Battling molluscs go to great lengths to avoid injury.
A female cuttlefish, in all her chromatic, multi-armed glory, is sure to catch the eyes of a few males during the breeding season. But is she worth a fight?
Rival males know that when push comes to shove, and a confrontation turns physical, both opponents risk ending up with a torn fin, a bleeding tentacle, or worse.
The dangers of a full-blown altercation have induced giant Australian cuttlefish to evolve a series of escalating displays that offer dueling males multiple chances to bow out before getting themselves into hot water, according to a study in Behavioural Ecology and Sociobiology.
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Lead author Alexandra Schnell from Macquarie University explains to The Science Explorer that their sequence of intensifying interactions allows males to “communicate different levels of aggression, providing opponents with a number of opportunities to make tactical decisions about whether to escalate to physical combat or whether to withdraw from a contest.”
The battle begins when a confident male approaches his enemy head-on, with his arms pale and slowly oscillating. If the second male responds by mirroring the challenger, they advance to the next phase. Here, the opponents hover side by side in what is known as the lateral display, which may transition to shovel display, where the cuttlefish scoop their inner arms up while splaying their outer arms down.
Like red deer with their spectacle of parallel walks and roars, and penguins with their banter of hisses and growls, the cuttlefish displays allow opponents to size each other up.
The entire sequence may be over in as little as 30 seconds, or get drawn out for up to 20 minutes. In that time, males gain key Intel about their opponent, and in the process, both parties can gauge who the victor would be if they were to proceed to physical fighting. And just knowing is normally enough to settle the dispute.
But failing resolution, the contestants enter into a real battle, which for cuttlefish means a full on pushing war. If things get really nasty, biting might ensue.
“Under different conditions, small males obtain matings through deceptive tactics, by mimicking the appearance and behaviour of a female,” said Schnell. “Hence, I thought it might be possible that males also convey unreliable or dishonest information whilst performing fighting displays.“
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But when Schnell and her colleagues brought male cuttlefish back to the lab and played them videos of males performing various displays to simulate a fight, the creatures did not live up to their reputation for deception.
Rather, at every stage of the contest, the cuttlefish proceeded to do precisely what their signals threatened — the earlier, milder displays were followed by more intense ones, and those fierce displays reliably predicted escalation to aggression.
That reliability is key, because it allows both contestants to weigh all of the risks when deciding whether to progress to a fight or to surrender.
After all of the buildup of threat displays, it’s usually an anticlimactic ending for cuttlefish foes. But their encounters serve an important function. The perceived victor can go on to court the object of his desire, and while the loser may have little to show, both can relish that they have managed to settle a dispute without injury — a feat for any organism.
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