Introducing two males

[Lj1981]

I am caring for a lost cat while the weather is cold -27celcius. He has no microchip and is very sweet. If I were to keep him are there any best steps to follow? My cat is neutered , the stray is not. I don’t want to make it hard on my old boy as he is 15 yrs old and recently lost his fur friend last year.

 

[cat nap]

Does the outdoor cat have a 'safe room' in your home, where you can keep him,...with his own food, water, and litterbox?
Totally separate from your resident 15 yr old cat.
(Bless you for taking in this homeless cat, and saving his life. I doubt that he would have done well, in temps that cold.)
.............................................

First I would take him to the Vet, and have him cleared for any medical issues, that might affect your cat.
With it being that cold, I doubt there would be fleas, but still best to check, and check for worms, etc.
(it sounds like you have already done this, since you know about no microchip, etc.)

Second, I would get him neutered.

Third,...to do cat-to-cat introductions....take a look at this Cat Site Article:
How To Successfully Introduce Cats: The Ultimate Guide – TheCatSite Articles

Basically, you create a cat-introduction Plan...and follow some steps...with Routine and Repetition.
Try to remember the 5 Senses approach to cat intros.

1. Hearing ...where the cats can hear each other, but not see each other.
2. then Scent....and especially the 'swapping the scents, mingling the scents' and 'allowing each cat's scents to be all over the home'...so much so...that your resident cat will recognize and accept the new cat as part of their territory. This is the part where "Scent swaps" and "Room Swaps" are practiced to get both cats' scents everywhere.
3. Visual is next,... but you are still doing Scent Exchange, and rewarding any good interactions with treats/food/praise. This can be done ...very, very gradually...by draping a bedsheet over the gate...and raising it higher and higher everyday...so the sight of the other cat...is not overwhelming.
4. Taste is using food and treats... to make positive associations and encourage more Acceptance.
5. Finally, Touch,....is when you've observed that your resident cat is no longer bothered by the smells, or sight of the new cat ..and you've noticed a huge decrease in your resident cat's fear responses.

** if you want to add further 'separation areas'...then I would suggest ...using wire shelving...as a swing type door.
Which can also be placed in a hallway...to block it off...or another open doorway, too.
You use 'zip ties' to connect to each other...and can use other 'zip ties' for hinges and closure hooks, too.

Check out this thread. See post #2 and post #4 for some visual ideas.
Featured - Door blockade for cats getting to know each other
and this online site, for a 'how to build' one:
How to Build a Free-Standing Cat, Dog, or Pet Gate Cheaply, Without Tools

Again, thank you for saving this outdoor cat.
You are a true cat guardian.

 

[Lj1981]

Yea, our cat has his room that is his and where he typically spends most of his days anyhow. We had them in separate rooms not seeing each other but getting smells of each other the last couple of days. The takennin cat has been hanging out in a dog run that is covered up Andy cat has seen him
Already. They cry at each other, but haven’t been approaching each other at all— just laying where they lay making a bunch of noise.

 

[calicosrspecial]

Yea, our cat has his room that is his and where he typically spends most of his days anyhow. We had them in separate rooms not seeing each other but getting smells of each other the last couple of days. The takennin cat has been hanging out in a dog run that is covered up Andy cat has seen him
Already. They cry at each other, but haven’t been approaching each other at all— just laying where they lay making a bunch of noise.

Great advice from cat nap.

I am happy to help on the intro. The goal is to build trust between them so that there is no fear of a physical nature, access to food or water or litter box, etc. We do this slowly but focusing on positive associations (using food) and positive encounters and reinforcing those to build trust.

I tend to take it slowly and go at the cat's pace in order to build that trust. So I limit visual contact until I feel it is most likely to be a positive where the cat's already think "I know that cat and that cat is not a threat".

Just let me know if you need help as it is a bit nuanced. But I do these all the time and it is important to do the intro properly in order to achieve success.

Thank you so much for caring for the stray!!!