By Raleigh McElvery
Animal communication is more nuanced than one might think. During confrontation between members of the same species, some animals communicate different levels of aggressive intent through distinct behavioral displays, as outlined by a theory known as the “hierarchical signaling hypothesis.”
This theory states that low-risk displays of aggression predict the performance of high-risk displays, and high-risk displays predict whether an escalation to actual physical combat will occur. By conveying different messages through distinct displays, opponents can communicate a hierarchy of threats.
This theory applies to giant Australian cuttlefish (Sepia apama), according to a recent paper by Alexandra Schnell of Macquarie University in Sydney, Australia, and colleagues, including MBL Senior Scientist Roger Hanlon.
Using a video playback technique to simulate a rival male opposing a live male subject, the study demonstrated that cuttlefish use different displays (distinct postures, specific movements, changes in skin color, etc.) to transmit “graded threats.”
Schnell’s findings support the notion that, like mammals and birds, cuttlefish (which are molluscs) also employ hierarchical signaling, despite having evolved earlier than vertebrates. Finding these patterns across such a diverse group of animals suggests that there are strong selective pressures driving organisms to use a hierarchy of threats during confrontation.
Top photo: Two male giant Australian cuttlefish (S. apama) fight one another on the spawning grounds in South Australia. Credit: Roger Hanlon
Schnell, A.K., Smith, C.L., Hanlon, R.T., Hall, K.C., Harcourt, R. (2016). Cuttlefish perform multiple agonistic displays to communicate a hierarchy of threats. Behavioral Ecology and Sociobiology, DOI: 10.1007/s00265-016-2170-7