Marine Mammals

Marine vertebrates

• Evolutionary tree

-convergent evolution

• Class Osteichthyes (bony fish)

• Class Chondrichthyes (sharks and rays)

• Class Reptilia (marine turtles, crocs, snakes)

• Class Aves (marine birds)

• Class Mammalia (whales, walruses, sea otters,

manatees, seals, sea lions)

An evolutionary tree of marine vertebrates

Class Mammalia

• Endothermic

• Breathe air

• Give birth to young that suckle

– Mammary glands

• Have hair

• Marine mammals often have streamlined shape, and dense fur +/or fatty tissue for insulation.

Marine mammals

Four major groups: Pinnipeds, Fissipeds,

Sirenians, Cetaceans

Order Carnivora (includes dogs, cats, bears)

•Pinnipeds (exclusively marine): seals, sea lions,

walruses

•Fissipeds (also includes dogs, cats, raccoons,

bears). Two marine species:

Sea otters and polar bears

Pinnipeds (exclusively marine):

sea lions, seals, walruses

Leave ocean to mate and raise young

Gregarious

Seals: no ear flaps, hind limbs fused as rear fins

Sea lions: ear flaps, hind limbs more mobile

Walruses: tusks, bottom feeders, arctic

Fissipeds:

Sea otters and polar bears

Sea otters

• Smallest marine mammal

• Two fur layers

– 650,000 hairs per square inch

• Eat sea urchins, mollusks, small fish

• Use rock as hammer

Fissipeds:

Sea otters and polar bears

Polar bears

• 3 m, 650 kg, 20 - 30 yrs

• Arctic

• Solitary

• Black skin, white hairs

• Acute sense of smell

– Smell a seal 32 km away

Order Sirenia

• manatees, dugongs

• 3 - 4 m, 50 - 60 yrs

• Warm tropical and subtropical waters

• Semi-social

• Only herbivorous marine mammals

• Decline due to human impacts

– Water pollution, boat motors

Order Cetacea

• Carnivorous and filter-feeding aquatic mammals

• Porpoises, dolphins, whales

• 79 species

• commonly use ecolocation (sonar)

• two groups: toothed whales and baleen whales

Suborder Odontoceti

• Toothed whales

• One blowhole

• Teeth to seize prey

• Feeding

– Killer whales: top carnivores

Suborder Mysticeti

• Baleen whales

• Two blowholes

• Baleen plates – filter feeders

– Plates grow to several feet in length

– May be several hundred in one animal

– Flat on outer edge, bristles on inner edge trap small organisms

Krill: food source for many baleen whales