Animal Behavior

Have you ever left a fruit bowl out for a while and return to discover a fruit fly settlement? But why is the fruit fly attracted to ripe fruit in the first place? In other words, what is the stimulus that tells them where to go? This analysis is part of a wider field called ethology, which is the study of animal behavior.

A stimulus may cause two types of animal movement. Kinesis, which is non-directional or random, or taxis, which is directional. An example of kinesis would be the movement of the flies in random directions when chased away. Conversely, an example of taxis would be the directed movement of the flies back towards the ripe fruit. This specific type of taxis is referred to as chemotaxis and since it is towards the stimulant, food, it is further defined as positive chemotaxis. An example of negative chemotaxis would be the fly moving away from an insect repellent. Another common type of taxis is phototaxis, which is movement is response to a light stimulus. Moths are showing positive phototaxis when they move towards a light source. On the contrary, cockroaches that scuttle away when the light is turned on are being negatively phototactic. Geotaxis, also known as grav