As we have already discussed in previous articles, there are many species of animals around the world that have decided to live in a collective, associative and participative way. That is, they have determined that the most effective means of survival is to live in a group. This situation may seem logical and natural, since life in a group undoubtedly provides great advantages: from thermal benefits and protection against predators, to reproductive and sexual selection advantages. But, as they say, “not all that glitters is gold”, and in these social systems we will see how this expression holds true.
As we know, group life is not always straightforward. There are a large number of actors involved, as well as external factors and agents that can be difficult for individuals to control. So, it is fair to assume that coexistence within a community also entails a series of costs, usually related to an increase in competition between individuals. Threats, attacks, stress are commonplace in many animal groups, actions which almost always involve the most dominant members of the group. But what exactly is dominance? In this article we are going to analyse animal social systems, and illustrate some of the advantages and disadvantages it brings.
What is dominance?
Dominance is a hierarchical social system based on the persistence of an agonistic behaviour among individuals. Behaviour related to competition, conflict and clashes, which occurs between one or more dominant individuals and others that are considered subordinate.
The development of aggressive behaviour is both the most representative pattern of this type of social system and the most influential in terms of the relationships that take place within a community. Aggression by dominant parties is a resource which results, among other things, more tolerant and submissive individuals. This installs a series of hierarchies which may ultimately ensure the cohesion of the group.
It’s important to note that dominance is not a fixed individual characteristic, rather a trait that depends on the context and environment in which animals develop. Interestingly, dominant behaviour seems to be increasingly prevalent in the most hostile environments; this is the case of the spotted hyenas (Crocuta crocuta) of the Kalahari desert, which are clearly more dominant than other individuals of the same species living in more favourable regions.
However, the external environment is not the only factor that can influence the appearance of dominant behaviour. There is a series of additional factors involved in dominance that we will now take a look at.
What are the factors involved in dominance?
As we’ve seen, the formation of groups and communities is usually determined by a system of dominance, according to which the most authoritative individuals establish and maintain a certain hierarchy. This hierarchy is not usually based on territorial superiority, but on an individual’s body size and the manifestation of secondary sexual characteristics. In other words, the most dominant specimens usually have larger bodies and very marked characters, regardless of their age, sex or their familiarity with their habitat.
The genotype is another of the factors that clearly play a role in the social systems of dominance. It is evident that the offspring of dominant individuals with an authoritarian tendency will also grow up to display dominant behaviour. That said, there are causes of aggressive behaviour that go beyond genetics. Let me give you a more specific example:
There are certain species of birds in which a pair of individuals may adopt the eggs of another breeding pair. In this sense, the behaviour of the parents towards their new chicks will be a determining factor in the future behaviour of the young, irrespective of the genotype. For example, the eggs of the great tit (Parus major), which are adopted by a dominant pair, will give birth to equally dominant chicks. How does this happen? The answer is clear: dominant females seek food more efficiently, and provide better care for their offspring.
This is clear evidence of the importance of the environment and behavioural patterns as contributing factors to dominance.
The advantages of being a dominant individual
Without a doubt, markedly dominant behaviour can be very helpful in many situations and can lead to significant advantages and benefits. As such, more authoritarian individuals enjoy greater reproductive success than subordinate individuals, have a higher survival rate and also have greater fat reserves, because they spend more time feeding.
Also, dominant individuals are less likely to suffer predation, as they often inhabit the least dangerous areas. On the other hand, subordinate individuals, who tend to inhabit the most peripheral territories, are far more exposed to predators.
Examples of this situation can be found in groups of ungulates or birds. In fact, thanks to a study carried out on the nocturnal birds of prey in the Scandinavian forests, it was observed that all the paridae (the family of passerines that includes the great tit and blue tit) that appeared in the pellets of the large birds of prey were subordinate specimens. How do they know this? Because these were individuals that had been ringed…
However, subordinate individuals may leave these adverse territories if conditions are too unfavourable, or if the dominant individuals in the group are overly aggressive, in order to locate a more suitable environment.
The drawbacks of being a dominant individual
In spite of the advantages that we’ve just outlined, the aggressive behaviour of the dominant animals often brings with it a range of negative consequences that can affect their everyday lives. For example, they have to face a greater number of fights, which not only causes a greater amount of stress and exertion, but also makes them more visible to predators.
One of the most striking disadvantages of dominance is that they always protect the subordinates (they defend the whole group in reality). This means that if the leader is absent at some point, the subordinates will have a lower survival rate and, consequently, the viability of the community will be compromised.
Finally, it should be noted that not all decisions made dominant individuals benefit the group. Nevertheless, subordinates tend to follow them. This is the case of baboons (Papio), that follow their leader very closely, even if this means obtaining less food for the group. This kind of cost must be shouldered by the group.