Cooperative hunting and gregarious behaviour in the zebra lionfish, Dendrochirus zebra

Cooperative hunting is considered one of the most ubiquitous forms of cooperative behaviour in animals, and has been extensively studied in a range of taxa, including birds, mammals, fish and insects (Packer and Ruttan 1988). The zebra lionfish, Dendrochirus zebra (Cuvier 1829), feeds on small crustaceans and fishes and has been previously described as a solitary predator in which individuals hunt exclusively by themselves (Moyer and Zaiser 1981). Here, we report the occurrence of cooperative hunting in D. zebra from coral reefs around Lizard Island, northern Great Barrier Reef, Australia (14°40′S, 145°28′E). During September–December 2012, three different pairings (2–3 individuals) of D. zebra were observed cooperatively hunting in the field, therefore offering insight into a thus far unknown social behaviour in this species (Moyer and Zaiser 1981). Furthermore, hunting behaviour was filmed with video cameras (GoPro, Woodman Labs; see supplementary material) in a laboratory setting. As in the field (Fig. 1a), D. zebra pairs were observed hunting together on six different occasions in groups of 2–3 individuals. In each case, individuals would swim towards prey (cardinalfishes, Apogon doerderlini) undulating their dorsal spines, using their web-like fins as a visual-barrier, together herding prey into a confined area. Individuals would then take turns striking at their prey (Fig. 1b). On several occasions, one individual would proceed to produce a jet of water directed towards the prey (believed to confuse/distract prey increasing the chance of a successful predatory event; Albins and Lyons 2012). This mode of hunting has been documented for the invasive red lionfish, Pterois volitans (Albins and Lyons 2012), and is likely an idiosyncratic trait of lionfishes. Contrary to earlier suggestions that D. zebra is a social recluse (Moyer and Zaiser 1981), the current findings suggest that D. zebra exhibits gregarious behaviour, living together in groups of 3 (Fig. 1c). To our knowledge, this is the first documented case of intraspecific cooperative hunting and gregarious behaviour in lionfish. Recent findings (Lönnstedt and McCormick 2013) suggest that this hunting behavior is mirrored by P. volitans, which could have implications for hunting effectiveness of invasive lionfish in the Caribbean.