Hunting in archerfish - an ecological perspective on a remarkable combination of skills.

Archerfish are well known for using jets of water to dislodge distant aerial prey from twigs or leaves. This Review gives a brief overview of a number of skills that the fish need to secure prey with their shooting technique. Archerfish are opportunistic hunters and, even in the wild, shoot at artificial objects to determine whether these are rewarding. They can detect non-moving targets and use efficient search strategies with characteristics of human visual search. Their learning of how to engage targets can be remarkably efficient and can show impressive degrees of generalization, including learning from observation. In other cases, however, the fish seem unable to learn and it requires some understanding of the ecological and biophysical constraints to appreciate why. The act of shooting has turned out not to be of a simple all-or-none character. Rather, the fish adjust the volume of water fired according to target size and use fine adjustments in the timing of their mouth opening and closing manoeuvre to adjust the hydrodynamic stability of their jets to target distance. As soon as prey is dislodged and starts falling, the fish make rapid and yet sophisticated multi-dimensional decisions to secure their prey against many intraspecific and interspecific competitors. Although it is not known why and how archerfish evolved an ability to shoot in the first place, I suggest that the evolution of shooting has strongly pushed the co-evolution of diverse other skills that are needed to secure a catch.