Ants are Among the Most Successful Animals 

Insects are the largest class of animals by number of species and may account for as much as 90% of all animal species. Also, they probably make up the largest group by biomass (total weight) of the terrestrial animals, and ants make up about 30% of this.

Ants are so successful because of several features of which the most important is their social behaviour. Individual ants have tiny brains but together the many ants of a colony can exhibit remarkable 'intelligence'.

Ants exhibit complex and apparently intelligent behaviour; they can navigate over long distances, find food and communicate, avoid predators, care for their young, etc. In the image above you will notice that the ants have cleared dirt from the 'highway' they are using to make it easier for the ants to travel along. Ants also build cities, farm other animals, cultivate crops and organise into a complex society analogous to that of humans; with social ranks such as monarchs, soldiers, workers and slaves. The complexity of their range of behaviour is comparable to mammals.

Many people used to think the queen centrally controlled the behaviour of the colony. This is not the case; instead, ants decide what to do based on the encounters and interactions with other ants, resulting in a dynamic network that coordinates the functions of the colony. Indeed, many ant species, particularly the invasive species, have multiple queens in each nest.

The individual ant can make many decisions alone, but when many ants co-operate and communicate, the decision making becomes more successful. This improved accuracy of decision-making is the so-called ‘wisdom of the crowds’ effect.

How does this complex behaviour of the colony come from the simple minds of individual ants?

The answer may be that complexity of individual ant behaviour may come from simple rules applied to a complex environment. In the context of the ant colony the complex environment includes, and may be dominated by, the behaviour of the other ants in the colony.

Examples of the simple rules individual ants follow may be something like these 5 rules for ants in search of food:

1. Avoid obstacles (ants will not aimlessly try to go through obstacles)
2. Wander randomly, in the general direction of a pheromone gradient
     - if no pheromones are sensed, execute random motion
3. If carrying food, produce pheromone at constant rate while walking
     - maybe follow a pheromone trail to the nest*
4. If not holding food and find food, pick it up
5. If holding food and find nest, drop food

*Because pheromone paths have some breadth, they tend to merge together into a trace that becomes straighter the more it is used.

It is probable that at the individual level ants are only as intelligent as other individual insects, but they may collect and use a greater variety of information that others. In navigation, ants are thought to use a variety of cues to navigate, such as sun position, polarized light patterns, visual views, pheromone gradients (moving toward stronger or weaker levels), wind direction, slope, terrain texture, step-counting … and more. This information is not collated to give an overall view of the world around them in the way we would. Instead each cue provides information to a separate module of the ant brain and each module influences the final behaviour.

So, we can say, although individual ants are not very intelligent, if we consider the whole colony as an individual organism it is highly intelligent.

See the 1-2-3 Ant Control Programmeto learn how to get rid of ants and keep them out of your house.

David Brittain
Kiwicare