Studying social hierarchies in ants will hopefully allow scientists to understand the nature of societies of other animals like primates. The new paper is published in The American Naturalist.
How do we understand animal societies that are led by a group of them, the alpha individuals?
Normally, research has revealed the inner workings of societies with a single individual as the only dominant one among them, a winner-loser situation – findings which are inadequate to provide insight into those communities that have more than one alpha monitoring them, a winner-winner situation. Therefore, to achieve this particular end, researchers from North Carolina State University, the University of Oxford and Arizona State University have put their minds together to shed light on winner-winner interactions.
Dominance is not necessarily dictated by winner-loser interactions. Rather, some dominance behaviours might actually be a win-win situation for all individuals of the group, explains lead author Clint Penick.
Penick and his team focused their efforts on the well-documented Indian jumping ant (Harpegnathos saltator) and analysed their behaviours and social hierarchy. This particular ant species is able to establish dominance without the need for physical harm: following the death of the queen of the colony, female workers will take to ritual fights to determine the identity of 10 dominant individuals without anyone being physical injured. This means that they actually have a team of worker queens, gamergates.
The occurrence of gamergates is an ideal example of a shared dominance hierarchy, as opposed to despotic (where one individual dominates over the others which are all considered to be subordinates) or linear ones (whereby a certain grading is established with the alpha on top, followed by a beta who governs all but the alpha, and so on).
The hierarchy in the H. saltator is set up through three behaviours:
- Biting – a clear winner-loser situation; one ant will bite the head of another.
- Policing – individuals challenging a dominant individual are restrained by subordinates.
- Duelling – no clear loser is established after two individuals fight each other with their antennae.
The duelling is thus described as being a winner-winner interaction as it does not culminate in the ‘making of a loser’. Penick explains this interaction in laymen terms as follows: “a couple of football players psyching each other up before a game”.
These three behaviours need to occur together for the situation to be a winner-winner one. On the other hand, if only biting happens to the exclusion of the other two, a linear hierarchy is eventually set up. Furthermore, with only biting and policing, a despotic hierarchy is created. The shared dominance hierarchy only occurs with the combination of all three behaviours.
The three types of hierarchies are present in other animal species, for example in lions and dolphins, and thus, the new study can be used to understand other such interactions pertaining to dominance.