Deceptive Courtship Signalling in Mourning Cuttlefish

Cuttlefish are a group of marine animals related to squid, octopuses and nautiluses. 'Cuttle' is a reference to their unique internal shell, the cuttlebone; and despite their name, cuttlefish are true mollusks.

Cuttlefish can change color, patterning and their shape to some extent in order to avoid predators or capture prey by blending into their natural surroundings. Male mourning cuttlefish (Sepia plangon) also have specific courtship patterns and color schemes they use in attracting females. When a female is nearby, the male will present to her a stripped courtship pattern on his mantle that indicates sexual interest. Females display a spotted pattern during these encounters. If the female likes what she sees, mating will ensue.

Some cuttlefish males have been observed to display the courtship pattern towards a female while simultaneously displaying a female pattern to a nearby rival male. This deception reduces the probability of aggressive behavior and courtship disruption on the part of the rival male, because he perceives two females, not another male displaying to a receptive female. Male cuttlefish who use deceptive split-signalling are often more successful at mating with females than males who don’t engage in split-signalling, but instead do it the old fashioned way by repelling the advances of other males – a tactic that requires much more energy and poses greater risks for injury.

Cuttlefish males will only use split-signalling under very specific circumstances, namely in the presence of one or more females and a single, lone male on the opposite side of his body, so that the deception works. When split-signalling deceptions are discovered by other males, they typically react with more aggression towards the deceptive male than they do towards rival males not using deceptive signalling. So split-signallers take a risk, but if they are skillful deceivers they are more likely to pass on their genes.