Foraging is defined as the searching for food, and through studies, it has been found that animals tend to choose a prey that gives the highest rate of energy return. Foraging behaviors can change for many animals because availability of food changed depending on the space and time. For instance, if there are low availability of prey, animals tend to eat all sizes of that prey. However, if the prey is readily available, animals tend to eat larger sizes of their prey.
Many animal species show rhythmical behavior, which can be in an annual cycle. For instance, mate selection in certain animals only occurs during certain seasons. For some animals such as the red deer, this is so that the babies are born in the spring when food is readily available. There can also be daily cycles such as diurnal sleep and nocturnal activity in hamsters.
Some species have exaggerated traits, which can be in the form of behavior or anatomical features. An example is the tail feathers of the peacock, that is very showy to attract mate. Such traits indicates fitness and the possession of good genes.