雄性乌贼战斗时不会虚张声势

Male cuttlefish¹ do not bluff². When their body language shows they are agitated³, they are. This was one of the findings from a study on the giant Australian cuttlefish in Springer's journal Behavioral Ecology and Sociobiology, led by Alexandra Schnell of Macquarie University in Australia. Animals have different ways to show aggression⁴ during confrontations⁵. Some animals try avoiding actual hand-to-hand fighting to reduce the risk of injury or even death. They prefer settling differences by using a repertoire⁷ of hierarchical agonistic or threat displays that signal their fighting ability or aggressive intent. 

 

Male giant Australian cuttlefish (Sepia apama) are known for their spectacular displays of aggression when jostling over females during the breeding season. These include rapid changes of skin colour and particular body movements. Fights can last up to twenty minutes but, more often than not, they do not include any real physical contact other than a bit of pushing and grappling. 

 

To further investigate the aggressive behavior of cuttlefish, Schnell's team combined field observations with the use of a video playback technique. They found that giant Australian cuttlefish produce multiple displays that convey a graded series of threats during contests between males of the same size. The early stages of such interactions predict which displays will be performed later in a confrontation⁶. In turn, these later displays reliably predict the chances of any physical aggression.

 

In the field, Schnell's team observed how males gradually progress from the initial low-risk visual signalling stage to the high-risk one, which entails⁸ actual physical aggression. Low-risk behavior is typically performed at a distance of more than a meter away, and seldom stimulates⁹ physical aggression in an opponent. 

 

During video playback sessions, males were shown life-sized videos of other cuttlefish in various stages of aggression. It was found that during the low-risk stage, cuttlefish use frontal displays to assess their opponents' level of aggression. The signaller faces his opponent. His mantle¹⁰ is down and out of sight of the rival, while his arms are typically white and move slowly.

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