Mammals

Mammals are warm-blooded creatures. Whether they live in a hot or cold climate, their body temperature remains constant. Mammals are vertebrates, having a backbone, and most give birth to live young.

The Importance of Mammals

Mammals play an important part of the food chain in one of three ways:

  • carnivores – diet consists of the meat of other animals
  • herbivores – diet consists of plants
  • omnivores – diet consists of both animals and plants

Mammals are a major food source for humans and a source of income for many. Hunting is a multi-million industry and the fur of many mammals is harvested to be sold.

Advances in science can, in a large part, be attributed to mammals’ role in laboratory study and it is through this study that advances have also been made towards the ethical treatment of animals and the evolution of the animal rights movement.

The quest for animals such as beavers and whales led to the exploration and colonization of many parts of the world, including Canada. Some mammals were hunted to the point of extinction, which created an awareness of their importance in biodiversity and helped to shape conservation guidelines.

Characteristics

Mammals share several common traits that make them unique:

  • Aortic arch: The main artery leaving the heart curves to the left.
  • Diaphragm: Separates the heart and lungs from the abdomen.
  • Hair: Mammals are the only animal or organism that can grow hair. All have some form of it.
  • Hinged lower jaw: Lower jaw is hinged directly to the skull instead of through a separate bone.
  • Mammary glands: These glands are found in both males and females, but develop fully only in females, which means only females can produce milk to feed their young.
  • Three middle ear bones: The hammer, anvil, and stirrup transmit vibrations from the eardrum.

Classification

Mammals are named for the Class of vertebrates they are classified under, Mammalia. Within this Class, there are three subclasses of mammals:

  • Eutheria: with a placenta, like a human or dog.
  • Metatheria: with a pouch like the kangaroo, known as marsupials
  • Prototheria: can lay eggs, like the duckbill platypus.

Only representatives of the eutheria subclass can be found in Alberta. Worldwide, this subclass is further divided into 18 orders:

  • Artiodactyla: even-toed ungulates, known as cloven-hoofed (pigs, hippos, giraffes, deer, etc.)
  • Carnivora: meat eating (wolves, bears, cats, etc.)
  • Cetacea: whale-like (whales, dolphins, and porpoises)
  • Chiroptera: finger-winged (bats)
  • Dermoptera: skin-winged (flying lemurs)
  • Hyracoida: hyraxes
  • Insectivora: insect eaters (shrews, hedgehogs, and moles)
  • Lagomorpha: hare like (rabbits, hares, and pikas)
  • Macroscelidia: elephant shrew
  • Perissodactyla: odd-toed ungulates (horses, rhinoceros, zebras, etc)
  • Pholidota: scaly anteaters (have no teeth, not related to other anteaters)
  • Primates: monkeys, apes, gibbons, etc.
  • Proboscidea: eat with nose (elephants)
  • Rodentia: gnawing (squirrels, rats, mice, etc.)
  • Scandentia: climbing mammals (tree shrews)
  • Sirenia: even toed (dugongs and manatees)
  • Tubulidentata: tube-toothed (aardvarks)
  • Xenarthra: anteaters, sloths, armadillos

Lifecycle

The young of most mammals grow inside the mother’s body. Gestation time (the time spent in womb) varies greatly, from as short as 12 days for the Virginia opossum to as long as 22 months for the African elephants. In most cases, the larger the animal, the longer the gestation period is.

Mammals nurse their young with milk and care for them until they are ready to live on their own. Baby mammals learn by copying the actions of their mothers.

 

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Updated: August 20, 2009