Dominance hierarchy is defined as a form of animal social structure in which a linear or nearly linear ranking exists, with each animal dominant over those below it and submissive to those above it in the hierarchy. Such a hierarchy is common amongst species of fish, birds like hens and mammals like baboons, wolves, etc. This concept was first suggested by Norwegian scientist Thorleif Schjelderup-Ebbe who studied the peaceful co-existence of hens in the same group. Read more to understand this concept in detail.
Nature of Dominance Hierarchy
Dominance hierarchy can be broadly differentiated into two types:
This kind of dominance hierarchy can be depicted with the help of a hierarchy pyramid. Here, individuals on a particular level use their power to dominate on other individuals that are in lower order or level but at the same time, they tend to be submissive to individuals in orders above them. Such individuals can be seen to get influenced by social interactions and they also tend to have a much better access to food and other facilities. This point was highlighted in behavior displayed by hens wherein, hens in the lower linear order ate their feed only after hens in higher linear order had eaten their share.
This refers to a dominance by one single individual on rest of the group or clan. The orders and instructions given by the pack leader or the troupe leader are followed submissively by the rest of the group members. There is no tussle for superiority between the followers.
Effects of Dominance Hierarchy
- The most common effect of dominance hierarchy is that the individuals in higher order have a better and prior access to food. Individuals in the lower order get the leftover feed after the dominant individual has had its feed.
- This alpha position also brings better mating opportunities thereby increasing chances of reproductive success and a healthier offspring. In case of species, where a single female mates with multiple males, the males naturally tend to be more aggressive to gain the dominant or alpha position.
- An important aspect connected to dominance hierarchy is that of territorial advantage in favor of dominant individual. This territorial advantage is important from point of view of nesting place, mating locations and ample supply of food. In invertebrates like bees and ants, this territorial advantages is in the form of a large queen chamber indisputably allotted to the queen bee or queen ant.
- In case of weakening or death of a dominant individual, the alpha position is assumed by one of the individuals of the immediate next order to the alpha position after a reasonable tussle between competing individuals. Once the dominant individual is selected, the aggression gradually subsides and the rest of the members turn submissive.
Dominance Hierarchical Displays
I have listed out the behavior patterns of a few animal species which follow the dominance hierarchical system in their routines.
I am using this generalized term to refer to animals that move around in packs such as wolves, wild dogs, hyenas, etc. Wolves or wild dogs that are in dominant position have a habit of marking their territories or dens by spraying their urine at prominent location around their territory. This is an instant signal for other pack members that this territory is off limits for them. Similarly, such marking helps keep prey animals away from the dominant individual's territory. It is easy to identify the dominant male when the pack is defending itself from a rival pack. At such times, the dominant male is usually the one with long puckered up ears and a straight vertical tail. Amongst the hyenas however, the alpha position is always assumed by females.
In case of insects like bees, wasps, ants and termites, there is one dominant queen for every colony. Let's take the instance of honey bees. Here, the queen bee has the monopoly of reproducing new worker insects while feeding on food provided by the workers bees. The queens are usually larger in size due to the extra nutrition that they receive. Similarly, the worker bees have some facial markings depending upon the linear hierarchical order they belong to. The worker bees do have active reproductive systems of their own but it is suppressed by staying functionally sterile.
There is a general aggression between prospective virgin queen bees bred within the colony during which they kill each other. Basically, it is a game of survival of the fittest and the emerging victor rules. Only in rare cases, a worker bee may reproduce, which can lead to dissolution of colony cohesion as there is a direct conflict with formation of hierarchy. Amongst ants, there is a likelihood of more than one queen ant in the same colony. This helps to keep the colony going on, in case the queen ant dies in an unpredicted attack on the colony. Such extra queen ants usually replace old queen ants or may go on to form a new ant colony of their own.
We often see schools of fish like those of herrings swimming in the ocean. Each school is generally led by an alpha fish and the movement of these schools depends upon hunger, time of the day, presence of light, presence of predator, water temperature, etc. There is supposed to be a uniformity and orientation in the movement of the fish at all times so that it can remain in the school. Each fish is allotted a hierarchical position in the school while it swims rapidly. In case, of any disorientation in the movement, there is likelihood that a single fish may get isolated thereby making it difficult for him to get back into the school. Swimming in schools provides the fish better protection from predators.
The whole concept of dominance hierarchy is so broad that it is difficult to put it into words. It differs between every species and may further be categorized as per the availability of basic means of survival such as food, water and territory. All I can say is that dominance hierarchy is displayed not just by animals but humans as well. This concept is recurring in nature and unavoidable.