In a paper published in PLoS ONE, researchers Redouan Bshary, Andrea Hohner, Karim Ait-el-Djoudi, and Hans Fricke reported on interesting inter-species behavior that they noticed while at the time researching cleaner wrasse behavior in the Red Sea.
What the team observed was an interesting joint hunting tactic employed by the coral grouper, Plectropomus pessuliferus, and the giant moray eel, Gymnothorax javanicus. They discovered that when coral groupers were in pursuit of their prey, the prey would sometimes take refuge within the reef structure. When this happened (depending on such factors as how hungry the grouper was at the time) the grouper would seek out the help of a nearby giant moray eel in order to get to the holed-up fish.
The thought process that Bshary’s group had was that alone there was no way the grouper was going to get the meal. With the help of the moray eel, the grouper stood a better chance of getting a meal as the fish either would stay in the reef structure and get eaten by the moray or it would flee and get eaten by the grouper.
What Bshary’s group observed was that after the grouper’s prey holed up in the reef structure, the grouper would search around the area until it found a giant moray eel in its den. The grouper would then signal to the eel by bobbing its head up and down several times that it had a fish cornered nearby. The grouper and moray would leave together and head over to where the fish was hiding in the reef structure. The grouper would then signal to the moray where the fish was located by again bobbing its head up and down over the area where the fish was last seen. The moray would enter the crevice and hunt down the prey. Either the prey would stay in the reef structure and get eaten by the eel or it would dart out of the structure and get eaten by the coral grouper. There was no sharing of the meal between the fish.
There are a number of interesting videos showing this behavior among the two animals: