It may be stereotyped, genetically programmed behaviour (as my friend GL felt obliged to point out), but the link my roomie Jenneke sent me is still the best case of gesturing fish I have seen (see earlier observations about the John Dory and the Octopus). In a spectacular study Redouan Bshary, Andrea Hohner, Karim Ait-el-Djoudi, and Hans Fricke show evidence of Interspecific Communicative and Coordinated Hunting between Groupers and Giant Moray Eels in the Red Sea. (PLoS Biology)

Say you organized a hunting party, how would you invite your friend the giant moray eel? (source)

Here are the video’s (PLoS Biology):

Video S1. A Grouper Shaking his Head to Invite a Moray Eel Resting in a Cave (1.1 MB WMV)
Video S2. Grouper and Moray Eel Swimming off Together after the Grouper Signalled (2.0 MB WMV)
Video S3. A Grouper Performing a Headstand Shaking of Its Head above the Hiding Place of a Prey That Escaped the Hunt (2.1 MB WMV)
Video S4. A Moray Approaches the Place Where the Grouper Performs Its Headstand Shaking (2.1 MB WMV)

At first sight it appears clear that here we have a gesturing fish. He shakes his head at a moray eel to invite him to hunt. He makes a movement to elicit a response. Does he intend to communicate? Here we face the only problem with calling the grouper’s behaviour gesturing. Can we ascribe intentions to a grouper, a fairly simple organism?

If you are a strict behaviorist and do not believe that the perception of intentionality should be studied at all, feel free to leave the room now. I am at the moment happy to accept human intentionality, and the same goes for apes, dolphins, dogs, and (why not) fish. In fact, in practice I even ascribe intentions to my computer, my car, and basically anything that moves or is suspiciously standing still 🙂

Don’t tell anyone though, I want to keep my freedom.

Reaction by Frans de Waal (PLoS): Fishy Cooperation
Report (Dutch) at Noorderlicht: Jacht op het Rif