A group of vertebrate animals form the class Mammalia, one of the six main classes of animals. These classes categorize animals with similar characteristics into specific groups. There are roughly 4500-5000 different species of mammals. This compares to 21,000 species of fish and 800,000 species of insects!

Primary characteristics of mammals are that:

  1. they are warm-blooded,
  2. they have a 4-chambered heart
  3. have 4 limbs (even though some such as the manatees, whales and dogongs lost their hind limbs through evolution),
  4. they have sweat glands,
  5. they have a single jaw bone
  6. with mammary glands, the females suckle their young.

Mammals first appeared on the earth in the Jurassic Period, about 200 million years ago and have colonized the entire earth. Mammals include some of the largest animals on earth such as the elephant and the whale, and some of the smallest, such as the bumblebee bat which is just an inch long and weighs 0.07 oz.

Other Information that might be useful

Warm Blooded

Mammals are warm-blooded and can keep their body temperature roughly the same regardless of the environmental temperature. This allows them to be active whenever they want to be and enables them to live in all sorts of environments.

Hair or fur, insulating layers of fat, plus sweat glands and panting allow mammals to regulate their body temperatures so they can live in cold or hot places, under ground, in trees, in caves, in the oceans and to fly through the air.

They All Have Hair (of some sort)

Although some mammals have lost their hair (some or all of it) like the mole rat and the whale, all mammals have either lots or a little hair. In fact, they are the only animals that have true hair. Hair is made of keratin and this substance is also responsible for fur, fingernails, hooves and claws.

Some animals are completely covered with hair while others have just a bit of hair like the ones who live in the sea – you’d need a magnifying glass to see the hair on the lips of young whales.

Producing Offspring

While most give birth to live offspring, only a few mammals lay eggs (including the platypus, these mammals are called monotremes),

Having mammary glands means females can produce milk with which to suckle their young. Producing live young puts limits on the number a female can have at any one time, but mammals care for their young for a period long enough to ensure the young are able to survive on their own. The length of time parents care for their young varies depending on the species; consider how long humans care for their offspring.

Mammals are divided into about 21 groups and within those groups approx. 5400 species are alive today.

Taxonomic Group  SpeciesAlive Today Comments
Aardvark 1 these are solitary, nocturnal animals whose primary food source are ants and termites – aardvark
Armadillos, sloths & anteaters 29 their backbones are uniquely jointed, they have a small brain and almost no teeth – includes anteaters, armadillos & sloths
Bats 997 these are the only mammals with wings and capable of true flight – both microbats & megabats
Carnivores 250 they are skilled predators that have evolved a keen sense of smell, sharp teeth, claws & superb eyesight – wolves, dogs, foxes, hyenas, cats, aardwolves, mongooses, racoons, bears & others
Cetaceans  88 these marine mammals have adapted well to living in water – they are primarily various whales
Colugos 2 they have a flap of skin between body and limbs making them skilled gliders and live in Southeast Asian forests – colugos
Elephant shrews  12 they are small mammals that have long noses and eat insects – various elephant shrews
Elephants 3 these are the biggest land animal living today – Asian, African & African Savannah elephants
Hares, rabbits & pikas 87 they have a short tail, wide-set eyes and long ears, and in the ecosystems they inhabit, they are an important prey species
Hoofed mammalseven-toed 225 their feet are structured so that body weight is borne on the 3rd & 4th toes – they include hippos, cows, pigs, goats, deer, sheep, llamas, antelope & others
Hoofed mammalsodd-toed 19 their feet are structured so that body weight is borne on the 3rd (middle) toe – they include tapirs, horses & rhinoceroses
Hyraxes 8 small herbivores with a multi-chambered stomach which enables them to digest tough plant material
Insectivores 365 small nocturnal mammals that feed on insects – including moles, hedgehogs, moonrats & shrews
Marsupials 250 they give birth to young in their early development and the offspring’s development continue in a pouch located on the mother’s abdomen, a marsupium- includes kangaroos, koalas, wombats, wallabies, bandicoots, opossums & numbats
Monotremes 5 different than other mammals, they lay eggs rather than giving birth to live offspring- the platypus and echidnas (4 species)
Pangolins 8 they have large plate-like scales covering their bodies – includes giant pangolin, tree pangolin, Chinese pangolin, Indian pangolin
Primates 356 they live in complex social units, some species have adapted to living in trees – monkeys, apes, humans & prosimians,
Rodents 2000 accounting for nearly 40% of all mammals, they have colonized every continent except Antarctica – includes porcupines, squirrels, beavers, guinea pigs, hamsters, rats & mice
Seals & sea lions 33 they have broad flippers, streamlined bodies and a thick layer of insulating blubber – walrus, sea lions, true seals & fur seals
Sirenians 4 these large aquatic mammals inhabit swamps, estuaries, rivers and coastal marine waters – dugong & 3 species of manatees
Treeshrews  19 these medium-sized mammals have a long tail and slender bodies

Mammals Africa – Lots of interesting information, regularly updated on African mammals.

Leave a Reply

Your email address will not be published.