An Introduction to Mammals

Mammals have successfully adapted to and colonized a wide variety of habitats including land, air, and water. Their widespread success is largely due to their ability to regulate their own body temperature. But mammals have also evolved many other unique adaptations to help them succeed in numerous environments, as is illustrated by their many forms of locomotion.

Mammals are endothermic, that is, they maintain a constant body temperature independent of their environment. This characteristic has enabled mammals to occupy a wide range of habitats since they can remain active in extreme temperatures. The hypothalamus, an area of the mammalian brain, maintains and monitors body temperature. By increasing metabolic rate, body temperature can be increased. By decreasing metabolic rate, body temperature can be decreased. Additionally, the ability to widen or constrict blood vessels provides another means by which heat can be carried to or restricted from parts of a mammal's body. Behavior also can help to regulate body temperature. Groups of mammals can huddle together for warmth or descend into cool burrows to avoid extreme heat.

Mammals are the only animals that have hair covering their body, a rod of cells that are strengthened by the protein keratin. The different types of hair mammals have include fur, whiskers, spines, and horns. Fur provides protection for the skin and insulates the animal. Whiskers provide sensory information for animals. Spines (such as the quills of a porcupine) provide protection.

The ways in which mammals move from place to place is greatly varied. Some mammals use four limbs to walk (such animals are referred to as quadrapedal) while others use only two (such animals are referred to as bipedal). The greatest differences in locomotion adaptation can be seen when comparing mammals from very different habitats. Dolphins, adapted for an aquatic lifestyle, have flippers to help them glide through the water. The jaguar, a terrestrial carnivore with explosive running power, is adapted for speed on land. The limbs of bats have evolved into wings enabling them to inhabit the skies.