Researchers have discovered two species that perform cooperative hunting.

The giant moray eel and grouper are normally solitary predators, but when the grouper loses it prey in deep crevices it will seek help from the eel.

Bshary and his colleagues followed fish around by snorkeling. They found groupers often visited giant morays resting in their crevices and rapidly shook their heads an inch or so from the eels to recruit them in a joint hunt. At times this call took place after a grouper failed in its hunt because prey escaped into a crevice the grouper could not get into but a giant moray might.

If the moray emerged, the grouper guided the eel to a crevice where prey was hiding. Groupers sometimes even performed a headstand and shook its head over a prey hiding place to attract moray eels to the site. At times the moray ate the fish it rooted out, while at other times the grouper did.