Marine MammalsClass Mammalia (Includes humans!)Includes porpoises, dolphins, whales, seals, sea

lions, walruses, sea otters, manatees, and dugongs.

Evolved from land ancestorsBreath with lungs, birth live young, have

mammary glands with milk, and hair.

Common FeaturesStreamlined body shape: Slippery skin or hair, flippers,

thin body shape.Generate internal body heat: High metabolic rates

produce heat which is kept insulated by fat or fur. Must be large to keep all that heat in.

Modified respiratory system: Collects and retains large amounts of oxygen. Some whales can hold breath for 90 minutes.

Osmotic adaptations: Kidneys can excrete concentrated and highly saline urine. Marine mammals swallow very little water and skin is impervious to water.

Order Cetacea79 living speciesThought to evolve from horses and sheep Include porpoises, dolphins, and whalesThick blubber provides insulationOne or two nostrils at the top of the head have special

valves to prevent intake of water and are used for breathing (blow holes).

Whales and dolphins have very large brains and form complex family and social groupings.

Dolphins are thought to be as intelligent as chimpanzees

Suborder Odontoceti and Mysticeti Odontoceti: Toothed whales.

Active predators Large brains for communication Includes orca (killer whales), dolphins, porpoises, and sperm whales Use echolocation or sonar to find food Some can use sound to stun, debilitate, or even kill prey Dolphins can produce sound at 229 decibels or as loud as a small

explosion

Mysticeti: Baleen whales. No teeth/filter feeders Eat mostly planktonic krill Live near surface Great Blue Whale is largest and weighs 3 tons! May live to be several hundred years old

Order Carnivora Includes sea lions, seals, and walruses Evolved from bears True seals have a smooth head with no external ears

Covered with short hair and soft underfur Graceful swimmers that eat fish

Sea lions can move well on land. Have small external ears and soft underfur Use front flippers for propulsion Often seen at aquariums

Walruses are largest (can weight 2 tons!) Use tusks to dig up infaunal clams which they crush and eat Can dive 300 feet!

CarnivoraSea Otters

Smallest marine mammal

Human demand for their soft fur almost made them extinct

Eat mollusks, crustaceans, and echinoderms

Use rocks to hammer shells of mollusks until they break

Order SireniaIncludes dugongs and manateesSiricis means mermaidThe only herbivorous marine mammalsAlso evolved from horses and other hooved mammalsGraze on sea grasses and algaeTemperate to tropical watersProtected but endangered: Many killed each year by

propellers of boats