@manhthieugia95 i was doing something like this for myself but lost my file, i was spawning cats ,seagulls,and rats and using the animations that the game doesnt use for cats, aparently someone was gonna have a pet cat in the game,cos there are too many animations of a "petting" cat in the files that you dont see the strays using,dogs have some unused animations as well.
from what i saw from the game, they have specific spawn points so to speak, so i dont think increasing amount if possible would do you any good.
you can do it yourself if you can bother,with menyoo or map builder,with menyoo you have the option to create some action set for it to follow whenever they spawn.
this was made for role playing https://imgur.com/a/pt5OP
you can see the cats have diferent sitting animations than strays,and the one in the back is sleeping sideways,strays dont do that.