No evidence that lionfish Pterois miles coordinate and reciprocate during hunts.

Decision rules underlying cooperative hunting can range from very simple to very complex. As lionfishes are naturally solitary hunters, an experimental study documenting active recruitment, coordination and alternating (potentially reciprocal) striking in dwarf lionfish Dendrochirus zebra received major attention. A hypothesis was that sophisticated coordinated hunting may also contribute to the successful invasion of another lionfish species, Pterois miles, in the Caribbean. However, we did not find recruitment signalling in P. miles in parts of its native range, the Red Sea. Here, we expand on these results, testing for coordinated movements and for alternation in strikes. We exposed subject pairs to inaccessible prey in three transparent housings. The two lionfish did not aggregate at the same prey housing or even share larger space units in the presence of prey. In a second experiment, we found that some alternation can be induced if prey items become alternately accessible at two corners, with each lionfish tending to monopolize one corner each. When the movement of prey is slow or even absent, we observed less alternation than expected by chance. In conclusion, P. miles in the Red Sea does not use any coordination to hunt prey.

No evidence for conspecific recruitment for cooperative hunting in lionfish Pterois miles.

Lionfish are common piscivores in the Indo-Pacific and invasive in the Caribbean. A fin flaring pattern, involving a rapid undulation of the caudal fin and sequential turning of both pectoral fins, was described in zebra lionfish as a signal to initiate cooperative hunting, and it was hypothesized that such hunting tactics may also exist in other lionfish species and contribute to their successful invasion in the Caribbean. Here, we investigated one of those invasive species, Pterois miles, in its natural range in the Red Sea. We did not observe evidence for cooperative hunting in the field. We complemented field observations with a laboratory experiment aimed at inducing subjects to recruit partners for cooperative hunts, exposing subjects to inaccessible prey in transparent housing as well as to a potential partner. We regularly observed the fin flaring pattern, but importantly, it was not directed at the partner. Thus, rather than being a signal, the fin flaring movement pattern seems to be a swimming mode in a confined environment. Furthermore, the two lionfish did not aggregate at the prey housing, reinforcing the field results that this species in the Red Sea does not depend on cooperation to hunt fish.