Interspecific Communicative and Coordinated Hunting between Groupers and Giant Moray Eels in the Red Sea

Redouan Bshary,Hans Fricke,Karim Ait-El-Djoudi,Andrea Hohner,Frans De Waal

doi:10.1371/journal.pbio.0040431

Abstract

Intraspecific group hunting has received considerable attention because of the close links between cooperative behaviour and its cognitive demands. Accordingly, comparisons between species have focused on behaviours that can potentially distinguish between the different levels of cognitive complexity involved, such as “intentional” communication between partners in order to initiate a joint hunt, the adoption of different roles during a joint hunt (whether consistently or alternately), and the level of food sharing following a successful hunt. Here we report field observations from the Red Sea on the highly coordinated and communicative interspecific hunting between the grouper, Plectropomus pessuliferus, and the giant moray eel, Gymnothorax javanicus. We provide evidence of the following: (1) associations are nonrandom, (2) groupers signal to moray eels in order to initiate joint searching and recruit moray eels to prey hiding places, (3) signalling is dependent on grouper hunger level, and (4) both partners benefit from the association. The benefits of joint hunting appear to be due to complementary hunting skills, reflecting the evolved strategies of each species, rather than individual role specialisation during joint hunts. In addition, the partner species that catches a prey item swallows it whole immediately, making aggressive monopolisation of a carcass impossible. We propose that the potential for monopolisation of carcasses by one partner species represents the main constraint on the evolution of interspecific cooperative hunting for most potentially suitable predator combinations.

Highlights

Cooperative hunting, i.e., the increase in successful prey capture observed when two or more individuals engage in a hunt, has been demonstrated in a wide variety of species [1,2,3,4]
We have presented several lines of evidence for interspecific communicative, coordinated, and cooperative hunting between two species of reef fish predators
We found the following: (1) individual groupers and moray eels frequently spent more time in association than predicted by a null model of chance encounters, (2) groupers actively signalled to elicit joint hunting and to recruit moray eels, (3) satiated groupers did not signal, and (4) both partner species increased their hunting success in association

Summary

Introduction

Cooperative hunting, i.e., the increase in successful prey capture observed when two or more individuals engage in a hunt, has been demonstrated in a wide variety of species [1,2,3,4]. Role differentiation implies that individuals will adopt roles that have a lower probability of personal success or a higher risk of injury than other roles would offer, e.g., hunts where some individuals act as chasers while others block the escape routes of prey. Such coordination is known for only a handful of species [5,6,7,8], all of which are mammals or birds. While simultaneous feeding on a prey carcass may occur in carnivores, access in these species is best predicted by individual rank and/or nepotistic toleration of related lower ranking individuals [4]

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