whales, Pygmy, &

Bowhead

Northern Right Whale

Southern Right Whale

Pygmy Right Whale

Bowhead Whale

b. Family Balaenopteridea (Rorguals)

Take in huge gulps of waterMany (more than 200) relatively short

baleen platesMany (32-100) long gular grooves: throat

pleats6 species; Blue, Fin, Sei, Bryde’s, Minke,

Humpback

Fin Whale

Sei Whale

Bryde’s Whale

Minke Whale

Humpback Whale

c. Eschirichtiidae (Gray Whales)Feed by scraping the bottom floorFewer baleen plates (130-180)No dorsal fin; 6-12 prominent dorsal

knucklesOne species; California Gray Whale

Gray Whale

B. Suborder Odontoceti (Toothed Whales)Peg-like teeth

Active hunters

More social than baleen whales

1. Family Physseteridae (Sperm Whales)

Spermaceti- white waxy material in head mistaken for sperm

Largest of the toothed whale; largest carnivore

No gular groovesDorsal fin or humpPrey on squid: Whale from Moby Dick

Sperm Whale

Size Comparison of Sperm Whale

2. Family Monodontidae (Narwhal and Beluga)Melon- fatty tissue used in echolocation8-11 irregularly shaped teethNo dorsal fin (to deal w/ sea ice or to

preserve body heat)Narwhal- long tusk thought to be used as

a show of dominance in males

Beluga Whale

Narwhal

3. Family Ziphiidae (Beaked Whales)Reversed sexual dimorphism- females are

larger than malesBeak is similar to dolphins1-2 pairs of teeth in lower jawFeed on bottom of ocean floorLongest dive-85 minutes

Beaked Whales

4. Family Delphinidae (Dolphins)

Largest familyMost intelligentConical teethCurved dorsal finIncludes Bottlenose, Orcas, Pacific White

sided dolphins and more.

Bottlenose Dolphin

Orca (Killer Whale)

5. Family Phocoenidae (porpoises)

Smaller than dolphinsRounded heads, smaller beak or absentFlattened spade shaped teethTriangular dorsal fin

Porpoise

River Dolphins (4 Families)

Most EndangeredTriangular, small dorsal finPoor eyesightLong beakMostly freshwater, one lives in brackish

estuariesFound in the Ganges in India, Amazon in

S.A., Yangtzee in China, and the La Plata River Dolphin in S.A.

Amazon River Dolphin

River Dolphins

B. Skeletal System

1. Axial skeletona. skull- reflects lifestyle of cetacean

1. Thorax- Sternum- collapsible2. Ribs- in odontocetes they have two heads and one or more costal cartilage for collapsing rib cage

2. Appendicular skeletona. The development of flippers has been

accompanied by an increase in the number of phalanges

b. Vestigial hip bone

Skeletal System of a Sperm Whale

Vestigal Hip Bone

C. Soft Body Anatomy

1. Dorsal fin and Flukes- Dorsal fin highly vascularized with a

counter current blood flow system- Cetaceans are capable of opening and

closing arteries and veins- vasoconstriction to preserve heat.

2. Blubber

Varies in thickness (up to 2 feet thick in bowhead whales)

Smaller whales- couple of inches Large whales- up to a foot

3. Muscles

Rich in myoglobin- keep oxygen level high in muscles

D. Feeding

1. Baleen Whales

a. Open mouth wide, taking in large quantities of water, and then closing mouth- Rorquals

b. By swimming through the water, mouth open- Right Whales

c. By using suction created when the tongue is pressed against a plate to draw water and food into the mouth- Gray Whales

FOOD

Plankton, copepods, krill, small fish

Size and flexibility of bristles and density is related to food preference (ex. If the whale eats plankton, it has very fine and dense bristles)

2. Odontocetes- toothed whales

PredatorsFOOD- mostly fish and small animals,

some seals

D. Swimming and Diving

1. Swimming- streamlined shape, dorsal fins, evenly distributed blubber

2. Diving- Have more blood with more red blood cells-

higher concentration of oxygen Heart rate slows, blood flow to the extremities

is reduced- bradycardia Collapse their lungs and rib cage squeezing

the air in the lungs into the blood- to help resist high pressure

E. Echolocation (“sonar”)

Animal emits sound waves, which travel about 5X faster in water than in air, and listens for the echoes that are reflected back from surrounding objects

Clicks- high pitched soundsMelon- helps to pass clicks forwardSpermaceti organ- filled with a waxy substance;

buoyancy regulator or sound reflectorOdontocetes use their oil filled jaw bones to

receive sound and direct it to the inner ear.

F. Behavior

Most cetaceans spend their entire lives in highly organized pods

Vocalization-Different sounds are associated with various moods and

social signalingsHumpback songs- canaries of the sea, sing specific

songs (vocalization)Breaching- out of waterStranding- swim to shallow water, it is a mystery why.

Migration

Cold to warm waters for giving birthFeed in polar regions (krill)Follow same patterns

Birth and Care of Young

Internal testes and penisGestation- 9-18 monthsBorn tail first- calf swims immediately to the surface once

bornLaboring mother are tended by one or more adultsCetaceans nurse with a pair of teats concealed in slits

along the body wall in the femaleMilk- produced by mammary glandsLow birth rate- one calf every three yearsSexually mature at age 7 to 14 yearshttp://www.enchantedlearning.com/subjects/whales/

anatomy/Repro.shtml