There are some peculiar symbiotic relationships on the reef and this newly uncovered one between a grouper and an eel may just take the cake (or the fish). Scientists and divers have seen groupers and eels working in tandem to hunt in the wild before, but there is not new evidence this is even more sophisticated than previously thought.
When a grouper has prey they can’t reach because they are out of reach in a crevice or hole, they often swim over to a moray eel and send the signal for help with a shake of its head. Then the grouper and eel swim off to where the prey is and signal with a headstand on where attack. The eel chasing out the prey and the grouper attacks. The eel gets the leftovers and both are happy.
But now, the research team of Alexander L. Vailemail, Andrea Manica and Redouan Bshary, have found out the groupers will actually remember which eels are better at this job and return to those more often. The same team that brought us the previous news about this dynamic relationship in Nature Communications, now has observed the groupers will actually learn which eel is the most helpful and aim to recruit these eels more often.
With eight Coral Trout (Plectropomus leopardus) in tanks in the lab along with life-sized fake moray eels plastic cut outs placed in rocky crevices and fake small prey fish both in the open and hidden in a crevice. The team noticed the fish would seek out the eel right off the bat when the prey was hidden. On top of this, they also toyed with the notion of a helpful or unhelpful eel.
The research team put two fake eels in the tank — one that would swim towards the prey and one that would swim away from the prey. On the first day of testing the grouper had six chances to recruit a partner, going after both eels equally. The surprise came the next day when the fish would go seek the help of the cooperative eel five times out and to the unhelpful one just once.
This sign of intelligence is something new for fish, a behavior only observed with experiments from chimpanzees. The study’s authors do note the fish’s behavior could be due to learning mechanisms, which do not necessarily require the flexibility of more complex cognition. However, it does prove that fish are a bit smarter than we previously thought. You can read more about this experiment in the latest issue of Current Biology.
[via National Geographic]