this is the second time i have tried to introduce my pairs (Cracky and wheezey, Chunky and Corn chip) they lived next to eachother for weeks, swapped hides everything. they had a good nuteral zone and everything was fine for hours when Chunky randomly attacked Wheezey i grabbed her fast, Chunky did a number on my hand. poor Corn chip and Cracky seem traumatized. this is not the first time Cracky has had a failed introduction and i feel tremendously guilty for trying again. i feel like a horrible owner for putting her and the rest through so much stress for not
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Hi and welcome
Merging two pairs of adult sows often fails because neither leader wants to lose their position. Being First Lady in a group is as high as a sow can rise in piggy society; the group is the social backbone of it. So merging two established groups has a very high fail rate.
Adult/older sow pairs, especially those past ideal pup-bearing age may also not necessarily accept a neutered boar (can happen with both the leader or the undersow who is not willing to lose her ranking in the hierarchy) or one younger sow. Two young sows (especially sub-teenage) can work because at that age, they are still learning the ropes in 'Cavy School' and cannot challenge for leadership. By going from a pair to a quartet of sows, the group dynamics also change noticeably. The under-sow will gain quite a bit in status and will be generally more accepting.
However, these are all only trends and everything relies on the personalities involved and the unique dynamics that happen between them - I have sow pairs that have happily accept a neutered/de-sexed husboar or a single baby, for instance (especially when the sow was very elderly and living with a somewhat younger boar).
When bonding on spec at home, you have to always brace for a failure and have to have a plan B at the ready. That is why we generally recommend rescue dating so you come home only with new piggies if acceptance has happened during the introduction at the rescue. I do however accept that there are a lot less rescues, even less good welfare standard rescues around in the USA compared to the UK.
I have got a room full of sows that will accept just one companion but that have steadfastly refused to accept others - but I have over the past years mostly adopted piggies stuck in rescue because of social issues and tried to find them a friend they were happy with. Before that, I had several smaller groups and before that one large group which I carefully built up around a leader with either piggies with a herd background or young piggies that would/could not challenge the leadership. It eventually failed in the second generation over a hostile leadership takeover.
For such a social species, guinea pigs have a social life that is every bit as complex as our human life when it comes to relationships...
Your two sow pairs should be able to live peacefully as neighbouring groups in adjoining cages or with a divider in a large enough cage because that is working with their social instincts again.
For more information:
Bonding and Interaction: Illustrated social behaviours and bonding dynamics
Adding More Guinea Pigs Or Merging Pairs – What Works And What Not?
Guinea Lynx :: US Guinea Pig Rescue and Shelter Organizations