Thanks to everyone for your advice and comments (and yes, Star and Artie are both very cute!). We know that Star was found in downtown Buffalo, so I'd have to guess that she was probably eating from garbage, rather than hunting. She was malnourished and clearly had a recent litter when found. However, she definitely remains fixated on the stairs and can't be distracted for a good long time when Artie makes an appearance. That's my big concern. Before I try to intro them again, I want to make sure Star understands "no" or "drop it"; problem is, she doesn't pick things up yet--she's just learning how to play! I'll update the list when I have news.