Marine Mammals. Marine vertebrates Evolutionary tree -convergent evolution Class Osteichthyes (bony...
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Transcript of Marine Mammals. Marine vertebrates Evolutionary tree -convergent evolution Class Osteichthyes (bony...
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