Selective signalling by cuttlefish to predators

Rather than simply escaping, prey animals often attempt to deter an attack by signalling to an approaching predator, but this is a risky strategy if it allows time for the predator to draw closer (especially when the signal is a bluff) [1,2]. Because prey are vulnerable to multiple predators, the hunting techniques of which vary widely, it could well be beneficial for a prey animal to discriminate predators and to signal only to those that are likely to be deterred. Higher vertebrates make alarm calls that can identify the type of predator to the signaller's conspecifics [3,4], and a recent study shows that squirrels direct an infrared deterrent signal specifically at infrared-sensitive pit-vipers and not at other snakes [5]. We show here that nai¨ve juvenile cuttlefish (Sepia officinalis L.) use a visual signal selectively during encounters with different predatory species. We analysed sequences of defensive behaviours produced by cuttlefish, to control for effects of relative threat level (or 'response urgency' [4]). This showed that a high contrast 'eyespot' signal, known as the deimatic display [6], was used before flight against visually oriented teleost fish, but not crabs and dogfish, which are chemosensory predators [7,8].