Marine Mammals Class Mammalia (Includes humans!) Includes porpoises, dolphins, whales, seals, sea lions, walruses, sea otters, manatees, and dugongs. Evolved from land ancestors Breath with lungs, birth live young, have mammary glands with milk, and hair.

Common Features Streamlined 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 Cetacea 79 living species Thought to evolve from horses and sheep Include porpoises, dolphins, and whales Thick blubber provides insulation One 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!

Carnivora Sea 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 Sirenia Includes dugongs and manatees Siricis means mermaid The only herbivorous marine mammals Also evolved from horses and other hooved mammals Graze on sea grasses and algae Temperate to tropical waters Protected but endangered: Many killed each year by propellers of boats