It depends where you are getting him from and his age.
If he is coming from reputable rescue who already has quarantined him, then you do not need to quarantine again.
If he is coming from anywhere else and is over 4 months of age then he needs to be quarantined in a separate room for two weeks.
If he is under 4 months of age then you must not quarantine at all. Baby piggies need constant companionship so you do not quarantine and instead you carry out the neutral territory bonding in the day you bring him home.
If piggy is over four months of age and after quarantine, then it is helpful to have the two piggies in separate but side by side cages for a few days before bonding day. This allows them to get used to each other and the smells prior. It is no indicator as to whether they will bond but it can help settle them and get used to each other before being put in the high stress situation of bonding.
To introduce they need to be put into neutral territory for several hours and left to see if they accept each other. If they do and are ok after a few hours then you clean out the cage they are to live in and then move them to the cage together. It then takes the next two weeks of being together to fully form their bond. You do not separate unless there is a fight. Be aware that it can still fail at any time during those first two weeks.
Do not just put the new piggy into your existing piggy’s cage. That will be seen as a territory invasion and will cause a fight - you must introduce somewhere else that your current piggy does not see as his territory.
If during their time in the neutral territory bonding pen things do not go well, then the bonding has failed and they must live in separate but side by side cages permanently.
Bonding and Interaction: Illustrated social behaviours and bonding dynamics
