Fishy Tag-Team Makes For Better Hunting, Science, 12/07/06
By Jennifer Cutraro
Source: ScienceNOW Daily News
|Better together. A grouper and moray eel team up for a hunt.
Credit: Redouan Bshary
Superstar wrestlers Hulk Hogan and Macho Man Randy Savage may have perfected the art of tag-teaming, but the benefits of the technique extend well beyond the wrestling ring. According to a new study, two unrelated species of coral reef fish communicate with each other to hunt jointly, improving their success. By combining their complementary hunting strategies, groupers and moray eels leave their prey with nowhere to hide.
Groupers are large predatory fish that hunt smaller fish in open water. Moray eels, on the other hand, slither through crevices in coral reefs and rocky substrates, nabbing the fish hiding from open water predators—such as groupers. Marine biologists have previously observed that groupers will sometimes follow moray eels and eat the fish they flush out from the reef's nooks and crannies. But nobody suggested that they talked about it first.
Yet that's just what behavioral ecologist Redouan Bshary of the University of Neuchâtel in Switzerland saw happen. While observing an individual grouper in his Red Sea field site, Bshary noticed the grouper swim right up to a moray eel tucked away in the reef and begin shaking its head. What Bshary observed next took him completely by surprise: The moray eel came out of its hole, and the two fish swam away together.
Bshary and his colleagues then studied a population of groupers and moray eels in a saltwater coral reef in Egypt's Ras Mohammed National Park. The researchers found that the head-shaking behavior entices an eel to come out of its hole and join the grouper, and that hungry groupers who have been unsuccessful on a solo hunt are more likely to recruit an eel as a hunting partner than satiated groupers are. They also observed that when groupers chased prey items into the reef, they would perform a "headstand" above the prey item's location and twitch their heads back and forth; in response, eels would swim to the location and enter the reef, trying to nab the tasty morsel for themselves.
In all, working with moray eels improved grouper hunting efficiency five-fold, the team reports in the current issue of PLoS Biology. Eels swimming with groupers also caught prey items, but the team did not observe any solitary eels catching prey and therefore could not gauge a change in their efficiency. The researchers report, however, that eels traveling with groupers are even more efficient hunters than the groupers are, capturing nearly twice as many prey items per hour.
Ecologist Chris Stallings Oregon State University in Corvalis cautions that this is not the first study to document groupers and eels hunting together, but he acknowledges the signaling behavior that initiates the tag-team between the two fish is "novel and exciting." Biologist Craig Packer of the University of Minnesota in St. Paul adds that the study shows that animals don't need big brains to cooperate. Many ecological models of cooperation between individuals are complicated, requiring long-term memory of different individuals, he says. But in this system, he says, a grouper just needs to find any old eel.