Trout seek out the best moray eels with whom to cooperate to get a meal
Fish are known to be intelligent, emotional, and clearly sentient beings. Now, a new and very significant experiment shows that coral trout actually rival chimpanzees in choosing the best moray eel with whom to cooperate to get a meal that both can share. An excellent review of this study titled "Fish as good as chimpanzees at choosing the best partner for a task" can be read here. The summary of the original essay (available only to subscribers) by the research team of Alexander Vail, Andrea Manica, and Redouan Bshary called "Fish choose appropriately when and with whom to collaborate" published in the journal Current Biology can be seen here. It reads:
Collaborative abilities are integral to human society  and their evolutionary origins are of great interest. Chimpanzees are capable of determining appropriately when and with whom to collaborate in a rope-pull experiment  - the only non-human species known to possess both abilities. Chimpanzees are thought to share these abilities with humans as a result of common ancestry  . Here, we show that a fish - the coral trout Plectropomus leopardus - has partner-choice abilities comparable to those of chimpanzees in the context of its collaborative hunting relationship with moray eels  . Using experiments analogous to those performed on chimpanzees  , but modified to be ecologically relevant to trout, we showed that trout recruit a moray collaborator more often when the situation requires it and quickly learn to choose the more effective individual collaborator. Thus, these collaborative abilities are not specific to apes and may be more closely linked to ecological need  than brain size or relatedness to humans.
In a nutshell, the trout recruit eel to help them obtain prey who buries itself in a crevice in a reef. The trout (and coral groupers as well) use head shakes and headstands to tell the eel where the prey is hiding. In addition, the trout know when they need a collaborator and pick the best eel with whom to work. In the laboratory experiments, "the trout were presented with out-of-reach food in the form of prey secreted in a crevice, and the possibility of a collaborator that took the shape of a model moray eel as fashioned by the researchers." And, when the trout were allowed to choose between two fake model eels, on of which was previously "a successful collaborator that flushed out prey and the other which swam in the opposite direction - the trout's ability to pick the successful partner was identical to that of the chimps" using data from prior studies.
Size doesn't matter: big brains aren't needed to perform complex cognitive tasks
Alexander Vail, the lead researcher who works at the University of Cambridge's Department of Zoology in the U.K. noted, "Our results show that, like chimpanzees, trout can determine when a situation requires a collaborator and quickly learn to choose the most effective one." In addition Dr. Vail points out, "This study strengthens the case that a relatively small brain - compared to warm-blooded species - does not stop at least some fish species from possessing cognitive abilities that compare to or even surpass those of apes."
Are animals really superhumans?
We need to be very careful when making cross-species comparisons and shouldn't use ourselves as the standard against which others are measured.
All of the researchers who partook in the above study "caution that the processes underlying such 'superficially similar' cognitive behaviour are not known, and that - as previous commentators have stated - complex behaviour doesn't always reflect a complex mind." My own take is that we need to be very careful how we use the word "complex", and there seems to be no reason to think that fish minds aren't very complex even if they may not be as complex as the minds of great apes. We really don't have very good measures of mental complexity that can be used in cross-species comparisons, and clearly, small fish brains serve the fish rather well, as do small bee brains (please see "The Birds and the Bees and Their Brains: Size Doesn't Matter").
Along these lines, I became aware of the fish-eel study right after watching a BBC TV show called "Superhuman Animals" and thought about how cross-species comparisons can be misleading and fraught with error. I wondered if some other animals are really "superhuman" because, for example, they can do things that we cannot do because they have incredibly sensitive eyes, noses, or ears and can see, sniff, and hear things that we are unable to perceive? Why are we -- and should we be -- the standard against which other animals are compared? Perhaps, in some arenas, we are actually "wee animals" when compared to others.
I don't find using phrases like "super this or that" or "wee this or that" to be particularly useful. Individuals have to be able to do what they need to do to be card-carrying members of their species and, from an evolutionary point of view, possessing different sensory and motor skills doesn't make members of different species better or worse than others. They simply do what they have to do to thrive and survive in their natural habitats.
For a while I've been working on an idea I call "the cognitive maximization hypothesis" that suggests that perhaps small-brained animals maximize the use of what they have -- their neural endowment -- and perhaps they use the relatively little they have more efficiently then do big-brained animals. Big brains in and of themselves don't really matter to the animals themselves and they do just fine with what they have. Future research will be needed to determine if this is so. The claim that humans use about 10 percent of their brain is a myth so perhaps the efficiency of processing information is a factor to consider. Regardless, small-brained animals do just fine in their own worlds. (For more discussion on this, see "Are Bigger Brains Better?" by Lars Chittka and Jeremy Niven.)
Big brains may be useful for those animals who need them, but small-brained animals do very well as long as they can do what they need to do to survive and thrive in their own worlds. The notion that small-brained animals are "less intelligent" than big-brained animals and also needs to be revisited.
The rapidly growing fields of comparative cognitive neuroscience and cognitive ethology (the comparative study of animal minds) continue to provide exciting information about the brains and incredibly active minds of other animals. What an exciting future lies ahead.
I hope that more and more people will come to realize that many other animals display what we often call "surprising" cognitive and emotional capacities, but if we keep open minds we see that they are not all that surprising at all if we pay attention to the lives of the animals themselves. Please stay tuned for more on the fascinating lives of the other animals with whom we share our magnificent and wondrous planet.