@geniusmusing It could be just one cat. No one has seen it happen, just smelled the odor.

I originally suspected it was the male, because I know they do this. I think he's still less than a year old. There's a female that is probably 13-15 years old that really does not like the male and a female that is probably about 4 months old.

The older cat is the last of a set of 3 that she got back then.