Dishonest signalling at its very best…

Have you ever heard anyone say “as two-faced as a (male) cuttlefish”? No, me neither, but that is certainly an idiom worth coining, given an astonishing natural history observation made by Culum Brown and colleagues on the Mourning Cuttlefish.

Cuttlefish are famous for being able to change colours, patterns, and skin textures very dramatically, both to communicate with each other and to camouflage themselves from predators. But the extent of this changeability is most clearly demonstrated in a very specific social situation: when a male is courting a female in the vicinity of a rival male.

Male-male aggression is common across animals, often as part of contests over mating access to females. A clever way in which males of many species avoid such contests is by trying to sneak under the radar of rival males. Male frogs, for example, often behave as “satellites”, wherein they just hang out in the general vicinity of a croaking male, trying hard to be inconspicuous but swooping in to mate with females who approach to investigate the source of croaking.

But courting a female can sometimes require males to be as showy as possible–females sometimes choose which males to mate with based on the males’ displays. So a male courting a female in the vicinity of a rival male suffers a dilemma: to be or not to be conspicuous?

Not a dilemma if you’re a male Mourning Cuttlefish! Witness the colour patterns of the male, at the right in the video below:

That’s right–that male is showing off his visual signals on the side of his body that faces the female he’s courting, but is being as inconspicuous as possible by mimicking female colour patterns on the side that faces the rival male (not visible in the video). Simply amazing. Moreover, this two-facedness is only displayed in this particular social situation, implying that cuttlefish assess and respond precisely to their social surroundings.

Apropos of some recent debate on whether or not natural history is in decline in academia, I think it’s heartening that this behavioural observation was reported, without a single statistical test, in a high impact journal . 


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