Transcript Marine Mammals Lesson 9.5

Marine Mammals Lesson 9.5
• 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
M. Parker
• 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.
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 = blowhole
• 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
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