Zoologger: The rules of fish Fight Club

[Shai]

Of course, we already knew that bettas have personality, but here's a really interesting article on what kind of personalities they specifically could have. The original article has neat links interspersed with the article text too, so it's worth clicking through.

http://www.newscientist.com/article/dn18378

The clue's in the name. Male Siamese fighting fish are so aggressive that they have the dubious distinction of being perhaps the only aquatic animal whose fights are the subject of organised gambling. Fighting fish will swim through rings or down runways for a chance to take a pop at a rival – and will even attack their own reflections.

Yet despite a predilection for using their sharp teeth to tear opponents apart and their tails to beat them to a pulp, a new study suggests that differences in the fishes' fighting styles reflect distinct personalities.

Some attack furiously and constantly, like boxers pummelling their opponents into submission, while others are more considered, carefully watching their opponents before deciding when to strike – like martial artists waiting for a sign of weakness. But why?

It's not surprising that the males fight when they feel that territory is being invaded. But they choose their battles, and their tactics, carefully, attacking sooner and more vigorously if the opponent has himself recently been fighting.

The fish also observe a hierarchy, fighting differently according to whether their opponent is senior or junior. Lashing out at a vastly superior competitor is a bad idea, and males don't do it – as long as they haven't lost track of the pecking order.

On patrol

Now Giuliano Matessi of the University of Copenhagen, Denmark, and colleagues have found that the males fall into two broad personality types: they're either "persistent", spending almost all their time patrolling the borders of their territory and signalling to their neighbours; or "sporadic", taking regular breaks to lurk somewhere away from their neighbours. If confirmed, Siamese fighting fish will have to be added to the ever-growing list of animals that seem to have distinct personalities.

Matessi's team placed individual fish in a cluster of tanks and looked at what happened to the different personality types when they were moved to a new tank, with a new set of neighbours. The persistent fish kept on patrolling and posturing, as before. This is consistent with an earlier study which showed that the more aggressive Siamese fighting fish tend to stay that way, no matter what changes are made to their environments.

However, the sporadic fish chose to spend a lot of time in positions where they could keep an eye on their neighbours without interacting with them. They became only slightly more aggressive.

The researchers suggest that the persistent fish prefer to take a direct approach to finding out about their neighbours, by jumping right in and competing with them. The sporadic fish, by contrast, are more inclined to eye up the competition for a while before doing anything.

The latter might seem a better strategy – know your enemy and all that – but it requires constant vigilance to work. If two sporadic fish who each happened to lose their last conflicts were to meet, they might both infer that the other is weak and attack relentlessly. And that would be a bad idea for all concerned.

Journal reference: Animal Behaviour, DOI: 10.1016/j.anbehav.2009.09.034