In biology and physics, animal locomotion is the study of how animals move, and is part of biophysics.
Much of the study is an application of Newton's third law of motion: if at rest, to move forwards an animal must push something backwards. Terrestrial animals must push the solid ground, swimming and flying animals must push against a fluid (either air or water). The topic splits into five disjoint categories:
- animal locomotion on land (walking and running)
- animal locomotion in air (flying)
- animal locomotion in water (swimming including fish and ducks)
- animal locomotion on the surface layer (small animals relying on surface tension such as the water strider)
- animal locomotion by water-walkers (the basilisk lizard ).
The distinction between the second and third topics is that in the second, the animal does not need to expend energy to defeat gravity; in or on the water, buoyancy counteracts the animal's weight.
