While ants can be irritating to humans, they don't generally pose a huge danger to us. However, groups of ants are often extremely aggressive to one another, frequently fighting to the death. A new paper in Proceedings of the Royal Society B studies the how ants' fighting tactics change when facing opposing groups of different sizes.

Red wood ants (Formica rufa) are very antagonistic, engaging in knock-down, drag-out brawls with other colonies. In the spring, the workers emerge from their burrows and often come across groups of workers from rival colonies. The groups will generally fight until one side is rendered helpless, and the group left standing wins the territory. But when the stakes are this high, what happens when the groups are unevenly matched?

By setting up battles with different numbers of ants on each side, the researchers found that ants in smaller groups fought much harder than those in larger groups did. When a small group of ants (five individuals) went up against larger groups (ten or more), ants in the smaller groups captured and attacked enemies at much higher rates than individuals on the opposing side did.

So, how does this happen? It seems that ants are capable of “numerical assessment,” and can somehow figure out whether they are in the smaller or the larger group. While scientists already know that animals such as lions, hyenas, primates, and birds have this ability, they aren’t yet sure how this cognitive skill works in any or all of these species.

However, despite their relative lack of enthusiasm, the larger groups still came out on top, exhibiting higher overall levels of aggression and lower numbers of fatalities. Despite fighting harder, the small groups couldn’t overcome their numerical disadvantage. While small groups may not be able to beat large ones, their higher individual levels of aggression can put a pretty big dent in their opponents’ fighting forces, and might be able to limit the overall success of these big groups.

Proceedings of the Royal Society B, 2010. DOI: 10.1098/rspb.2011.0062 (About DOIs).