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# Characteristics of Mammals

What is a mammal? There are over 5000 species of mammals and a great amount of variety among them. The hog-nosed bat weighs only 1.5 grams and the largest mammal a blue whale can weigh up to 300,000 pounds.
A wolf may travel an area of 400 square miles but a mole rat may never leave its burrow. A horse will eat plants it’s entire life and a lion is an efficient hunter. There are over 4,000 different species of mammals but what makes a mammal unique?
• All mammals have a backbone and spinal cord. The vertebrae protect the spinal cord which delivers electrical signals from the brain throughout the body. These electrical signals help mammals run, jump, swim, and many other tasks.
• All mammals have hair. The hair protects the mammal from the sun, freezing rain, and slows evaporation of moisture.
• Mammals have special glands called mammary glands that secrete milk which allows mammals to provide milk for their young. The young of mammals depend on this milk at the beginning of their life. The hooded seal only nurses her young for 4 days and an orangutans nurse their young for 7 years.
• Mammals also have sweat glands that help them cool down when it is hot outside.
• Mammals have a four chamber heart. This heart has two upper chambers called atriums and two lower chambers called ventricles. The four chamber heart allows mammals to pump large volumes of blood and oxygen throughout their body.
• Mammals have different types of teeth which serve many purposes.
• Mammals are endothermic or warm-blooded which means they can generate internal heat to moderate body temperature. Their body temperature does not rely on their surroundings like the temperature of reptiles.
• Mammals have a unique jaw shape. Their lower jaw or mandible forms a
• joint, in other words, it articulates with the skull. They also have an arch called the zygomatic arch.
• Almost all mammals have external ears which allow them to hear. The platypus does not have external ears but hears with its bill along with several marine mammals like the dolphin don’t have external ears. The large external ears of an elephant allow it to hear and help cool the elephant.

Lions
Tigers
Lynx
Cats
Elephants
Fox
Wolve
Rhinoceroses
Llamas
Camels
Bears
Giraffes
Deer
Weasels
Mongoose
Hyenas

Seals
Antelopes
Beavers
Squirrels
Voles
Manatees
Lemmings
Lemurs
Anteaters
Shrews
Monkeys
Gorillas
Wallabies
Bats
Seals
Porcupines

Gazelles
Shrews
Deer
Humans
Dogs
Martens
Skunks
Otters