It is commonly thought that animals can be arranged along a ladder of intelligencea sort of modern-day Scala Naturaewith humans inevitably at the top, followed by our close relatives, the primates, all the way down to fish and other slimy creatures. Over the past decade, this ladder has been challenged by claims of high intelligence and great social complexity in other animals. For example, spotted hyenas establish hierarchies in which dominant females support the rank contests of their daughters. Bottlenose dolphins form "political" coalitions every bit as complex as those of chimpanzees. Caledonian crows not only use tools in the wild, but also modify tools in the lab, an ability once thought to define humans.

And now come the fish. In an article published today in PLoS Biology, Redouan Bshary from the University of Neuchtel and colleagues describe the astonishing discovery of coordinated hunting between groupers (Plectropomus pessuliferus) and giant moray eels (Gymnothorax javanicus) in the Red Sea. These two species make a perfectly complementary pair. The moray eel can enter crevices in the coral reef, whereas the grouper hunts in open waters around the reef. Prey can escape from the grouper by hiding in a crevice and from the moray eel by leaving the reef, but prey has nowhere to go if hunted by a combination of these two predators. The article offers a description and accompanying videos, such as the one showing a grouper and eel swimming side by side as if they are good friends on a stroll. It also offers quantification, which is truly hard to achieve in the field, of the tendencies involved in this mutually beneficial arrangement. The investigators were able to demonstrate that the two predators seek each other's company, spending more time together than expected by chance. They also found that groupers actively recruit moray eels through a curious head shake made close to the moray eel's head to which the eel responds by leaving its crevice
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Contact: Natalie Bouaravong
press@plos.org
415-861-8345
Public Library of Science
4-Dec-2006