Rabbitfish help one another in a way that had been observed only in mammals and highly social birds, according to a new study.
Pairs of these tropical fish will cooperate: While one has its head down feeding in the crevices of coral reefs, the other holds its head at an upward angle, apparently watching for predators.
The fish take turns between feeding and keeping a lookout, said Simon Brandl, a behavioral ecologist at James Cook University in Australia and one of the study’s authors.
He added that when one is down, in 90 percent of cases, the other has its head up. He and his colleagues reported their findings in the journal Nature Scientific Reports.
Dr. Brandl and his colleagues observed this form of cooperation in male-female pairs and in same-sex pairs a sign that this is a complex social behavior.
If it occurred in only male-female pairs, it makes sense for the male to help out the female to improve fertility, Dr. Brandl said.
But this behavior, he added, is an example of reciprocal cooperation, more often seen in mammals like chimpanzees and humans.
Fish deserve more attention from researchers studying animal behavior, Dr. Brandl said. There are likely to be species even more clever than rabbitfish.
Rabbitfish are not the sharpest fish of the bunch, Dr. Brandl said.
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