Marine Mammals Marine vertebrates Evolutionary tree convergent evolution

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