Thank you. A lot.
I made two mistakes:
1) did not quarantine the new chin, decided to do it as of today since I didn’t know that
2) introduced them the same day i got a new chin.
The cage is enough for the two of them, it is split in 2 parts so that they can see each other but not touch each other or fight. Each has their own food container, water etc. Everything is separated.
We are going to keep it like that in the weeks to come, as you suggested, so that the new chin gets more comfortable with the new surrounding and so that both of them get familiar with seeing each other.
Just for future reference, a quarantine period is honestly a good thing to do with most animals. It's less of a viable option with pets like dogs and cats, just because they tend to have free roam of people's homes and/or yards, but for anything that's kept in an enclosure (rodents, reptiles, rabbits, birds, etc.), it's generally recommended to keep new animals in a separate room from anything they're closely enough related to to pass on disease (so keep small mammals, even if they're different species, quarantined from one another, same for reptiles and amphibians). Most people recommend a quarantine of at least 30 days before moving the new animal into the same room as any related (by species/family/genus) animals you already have, and only move the new animal into the same room if they've had a clean bill of health for that full 30 days. Some people recommend quarantines longer than 30 days, but it often depends on the specific situation. 30 days is a good minimum to start with.
Let your new boy adjust to his new home and put on some size. When you do introduce them, you want to do it in as neutral an area as possible, don't just throw them in the same cage together and hope for the best. Do a series of short, closely supervised intros in a neutral, well-cleaned area that neither feels is their "territory." Separate them immediately if they start to fight, fur slip, or if there's intense chasing. Only once they can coexist peacefully in a neutral area for several.sessions with no aggression should you try putting them together in the same cage.
And keep in mind that chin intros can take weeks, months, or even years. And some chins just don't get along and will never want to share a cage, so be prepared for that possibility. If there's ever any blood drawn at any point in the intro process, then that's when you need to call the introduction a failure and just plan to keep them separate for the rest of their lives. Drawing blood is an indication that they're trying to kill each other.....and severe injury or even death is a real possibility once they start drawing blood. Not all chins get along with all other chins, and some are just really territorial and don't want to share their space.
