Welcome to the forum
I’m sorry to hear this.
Unfortunately putting four boars together doesn’t work (particularly where teenage or young adult piggies are involved - older boar carer groups (ie with piggies older than 4-5 years) can sometimes function), it has an almost 100% failure rate. They find it very hard to function due to the fact you can only have one dominant piggy in any group (and finding boars so laid back that they are happy to live in a herd is incredibly hard)
As you had two (presumably established) pairs there were two dominant boys (one in each pair) so as soon as you put those two together, a clash will happen as they both defend their position. Neither one is ever going to be prepared to back down and thus it fails (fights and injuries usually occurring).
Space is also another factor - a cage larger than four square metres would be needed but even with that space they are still not going to be able to function a hierarchy - the space just means they can get away from each other rather than have a harmonious group.
Unfortunately a consequence of a boar quartet attempt is that it can break bonds between the original pairs, so once the quartet fails the pair also does.
The common outcome of boar quartet attempt/failure is one pair remains intact but the other doesn’t overcome the disruption and also fails - so a pair and two singles. We have also seen cases of members finding us post-attempt where all bonds have been broken and they’re left with four single piggies.
It would be best to leave the two of them apart for a few days to calm down.
You may decide at that point that they are both happier and as such they would be best to be kept separate permanently.
Alternatively, in a few days time you may decide to put the two of them back into neutral territory (do not reintroduce them in a cage which either one of them are as their territory) to allow them to decide if they wish to go back together. It will become clear quite quickly whether it will work or not.
Do prepare that it may now mean they would prefer to stay side by side in separate cages permanently.
I have added a few of guides below which explains everything more fully, and including the bonding guide
Keep us posted on how things go
Adding More Guinea Pigs Or Merging Pairs – What Works And What Not?
Boars: Teenage, Bullying, Fighting, Fall-outs And What Next?
Bonding and Interaction: Illustrated Bonding Dynamics and Behaviours
