Aggression is used by various animals to acquire resources such as food. Researchers on the African savannas commonly enjoy keeping track of which hyenas killed a wildebeest, which lions took the carcass from them (or vice versa), and which jackals and vultures competed to snatch a morsel before being chased away. These forms of battles create a spectacular scene to watch. Most creatures do not generally clash in this way. The wildebeest being beaten over didn’t, in life, stage bloody battles with other wildebeest over which among them would graze a plot of grass.
Competition requires lots of energy, and many species seem to minimize such conflicts. In some animals there are postures of surrender that tame the aggressor of the like species. The monkey faces away, the wolf rolls over, and the assailant ceases. What does an attacker experience whose assault is stopped in this action? For many animals the creature potentially to be its closest competitor, to want the same foods or similar nest sites, is one of its species, in a few cases, its own partner. Research remarks that size variation in some species adds to the survival advantage. For example, a female osprey is larger than her mate; they gather fish of various sizes, which lowers rivalry between them, increasing their collective food supply.
It has been observed that parrots seem to enjoy having enemies. This could in a way, boost flock solidarity, prevent interbreeding between species, strengthen the pair bond, or hold other valuable function. In chickens, there is such a thing called “pecking orders,” ethologists have observed these behavior in many flocks. This behavior is now identified as dominance hierarchies.
The notion of dominant and submissive animals has obtained a growing popularity in species in the same way as the idea that aggression is valuable as it helps a creature dominate.
In subsequent years the dominance hierarchy idea became more questionable, with a couple of scientists postulating if such hierarchies are genuine or merely a product of human perception. It is worth taking note that among wild flocks, chickens do not organize strict pecking orders as they do in poultry farms.