Originally Posted by Viva
Proven where? You can't really do a fair experiment unless you're using WILD bettas. As far as I know, there aren't many animals that exist on earth who fight with their own kind on sight, and ignore all other aspects. A living creature's purpose in life is to create more life, and fighting to the death with its own species seems kind of backwards from a psychological standpoint.
Betta fish will show aggression regardless of territory. I shouldn't have to prove that or cite references. If you haven't experienced that first hand then you haven't owned enough bettas.
Research studies with males always show that they will fight regardless of anything, with some exceptions. They tend to be more interested in foraging the bottom in some circumstances than fighting. Bettas without cover show more aggression then bettas with cover. It's also a fact that two bettas can be placed in a very large pond with more then enough room for both, yet both will still fight endlessly.
There are papers on this, but unfortunately most of us hobbyists are forced to just assume or go by what we've all heard and read from each other. Most of the research papers I have seen I've had to pay to download. That sucks.
Females are much more different and will setup a hierarchy. At various times I've noticed my females seem to prefer one part of the tank as if they have territory, but many days later she's keeping to another part of the tank and will chase others no matter where they are if she feels she's above them.
So I've had to rebuild my female population several times. I have tried rearranging the tank, adding them in order of aggression, just adding new ones in groups, adding a new one individually and I seem to not get any different results. As soon as I add a new girl depending on her aggression the balance is upset and they all rearrange the hierarchy! If the new female is more docile then I almost see no change in the pecking order and it's as if nothing had changed.
The only reliable method I have found in controlling their behavior was if I wanted to adjust the aggression of a female I could put her in a transparent box so she and the others have view of each other, but could not fight. The longer the female remained in the box the less aggressive she turned out to be when I released her. I've done this on 3 occasions. One female that was so aggressive she would attack all the others leaving their fins in ruin. I put her in the box for 48 hours and released her. She then began to only attack periodically but only the lighter colored females. I put her back in the box and kept her there for 7 days then released her again. Now she attacks no one and the alpha prior to her seems to be the only chaser. The previously aggressive female now seems to accept being much lower in the pecking order and on occasion is the one being chased.