Octopus mimicking its follower reef fish

Abstract

We describe a possible example of social mimicry between Octopus insularis and the small grouper Cephalopholis fulva, which frequently associate during foraging at Fernando de Noronha Archipelago, Brazil. The octopus, when swimming backwards, jet‐propelled, becomes similar in colour and shape to accompanying C. fulva individuals and is therefore less conspicuous within the fish group. We regard this as an instance of social mimicry, a form of protection against visually‐oriented predators in which different species similar in shape and colour mingle for the advantage of grouping. Even when swimming backwards alone, O. insularis may become similar to foraging C. fulva individuals, another putatively protective behaviour. We suggest that the feeding association commonly found between O. insularis and C. fulva minimized the evolutionary costs for the origin of mimicking by the octopus.

†Retired and associated as voluntary researcher.

Keywords:

• social mimicry
• Octopus insularis
• Cephalopholis fulva
• foraging association
• Fernando de Noronha Archipelago

Acknowledgements

We thank J.M. da Silva Jr (Centro Golfinho Rotador) for logistic support, the Águas Claras and Atlantis diving centres for logistical help, C.A. Magalhães for discussions, R. Dunn and S. Wismer for reviewing the manuscript, and the Ibama for issuing study permits at Fernando de Noronha Archipelago. The CAPES, CNPq and FAPESP provided financial support.

Notes

†Retired and associated as voluntary researcher.