Adding More Guinea Pigs Or Merging Pairs – What Works And What Not?

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Mar 10, 2009
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Coventry UK
The temptation is always there when you have two adorable and happily settled guinea pigs to stick in another one into a generous cage or to merge your two pairs of guinea pigs. This however can rather easily end in disaster if you do not respect your guinea pigs and their social needs and quirks. Bonding is not quite as easy as introducing your piggies for a happy ever after for you!
Even your pairs may not always be as stable or happy as they grow older. Not all singles will immediately fall in love when seeing another piggy. Some can be actually rather challenging to bond.
Here is more information on on pairs and single piggies, which you want to read so you can take likely future challenges into consideration and plan better ahead.
Single Guinea Pigs - Challenges and Responsibilities
A Closer Look At Pairs (Boars - Sows - Mixed)

This guide here is taking you in detail through the combinations with a look as to which are more or most likely to end up with problems or an outright disaster and those that have a much better chance of success. It is of course always only generalisation but after well over a decade of existence and answering hundreds of relationship questions and cries for help, we feel we can comment on which constellations we are much more often asked for help than others.

Trios are the most difficult guinea pig constellation to get right as most of them end with some kind of 2+1 outsider constellation, whatever the age or gender combination. However, sub-adult boar trios have about a 90% risk of ending up with the need to split before the boars reach a hormonally somewhat more settled adulthood.
Even adding a baby boar to an adult trio can destabilise the existing bond and lead to the boar pair falling out with other. At the worst (and we have seen this happen a few times), you can end up with three single boars that won’t go together.
Boar trios work best with a disabled/carer companion setting or with older boars whose testosterone has run out, unless the boars have moved together through their own choice.

The same goes for boar quartets, only even more so! There is a near total fall-out rate for boar quartets with younger boars. In our long term experience, you are most likely to end up with one pair and 2 single boars, but we have had members ending up with 4 single boars that would not go back with each other again. This goes for both starting out with 4 baby boars (being related doesn’t matter one bit) or for merging two bonded pairs. With a very few exceptions, boar quartets only work with older or disabled boars. Never count on you being that exception!
The only (very few) longer term successful boar quartets I know of provide either a very large habitat that allows each boy to have their own space, involves different disabled/carer companion group dynamics or an old age pensioner group where testosterone has long since fizzled out and the boys are more like sows without the need to dominate the boar world.
If you want to add more boars to your household, please opt for a second separately bonded pair.

Large groups
If you want a stable boar group, you need lots of space (ideal 1 sq metre per boar) and ideally more than 10 boars to form a stable bachelor herd. You will still need extra accommodation in case there are problems or you need hospitalisation and/or quarantine.

Adding a third sow to a well bonded couple can work, but it can also be an outright failure depending on the personality constellation. The outsider problem is also a concern. In my own experience, trying to introduce a single guinea pig to a well bonded pair has been the bonding that has most often failed.

The exception is introducing a neutered boar, as he is a natural outsider who is not part of the sow hierarchy.
However, he has to be accepted by both sows, which does not necessarily happen.
A neutered boar can also not heal the relationship between two squabbling sows; he is inevitably going to associate with just one of them if there is a rift.

In any case, if you want to add just one guinea pig to a bonded sow pair (sow or neutered boar), you’d do best to date them at the a rescue for compatibility and mutual liking or better have a plan B at the ready in case the bonding is not working out the way you want to.

When you want to merge two bonded pairs of sows, it works best if the pairs are of different ages and one of them is ideally not yet fully grown. This means that the leadership cannot be challenged. It also means that each sow has a closer friend and an outsider situation is much less likely as you start seeing group dynamics emerge. Three sows and a neutered boar can also work.
Acceptance of a younger pair of sows is much more likely to happen than that of a single sow - but as with all piggy bonds, it is not working in all cases.

Acceptance between two adult pairs, especially between two dominant group leaders, is a very different kettle of fish and much less likely! It very much depends on how personality combination in this case and even more so on the willingness of one of the two leader piggies to step down, which is not quite likely.

If at all possible, opt for additions where the existing hierarchy is not upset, but be aware that what looks good on paper may necessarily work out in reality. I have got a nice cupboard full of t-shirts on that score!
The older sows get, the less they are generally accepting of new company; as ever with notable exceptions. Whereas when they are really old, they may again appreciate a snuggle buddy...
Fear-aggression with new piggies is much more a problem in sows than in boars; but then they have more of a status problem when it comes to the sow hierarchy in a group.
All you can do, is giving it a try. You can never predict the outcome. Misfits groups can work surprisingly well whereas other piggies prefer their own queendom but still appreciate company through the bars.

Mixed gender pairs and groups
Neutered boar and sow / spayed sow and full boar pair
This is overall the most stable bond of all guinea pig pairings. Crucial is mutual liking and initial acceptance as not all personalities harmonise - two dominant characters will inevitably clash. It pays to date for initial acceptance, but after that it is pretty much plain sailing all the way!
Please be aware that adding a second sow to a happily bonded cross gender pair may not necessarily work; she will be seen as an intruder into a cosy twosome. In this case, it can work better trying a couple of youngsters as that creates a mini-group with different dynamics and elevates the status of the original sow enormously.
The same applies also for a spayed sow and full boar pairing; but as spayed sows are A LOT rarer in most places, the second is not often an option.

Groups with 1 neutered boar
Any group with just one neutered boar and any number of sows can work.
The crucial point in my own experience is that any newly introduced sows should be ideally either submissive or already used to living in a group. Introducing dominant sows or those not used to a larger group can fail. Ideally you build up a larger group around one dominant leader, whether that is a neutered boar or a sow; all the other new guinea pigs should not be able to challenge this.

When adding guinea pigs without dating, you have to always have an alternative solution at the ready, in case the bonding doesn't come off. You also have to keep in mind that group dynamics change over time, and not always necessarily to the better. I have and have had a fair number of neutered boars living with one to up to thirteen sows. While having a large group can be fascinating, it can also give you major headaches. Generally smaller groups of 4-6 piggies with or without a 'husboar' (a married neutered boar) seem to work best in terms of long term stability.

Groups with 2 neutered boars
Merging two neutered boars with two sows is a big NO NO!
This grouping will pretty much always end up with fights as soon as the sows come into season.
You need two VERY laid-back boars to pull that one off as an exception of the rule!
You'd better opt for two separate mixed gender pairs, which are the most stable of all piggy constellations.
PS: The same goes for two full boars with a spayed sow or two - you are highly likely to end up in trouble sooner rather than later!

Large groups with any number of sows and neutered boars
Again, if you want to have a number of neutered boars and sows living together, you need LOTS of space to pull it off in order to allow the various subgroups to have their own space and territory, like ideally at least half a room or a whole room.

As an example for a good place that works, I am linking in a German facebook page.
They have got a fully enclosed sizeable patio garden with avian protection over the top as well, and a dedicated side building for their around 60 guinea pig to use for their frail guinea pigs with extra care needs as well as protection during cold snaps. All boars are neutered.

You will find that the guinea pigs organise themselves in small sub-groups that live together. Often several sows are associating with a neutered boar of their choice or some bachelor boars hang out together. This mirrors the way guinea pig society is wired to work and explains why some group bondings work and others don't. -

We can all dream... here is somebody who has made that dream come true!
Faszination Meerschweinchen
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