Japanese pygmy squid (Idiosepius paradoxus) use ink for predation as well as for defence

Abstract

Inking is one of the defensive tactics in cephalopods. By observing the predatory behaviours of Japanese pygmy squid (Idiosepius paradoxus) towards three crustacean prey species (Neomysis intermedia, Latreutes acicularis, and Palaemon serrifer), we found that ink is also used for predation. Inking behaviour during predation was observed 17 times in 322 trials. Squid successfully attacked prey after inking in 13 cases (8 trials with L. acicularis and 5 trials with P. serrifer). Ink was never used to attack N. intermedia despite the fact that this was the most commonly captured prey. Ink use during attacks can be divided into two types: (1) squid release ink between themselves and the prey and then attack through the ink cloud, and (2) squid release ink away from the prey and then attack from another direction. The success rate of ink attacks differed significantly between the two prey species on which ink attacks were made.