Nobody likes being the third wheel, especially when it comes to matters of love. In fact, in the world of cuttlefish, such an odd number will lead to aggressive fighting complete with dramatic zebra-stripe patterning, grappling, biting, and barrel rolling!
My research team was fortuitous enough to encounter such a battle in Çeşmealtı, a seaside village belonging to the city of Izmir in Turkey. Beneath this elongated embayment, two male European common cuttlefish, Sepia officinalis, fought belligerently in the hope of winning over a single female. The imagery recorded during this encounter allowed us to describe the aggressive behaviours using mathematical models that are used to investigate interactions between individuals and how they come to make certain decisions. These models, known as game theory models, can be applied to fighting interactions to help us predict how conflict is settled between two rivals.
Image caption: two male cuttlefish competing for a female in the Turkish Aegean Sea (photo credit: Justine Allen & Derya Akkaynak).
“ the pattern of fighting behaviour was more consistent with a mutual assessment fighting strategy–a strategy that assumes that the rivals evaluate their own fighting ability relative to the fighting ability of their opponent”
The recorded battle features two males that escalate the fight at the same rate, until one cuttlefish clearly demonstrates that he is tougher, causing the rival to retreat. When the behaviours were analysed in the context of game theory, the pattern of fighting behaviour was more consistent with a mutual assessment fighting strategy––a strategy that assumes that the rivals evaluate their own fighting ability relative to the fighting ability of their opponent. This fighting strategy is assumed to be more superior than self-assessment fighting strategies because animals can minimise costly and futile persistence by gathering information about their opponent.
To confirm that this is the fighting strategy that is widely used by common cuttlefish, we need to go back to the drawing board and analyse more fights. Nevertheless, rare and vigorous field observations like these can complement and guide future lines of inquiry. Furthermore, researchers can obtain a more comprehensive understanding of the life history of a species by analysing freely behaving animals in nature.
Published article: Allen JJ, Akkaynak D, Schnell AK, Hanlon RT. (2017). Dramatic fighting by male cuttlefish for a female mate. American Naturalist 190, 144–151