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MARINE MAMMALS
Chapter Outline
CHARACTERISTICS OF MARINE
MAMMALS
SEA OTTERS
POLAR BEARS
PINNIPEDS: SEALS, SEA LIONS, AND
WALRUSES
CETACEANS: WHALES AND THEIR
RELATIVES
General Characteristics of Cetaceans
Adaptations for Diving
Cetacean Behaviors
Spy Hopping
Chapter Objectives
• Describe the general characteristics of marine mammals.
• Interpret a cladogram of marine mammal evolution.
• Identify the characteristics and adaptations of sea otters.
• Explain the reasons sea otter populations were in decline and how they have
recovered.
• Identify the characteristics and adaptations of the sirens.
• Compare and contrast the sirens: manatees, dugongs, and sea cows.
• Identify the characteristics and adaptations of the cetaceans.
Key Terms
homeothermic
mammary glands
placental mammals
placenta
pinnipeds
blowhole
blubber
the bends
alveoli
myoglobin
baleen
keratin
bubble net
rorquals
bosses
Chapter Summary
1. Mammals can be distinguished from other animals by their body covering of hair,
2. Sea otters inhabit the northern Pacific Ocean. Instead of thick layers of blubber, this
animal has a thick coat of fur to keep it warm. Sea otters usually stay close to shore,
3. The polar bear is a top predator in the Arctic, feeding on seals, walrus pups, and
4. Pinnipeds have four limbs that are modified into flippers. This group includes seals,
sea lions, elephant seals, and walruses. Although they are more at home in the water,
5. Eared seals, which include fur seals and sea lions, have visible external ears. True
seals and walruses lack external ears. Eared seals use their front limbs primarily to
6. Walruses are restricted to the Arctic seas, where they feed on fishes, crustaceans,
7. Sirenians are represented by manatees and dugongs. Although at one time these
8. The mammals that are most suited to life in the sea are the cetaceans. The forelimbs
of cetaceans are modified into flippers, and hind limbs are absent. Their tail forms a
9. Baleen whales have enormous mouths that contain plates of baleen instead of teeth.
The baleen consists of fused keratin fibers, and it strains planktonic food, mainly
10. Toothed whales include sperm whales, dolphins, porpoises, killer whales, and
11. Perhaps the best known of the toothed whales are the dolphins that perform in
shows at numerous aquariums and oceanariums. Dolphins are strongly social
12. The ears of toothed whales are modified to receive a wide range of water vibrations.
This adaptation improves the animal’s ability to hear underwater and refines its
Chapter Outline
I. Characteristics of Marine Mammals
A. Homeothermic.
B. Mammary glands.
C. Placentas.
II. Sea Otters
A. Live in pacific coastal areas of North America.
IV. Pinnipeds: Seals, Sea Lions, and Walruses
A. Pinniped characteristics.
B. Swimming and diving.
C. Reproduction in pinnipeds.
D. Eared seals.
1. Sea lions.
VI. Cetaceans: Whales and Their Relatives
A. General characteristics of cetaceans.
1. Blowhole.
B. Adaptations for diving.
C. Cetacean behaviors.
1. Spy-hopping.
3. Slapping.
D. Reproduction and development.
E. Types of whales.
1. Baleen whales.
a. Right and bowhead whales.
2. Toothed whales.
a. Sperm whales.
3. Echolocation.
4. Dolphin communication.
Suggestions for Presenting the Material
1. Play different audio clips of whale songs and/or vocalizations in class, and discuss
2. Nature centers may have biological materials available for loan to educators, such as
marine mammal fur samples, baleen, and skulls. Contact your local natural history
museum for more details.
3. Have students brainstorm and list similarities and differences between the problems
faced by sea otters on the Pacific coast and by manatees on the Gulf coast. What are
creative solutions to address these problems?
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Classroom Discussion Ideas
1. What reproductive characteristics of great whales have hindered recovery of their
populations, despite whaling having been banned since 1972? Why has it taken so
long for whales to recover?
2. How could global warming affect the migratory life cycles of baleen and toothed
whales?
Videos, Animations, and Websites
Videos
Sea Lions, a California Adventure. (DVD, Rio Films, 2004)
Marine researchers and scientists in California and Mexico discuss the natural history,
Explore the Wildlife Kingdom: Dolphins—Tribes of the Sea. (DVD, Reel Productions
LLC, 2006)
A look at human and dolphin interactions across the globe, from encounters in the wild
to sophisticated intelligence tests in the laboratory.
Whales in Crisis. (DVD, National Geographic, 2006)
An informative look at pilot, humpback, bowhead, and killer whales and the
conservation issues surrounding them.
Animations
Blue Whale Interactive.
An interactive look at the anatomy, physiology, and behavior of blue whales.
Websites
American Cetacean Society.
The oldest whale conservation organization in the world. Fact sheets on numerous
Voyage of the Odyssey.
Presents results of a five-year study of the world’s oceans by the Ocean Alliance, with
Polar Bears International.
Describes current research and management actions being taken to protect polar bears
US Navy Marine Mammal Program.
Describes the various applications of marine mammals in underwater operations, and
Suggested Answers to End of Chapter Questions
Multiple Choice
1. c. mammary glands
Matching
1. c.
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Short Answer
1. What factor contributed to the near extinction of the sea otter?
Sea otters were hunted to near-extinction for their valuable dense fur, used to
2. How do polar bears withstand the Arctic cold?
Adaptations of polar bears to withstand the Arctic cold include: a large body,
3. List three characteristics that would help you distinguish a fur seal from a true seal.
A fur seal is distinguished from a true seal by: 1) the presence of external ears
4. Explain the function of the large proboscis in the male elephant seal.
5. Explain how the arrangement of blood vessels in the flippers and tail flukes of
cetaceans helps them retain body heat.
The flippers and tail flukes of cetaceans utilize a counter-current mechanism of
6. Describe the changes that occur in the bodies of diving mammals when they dive.
When diving, the following changes occur in cetaceans: 1) peripheral
7. What is spy hopping?
8. Explain how toothed whales use echolocation to navigate.
Toothed whales navigate with echolocation by producing sounds that reflect off of
Chapter 12 139
9. Describe how baleen whales feed.
Baleen whales engage in batch feeding, swimming though dense schools of krill or
10. How could you distinguish between a manatee and a dugong?
11. Why do mammals produce fewer offspring than most other animal groups?
Mammals produce fewer offspring than other animal groups because it is
Thinking Critically
1. Some marine mammals are polygamous. What is the advantage of this lifestyle?
In polygamous mating systems, males fight for reproductive access to a group of
2. From an ecological standpoint, why aren’t more of the large marine mammals
predators of birds and other mammals?
Seabirds and marine mammals occupy top positions in the marine food web.
3. Toothed whales use echolocation to find their prey, but baleen whales do not. Why?
It is unnecessary for baleen whales to use a system like echolocation to find their
140 Marine Mammals
Suggested InfoTrac® Articles
“What Are They Doing Down There?” Chadwick, D.H. National Geographic, (2007).