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Introduction to the Marine Mammals

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									                    Introduction to the Marine Mammals
   Mammal- Any of various warm-blooded vertebrate animals of the class
    Mammalia, characterized by a covering of hair on the skin and, in the female,
    milk-producing mammary glands for nourishing the young.
   Marine Mammals
       o Have similar adaptations for the marine environment
               Body Size
               Streamlined Shape
               Insulation
                      Dense fur or blubber
               Modified skeleton
                      Shortening of appendages
                      Loss of hind limbs
               Similar Physiological Adaptations
                      For diving, thermoregulation, osmoregulation,
                         communication and orientation
       o Have similar habitat requirements
               Require the aquatic habitat for survival
                      They can therefore be used as indicators of habitat
                         degradation.
       o Many have been exploited by humans to the point of near extinction
       o Three Orders
               Carnivora- The mammalian carnivores, includes cats and dogs
                      Suborder Pinnipedia (‘fin’-‘footed’)
                            o Most marine of the Carnivora
                            o Use fat and/or fur for insulation
                            o Deep divers
                            o Must return to land in order to give birth
                            o Family Otariidae
                                     Sea lions and fur seals
                                     The “Eared Seals”
                                     Hind flippers rotate under the body to permit
                                       walking or running on land
                                     Swim by using the large fore flippers
                                     Dense fur that consists of long, coarse hairs
                                       and thick underfur in which air is trapped to
                                       promote insulation
                                     Tend to have a temperatue-to-subtropical
                                       distribution
                            o Family Phocidae
                                     True Seals
                                     Lack ears, sometimes called “earless seals”
                                     Unable to rotate the hind limbs forward
                                       under the body and therefore don’t move
                                       well on land.
                                     Swim by using the hind flippers.
                        Small pectoral flippers are used for steering.
                        Blubber is used for insulation
                        Excellent diving abilities
                        Phocids are relatively large compared to
                         Otariids
                      Phocids are found throughout the world’s
                         oceans
              o Family Odobenidae
                      Walruses
                      One species, Odobenus rosmarus]
                      Large tusks
                      Can rotate hind flippers under the body
                      Use both front and hind flippers to swim
                      No external ear
                      Naked skin with only a few sparse hairs
        Other Marine Carnivora
              o Family Ursidae
                      Polar Bears
                      Found only in the Arctic
              o Family Mustelidae
                      Otters
                              Sea otters of the pacific coast of
                                 N.America and Russia
                              Marine Otter of Chile and Peru
                      Extremely dense fur
                      Flattened hind feet for propulsion in water
                      Axillary flap of skin to hold or store food
                         and tools
                      Horizontally flattened tail
   Cetacea- Whales dolphins and porpoises
        Evolved from ariodactyls, even-toed ungulates such as
          cows or pigs
        All are large, ranging from 2m to >30m
        Streamlined body form with minimal protuberances that
          could cause drag
              o Ex: They all lack external ears, reproductive organs,
                 appendages and are generally hairless
                      Vestiges of the pelvic girdle
                      Some have hair during fetal development
        Elongated skull with overlapping bones
        Dorsal positioning of the blowhole
        Subdermal blubber that can be 10’s of centimeters thick.
        Porous, oil-filled bones
        Multiple stomach compartments
        78 living species in two suborders
              o Mysticeti (baleen whales)
       Have baleen- a keratin-based brushlike
        adaptation suspended from the upper jaw
     Dorsally symmetrical skull
     Two blowholes
     Non fused mandible
     Tend to be large
            Smallest mystecete, the Pygmy Right
                Whale is >6m
     Family Balaenidae
            4 Species:N. and S. right Whale,
                Bowhead and Pygmy Right Whale
            Extremely convex profile of upper
                surface of skull
            No dorsal fin
            No gular grooves
     Family Balaenopteridae
            6 species: Blue, Fin, Sei, Bryde’s,
                Minke and Humpback
            Flat profile to skull
            Small triangular dorsal fin
            Numerous gular grooves run from
                the snout to umbilicus
     Family Eshrichtiidae
            1 species: Gray whale
            slightly convex profile to skull
            no dorsal fin: aseries of ‘Knuckles”
                above the audal peduncle
            2-4 short gular grooves: benthic
                feeder
o Odontoceti (toothed whales)
     Possess teeth in one or both jaws.
     Dorsally asymmetrical skull
     A single blowhole
     Fused mandible
     Vary in size
            Some dolphins are <2m
            The sperm whale is 18m
     Family Physeteridae
            3 Species: Sperm whale, Pygmy and
                Dwarf sperm whale
            Dorsal hump or small dorsal fin
            Large bulbous head with spermaceti
                organ
            Flukes notched
                              Well developed conical teeth in
                               lower jaw only, fit into sockets in
                               upper jaw
                      Family Ziphiidae
                             18 species: Beaked whales
                             2 gular grooves
                             Small dorsal fin
                             Slender rostrum (beak)
                             Flukes not notched
                             1-2 pairs of teeth confined to lower
                               jaw
                      Family Monodontidae
                             3 Species: Beluga, Narwal, and
                               Irrawaddy Dolphin
                             Generally no dorsal fin or small
                               dorsal fin
                             Head blunt, no beak
                             Flukes notched
                             All cervical vertebrae free
                      Family Platanistidae
                             5 Species: River Dolphins
                             Small dorsal fin
                             Jaws form a long beak
                             Flukes notched
                             Many well developed conical teeth
                               in both jaws
                      Family Delphinidae
                             32 Species: Dolphins, including the
                               Orca
                             Large dorsal fin (except right whale
                               dolphin)
                             Jaws form a beak or head gibbose
                               (hump)
                             Flukes notched
                             Well developed conical teeth in both
                               jaws or in lower jaw only
                      Family Phocoenidae
                             6 Species: Dorsal fin large and
                               triangular
                             Head blunt, no beak
                             Well developed to poorly developed
                               spatulate teeth in both jaws
   Sirenians- Manatees and Dugongs
         Evolved from elephants and other subungulates
         Skin lacks hair
   Well developed vibrissae (whiskers)
   Well developed layer of fat
   Pectoral limbs modified as flippers
   Hind limbs absent
   Tail modified into flukes
   Ears absent
   Family Dugongidae
        o 1 Species Dugong dugon
        o Nails absent
        o Tail modified into notched flukes
        o Male and female approximately the same size
   Family Trichechidae
        o 3 Species of Manatee
        o Vestigial nails present
        o Tail modified into rounded paddle
        o Male and female approximately the same size

								
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