Various Methods of Mammalian Locomotion

How Mammals Overcome Friction and Gravity to get Around

Oct 1, 2009

The various ways that mammals move around is diverse. They swim, run, crawl, walk, hop and some even fly.

Locomotion requires a lot of energy to overcome gravity and friction, two forces that tend to keep things stationary. Running mammals generally require more energy than swimming, as do flying mammals, of which there are only bats that really fly as opposed to gliding.

Swimming Mammal Locomotion

For mammals that are specialized for swimming, being buoyant means that they don’t need to use much energy overcoming gravity as opposed to terrestrial or flying mammals. Water is however, much more dense than air, so the problem of friction or drag, needs to be overcome.

Thus, most marine mammals have a streamlined fusiform shape (torpedo-like), which allows their sleek bodies to move through the water. They are able to swim showing almost no water turbulence, even at high speeds. Swimming is the most energy efficient means of transport.

Terrestrial (Land) Mammal Locomotion

Terrestrial mammals walk, hop, crawl, jump and run. These animals need to support themselves and move against gravity. When land animals move, leg muscles expend energy to propel them forward and prevent them from falling over. Mammals on land have therefore evolved strong skeletal support and powerful muscles.

One example is the kangaroo, which hops or jumps to move around. Muscles in the hind legs of the kangaroo need to generate a lot of power. As a kangaroo lands, tendons in the hind legs store energy that is available for the next jump.

The higher the jump, the more energy the tendons store for the next jump. This makes hopping an energy efficient form of locomotion for the kangaroo because it reduces the total amount of energy needed.

Maintaining balance is important for land mammals. When a bipedal or quadrupedal animal moves, its center of mass rises and falls with the gait. The kangaroo’s large tail helps with balance when it is hopping and also acts like a tripod leg when the kangaroo is stationary.

Biped animals such as humans or apes will often keep one foot on the ground to maintain balance during walking. Quadrupedal animals such as the cat or horse will keep three feet on the ground while walking. When running, whether they be bipedal or quadrupedal, there may be times when no feet are touching the ground, however, momentum keeps the animal from falling.

Flying Mammal Locomotion

For the flying mammal, the bat, gravity poses the biggest problem. Air offers no buoyant support so bats must utilize the principles of aerodynamic lift. There is less need for bats to be streamlined like marine mammals because air produces less drag than water.

Wing movement during flight generates forces that propel the bat forward and keeps it up in the air. The downstroke of the wing creates thrust and lift, which opposes drag and weight. The wing being driven downward and forward pushes air downward and backward, thus creating an upward and forward thrust.

While all forms of locomotion requires energy, running or walking is less efficient than flying or swimming because muscles are used for deceleration as well as acceleration, however, all mammals have evolved to enhance their locomotory efficiencies to save energy.

Randall, Burggren & French, 2002, ‘Energy Expenditure: Body Size, Locomotion and Reproduction’, in Animal Physiology, Mechanism and Adaptations, ed. W.H. Freedman and Company, New York, chapter 16.

Campbell and Reece, 2002, 'Sensory and Motor Mechanisms', in Biology 6th edition, ed. Benjamin Cummings, San Francisco, chap 49

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