Hierarchy Pecking Order Year 13 Biology

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What is a Hierarchy? In a hierarchy, a group, consisting of individuals of the same species, is ranked in order of dominance from the alpha individual (“top dog”) down to subordinate individuals. A hierarchy determines an order of precedence for access to food, mates and breeding sites.

How is the hierarchy established? The order of dominance is established competitively -usually by brief fights.

What are the advantages in having a hierarchy? Once the hierarchy is established, it reduces competition and aggressiveness within the group.

Linear and Complex Hierarchies Hierarchies may be linear (with a ‘peck order’) or they may be more complex and involve coalitions and alliances, as in many primates.

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How is rank indicated and maintained? By posture and displays. Dominant individuals usually make themselves look larger, stronger and fiercer.

Subordinate individuals show submissive or appeasement behaviour, which stops the other animal from attacking it.

Facial expressions in dogs

What are these cats showing?

What are the advantages of living in a hierarchy? Aggression is reduced. Resources are allocated such as nests, food and mates therefore reduced aggression again. The best individuals with the best territory, food and mates passes down the “best” genes.

Advantages continued… The dominant members of the group protect the weaker ones. The weaker members of the group help raise the young of the stronger members, ensuring survival of stronger members.

Disadvantages of living in a hierarchy If resources are scarce, more members of a group may die. Individuals lower in the pecking order may be the target of much aggression.