Function, mechanisms and ontogeny of collaborative hunting in the yellow saddle goatfish (Parupeneus cyclostomus)

Cooperation is great interdisciplinary interest because we need to reconcile its occurrence with evolutionary theory and its emphasis on self-regarding individuals. Coordinated hunting in various vertebrates has attracted a lot of attention because it provides the opportunity to study the evolution and stability of cooperation, the potential links between cooperation and cognitive abilities, and the development of the ability to perform highly coordinated actions. The problem until now has been that all studies on coordinated hunting have been field observations and hence correlative. We propose for the first time an experimental study, using yellow goatfish as study species. Yellow goatfish are the first fish species described as collaborative hunters where individuals play different roles during a hunt (‘chasers’ and ‘blockers’), and they encircle prey hiding in coral crevices and try to pry it out by inserting their barbels. We have designed an experimental setup where the goatfish will be confronted with mobile invertebrate prey hiding in a tunnel system. Cameras that are installed above and below will allow us to conduct detailed behavioural analyses 1) to test the relationship between group size and hunting success, 2) to find out whether the cooperation is a by-product of self-regarding behaviour or proper reciprocity based on mutual investments. The laboratory experiments will be complemented with field observations on yellow goatfish of all size classes. We will describe their foraging techniques in detail in order to document any changes in the complexity of coordination with other individuals during the ontogeny. We consider it likely to find significant changes as yellow goatfish change their diet during ontogeny, switching from invertebrate prey to fishes. In order to determine whether yellow goatfish train coordination from early on in order to prepare for collaborative hunting on mobile fish as adults, we will compare the foraging techniques of small yellow goatfish with the foraging techniques of juveniles of closely related goatfish species that hunt solitarily as adults. In conclusion, our study is novel because we will be the first to test whether collaborative hunting yields benefits to all participants in the first fish species described to hunt in collaborative way. We will then compare our data with the results from studies on birds and mammals in order to evaluate the role of cognition and learning during ontogeny for the ability to perform complex coordination.