Mammalia - Mammals

Kingdom - Animalia
    Phylum - Chordata
        Subphylum - Vertebrata
            Class - Mammalia

Basic Features:

Mammals are a Class in the Subphylum Vertebrata of the Phylum Chordata, so they have all of the characteristics of both of these groups in addition to the following:

• Waterproof skin with hair or fur.
• Endothermic, warm blooded.
• Give birth to live young.
• The young are supplied with milk from mammary glands by the mother(from which the group gets their name).
• Three middle ear bones.
• Heterodont dentition, different types of teeth.

What do mammals eat?

There are about 5,500 mammal species so far described and between them, they eat just about everything they can lay their jaws on. Some are very specialized such as anteaters, others will eat anything and everything as do rats. Here are a few notable dining preferences.

Grass - most mammals by sheer numbers are herbivores and many mammalian herbivores eat grass. Grass is tough stuff to deal with and takes time to digest and most non-mammals just can't deal with it. Mammals have a perfect combination of large size and a warm body temperature to enable them to handle eating grass. It takes time to ferment the tough leaves and stems and break down the compounds that are there for the taking if you can get at them. As it happens mammals can't actually do this themselves, they need a gut fauna of bacteria to do it for them. They start with strong grinding teeth and jaw muscles and then move on to complex and/or long digestive systems that create a perfect place for the bacteria to grow to work on the grass for long enough to break it down. Cattle, deer, sheep, goats, rabbits, antelope, gazelle, horses and a whole host of other mammals just love grass!

Other tough plant material such as leaves, and bark, plant shoots and twigs. For the same reason and in the same way as they can eat grass, many mammals can tackle even tougher stuff too. Goats, giraffes and elephants for instance can get nutrition from materials that most animals would get next to nothing from at all.

Insects:

• Bats in particular like to eat insects. Some small bats can eat about 1,000 mosquitoes an hour in the summer. Bats can get through 50-100% of their body weight in insects in a night. There is a place in Texas called Bracken Cave where 30 million Mexican free-tailed bats live, between them they get though around 250 tons of insects a night in summer. Bats will however catch and eat just about any flying insect they can get, moths, flies, beetles etc.
  
  
• Anteaters, armadillos, pangolins, echidnas and aardvarks are specialist eaters of ants and termites.
  
  
• Humans - insects are regarded as a delicacy in some parts of the world, flying ants in many parts of Africa and many kinds of insects in S.E. Asia.

Krill - this small Antarctic crustacean related to and looking like a swimming shrimp is one of the most populous animals by numbers and weight on earth. It is the staple food of the mis-named crabeater seal which is the second most numerous large mammal on earth after man. It is also eaten in huge quantities by the great whales, at the rate of 3-4 tonnes a day by a single large blue whale in the Antarctic summer for instance. When the whales were decimated by hunting, the population of Antarctic Fur Seals increased around the island of South Georgia to a current level of around 4 million

Other mammals - we've all seen hunting scenes on wildlife documentaries by wolves, polar bears, lions, tigers and other big cats and in the main they are hunting other mammals whether they be deer, antelope, seals or just anything smaller than they are that has happened to catch their eye.

What eats mammals?

If you're a small mammal such as a mouse, lemming, or rabbit, then just about any carnivore that is bigger than you will try to eat you. This may be another mammal such as a member of the cat or dog families or a bird of prey, many of which eat small mammals exclusively or opportunistically.

Even if you're quite a large mammal such as a deer, antelope, giraffe, buffalo or wildebeest, other mammals such as large pack hunting members of the cat and dog families but also bears depending on where you live. It is almost entirely the young or old or infirm that are hunted and killed in this way, large adult mammals in good condition can usually run away or protect themselves from predators. An adult giraffe or zebra can kill or maim a adult lion with a single kick for instance.

Even large whales are not immune, killer whales or Orcas will chase young whales or elderly or sick adults of much larger species. They kill them by biting the huge tongue which leads to the whale bleeding to death, sometimes the rest of the whale is left to sink and only the tongue is eaten.

Polar bears - feed by preference on seals that they catch on the sea ice.

Many snakes target mammals. Snakes can see in infra-red as they are cold blooded, this gives them a night vision to spot and attack small mammals many of which are nocturnal.

Man - of course, many of our favourite foods are mammals, especially beef, pork and lamb.

The group includes:

Like most groups of living things, the status of mammal groups, whether they are Classes, Orders, infraorders, subclasses etc. is something that is currently changing and somewhat confusing as to what they should be called. I have named some of the major groups without saying which level the group is (class, order, etc.) as doubtless the hierarchy will change whereas the names are relatively constant. The following list is representative but not complete:

• Artiodactyla - Even-toed ungulates (hoofed animals), the weight is carried almost equally on the third and fourth toes which allows them to traverse uneven surfaces - pigs, cattle, sheep, goats, deer, antelopes, giraffes, hippos.
  
  
• Carnivora - Carnivores, though mammals in other groups can be carnivores too. Land animals in the main with prominent canine teeth and carnassial teeth for shearing meat, usually powerful sharp claws. - wolves, dogs, foxes, cats, bears, skunks, badgers, seals, otters
  
  
• Cetacea - Marine mammals including all whales, dolphins and porpoises. Evolved about 50 million years ago from land animals. The most adapted of all mammals for living in water and amongst the most intelligent of all animals.
  
  
• Chiroptera - Bats. The only mammals that are active fliers capable of sustained true flight rather than simply gliding. The arm and fingers are developed into a frame-work to carry a skin membrane. About 20% of all mammal species are bats. They are surprisingly slow breeders and long lived for their size, mainly having one offspring a year and living for 5-6 years, even up 30-40 years if they are lucky  - fruit bat, vampire bat, flying fox, pipistrelle.
  
  
• Edentata (Xenarthra) - A group only found today in the Americas, there were a number of giant members of the group that are now all extinct - anteaters, sloths, armadillos.
  
  
• Hyracoidea - Hyraxes. A small group of 4 species that look quite like rodents about 2-5kg in weight though are more closely related to elephants.
  
  
• Lagomorpha - An almost exclusively herbivorous group with an unusual double-digestion where food is initially fermented in a part of the gut called the caecum, then voided as moist pellets which are immediately eaten again, after the second time through they are voided as dry pellets - rabbits, hares, pikas.
  
  
• Macroscelidea - elephant shrews. Small very active insectivorous mammals with elongated snouts.
  
  
• Perissodactyla - Odd-toed ungulates (hooved animals) the middle toe on each hind limb is usually the largest, the others may be much smaller or even absent altogether - horses, rhinos, tapirs.
  
  
• Pholidota - Scaly anteater or pangolin. Uniquely covered in overlapping keratin scales that it uses as armour when threatened and rolls up into a ball.
  
  
• Primates - A group that originally evolved as tree-dwellers, some members then came down onto the ground, most species spend at least some part of their lives in trees. Opposable thumbs and prehensile tails in some species. Vision is the main sense at the expense of smell. Relatively slow reproductive rates but longer lifespans - baboons, gibbons, apes (no tail) humans, lemurs, monkeys (with a tail).
  
  
• Proboscidea - Trunked animals, more numerous and varied species in the past, just three surviving species today - African elephant ttwo species-maybe), Indian elephant.
  
  
• Rodentia - The largest of the mammal groups with around 40% of species. Defined by having a pair of incisor teeth in each jaw that grow continually and must be kept short by gnawing. Generally small animals often with highly developed social behaviour. Mainly herbivorous or omnivorous - mice, rats, squirrels, beavers, porcupines, gerbils, hamsters, guinea pigs.
  
  
• Sirenia - Fully aquatic herbivores of rivers, lakes and sheltered coastal waters. The forelimbs are paddle-like and the tail is a paddle for propulsion, the hind limbs have degenerated - dugongs, manatees.