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Marine Mammal

 
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Marine mammal
 
 
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Marine mammals are a diverse group of roughly 120 species of mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
 that are primarily ocean
Ocean

An ocean is a major body of Seawater, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a World Ocean that is customarily divided into several principal oceans and smaller seas....
-dwelling or depend on the ocean for food. They include the cetaceans (whales
Whale

Whales are marine mammals of order Cetacea which are neither dolphinsmembers, in other words, of the families Oceanic dolphin or River dolphinnor porpoises....
, dolphins
Dolphin

File:Bottlenose_Dolphin_KSC04pd0178.jpgDolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in seventeen genus....
, and porpoises
Porpoise

Porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen....
), the sirenians (manatees
Manatee

Manatees are large, fully aquatic marine mammals sometimes known as sea cows. The name manat? comes from the Ta?no, a pre-Columbian people of the Caribbean, meaning "breast"....
 and dugong
Dugong

The dugong is a large marine mammal which, together with the manatees, is one of four living species of the order Sirenia. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's Sea Cow , was hunted to extinction in the 18th century....
), the pinnipeds (true seals, eared seals and walrus
Walrus

The walrus is a large pinniped marine mammal with a discontinuous circumpolar distribution in the Arctic Ocean and sub-Arctic seas of the Northern Hemisphere....
), and several otters (the sea otter
Sea Otter

The sea otter is a marine mammal native to the coasts of the northern and eastern Pacific Ocean. Adult sea otters typically weigh between 14 and 45 Kilogram , making them the heaviest members of the Mustelidae, but among the smallest marine mammals....
 and marine otter
Marine Otter

Marine Otters are rare and poorly-known marine mammals of the weasel family . They are the most exclusively marine species of the otters of South America, and rarely even venture into freshwater or estuarine habitats....
).






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Humpback Whale Underwater Shot
Marine mammals are a diverse group of roughly 120 species of mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
 that are primarily ocean
Ocean

An ocean is a major body of Seawater, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a World Ocean that is customarily divided into several principal oceans and smaller seas....
-dwelling or depend on the ocean for food. They include the cetaceans (whales
Whale

Whales are marine mammals of order Cetacea which are neither dolphinsmembers, in other words, of the families Oceanic dolphin or River dolphinnor porpoises....
, dolphins
Dolphin

File:Bottlenose_Dolphin_KSC04pd0178.jpgDolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in seventeen genus....
, and porpoises
Porpoise

Porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen....
), the sirenians (manatees
Manatee

Manatees are large, fully aquatic marine mammals sometimes known as sea cows. The name manat? comes from the Ta?no, a pre-Columbian people of the Caribbean, meaning "breast"....
 and dugong
Dugong

The dugong is a large marine mammal which, together with the manatees, is one of four living species of the order Sirenia. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's Sea Cow , was hunted to extinction in the 18th century....
), the pinnipeds (true seals, eared seals and walrus
Walrus

The walrus is a large pinniped marine mammal with a discontinuous circumpolar distribution in the Arctic Ocean and sub-Arctic seas of the Northern Hemisphere....
), and several otters (the sea otter
Sea Otter

The sea otter is a marine mammal native to the coasts of the northern and eastern Pacific Ocean. Adult sea otters typically weigh between 14 and 45 Kilogram , making them the heaviest members of the Mustelidae, but among the smallest marine mammals....
 and marine otter
Marine Otter

Marine Otters are rare and poorly-known marine mammals of the weasel family . They are the most exclusively marine species of the otters of South America, and rarely even venture into freshwater or estuarine habitats....
). The polar bear
Polar Bear

The polar bear is a bear native to the Arctic Ocean and its surrounding seas. The world's largest carnivore found on land, and shares the title of largest land predator with the Kodiak Bear, an adult male weighs around , while an adult female is about half that size....
 is also usually grouped with the marine mammals.

Marine mammals evolved from land dwelling ancestors and share several adaptive features for life at sea such as generally large size, hydrodynamic body shapes, modified appendages and various thermoregulatory
Thermoregulation

Thermoregulation is the ability of an organism to keep its core temperature within certain boundaries, even when the surrounding temperature is very different....
 adaptations. Different species are, however, adapted to marine life to varying degrees. The most fully adapted are the cetaceans and the sirenians, whose entire life cycle takes place under water, whereas the other groups spend at least some time on land.

Despite the fact that marine mammals are highly recognizable charismatic megafauna
Charismatic megafauna

Charismatic megafauna are megafauna with widespread popular appeal that environmental activists use to achieve conservation movement goals well beyond just those species....
, many populations are vulnerable or endangered due to a history of commercial exploitation for blubber
Blubber

Blubber is a thick layer of Blood vessel fat found under the skin of all cetaceans, pinnipeds and sirenians....
, meat
Meat

In modern English usage, meat most often refers to animal biological tissue used as food, mostly skeletal muscle and associated fat, but it may also refer to offal, including livers, skin, brains, bone marrow, kidneys, in some countries lungs, and a variety of other internal organs as well as blood....
, ivory
Ivory

File:Ivory decoration.jpgIvory is formed from dentine and constitutes the bulk of the teeth and tusks of animals such as the elephant, hippopotamus, walrus, mammoth and narwhal....
 and fur
Fur

Fur is a Hair of any non-human mammal, also known as the pelage. It may consist of short ground hair, long guard hair, and, in some cases, medium awn hair....
. Most species are currently protected from commercial exploitation.

Groups

There are some 120 extant species of marine mammals, generally sub-divided into the five groups bold-faced below.

  • Order
    Order (biology)

    In Biological classification used in biology, the order is a taxonomic rank between class and family . The superorder is a rank between class and order....
     Sirenia
    Sirenia

    Sirenia is an order of fully aquatic, herbivore mammals that inhabit rivers, estuaries, coastal marine waters, swamps, and marine wetlands. The order evolved during the Eocene epoch, more than 50 million years ago....
    : Sirenians
    • family Trichechidae: manatees (3 species)
    • family Dugongidae: dugong (1 species)
  • Order Cetacea
    Cetacea

    The order Cetacea includes whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general....
    : Cetaceans
    • Suborder Mysticeti: Baleen whales (14 or 15 species)
    • Suborder Odontoceti: Toothed whales (around 73 species)
  • Order Carnivora
    Carnivora

    The diverse Order Carnivora includes over 260 species of eutheria mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal....
    ,
    • superfamily Pinniped
      Pinniped

      Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semi-aquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae ....
      ia
      • family Phocidae: true seals (around 20 species)
      • family Otariidae: eared seals (around 16 species)
      • family Odobenidae: walrus
        Walrus

        The walrus is a large pinniped marine mammal with a discontinuous circumpolar distribution in the Arctic Ocean and sub-Arctic seas of the Northern Hemisphere....
         (1 species)
    • family Mustelidae
      Mustelidae

      Mustelidae or Mustelids , commonly referred to as the weasel family, is a family of carnivora mammals. The Mustelidae is a diverse family and the largest in the order Carnivora, at least partly because it has in the past been a catch-all category for many early or poorly differentiated taxa....
      • sea otter
        Sea Otter

        The sea otter is a marine mammal native to the coasts of the northern and eastern Pacific Ocean. Adult sea otters typically weigh between 14 and 45 Kilogram , making them the heaviest members of the Mustelidae, but among the smallest marine mammals....
         (Enhydra lutris)
      • marine otter
        Marine Otter

        Marine Otters are rare and poorly-known marine mammals of the weasel family . They are the most exclusively marine species of the otters of South America, and rarely even venture into freshwater or estuarine habitats....
         (Lontra felina)
    • family Ursidae
      • polar bear
        Polar Bear

        The polar bear is a bear native to the Arctic Ocean and its surrounding seas. The world's largest carnivore found on land, and shares the title of largest land predator with the Kodiak Bear, an adult male weighs around , while an adult female is about half that size....
         (Ursus maritimus)


The sirenians and cetaceans are thought to be descendent from an ungulate
Ungulate

Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving....
 ancestor, while the pinnipeds, otters and polar bear are descended from a caniform ancestor. The morphological
Morphology (biology)

The term morphology in biology refers to form, structure and configuration of an organism. This includes aspects of the outward appearance as well as the form and structure of the internal parts like bones and organs....
 similarities between these diverse groups are a result of convergent
Convergent evolution

Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action....
 and parallel evolution
Parallel evolution

Parallel evolution is the independent evolution of similar traits, starting from a similar ancestral condition due to similar environments or other evolutionary pressures....
.

Several groups of marine mammals existed in the past that are not alive today. In addition to the ancestors of the modern day whales
Evolution of cetaceans

The cetaceans are descendants of land-living mammals. Their terrestrial origins are specifically indicated by:* Their need to breathe air from the surface;...
, seals, and manatees, there existed desmostylia
Desmostylia

The Desmostylia are an extinct order of marine mammals which existed from the Arikareean age of the late Oligocene epoch to the Tortonian age of the late Miocene epoch ....
ns, cousins of the manatees, and Kolponomos
Kolponomos

Kolponomos is an extinct genus of marine mammal bears which existed from the Hemingfordian age to the Aquitanian age of the Miocene epoch, about 20 million years ago....
, a species of clam-eating marine bears not related to the modern polar bear.

Adaptations

Since mammals originally evolved on land, their spine
Vertebral column

In human anatomy, the vertebral column is a column of 24 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsum aspect of the torso, separated by spinal discs....
s are optimized for running, allowing for up-and-down but only little sideways motion. Therefore, marine mammals typically swim by moving their spine up and down. By contrast, fish normally swim by moving their spine sideways. For this reason, fish mostly have vertical caudal (tail) fins, while marine mammals have horizontal caudal fins.

Some of the primary differences between marine mammals and other marine life are:

  • Marine mammals breathe air, while most other marine animals extract oxygen from water.
  • Marine mammals have hair. Cetacea
    Cetacea

    The order Cetacea includes whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general....
    ns have little or no hair, usually a very few bristles retained around the head or mouth. All members of the Carnivora
    Carnivora

    The diverse Order Carnivora includes over 260 species of eutheria mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal....
     have a coat of fur or hair, but it is far thicker and more important for thermoregulation
    Thermoregulation

    Thermoregulation is the ability of an organism to keep its core temperature within certain boundaries, even when the surrounding temperature is very different....
     in sea otters
    Sea Otter

    The sea otter is a marine mammal native to the coasts of the northern and eastern Pacific Ocean. Adult sea otters typically weigh between 14 and 45 Kilogram , making them the heaviest members of the Mustelidae, but among the smallest marine mammals....
     and polar bears
    Polar Bear

    The polar bear is a bear native to the Arctic Ocean and its surrounding seas. The world's largest carnivore found on land, and shares the title of largest land predator with the Kodiak Bear, an adult male weighs around , while an adult female is about half that size....
     than in seals
    Pinniped

    Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semi-aquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae ....
     or sea lions. Thick layers of fur contribute to drag while swimming, and slow down a swimming mammal, giving it a disadvantage in speed.
  • Marine mammals have thick layers of blubber
    Blubber

    Blubber is a thick layer of Blood vessel fat found under the skin of all cetaceans, pinnipeds and sirenians....
     used to insulate their bodies and prevent heat loss. Sea otters and polar bears
    Polar Bear

    The polar bear is a bear native to the Arctic Ocean and its surrounding seas. The world's largest carnivore found on land, and shares the title of largest land predator with the Kodiak Bear, an adult male weighs around , while an adult female is about half that size....
     are exceptions, relying more on fur and behavior to stave off hypothermia.
  • Marine mammals give birth. Most marine mammals give birth to one calf or pup at a time.
  • Marine mammals feed off milk as young. Maternal care is extremely important to the survival of offspring that need to develop a thick insulating layer of blubber
    Blubber

    Blubber is a thick layer of Blood vessel fat found under the skin of all cetaceans, pinnipeds and sirenians....
    . The milk from the mammary gland
    Mammary gland

    Mammary glands are the organ s that, in mammals, produce milk for the sustenance of the young. These exocrine glands are enlarged and modified sweat glands and give mammals their name....
    s of marine mammals often exceeds 40-50% fat content to support the development of blubber in the young.
  • Marine mammals maintain a high internal body temperature. Unlike most other marine life, marine mammals carefully maintain a core temperature much higher than their environment. Blubber
    Blubber

    Blubber is a thick layer of Blood vessel fat found under the skin of all cetaceans, pinnipeds and sirenians....
    , thick coats of fur
    Fur

    Fur is a Hair of any non-human mammal, also known as the pelage. It may consist of short ground hair, long guard hair, and, in some cases, medium awn hair....
    , bubbles of air between skin and water, countercurrent exchange
    Countercurrent exchange

    Countercurrent exchange along with Concurrent exchange comprise the mechanisms used to transfer some property of a fluid from one flowing current of fluid to another across a semipermeable membrane or thermally-conductive material between them....
    , and behaviors such as hauling out, are all adaptation
    Adaptation

    Adaptation is the process, which takes place under natural selection, whereby an organism becomes better suited to its habitat. Also, the term may refer to some characteristic which stands out as being especially significant in the organism's survival....
    s that aid marine mammals in retention of body heat.


The polar bear
Polar Bear

The polar bear is a bear native to the Arctic Ocean and its surrounding seas. The world's largest carnivore found on land, and shares the title of largest land predator with the Kodiak Bear, an adult male weighs around , while an adult female is about half that size....
 spends a large portion of its time in a marine environment, albeit a frozen one. When it does swim in the open sea it is extremely proficient and has been shown to cover 74 km in a day. For these reasons, some scientists regard it as a marine mammal.

Research


Considerable research has been conducted on the incidence of diseases that afflict marine mammals in the marine environment. This work has addressed leptospirosis
Leptospirosis

Leptospirosis is a infectious disease zoonotic disease caused by spirochaetes of the genus Leptospira that affects humans and a wide range of animals, including mammals, birds, amphibians, and reptiles....
, phocine herpesvirus, neurological diseases, toxicology and other pathologies affecting marine mammals. Entire research organizations have developed such as the Marine Mammal Center to focus upon the rehabilitation and research functions of marine mammals.

See also

  • Institute for Marine Mammal Studies
    Institute for Marine Mammal Studies

    The Institute for Marine Mammal Studies is a major non-profit organization established in 1984 for the education, conservation, and research on marine mammals in the wild and in captivity....


External links

  • by the National Academy of Sciences
    United States National Academy of Sciences

    The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine."...
     entitled Marine Mammal Populations and Ocean Noise, is available for free online reading and research
  • University of Washington Libraries Digital Collections -- An ongoing digital collection of images related to marine and aquatic mammals.