Animal locomotion

Locomotion is the scientific term for how animals move from one place to another. In the field of ethology, which is the study of animal behavior, researchers look at how different species navigate their worlds. Animals move for several vital reasons. They must find food and locate mates. They also seek out suitable microhabitats or try to escape from predators. Because movement is essential for survival, natural selection has shaped the specific mechanisms animals use.

There are two main categories of movement: self-propelled and passive locomotion. Self-propelled locomotion occurs when an animal uses its own energy to move. This includes running, swimming, jumping, flying, and soaring. Passive locomotion is different because the animal depends on its environment for transportation. Examples include sailing, kiting, or riding on other animals, a process known as phoresis. The structures used for these movements, such as legs, wings, or fins, are called locomotory organs.

Aquatic locomotion requires animals to manage buoyancy and drag. Buoyancy is the ability to stay afloat. If an animal is less dense than water, it stays afloat with little energy. However, moving horizontally through water is difficult because drag is much greater than in air. Many fish use a fusiform body shape, which is torpedo-like, to move efficiently. Most fish generate thrust by oscillating their bodies from side to side. This wave motion ends at a large tail fin. Other fish, like electric rays, use pectoral fins for labriform swimming.

Cephalopods and marine mammals use different aquatic strategies. Some cephalopods use jet propulsion. They take in water and then squirt it out in an explosive burst to move fast. Marine mammals, such as dolphins, oscillate their bodies in a dorso-ventral direction, which means up and down. Dolphins can also engage in interesting behaviors like surfing on waves. Benthic locomotion refers to animals that live on or near the bottom of the sea. Echinoderms use tube feet with suction-pad tips to move. They use muscle contractions and mucus to create adhesion to the seabed.

Aerial locomotion is a major challenge due to gravity. Flying animals must generate lift to overcome the downward pull of the earth. Active flight has evolved independently at least four times in history. Insects were the first to fly, approximately 400 million years ago. Pterosaurs followed around 220 million years ago. Birds evolved flight about 160 million years ago. Bats were the last major group to develop flight, roughly 60 million years ago.

Some animals use gliding, or volplaning, instead of constant flapping. Gliding is a form of heavier-than-air flight that uses no thrust. It allows an animal to travel horizontally while descending. Many animals glide, including flying squirrels and certain snakes. Some birds use soaring to stay aloft without flapping. They use rising air currents like thermals or ridge lift. Albatrosses use dynamic soaring near the surface of the sea. Even some aquatic animals like the Pacific flying squid use gliding to escape predators.

Terrestrial locomotion requires a strong skeletal and muscular framework for support. On land, animals must overcome inertia and maintain balance. Some animals use saltation, which is the scientific term for jumping. While many animals run, only a few use jumping as their primary way to move. Examples include kangaroos and rabbits. The Australian rocket frog is an incredible jumper. It can leap over fifty times its own body length.

Locomotion methods are often specialized based on energy needs. Migratory animals, like the Arctic tern, travel vast distances. Their locomotion mechanisms are designed to cost very little energy per unit of distance. In contrast, animals that must escape predators quickly use energetically costly locomotion. These methods are much faster but require more fuel. Whether an animal is a small beetle larva or a large whale, its method of movement is a specialized tool for survival.