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, yrs Arctic Solitary Black skin, white hairs Acute sense of smell – Smell a seal 32 km away

Order Sirenia manatees, dugongs m, 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