Marine Mammals Lesson 9.5 Great white shark, hump-backed whale breaching, sockeye salmon spawning, male and female elephant seals.

Diverse groups of land mammals that have adapted to life in the ocean: all have hair, bear live young and nurse their offspring They include: -sea otters and polar bears -seals, sea lions and walruses -manatees and dugongs -whales, dolphins and porpoises

Sea Otters Sea otter is the smallest marine mammal and has no blubber layer insulation from air trapped in its thick fur. Otters use tools like rocks to crush shells of abalone and other shellfish Otters help to keep kelp forests healthy by eating sea urchins, which graze on kelp This helps preserve biodiversity of ocean food web Hunted for its fur and killed by fishermen, its numbers have declined

Polar Bears Polar bears are semi-aquatic spend much of their lives on drifting Arctic ice. They feed primarily on seals, but also whale and walrus carcasses. Male polar bears may grow to 10 feet tall and weigh over 1400 lb. Females may reach seven feet and weigh 650 lb. Polar bears have been known to swim 100 miles at a stretch. They are found in the Arctic, Alaska, Canada, Russia, Greenland, and Norway. Humans are their main predators Global warming threatens polar bear populations by melting the sea ice, which is their main habitat.

Seals, Sea Lions and Walruses Have paddle-shaped flippers for swimming, but must rest and breed on land ”Blubber” = thick layer of fat for insulation, food reserve and buoyancy Many are large, which helps to conserve body heat in cold waters Elephant seals are the largest: males can be 20 ft long and up to 5,000 lb. Elephant seals can dive for 1.5 hours without coming up for air Walrus tusks are used for defense and to anchor the animal to the ice. M. Parker

Elephant seal research at Sonoma State University Dr. Dan Crocker with a bull elephant seal (anesthetized!) at Ańo Nuevo State Park in San Mateo County, fitting it with tracking devices to study its diving physiology and migration patterns. The scars on the seal’s back and snout are from fighting with other males during the breeding season, which is the only time that males are found on land. Females stay longer to give birth and wean their pups.

Manatees and Dugongs Sirenians, also known as “sea cows,” are named for mermaids These gentle mammals are related to elephants! only marine mammals that are strict vegetarians, feeding on sea grasses and other vegetation Manatees larger, up to 15 ft long and over 1,300 lb. Hunted by humans for oil-rich blubber and meat Slow reproduction– 1 calf every 3 yr. Manatees found in Atlantic Ocean, the Amazon, Florida, S. Africa Dugongs only marine, from E. Africa to western Pacific islands. Manatees have been injured and killed by collisions with boat propellers in Florida; now have speed restrictions in some manatee habitats

Dolphins, Porpoises and Whales Along with sirenians, most complete transition to marine life; spend their entire lives in the water. convergent evolution: these animals look very fish-like, but breathe air, are warm-blooded and nurse their young. Front flippers only, some have dorsal fins like fish Blubber for insulation, buoyancy Hair almost absent Nostrils on top of head = blow-hole Many highly intelligent– male humpback “songs” thought to communicate mating fitness Can be heard for 100 miles!

Some of the world’s whales

Baleen whales Largest whales on earth are krill Largest whales on earth are baleen, which eat tiny shrimp-like animals called krill No teeth, but rows of flexible fibrous plates made of keratin that hang from the upper jaws. It filter-feeds by gulping a huge mouthful of water and squeezing it out through the baleen to strain out food particles Largest baleen whales are the blue whales -- can reach lengths of 80-110 ft; weight up to 140 tons! (That is 280,000 lb!) If the average teenager weighed 140 lb, 2000 teens = one blue whale!

80 species of toothed whales, including dolphins and porpoises Numbers of teeth vary from 2 (narwhal) to over 100 in some species of dolphins Most smaller than baleen whales, although killer whales can reach 26 Largest is sperm whale (“Moby Dick”) at 60+ ft. Toothed whales eat fish, squid, shrimp, penguins, pinnipeds.

March 2012 whale hunting in the Southern Ocean near Australia Humans have hunted whales for centuries Subsistence vs. commercial hunting (Inuits vs. Japan, Norway, Iceland) Very controversial animal rights issue (Green Peace, Sea Shepherd)

A happy note: the annual gray whale spring migration of females and calves, from Baja California to Alaska is happening now. You can watch this migration on the Sonoma and Marin coasts! gray whale and calf